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IRC:SP:11-1984

HANDBOOK OF QUALITY CONTROL FOR CONSTRUCTION OF ROADS AND RUNWAYS

(Second Revision)

Published by :

INDIAN ROADS CONGRESS
Jamnagar House, Shahjahan Road,
New Delhi 110011
1984

Price ₹ 300
(Plus packing & postage)

INTRODUCTION

Quality control of construction materials and product is an essential requirements for obtaining improved and uniform standard of roads. Towards this end, a three-day Symposium on ‘Quality Control in the Construction of Roads and Runways,’ was organised under the joint auspices of the Indian Roads Congress and the Central Road Research Institute in New Delhi from 27th to 29th February, 1968. At the concluding Session of this Symposium, the following resolutions were adopted :

1. that quality control of materials and the end product together with process involved should form an integral part of construction specifications of road and runway projects, and that materials survey be carried out for each project at the rough estimate stage;
2. that wherever necessary, the existing specifications be reviewed so as to be realistic and to provide for adequate quality control measures fair to all concerned;
3. that adequate financial outlay be provided in the form of either a basic budgetary provision or as a percentage of each project estimate to meet the expenses of quality control;
4. that a Committee of experts be set up to prepare a handbook giving all the details of quality control code and that the handbook be reviewed periodically based on experience gained;
5. that short term training programmes be organised to provide the requisite trained personnel for quality control.

In pursuance of Resolution No. 4, a Committee consisting of the following members was constituted for drafting the Handbook:

The above Committee, in turn, constituted four Subcommittees to prepare drafts of various Sections. Later, the Committee decided that, before finalising the Handbook, its main tentative recommendations regarding the quantum of testing, control tests, acceptable tolerances and method of interpretation of results, in a summarised form, be placed before the National Seminar on Roads and Bridges at Bombay in October, 1968 for wider discussion. For this purpose, a Working Group consisting of Dr. M.L. Puri, Dr. M.P. Dhir and Shri R.P. Sikka was entrusted with responsibility of preparing the required summary for circulation to the delegates attending the National Seminar.

The Recommendations of the National Seminar were discussed by the Committee and in light of the discussions, a drafting Subcommittee comprising Prof. C.G. Swaminathan, Shri T.K. Natarajan and Dr. M.L. Puri was formed to complete the draft.

The draft prepared by the Subcommittee was discussed by the Committee in a series of meetings and a Working Group consisting of Shri R.P. Sikka, Dr. M.P. Dhir and Dr. M.L. Puri processed the same. It was then considered by the Executive Committee of the Indian Roads Congress, in its meeting held at Gandhinagar on 25-11-72. Thereafter, the Council of the Indian Roads Congress at its meeting held at Gandhinagar on the same day finally approved the draft of this Handbook of Quality Control for being published as a Special Publication of the Indian Roads Congress.

The Manual was revised in 1977 (First Revision) to incorporate the new standards on surface evenness approved by the I.R.C. Council at its Meeting held in Madras on 28.8.76. The second revision includes the prescribed equipment for different laboratories and the forms to be used for recording the results of observation/test results by the field officers.

CHAPTER 1
GENERAL

1.1. Need for Quality Control

1.1.1.

Quality control is an essential part of any production process and highway constructions are no exception. Quality control is an important requirement for highway construction for ensuring quality and for creating durable national assets. The need for quality control on these constructions has increased considerably in recent times due to a significant increase in traffic intensities, and the level of service expected of highway facilities. Improved level of service of the highways will result in considerable savings in vehicle operating cost and in favourable road user reaction and public opinion. Quality control in the form of sensory checks which are intrinsically subjective and qualitative is grossly inadequate for present-day needs and must instead be based on proper objective and quantitative measurements.

1.1.2.

It is common knowledge that quality control, besides leading to constructions of improved quality and uniformity, and ensuring a more economical utilisation of materials, also affords a significant reduction in user costs, in terms of lower costs of vehicle operation, transportation and maintenance. The extra cost of exercising quality control being only a fraction of the resulting benefits, is a highly economical proposition, in as much as on an average project it is estimated that the cost of exercising quality control would be just 1½ to 2 per cent of the construction cost. On the other hand, the direct and indirect economic return from quality control could be of the order of 5 to 10 per cent of the total construction cost and even more.

1.2. Pre-requisites for Quality Control

The pre-requisites for effective control of highway constructions are :

1. Construction specifications and estimates should provide for effective quality control.
2. Adequately trained staff and equipped agency for exercising quality control should be set up.
3. Periodic appraisal of the quality control data should be made not only for implementation during construction but also for effecting possible improvements in quality control and construction techniques themselves.
4. Updating of knowledge by on job training.

1.3. Organisational Set-np for Quality Control

1.3.1.

The requirements of a quality control organisation will obviously vary on different projects depending on the departmental set-up of the concerned highway agency. For. example, the organisation of quality control work at a single centrally situated large project will need to be on quite different lines than at average sized scattered projects. In this chapter only the broad guidelines for the organisation of quality control work at road projects are discussed. The actual set-up may be evolved in the background of various factors involved. For the suggested pattern of quality control set-up in this handbook a typical Organisational set-up has been drawn up and shown below:

Organisational Chart of Quality Control Set-up

4

1.3.2.

In any organisational set-up, the central agency has an important role as regards implementation of quality control standards by way of drafting and constant review of the quality control criteria included in the construction specifications. The implementation of quality control in the field would normally involve three sub-agencies viz. the construction staff of the Engineer-in-Charge, the constructing agency and the quality control team. The construction staff and quality control teams must have distinctly defined functions and inter-relationships so as to avoid possible conflicts. The quality control team may consist of staff of regional laboratories and field laboratories working under the technical direction of the Central Laboratory.

1.3.3.

As far as the field laboratories are concerned, the periodic quality control data collected by them should be promptly fed to the site engineer, as the latter is responsible for ensuring quality and speed of construction. In addition, the data will also be submitted to the Superintending Engineer/Chief Engineer as well as to the Head of the Central Laboratory; to the former with a view to ensure continuity as well as compatibility of the specifications in practice, and to the latter for purpose of feedback. This may be regarded as a tentative recommendation, subject to review and modification, as and when experience accumulates.

1.3.4.

The expenditure on quality control may be charged to the works and the staff as well as equipment shifted from project to project depending upon the requirements. The quality control staff should not be on work-charged basis but form part of regular staff and be properly trained for the work they are required to handle, for which suitable training facilities should be afforded by the department, either in their own Central Laboratory or any other Laboratory. To provide for the cost of quality control, it is suggested that this may be included as a distinct item in the various work estimates.

1.4. Types of Quality Control

1.4.1.

Over the years, two types of methods have emerged for exercising quality control during the construction of works. One is generally known as 'Process control' and the other as ‘End5

result’ type of control. In the former, the designer makes the decisions regarding the type of equipment, the procedure of construction and the amount of work required to obtain the desired result. In the 'End result' type of control, the construction agency, which may be a private contractor, has a free hand in the selection of construction methods and equipment to achieve the desired end product.

1.4.2.

The choice of either type of control is largely a matter of judgment, depending on the magnitude of the job, different environmental factors involved and the available facilities. In India, gradually the trend is towards ‘End result’ type of working on highway pavement and embankment construction jobs. But in several situations, for example on small jobs, or where input type of tests like material gradation and purity of lime are to be carried out, expediency would be in adopting ‘Process type’ of control. Because of circumstances, a combination of the ‘Process’ and ‘End result' types of control will continue to be adopted in India, depending on the nature and size of the job.

1.4.3.

In the ‘End result’ type of specification, the field engineering personnel carry out tests on finished work at regular intervals to evaluate whether it meets the specification requirements or not. On the other hand, in ‘Process type' control, the responsibility of field personnel is to make sure that the work in its different phases is executed in the manner predetermined and laid down in specifications.

1.4.4.

The details given in this Handbook arc for a combination of ‘Process’ and 'End result' types of quality control which is generally being practised in this country.

1.5. Specifications for Work

The handbook draws heavily upon the existing Standards/ Specifications of Indian Roads Congress by way of abstracting essential requirements of construction for the various items of work. Reference is given to the relevant Standards at appropriate places in the Handbook. A complete list of all the standards referred to with their full title is included at Appendix 1.6

1.6. Control of Materials

1.6.1.

The quality control tests on materials indicated in the subsequent chapters, are intended essentially to be carried out on the material brought to site. However, at times, from practical and other considerations, some testing could be done advantageously at the material source. In these circumstances, The Engineer-in-Charge may do additional testing at site as may be found necessary to ensure that the materials being incorporated in the construction are of specified quality.

1.6.2.

All the materials brought to the site shall be stacked and stored as specified so as to prevent deterioration or intrusion by foreign matter and to ensure the preservation of their quality and fitness for work. Materials which have been improperly stored or have been stored for long periods shall be re-tested where their suitability for incorporation in the work is in doubt.

1.7. Test Procedures

1.7.1.

The procedure for testing of different materials and work shall be in accordance with the relevant standards of Indian Bureau of Standards where these are available. Reference has been drawn to these standards at appropriate places in the Handbook. A consolidated list of the standards with their full title is at Appendix 2.

1.7.2.

Where specific procedure of testing is not indicated, the tests shall be carried out as per the prevalent accepted engineering practice to the direction of the Engineer-in-Charge.

1.8. Frequency and Extent of Testing

The frequency and extent of testing indicated in the Handbook is the minimum considered necessary for normal conditions. It is envisaged that additional testing shall be carried out for abnormal conditions where variations may be excessive or where circumstances so warrant otherwise.

1.9. Acceptance Criteria

1.9.1.

Acceptance Criteria for different items of work where sufficient experience was available have been setforth in the Handbook in respective chapters. For other items, acceptance7

may be based on minimum values or statistical analysis as is considered judicious.

1.9.2.

For effective control on quality of materials and work, it will usually be necessary to lay down the acceptance criteria in the contract documents.

1.10. Range of Equipment for a Central, Regional and Field Testing Laboratory

1.10.1.

Range of equipment required for a central, regional and field testing and control laboratories is indicated in Appendix 3 for guidance. The list includes such equipment as will normally be required for quality control operations spelt out in the Handbook. Individually, quality control units could be suitably equipped with the help of this list depending on the type and volume of work to be controlled. Special equipment as given in the appendix can be procured depending upon the requirement.

1.10.2. Testing facilities :

Testing facilities should comprise Laboratories at Central, Regional and Field levels. The Central laboratory located at headquarterswill (a) provide testing facilities for tests of specialized nature, (b) act as regional laboratory for works circle (s) at headquarters, (c) act as the nodal laboratory for Research schemes in the State and Central sectors,

(d) bring out manuals for testing procedures. The Central laboratory headed by the Director, may have for quality control work, scientists from Geology, Chemistry and Physics disciplines. The list of suggested equipment to be provided in Central laboratory are avilable at Appendix 3.

The Regional laboratories located at circle level will be headed by Executive Engineers (Quality Control) assisted by scientists from Geology, Physics and Chemistry disciplines. Regional laboratories will provide testing support to the (a) Engineers working in the circles and (b) Research teams from Central and State Highway R & D institutions. In addition they shall provide all facilities for training of all the Quality Control staff in the Region. The list of suggested equipment to be provided in Regional laboratories is given at Appendix 3.

It is neither feasible nor advisable to send samples for routine8

tests all the way to the Regional laboratories and delay the work for want of test results. Setting up facilities for basic tests at the level of Junior Engineer/Engineering subordinate is therefore necessary. Some other equipments may have to be provided at sub Divisional/Divisional level. A list of equipment suggested to be provided at Site/Sub divisional/Divisional level can be seen at Appendix 3.

1.11. Recording of the Test Results

The tests shall be carried out in accordance with the standard procedures and the results shall be recorded in the proformae given at Appendix 4. It is desirable that of the total tests, 70 per cent are carried on by the Junior Engineer, 20 per cent by the Assistant/ Deputy Engineer and the remaining 10 per cent by the Executive Engineer. The test result record registers shall be presented with every third running bill so that the payments get linked with the assured quality of work.

1.12. Training for Quality Control

In order to bring awareness in the officers of department and to up date their knowledge of methods of testing, regular workshops on quality control should be held. To make the participants aware of basic necessities like specifications, required test acceptance criteria, frequency of testing and methodology of tests for understanding the quality control system and operation of regional/field laboratories. The training could be imparted by known road research institutes or through on job training.

1.13. Scope of the Handbook

1.13.1.

This Handbook is intended to be a handy reference for the general work of quality control at various highway constructions. It is not in any way meant to be a substitute for the relevant departmental specifications for construction and materials, but only as a guide to complement these. For certain items, where need was felt, broad guidelines on salient construction features have been included in the Handbook. These are for guidance only and should not be taken to constitute specifications.

1.13.2.

Even though the Handbook is intended mainly for highway constructions, it will be found equally advantageous for a number of facets of runway constructions as well.9

CHAPTER 2
EARTHWORK

2.1. General

2.1.1.

It is the responsibility of the field engineer to ensure that the density assumed by the designer is achieved at the expected moisture content. The way to ensure this is to test samples for moisture and density and to take appropriate corrective measures, as necessary. The rate of testing on a given project would depend on several factors, such as the homogeneity or otherwise of the material from the borrowpits, the nature and quantum of machinery or manual labour employed, and terrain conditions, so that the number of particular tests to be conducted for say 1000 cubic metres of the material involved, would entirely be a matter of engineering judgment. Therefore, the frequency of testing indicated at the end of this chapter should be regarded as indicative of the minimum number of tests to be conducted with full realisation of the fact that the rate of testing would have to be increased if circumstances so warrant.

2.1.2.

Discussion of other aspects such as the minimum densities to be obtained, selection of rolling equipment, thickness of layer, etc., are considered to be outside the scope of this chapter. For guidance in this respect, reference should be made to the relevant specifications, IRC : 36-1970 “Recommended Practice for Construction of Earth Embankments for Road Works”.

2.2. Earthwork — Materials and Process Selection of Soils

2.2.1.

The soil to be used for making up the embankment shall be free from stumps and root rubbish which might affect the stability of the embankment.

2.2.2.

The selection of materials for construction of the embankment shall be made after conducting necessary soil surveys and laboratory investigations, as set out in IRC : 36-1970.

2.2.3.

Only approved materials should be utilised in the body of the embankment.

2.2.4. Processing and placement :

To obtain adequate compaction, the embankment shall be constructed in uniform layers. Due care shall be exercised to ensure that loose thickness of each layer does not exceed the specified limits. Successive layers of embankment shall not be placed until the layer under construction has been thoroughly compactedto satisfy the specified requirements.

2.2.5.

After adjusting the moisture content whether at the road side or at borrow area, (making due allowance for evaporation losses), the soil shall be processed by means of graders, harrows, rotary mixers, other suitable equipment or even manually if no equipment is available until the moisture distribution is reasonably uniform. Clods or hard lumps of earth where present shall be broken down to sizes preferably of the order of 5 cm but under no circumstances shall the maximum size of clods exceed 15 cm when soil is being placed in the body of the embankment and 6 cm when it is being placed in the top 50 cm of the embankment.

2.2.6. Moisture content at the time of compaction :

Unless otherwise specified, the moisture content of each layer of soil at the time of compaction except in the case of highly expansive soils should be at optimum moisture content subject to the permitted tolerances. Highly expansive soils such as black cotton soil should be compacted at the specified moisture content which is usually on the higher side of the optimum moisture content. The tolerance limits for variation of moisture content from the specified moisture content are normally + 1 per cent and — 2 per cent.

2.2.7.

Densities to be aimed at in the compaction process shall be chosen with due regard to factors such as soil type, height of embankment, drainage conditions, position of the individual layers and type of plant available for compaction.

2.2.8.

Each compacted layer shall be tested in the field for density and accepted before the operations for the next layer commence.14

2.3. Trial Compaction

2.3.1.

In situations where no previous record or experience concerning the needed number of passes with a particular rolling equipment relating to a particular soil type is available, it may be desirable to conduct field trials on compaction so as to obtain data which would serve as an aid to planning of compaction operations.

2.3.2.

A test area about 20 m long and 5 m wide is prepared after removing the top soil. The fill material to be used is spread over this area, the depth of the loose layer being 25 cm. The mositure content of the soil should be as specified subject to the tolerance limits indicated.

2.3.3.

The test layer is then compacted with the type of compaction plant decided upon, and the mean dry desnsity to the full depth determined over the range of about 4 to 16 passes. The number of passes required are dependent upon the weight and type of rollers employed. The dry density shall be determined in accordance with IS: 2720 (Part-XXVIII) and the mean of 5 determination should be obtained for each compaction condition. The mean dry densities are plotted against the number of roller passes. From this graph, the approximate number of passes required for the compaction equipment to obtain the specified dry density is determined.

2.4. Quality Control of Earthwork

2.4.1.

Quality of fill material and its compaction shall be controlled through exercise of checks on the borrow material, compaction process, or the end-product, singly or in combination as directed. However, in every case, the end-product must conform to the construction specifications.

2.4.2.

Details of control tests on borrow materials and compaction are dealt with in Clauses 2.5. and 2.6.

2.5. Control Tests on Borrow Material

2.5.1.

The particular type of tests required to be conducted on the borrow material and their frequency would depend on interplay of several factors such as the nature of plant or machinery employed on the project, the quantum of manual labour in-15

volved, the nature of specifications to be followed whether they call for particular tests on borrow materials, the uniformity or otherwise of materials coming out of borrowpits, terrain conditions, etc. The recommended frequencies indicated in the succeeding paragraphs and in Table 2.1. are therefore only to be taken as applicable to routine cases. These tests are meant to verify during execution of the work that the material coming to site conforms to specifications. for borrow material and should be regarded as distinct from the test referred to in Clause 2.2.2. which relate to the initial selection of soils for embankment construction. All the tests would not be applicable on all projects. Depending upon site conditions, etc., only particular tests may be found necessary for a particular project. The frequency of testing indicated releates generally to the minimum number of tests to be conducted. The rate of testing would have to be stepped up much more than is herein indicated, depending upon the heterogeneity of the material and the compaction technique adopted in any particular project.

2.5.2. Gradation (IS: 2720—Part IV)-1965 :

At least, one test for each kind of soil. Usual rate of testing, 1-2 tests per 8,000 m³ of soil. The test would be necessary only if specifications call for checks using gradation or grain-size distribution as a criterion for selecting the soil. However, sand content determinations should be carried out invariably, at the rate of 1-2 tests per 8000 m³

2.5.3. Plasticity index (IS: 2720—Part V)-1970 :

At least, one test for each kind of soil. Usual rate of testing 1-2 tests per 8000 m³ of soil.

2.5.4. Proctor test (IS: 2720—Part VII)-1965 :

This test is performed to ensure that soil of requisite quality is coming out of borrow areas as also to provide information on optimum moisture content and maximum laboratory dry density. Usual rate of testing, 1-2 tests per 8000 m³ of soil.

2.5.5. Deleterious constituents (IS: 2720—Part XXVII)-1968 :

The soil shall be free of harmful salts like sodium sulphate and organic matter (permissible limits) of 0.2 and 1 per cent respectively. The tests will be done as and when required.16

2.5.6. Natural moisture content (IS : 2720—Part 11-1973) (Second Revision):

One test for every 250 m³ of soil. The natural moisture content of the soil coming out of the borrowpits will have to be determined in order to evaluate how far the natural moisture content tallies with the optimum value and whether further addition or reduction of water content would be necessary.

2.5.7.

Table 2.1. gives a summary of the tests for borrow materials discussed above along with minimum desirable frequencies.

2.6. Compaction Control

2.6.1.

Compaction control mainly involves two operations, namely, control of moisture content just before compaction and density of compacted layer.

2.6.2. Moisture content determinations :

Moisture content determinations for compaction control shall be in addition to those on borrow material spelt out in Clause 2.5.6. This test is necessary for ensuring proper moisture content at the time of compaction which significantly influences the density results. Usual rate of testing should be 2-3 tests per 250 m³ of soil.

2.6.3. Density measurements :

Except when otherwise directed, at the last one measurement of density shall be made for each 1000 m² of compacted area. Test locations shallbe chosen only through predetermined random sampling techniques. Control shall not be based on the result of anyone test but on the mean value of 5-10 density determinations. The number of tests in one set of measurements shall be 5 as long as it is felt that sufficient control over borrow material and the method of compaction was being exercised. But if there be any doubt about this control, or considerable variations are observed between individual density results, the number of tests in one set of measurement shall forth with be increased to 10. The acceptance of results shall be subject to the condition that the mean dry density equals or exceeds the specified density and the standard deviation for any set of results is below 0.08 gm per cc.17

2.6.4.

In general, the control at top subgrade layers of the formation shall be more strict than stated above with density measurements being carried out at the rate of 1 test per 500-1000 m² of compacted area. Further, for the determination of mean density and standard deviation (refer Chapter 8), the number of tests in one set of measurements shall not be less than 10. Acceptance of the work shall be subject to the same conditions as stipulated in Clause 2.6.3.

2.6.5.

Table 2.2. sets out the minimum desirable frequency of tests for compaction control.

CHAPTER 3
SUB-BASE COURSES

3.1. General

3.1.1.

The following sub-base courses are dealt with in this Chapter :

1. Stone Soling
2. Brick Soling
3. Water Bound Macadam Sub-base
4. Soil-Gravel/Moorum Sub-base
5. Mechanically Stabilized Soil
6. Lime Stabilized Soil
7. Cement Modified Soil
8. Sand-bitumen Mix

3.2. Stone Soling

3.2.1. General

3.2.1.1.

Stone soling, as a rule, is gradually becoming outmoded as a sub-base owing to its inferior load spreading properties as well as the liability to sink into poor or slushy subgrades. However, where it is still used, control on the materials and works should be exercised as described hereunder.

3.2.2. Materials

3.2.2.1.

Before incorporation in the work, the materials for stone soling shall be checked for specification requirements either at the quarry or at the site.

3.2.2.2.

The stones shall be granite, limestone, sandstone, etc., as specified, reasonably free from laminations, foreign matter, unsound and weathered fragments and be in a clean condition.

3.2.2.3.

The filler material shall be sand or any other granular material having a plasticity index of not more than 6.

3.2.3. Processing and construction

3.2.3.1. Preparation of subgrade :

The subgrade shall be checked for line, grade and cross-section as spelt out in Chapter 7. All irregularities beyond the permitted tolerances shall be rectified. Soft and yielding places and ruts shall be corrected and rolled until firm.

3.2.3.2. Soling work :

The following points shall be kept in view during execution:

1. The stones shall be laid and seated properly by hand as specified.
2. All voids should be filled, first by wedging in spalls and then with filler material accompained by sprinkling of water, brooming and rolling.
3. Rolling shall commence at the edges, progressing gradually towards the centre parallel to the centre line of the road except at superelevated portions where it shall proceed from the inner edge to the outer.
4. The finished surface shall be checked for line, level and regularity as indicated in Chapter 7.

3.2.4. Control tests and their frequency

3.2.4.1.

Quality control tests on materials and work as well as their minimum desirable frequency shall be as shown in Table 3.1.

3.2.5. Rectification of surface irregularities

3.2.5.1

Irregularities present in the finished surface beyond the tolerances specified in Chapter 7 shall be rectified in the following manner :

When the finished surface is too high or too low, the soling shall be dismantled to the full depth and reconstructed as specified. In no case shall the filling of depressions with filler material be permitted.

3.3. Brick-Soling

3.3.1. General

3.3.1.1.

Bricks for soling works may be laid in one or more layers either flat or on edge.

3.3.2. Materials

3.3.2.1.

The quality of bricks shall be checked for specfica-tion requirements before their incorporation in the works. Bricks to be used shall be of full size and brickbats shall not be used.

3.3.2.2.

The filler shall be sand or any other material having a plasticity index of not more than 6.

3.3.3. Processing and construction

3.3.3.1. Preparation of subgrade:

Clause 3.2.3.1. shall apply.

3.3.3.2. Soling work :

The following points shall be kept in mind while executing the work :

1. The bricks shall be hand laid with each brick touching the other.
2. Pattern for laying of bricks, such as herringbone, shall be as specified. When more than one layer is to be constructed, the bricks should be so laid as to break joints in successive layers.
3. The material used for filling the interstices shall be sand or any other mineral matter with plasticity index not exceeding 6.

3.3.4. Control tests and their frequency

3.3.4.1.

Quality control tests on the materials and the work and their minimum desirable frequency shall be as indicated in Table 3.2.25

3.4. Water Bound Macadam Snb-base

3.4.1. General :

For use as sub-base water bound macadam shall be constructed with oversized aggregates of 40-90 mm size. The materials used and the work shall conform to the requirements of IRC: 19-1977 and their quality shall be controlled on the same lines as outlined in Chapter 4 for water bound macadam base course.

3.5. Soil-Gravel/Moorum* Sub-base

3.5.1. General :

This type of sub-base is constructed using moorum, soil-gravel mixtures and similar naturally occurring low-grade materials.

3.5.2. Materials :

The materials shall be in accordance with the specifications as laid down.

3.5.3. Processing and construction

3.5.3.1. Preparation of subgrade :

Clause 3.2.3.1. shall apply.

*Moorum is the name usually given to naturally occurring materials formed by disintegration of rock.26

3.5.3.2. Construction of sub-base :

The following points shall be kept in mind during execution of the work :

1. Before compaction, moisture content of the material shall be brought to the desired level.
2. Rolling shall commence at the edges, proceeding gradually towards the centre parallel to the centre line of the road, except at superelevated portions where it shall proceed from the inner edge to the outer. Rolling shall be continued till the specified density is achieved.
3. The surface after rolling shall be well closed, free from movement under compaction plant, any compaction planes, ridges, cracks or loose material.
4. After rolling, the sub-base layer shall be checked for density, the control and permissible tolerances for which shall be the same as set out in Clause 2.6.4. This presupposes that Proctor density is known through prior testing.
5. Unless otherwise specified, no traffic of any description shall ply directly over the finished sub base.

3.5.4. Control tests and their frequency :

Quality control tests on materials and work with their minimum desirable frequency are indicated in Table 3.3.

3.5.5. Rectification of surface irregularities

3.5.5.1.

Where surface irregularities of the finished sub-base layer fall outside the specified tolerances given in Chapter 7, the same shall be rectified. If the surface is too high, it shall be trimmed and suitably compacted. If it is too low, the deficiency shall be corrected by adding fresh material. The degree of compaction and the type of material to be used shall conform to the specification requirements.

3.6. Mechanically Stabilized Soil

3.6.1. General

3.6.1.1.

Mechanical stabilization is mainly of three different types, namely, stabilization of sandy soils with admixture of clay, stabilization of clayey soils with admixture of sand and stabilization with soft aggregates.

3.6.2. Materials

3.6.2.1.

The blending/grafting materials used for mechanical stabilization shall be checked for specification requirements.

3.6.3. Processing and construction

3.6.3.1. Preparation of subgrade :

Clause 3.2.3.1. shall apply.

3.6.3.2. Mixing and laying of stabilized soil :

The following Points shall be kept in mind while executing the work :

1. Stabilization shall be carried out preferably by mechanical means. In all cases, it shall be ensured that the plant used and methods adopted are capable of pulverising the soil to specified degree to full thickness of the layer being processed and of achieving the desired degree of mixing and uniformity of the stabilized material.
2. In the event of manual mixing, it shall be ensured that there has been uniform mixing of various ingredients to the full depth of layer processed.
3. Degree of pulverisation shall be as specified.
4. Grading and plasticity index of mixed material, where specified, shall be checked.28
5. Before compaction, moisture content of the mixed material shall be brought to the desired level, which in general is the same as the optimum moisture content.
6. In the case of stabilization with aggregates, it shall be ensured that the aggregates are evenly dispersed in the stabilized layer.
7. Rolling shall commence at the edges, proceeding gradually towards the centre parallel to the centre line of the road, except at superelevated portions where it shall proceed from the inner edge to the outer. Roiling shall be continued till the specified density is reached.
8. The surface after rolling shall be well closed, free from movement under compaction plant, any compaction planes, ridges, cracks or loose material.
9. After rolling, the sub base layer shall be checked for compaction, the control and permissible tolerances of which shall be the same as set out in Clause 2.6.4. This presupposes that Proctor density is known through prior testing.
10. The surface shall be cured as specified.
11. The finished surface shall be checked for line, level and regularity in accordance with Chapter 7.
12. Unless otherwise specified, no traffic of any description shall ply directly over the stabilized layer.

3.6.4. Control tests and their frequency

3.6.4.1.

Quality control tests on materials and work with their minimum desirable frequency shall be as indicated in Table 3.4. Specific tests and their frequencies on soft aggregates where required to be used are also included in Table 3.4. Where for any test, the procedure of testing is not indicated, the same shall be performed as per accepted engineering practice.

3.6.5. Rectification of surface irregularities

3.6.5.1.

Where surface irregularity of the stabilized layer falls outside the tolerances mentioned in Chapter 7, the same shall be rectified. If the surface is too high, it shall be trimmed and suitably compacted. If it is too low, the deficiency shall be corrected by adding fresh material. The degree of compaction and the type of material to be used shall conform to the specification requirements.29

3.7. Lime Stabilized Soil/Moorum

3.7.1. General :

Besides lime stabilized soil, this sub-section covers constructions involving stabilization with lime of materials like moorum.

3.7.2. Materials :

Lime, at delivered at site, shall be checked for purity and available calcium oxide content as specified. The quantity of lime for incorporation in the soil related to its calcium oxide content, shall be expressed as per cent by weight of the dry soil. The lime content shall be predetermined on the basis of laboratory tests.30

3.7.3. Processing and construction

3.7.3.1. Preparation of subgrade :

Clause 3.2.3.1. shall apply.

3.7.3.2. Stabilization :

The following points shall be kept in mind while executing the work :

1. Stabilization shall be carried out preferably by mechanical means. If single pass stabilisers are not available, rotavators or agricultural machinery like ploughs and disc harrows shall be made use of. In every case, it shall be ensured that the plant used and methods adopted are capable of pulverising the soil to specified degree over the full thickness of layer being processed and of achieving the mixing and uniformity of the stabilized material to desired degree.
2. In the case of manual mixing, it shall be ensured that there has been a uniform mixing of lime and soil to the full depth of the layer processed.
3. Degree of pulverisation shall be as specified.
4. Mixing shall be uniform and no streaks of free lime shall be visible.
5. After mixing, the lime content of the mix shall be determined. The lime content values shall conform to the following (also see foot note under Table 3.5):
   1. Moving average of 10 tests not to be less than the specified lime content.
   2. No test value to be less than 75 per cent of the specified lime content.
6. Before compaction, moisture content of the mixed material shall be brought to the desired level, which, in general, is the optimum moisture content.
7. It shall be ensured that the time interval between mixing of lime with soil and compaction does not exceed three hours.
8. Rolling shall commence at the edges progressing gradually towards the centre parallel to the centre line of the road, except at superelevated portions where it shall proceed from the inner edge to the outer. Rolling shall be continued till the specified density is achieved.
9. Care shall be taken to ensure that during rolling the compaction plant does not bear directly on hardened or partially hardened treated material previously laid except as may be necessary for achieving the desired compaction at the joints.31
10. The surface after rolling shall be well closed, free from movement under compaction plant, and any compaction planes, ridges, cracks or loose material.
11. After rolling, the sub-base layer shall be checked for compaction the control and the permitted tolerances of which shall be the same as set out in Clause 2.6.4. This presupposes that Proctor density is known through prior testing.
12. The finished surface shall be checked immediately after laying for line, level and regularity in accordance with Chapter 7.
13. The surface on completion shall be cured for 7 days soon after which subsequent pavement courses shall be laid to prevent the surface from drying out and becoming friable. No traffic of any description shall ply directly over the stabilized layer.

3.7.4. Control tests and their frequency

3.7.4.1.

Quality control tests on materials and work with their minimum desirable frequency are indicated in Table 3.5. Where for any test the procedure of testing is not indicated, the same shall be performed in accordance with accepted engineering practice.

3.7.5. Rectification of surface irregularities

3.7.5.1.

Where the surface irregularity of the stabilized layer falls outside the specified tolerances given in Chapter 7, the same shall be rectified.

3.7.5.2.

Where the surface is top high, the same shall be suitably trimmed while taking care that the material below is not disturbed by this operation.

3.7.5.3.

However, where the surface is too low, the same shall be corrected as described hereafter. When the time elapsed between detection of irregularity and the time of mixing of the material is less than 3 hours, the surface shall be scarified to a depth of 50 mm, supplemented with freshly mixed material as necessary and recompacted to the requirements. Where the elapsed time is more than 3 hours, the full depth of the layer shall be removed from the pavement and replaced with fresh material as specified.32

3.8. Cement Modified Soil

3.8.1. General

3.8.1.1.

Cement modified soil is envisaged to be with lower -cement content for use as sub-base, as distinct from soil-cement intended to be used for base courses.

3.8.2. Materials

3.8.2.1.

Soil proposed for cement stabilisation shall not have a sulphate content of more than 0.2 per cent. The cement used shall be checked for compliance with the requirements of IS: 269-(1967), 455-1967 (Second Revision) or 1489-1967 (First Revision) as applicable. The quantity of cement for incorporation shall be expressed as a percentage by weight of dry soil. This shall be predetermined on the basis of laboratory tests.33

3.8.3. Processing and construction

3.8.3.1. Preparation of subgrade :

Clause 3.2.3.1. shall apply.

3.8.3.2. Preparing and laying of cement modified soil sub-base :

The operations involved in processing and construction of cement-modified soil are the same as those for lime stabilized soil except that the stabilizing material will be cement instead of lime. As such, Clause 3.7.3.2. shall apply but for the maximum time interval between mixing of cement with soil and compaction which shall be 2 hours in this case.

3.8.4. Control tests and their frequency :

Quality control

tests on the materials and the work and their minimum desirable frequency shall be as indicated in Table 3.6. Where for any test the procedure of testing is not indicated, the same shall be carried out as per the prevalent engineering practice.

3.8.5. Rectification of surface irregularities :

Clause 3.7.5.

shall apply except that the time criterion spelled out in Clause 3.7.5.3. shall be 2 hours in this case.

3.9. Sand-bitumen Mix

3.9.1. General:

Sand-bitumen can be used both as subbase and base, the composition being designed accordingly.

3.9.2. Materials

3.9.2.1.

Sand shall be non-plastic. The per cent fraction finer than 75-micron sieve shall be within the range of 5 and 10.

3.9.2.2.

Binder shall be as specified. The per cent binder content in the sand-bitumen mix shall be predetermined in the laboratory.

3.9.3. Processing and construction

3.9.3.1. Preparation of subgrades :

Clause 3.2.3.1. shall apply.

3.9.3.2. Sand-bitumen mix laying :

The following points shall be attended to while executing the work :

1. Mix proportions of constituent materials shall be as specified.
2. Where sand is found to be wet, it shall be dried before mixing with binder.
3. The means adopted for mixing shall be as specified and it shall be ensured that sand particles are uniformly and properly coated with binder.
4. The sand-bitumen mix shall be laid at site and if the binder is a cutback aerated for about 24 hours. It shall then be regarded to proper camber and rolled.
5. For this type of construction, edge confinement shall be provided.
6. The thickness of individual layer of sand-bitumen mix shall be as specified.
7. Provisions regarding rolling shall be the same as described in Clause 3.7.3.2. (viii-x).
8. After rolling, the compacted layer shall be checked for density as laid down.
9. The finished surface shall be checked for line, level and regularity in accordance with Chapter 7.35

3.9.4. Control tests and their frequency :

Quality control tests on the materials and the work and their minimum desirable frequency shall be as indicated in Table 3.7.

3.9.5. Rectification of surface irregularities :

Where the surface irregularity of the sand-bitumen layer sub-base is outside the specified tolerances as given in Chapter 7, it shall be rectified. The rectification shall be done while the mix is still workable. Where the surface is too high, the same shall be suitably trimmed while taking care not to disturb the material below. Where the surface is too low, the depressed areas shall be filled up with sand-bitumen mix and rolled according to specification.36

CHAPTER 4
BASE COURSES

4.1. General

4.1.1.

The following base courses are dealt with in this Chapter :

1. Water bound macadam:
   1. Surfaced
   2. Unsurfaced
2. Bituminous penetration macadam
3. Built-up-spray grout
4. Bituminous macadam
5. Soil-cement base
6. Lean concrete
7. Lime puzzolana concrete
8. Sand-bitumen base

4.2. Water Bound Macadam

4.2.1. General :

Water bound macadam may be used as a base course under a surfacing or as a wearing course without any surfacing. In either case, the construction shall generally be in accordance with IRC: 19-1972.

4.2.2. Materials :

All materials used in WBM construction, viz., coarse aggregates, screenings and binding material shall be checked in advance of their incorporation in the works for specification requirements, either at the quarry or at site.

4.2.3. Processing and construction

4.2.3.1. Preparation of subgrade/sub-base :

This shall be checked for line, grade and section in accordance with Chapter 7. Ruts or soft yielding places shall be corrected suitably and rolled until firm. Arrangement of lateral confinement of aggregate shall be checked before starting to spread of materials. If necessary, the surface shall be scarified and reshaped to the required grade and camber.

4.2.3.2.

The following points shall be carefully attended to while executing the work :

1. Quantity and uniformity of spread of materials shall be checked by template (see Chapter 7).
2. Segregation of coarse and fine aggregates shall be avoided.
3. Rolling operations shall begin from edges, proceeding gradually to the centre while lapping each preceding rear wheel track by one half width. The weight and type of the roller shall be relevant to the type of coarse aggregate. At horizontal curves, rolling shall proceed from the inner edge to the outer. No rolling shall be carried out when it causes a wave-like motion due to softness of the subgrade/sub-base. Irregularities that develop during rolling shall be rectified either by adding or removing aggregate. In no case shall screenings be added to make up depressions. Rolling shall be discontinued when the aggregates are partially compacted with void space sufficient to permit application of screenings. However, where screenings are not to be used, compaction shall be continued until the aggregates are thoroughly keyed.
4. Screenings shall be applied in three or more applications to fill the interstices while dry rolling is continued. Vehicles carrying screenings shall be so operated as not to disturb the coarse aggregates.
5. It should be ensured that the sub-base/subgrade does not get damaged due to addition of excessive quantities of water during construction.
6. Binding material, if required, shall be added after the application of screenings. It shall be introduced at a uniform rate in two or more applications accompanied by copious sprinkling of water so as to form a slurry which could be swept with brooms to fill the remaining voids. Rolling shall be continued till full compaction is achieved.
7. No traffic shall be allowed till the macadam sets. In case of surface treated water bound macadam, the surfacing shall be laid only after the macadam base is completely dried.
8. The finished surface shall be checked for line, level and regularity in accordance with Chapter 7.40

4.2.4. Control tests and their frequency :

Quality control tests on the materials and the work and their minimum desirable frequency shall be as indicated in Table 4.1.

4.2.5. Rectification of surface irregularities :

Where the surface irregularities of water-bound macadam base are outside the tolerances mentioned in Chapter 7, the same shall be rectified by removing to full depth the aflected area, which should not be less than 10 m², and relaying with fresh materials. In no case shall depressions be filled up with screenings or binding material.

4.3. Bituminous Penetration Macadam

4.3.1. General:

Construction of bituminous penetration macadam base shall in general be carried out in accordance with IRC: 20-1966. Control over the quality of materials and work shall be exercised as set forth hereunder.41

4.3.2. Materials

4.3.2.1. Coarse aggregates :

The aggregates should be checked for conformity with the requirements stipulated in IRC: 20-1966.

4.3.2.2. Bituminous binder :

The type and grade of bituminous binder shall be as specified. The binder shall be checked for its quality before and during construction as may be required.

4.3.3. Processing and construction

4.3.3.1. Preparation of subgrade/sub-base :

Clause 4.2.3.1. shall apply.

4.3.3.2. Construction of bituminous penetration macadam base course :

The following points shall be given proper attention during construction:

1. The coarse aggregates shall be spread uniformly and checked by template (see Chapter 7).
2. Provision for rolling and checking of finished surface shall be the same as in Clause 4.2.3.2. Provided however that rolling shall stop before the voids are closed to such an extent as to prevent free and uniform penetration of binder and key aggregates.
3. Bituminous penetration macadam work shall not be carried out when the atmospheric temperature in shade is less than 16°C or when the underlying course is damp or wet.
4. The specified quantity of approved binder shall be sprayed at the appropriate application temperature, preferably using mechanical sprayers. The ends of the stretch shall be covered with thick paper so as to avoid double spraying of binder. The rate of spray of binder shall be frequently checked and regulated to be within 2½ per cent of the specified rate of application. Excessive deposits of binder shall be immediately removed.
5. Key stones shall be uniformly spread immediately after the application of bituminous binder by mechanical or manual means. The surface shall be broomed to obtain a uniform distribution of key stones and rolled.

4.3.4. Control tests and their frequencies :

Quality control tests on the materials and the work and their minimum desirable frequencies shall be as indicated in Table 4.2.42

4.3.5. Rectification of surface irregularities :

Vide Clause 4.2.5.

4.4. Built-up Spray Grout

4.4.1. General:

Construction of built-up spray grout shall generally be done in accordance with IRC : 47-1972. The quality of materials and work shall be controlled on the same lines as outlined in Clause 4.3. for bituminous penetration macadam.

4.5. Bituminous Macadam

4.5.1. General :

Construction of bituminous macadam premix base shall generally be done in accordance with IRC : 27-1967. For ensuring the requisite quality of materials, and work, the important points to be kept in view and the control tests to be carried out are set forth below.43

4.5.2. Materials

4.5.2.1.Coarse aggregates :

The aggregates shall be checked for the requirements spelt out in IRC:27-1967.

4.5.2.2. Bituminous binder :

Clause 4.3.2.2. shall apply.

4.5.3. Processing and construction

4.5.3.1. Preparation of subgrade/sub-base :

Clause 4.2.3.1. shall apply. In addition, the surface shall be thoroughly cleaned, first with wire brushes and finally by dusting with sacks.

4.5.3.2. Construction of bituminous macadam :

Proper attention shall be paid to the following points during construction :

1. The bituminous macadam construction shall not normally be carried out when the atmospheric temperature (in shade) is less than 16°C or when the underlying course in damp or wet.
2. All mechanical equipment, like hot-mix plant, paver roller, etc., shall be checked tor their work worthiness.
3. Where specified, a tack coat of bituminous binder shall be applied on the base/sub-base and control shall be exercised on the rate uniformity and temperature of its application.
4. Mix proportions of the constituent materials shall be as specified. Binder content with mix shall be checked periodically and controlled so that there is no variation beyond ±0.3 per cent by weight of the total mix.
5. Unless otherwise specified, mixing of aggregates and binder shall be carried out in hot-mix plant.
6. Binder and aggregate temperatures shall be consistent with proper mixing and laying of the mix and be within the specified limits.
7. Mix shall be spread uniformly preferably using a paver-finisher to the correct thickness, grade and camber. Temperature of the mix at the time of laying and rolling shall be within the specified limits.
8. The roller shall proceed on to fresh material with the drive wheel leading. Rolling shall commence from the edges and progress towards the centre except on superelevated curves where the rolling shall commence from the tower edge and progress towards the upper edge. The rolling shall be continued, with off-set of half rear wheel width, till the layer has been fully compacted. The wheels of the roller shall be kept moist to prevent the mix from adhering to them and being picked up but in no case shall fuel/lubricating oil be used for this purpose.44
9. Longitudinal joints and edges shall be constructed true to the delineating lines parallel to the centre line of the road. All joints shall be cut vertical to the full thickness of the previously laid mix and the surface painted with hot bitumen before placing fresh material.
10. Traffic shall not be normally allowed on the course till the mix has cooled down to the surrounding temperature.
11. The finished surface shall be checked for line, level and regularity in accordance with Chapter 7.

4.5.4. Control tests and their frequencies:

Quality control tests on the materials and the work and their frequencies shall be as indicated in Table 4.3.

4.5.5. Rectification of surface irregularities :

Where the surface irregularities of the bituminous premix macadam base course are outside the tolerances given in Chapter 7, these shall be rectified as per procedure given in Clause 4.2.5.

4.6. Soil-Cement Base

4.6.1. General :

As distinct from cement modified soil, this construction is envisaged to be of base course quality with mix designed as per strength and durability considerations.

4.6.2. Materials :

Clause 3.8.2. shall apply except that the materials shall be proportioned to achieve the specified compressive strength.

4.6.3. Processing and construction

4 6.3.1. Preparation of subgrade/sub-base :

Clause 3.2.3.1. shall apply.

4.6.3.2. Preparing and laying soil-cement base :

Clause 3.8.3.2. shall apply.

4.6.4. Control tests and their frequency :

Quality control tests on materials and work and their minimum desirable frequency shall be as indicated in Table 4.4. Where for any test, the procedure of testing is not indicated, the same shall be carried out as per prevalent engineering practice.

The strength of the material mixed at site shall be controlled by carrying out cube strength tests. It shall be ensured that in a set of ten test results, the average strength shall be equal to or more than the specified strength and that not more than one test shall give a value less than the specified value by more than 10 per cent.

4.6.5. Rectification of surface irregularities :

Clause 3.8.5. shall apply.46

4.7. Lean Concrete

4.7.1. General

4.7.1.1.

This type of construction is suitable as a base both for flexible and rigid pavements.

4.7.2. Materials :

All materials, viz. cement, sand, coarse aggregates and water used in construction shall satisfy the relevant specification requirements. The mix proportions for lean concrete shall be predetermined in the laboratory so as to obtain the specified compressive strength at 28 days.

4.7.3. Processing and construction

4.7.3.1.

Preparation of sub-grade/sub-base/base : Clause 3.2.3.1. shall apply. In addition, where the lean concrete is to be47

laid over an absorbent subgrade/sub-base/base, the latter shall be kept moist so as to prevent absorption of water from the concrete mortar.

4.7.3.2. Mixing and laying of lean cement concrete :

Attention should be paid to the following points while carrying out the work :

1. Unless otherwise permitted, the mix shall be prepared in a power-driven batch mixer of approved type.
2. Proportioning of constituent materials including water shall strictly be as specified. Due allowance shall be made for the free moisture content of aggregates.
3. Concrete immediately after mixing shall be transported for placement in such a manner that segregation or loss of constituent materials is avoided.
4. Concrete shall be spread uniformly and the surface struck off with surcharge over the desired finished level. The amount of surcharge shall be determined in the field by actual trial. The surcharge shall be uniform over the entire area and the concrete as spread shall be to the same camber and slope as desired in the finished surface.
5. No joints other than construction joints shall be provided.
6. Concrete shall be compacted with a suitable roller within the period specified which will not exceed 2 hours since mixing of the material.
7. During compaction, the grade and camber of the surface shall be checked and all irregularities corrected by removing or adding fresh material.
8. Where lean concrete is to be laid in two layers, the second layer shall be placed within one hour of compaction of the lower layer.
9. A minimum of 72 hours of curing shall be done before placing the next pavement course. If the next pavement course is not laid immediately after this period, curing of the lean concrete shall continue subject to a maximum period of 14 days.
10. Strength of lean concrete shall be controlled by carrying out cube strength tests. It shall be ensured that in a set of ten test results, the average strength shall be equal to or more than the specified strength and that not more than one test shall give a value less than the specified value by more than 10 per cent.48

4.7.4. Control tests and their frequency

4.7.4.1.

Quality control test on the materials and the work and their minimum desirable frequency shall be as indicated in Table 4.5.

4.7.5. Rectification of surface irregularities

4.7.5.1.

The finished surface shall be checked for line, level, grade and surface finish as in Chapter 7. The checking and rectification should be effected when the mix is still plastic. Surface irregularities left in hardened layer will have to be removed by cutting out sufficiently large patches and relaying to specification.

4.8. Lime-Puzzolana Concrete

4.8.1. General :

This type of construction is suitable as a base both for flexible and rigid pavements.

4.8.2. Materials :

All materials, viz., lime-puzzolana mixture, sand, coarse aggregate and water used in construction shall satisfy the relevant specification requirements. The mix propor-49

tion for the concrete shall be predetermined in the laboratory so as to obtain the specified compressive strength at 28 days.

4.8.3. Processing and construction

4.8.3.1. Preparation of subgrade :

Clause 3.2.1. shall apply.

4.8.3.2. Mixing and laying of lime puzzolana concrete :

The procedure of mixing, transporting, placing, compacting, curing and strength control shall be the same as that for lean concrete vide Clause 4.7.3.2.

4.8.4. Control tests and their frequency

4.8.4.1.

Quality control tests on the materials and the work and their minimum desirable frequency shall be as indicated in Table 4.6.

4.8.5. Rectification of surface irregularities :

Clause 4.7.5.1. shall apply.

4.9. Sand-bitumen Base

Clause 3.9. shall apply.50

CHAPTER 5
BITUMINOUS SURFACE COURSES

5.1.

The following bituminous surface courses are dealt with in this Chapter :

1. Single and two coat bituminous surface dressing.
2. Surface dressing using pre-coated aggregates.
3. Thin bituminous premix carpet.
4. Asphaltic concrete surfacing.

5.2. Single and Two-coat Bituminous Surface Dressing

5.2.1. General :

Construction of bituminous surface dressing in single or two coats shall generally follow the specifications laid down in IRC: 17-1965 and IRC:23-1966 respectively.

5.2.2. Materials

5.2.2.1.

The materials, namely, aggregates and binder should be checked for specification requirements stipulated in IRC: 17-1965 and IRC:23-1966 as applicable.

5.2.3. Processing and construction

5.2.3.1. Preparation of base :

All depressions or potholes in the base on which surface dressing is to be laid shall be properly made up and compacted to the required lines, grade and section. Any fat patch on the existing surface shall be corrected. The surface shall be thoroughly cleaned of any caked earth and other matter before the binder is applied. Where the base is an old bituminous surfacing, the extent and manner of rectification will be as indicated. Where specified, bituminous prime coat shall be applied and cured before laying the surface dressing. The edges of the surface to be treated shall be properly defined The prepared base shall be checked for line, grade and section in accordance with Chapter 7 and all irregularities beyond the permitted tolerances corrected.

5.2.3.2. Construction of bituminous surface dressing :

While executing the work, the following points shall be kept in mind :

1. No surface dressing work shall be carried out if
   1. atmospheric temperature in shade is less than 16°C, or
   2. base is damp, or
   3. construction materials are damp, or
   4. the weather is fogey, rainy or dusty.
2. The work should be so Organised that no traffic or dust gets on to the cleaned or bituminous painted base.
3. The specified quantity of approved binder shall be sprayed at the appropriate application temperature, preferably using mechanical sprayers. The ends of the stretch shall be covered with thick paper so as to avoid double spraying of binder. The rate of spray of binder shall be frequently checked and regulated to be within 2½ per cent of the specified rate of application. Excessive deposits of binder shall be immediately removed.
4. Immediately after application of the binder, cover aggregates of approved quality shall be spread uniformly at the specified rate. If necessary, the surface shall be broomed to ensure uniform spreading of aggregate.
5. Cover aggregates shall be immediately rolled with roller of approved weight. Rolling shall commence at the edges progressing gradually towards the centre parallel to the centre line of the road except at superelevated portions where it shall proceed from the inner edge to the outer. Rolling operation shall continue till all aggregates particles are firmly embedded in the binder. Excessive rolling resulting in the crushing of aggregates shall be avoided.
6. The second coat, if specified, shall be applied immediately after laying of the first coat.
7. Generally, no traffic shall be allowed on the finished surface for 24 hours. If allowed, its speed shall be restricted to 16 km per hour during this period. If cut-back bitumen has been used, the finished surface shall be closed to traffic till the binder is adequately cured.

5.2.4. Control tests and their frequency :

Quality control tests on the materials and the work and their desirable frequency shall be as indicated in Table 5.1.54

5.2.5. Rectification of surface irregularities :

Surface dressing by itself cannot remove any undulations present in the base or the surface on which it is applied. It is therefore essential that all operations of rectifications to meet the requirements set out in Chapter 7, be carried out on the receiving surface before the work of surface dressing is begun.

5.3. Surface Dressing with Pre-coated Aggregates

5.3.1. General :

Construction of bituminous surface dressing with pre-coated aggregates shall generally be carried out in accordance with IRC : 48-1972. The construction is similar to conventional surface dressing except that the cover aggregates are lightly pre-coated with binder. As such the quality of materials55

and work shall be controlled on the same lines as set out in Clause 5.2. with additional checks on the following aspects :

1. At the time of mixing, the binder and cover aggregates shall be at their appropriate temperatures.
2. Coating of the aggregates with binder shall be uniform.
3. The aggregates after coating shall be aerated and cooled properly before using them in work. During cooling, these shall not be piled in big heaps and care shall be taken to protect them from dust.

5.4. Thin Bituminous Premix Carpet

5.4 1. General :

Thin bituminous premix carpet may be constituted from open graded or closely graded mixes as specified. Where the mix is open graded, the carpet is generally provided with a seal coat. The construction for open-graded premix surfacing shall be in accordance with IRC: 14-1970.

5.4.2. Materials:

The materials, namely, aggregates and binder should be checked for specification requirements (IRC : 141970 or other relevant specification).

5.4.3. Processing and construction

5.4.3.1. Preparation of base :

Clause 5.2.3.1. shall apply.

5.4.3.2. Construction of premix carpet :

The following points shall be properly attended to during construction of this type of surfacing :

1. Mix proportion of constituent materials shall be as specified. Binder content in the mix shall be checked periodically and regulated to be within 2½ per cent of the specified quantity.
2. Tack coat, where necessary, shall be applied uniformly over the prepared base at the specified rate.
3. Mixing shall preferably be done in mechanical mixers.
4. Where straight-run bitumen is used, the aggregates should be suitably heated prior to mixing with binder. The binder heated to appropriate temperature should be mixed with aggregates until the latter are thoroughly coated.
5. The mixed materials shall be spread evenly with rakes or spreaders to specified thickness and camber.56
6. Rolling shall start immediately after the material is spread. The wheels of the roller shall be kept moist to prevent the premix from adhering to the wheels and being picked up but in no case shall the use of fuel lubricating oil be permitted for this purpose.
7. Where specified, a seal coat comprising premix sand or liquid seal and fine aggregates shall be evenly applied and rolled. The points to be attended to during application of seal coat shall be the same as those for Surface Dressing (Clause 5.2.) and Thin Premix Carpet (Clause 5.4.) when the seal is of liquid type and premix sand respectively.
8. When straight-run bitumen is used, traffic may be allowed immediately after the carpet has cooled down to the surrounding temperature but with restricted speed of 16 KMH for the next 24 hours. However, where cut-back bitumen is used, traffic shall not be permitted till the binder is cured.
9. The finished surface shall be checked for line, level and regularity in accordance with Chapter 7.

5.4.4. Control tests and their frequency :

Quality control tests on materials and work with their desirable frequency are indicated in Table 5.2.

5.4.5. Rectification of surface irregularities :

Premix carpets can improve the evenness of an existing surface only in a limited way. Therefore, if there are large irregularities in the surface these should be rectified just prior to laying of the carpet. Where the surface irregularities of the finished carpet are outside the tolerances given in Chapter 7, these should be rectified in the manner described here. If the surface is too high, it shall be cut out and replaced by fresh materials laid and compacted to specifications. Where the surface is too low, the depressed portion shall be filled up by fresh material laid and compacted to specifications. At times, it would be found advantageous/necessary to have an enlarged area for the patch.

5.5. Asphaltic Concrete Surfacing

5.5.1. General:

Asphaltic concrete surfacing shall, in general, be constructed in accordance with requirements of IRC 29-1968.57

5.5.2. Materials :

All materials, viz., bituminous binder, filler and fine and coarse aggregates, shall satisfy the specification requirements laid down in IRC : 29-1968.

5.5.3. Processing and construction

5.5.3.1. Preparation of base :

Provisions of Clause 5.2.3.1. shall apply. If necessary, a bituminous levelling course shall be laid to make up undulations.

5.5.3.2. Construction of asphaltic concrete surfacing :

While carrying out this type of construction, the following points shall be properly attended to :

1. Gradation of combined aggregates and binder content shall satisfy the design criteria of the relevant IRC specification.58
2. The design mix proportions arrived at in the laboratory shall be based on representative samples of materials actually available at the site and shall be followed to the maximum extent possible. In the event there is a change in the material available at site, a fresh job-mix formula shall be arrived at. In all cases, variations from the job-mix formula shall be within the specified limits.
3. Tack coat where necessary shall be applied over the prepared base at the specified rate before laying the surfacing.
4. Mixing plant shall be of adequate capacity to yield a mixture of proper and uniform quality. It should have the necessary accessories such as aggregate feeder, dryer, weight or volume batcher, binder heater, binder measuring unit, filler feeder unit and mixing unit.
5. Quantities of various sizes of aggregates shall be fed to the dryer in such proportions that the resulting combination complies with the job-mix formula. This shall be strictly followed on small plants with no gradation control unit.
6. The temperature of binder at the time of mixing shall be in the range 150°-177°C and of aggregates in the range 155°- 163°C. Care should be taken so that the difference in temperature between the aggregates and the binder does not exceed 14°C.
7. Mixing time should be shortest possible to obtain uniform distribution of the binder and a homogenous mix.
8. Binder content with mix shall be checked periodically to ensure that the same conforms to specification. A variation in binder content of ± 0.3 per cent by weight of total mix shall, however, be permissible.
9. The mix shall be carried to the site by tipper trucks and spread and compacted to obtain a carpet of required thickness. Spreading shall be done by self-propelled mechanical pavers provided with screeds for spreading, tamping and finishing the mix true to grade, line and cross-section. The temperature of mix at the time of laying shall be in the range 121°—163°C.
10. Soon after laying of the mix, rolling shall be started with 8 to 10 tonnes rollers at a speed not more than 5 km per hour. Rolling operation shall progress with the drive wheel of the roller in the direction of the paving, starting from the low side of the spread and proceeding towards the high side. The initial breakdown pass shall be made as soon as possible, i.e., as soon as the roller can be operated without its wheels picking up the mix. When adjoining lanes are placed, the same, rolling procedure shall be followed after compaction of the fresh mix at the longitudinal joint with 15 to 20 cm of the roller width (with the remaining roller width on the previously compacted lane). The mix shall be further compacted59

    and surface finished with suitable pneumatic and tandem rollers. The final rolling shall continue till the mix is fully compacted and little or no roller marks are left on the surface. The density shall not be less than 95 per cent of the laboratory density. During rolling, the roller wheels shall be kept moist to prevent the mix from adhering to the wheels and being picked up but in no case shall the use of fuel/lubricating oil be permitted for this purpose.

11. Longitudinal joints and edges shall be constructed true to the delineating lines parallel to the centre line of the road. All joints shall be cut vertical to the full thickness of the previously laid mix and the surface painted with hot bitumen before placing fresh material. Transverse joint shall be staggered.
12. Traffic shall bc allowed on the surface only when the carpet after final rolling has cooled down to the ambient temperature.
13. The finished surface shall be checked for line, grade and regularity in accordance with Chapter 7.

5.5.4. Control tests and their frequency :

Quality control tests on the materials and the work and their frequency shall be as indicated in Table 5.3.

5.5.5. Rectification of surface irregularities :

Where the surface irregularities of the asphaltic concrete are out side the tolerances given in Chapter 7, these shall be rectified as per the procedure given in Clause 5.2.5.61

CHAPTER 6
CONCRETE PAVEMENTS

6.1. General

6.1.1.

Construction of concrete pavements shall in general follow the guidelines given in IRC : 15-1981 entitled “Standard Specifications and Code of Practice for Construction of Concrete Roads.”

6.1.2.

For tools, equipments and appliances required for the work and for the proper upkeep thereof, reference should be made to IRC : 43-1972 entitled “Recommended Practice for Tools, Equipments and Appliances for Concrete Pavement Construction”.

6.2. Materials and Mix Proportions

6.2.1.

All materials, viz., cement, coarse aggregates, fine aggregates and water shall be checked for specification requirements in advance of their incorporation in the work.

6.2.2.

Proportioning of different aggregate fractions shall be so controlled that the combined aggregate grading falls within the specified limits of gradation. In case of non-compliance, the proportioning of the various aggregate fractions shall be suitably adjusted based on actual gradation of the different fractions. Statistical approach to this problem is explained in Chapter 8.

6.2.3.

Mix proportions for concrete shall be predetermined on strength basis using representative samples of materials proposed to be actually utilised in the work. While proportioning, adequate allowance should be made for the expected strength variations so as to ensure the specified minimum strength in the field, subject to the permitted tolerances. Guidance in this regard can be had from IRC : 44-1972 and IRC : 59-1976 for continuously and gap graded mixes respectively.

6.2.4.

Where cement from more than one source is to be used, proportions for the mix shall be determined for each cement. In such cases, cement from different sources shall be

stored and used separately and a record of the type or brand used shall be maintained.

6.2.5.

All materials required for the work shall be stored and handled in a manner so as to prevent deterioration or intrusion of foreign matter and to ensure the preservation of its quality and fitness for the work (Ref. IRC : 15-1981).

6.2.6.

Quality control tests on the materials as well as their frequencies shall be as indicated in Table 6.1.

6.3. Processing and Construction

6.3.1. Weather and seasonal limitations :

Unless special precautions as specified are taken, concreting shall not be done during extreme weather conditions, e.g., during monsoon months, and when atmospheric temperature in shade is above 40°C or below 4°C. For guidelines for construction of cement concrete pavements in hot weather, reference may be made to IRC : 61-1976.

6.3.2. Preparation of base

6.3.2.1.

The base to receive the cement concrete shall be checked for line, grade and cross-section as spelt out in Chapter 7. All irregularities beyond the permitted tolerances shall be rectified as specified.

6.3.2.2.

Where concrete is to be laid over an absorbent surface, the latter shall be kept moist in saturated surface dry condition or covered over by a water-proof kraft/polyethylene sheeting as specified so as to prevent absorption of water from the concrete mortar.

6.3.2.3.

Where required, the strength of the base shall be checked for 'k' value by carrying out plate bearing test.

6.3.3. Fixing of formwork

6.3.3.1.

The formwork shall be of correct shape, free from bends and kinks and sufficiently rigid to maintain its shape and position under the weight and working conditions of the laying and compacting equipment. It shall be set to true lines and levels and securely fixed in position to prevent any subsequent disturbance during compaction. Trueness of the formwork from the specified profile shall be checked and any deviation greater than 3 mm in 3 m rectified. No deviation shall, however, be permitted at the joints.

6.3.4. Manufacture and placement of concrete

6.3.4.1.

Unless otherwise permitted, the coarse and fine aggregates shall be proportioned by weight in an approved weigh batching plant. The weighing mechanism shall be regularly checked for accuracy, once daily before the work starts, over the full working range by means of a standard set of weights.67

6.3.4.2.

Cement may be measured either by weight or by bags. Where cement is used in full bags, frequent checks shall be made to see that the bags contain the full specified weight of cement and any shortage of weight made good. Alternatively, 10 per cent of the bags in a consignment shall be weighed in advance and batch-weight of materials adjusted on the basis of average weight for the consignment. Water may be measured by volume using standard measures. The designated water-cement ratio shall be strictly adhered to and due adjustments made in the water to be added on account of free moisture content in the aggregates. Suitable adjustment in the weights of aggregates, due to moisture in them, shall also be made.

6.3.4.3.

Where volume batching is permitted, every effort should be made to minimise variations in batching by following a standard filling procedure. Also the volume of fine aggregates in a batch shall be duly corrected for bulking.

6.3.4.4.

Mixing of concrete shall be done in a power driven batch mixer of approved type that will ensure a uniform distribution of materials throughout the mass. The minimum mixing time shall be fixed in relation to the mixer type and capacity and adhered to strictly.

6.3.4.5.

Workability of concrete shall be checked as specified by performing “slump test” or “compacting factor test” in accordance with IS: 1199. Frequency of testing shall be as indicated in Table 6.2. The permissible tolerances from the specified value for workability shall be :

Necessary adjustment in water content, keeping the same water-cement ratio, shall be made where variations beyond the permitted tolerances are observed so as to bring workability within the specified limits.

6.3.4.6.

Immediately after mixing, the concrete shall be transported for placement in such a manner that segregation or loss of constituent materials is avoided in transit.68

6.3.4.7.

Concrete shall be placed on the prepared base between the formwork in such a manner as to avoid segregation and uneven compaction. Concrete shall not be dropped from a height greater than 90 cm and shall be deposited within 20 minutes from the time of discharge from the mixer. It shall be laid in a horizontal layer as near to the final position as possible thereby avoiding all unnecessary rehandling.

6.3.4.8.

Adequate surcharges of concrete shall be given over the desired finished level. The amount of surcharge shall be determined in the field by actual trial. The surcharge shall be uniform over the entire area and the concrete as spread shall be to the same camber and slope as the required finished surface.

6.3.4.9.

The concrete shall be compacted fully using vibrating screeds and/or internal vibrators as specified. The vibrating screeds and internal vibrators shall conform to IS : 2506 and IS : 2505 respectively. Compaction shall be so controlled as to prevent excess mortar and water working on to the top due to overvibration.

6.3.4.10.

During compaction, any low or high spots shall be made up by adding or removing concrete.

6.3.4.11.

After longitudinal floating has been completed but while concrete is still plastic, the slab surface shall be tested for trueness with a 3 m straight edge in accordance with the procedure set forth in Chapter 7. Any depressions or high spots showing departure from the true surface shall be immediately rectified. High spots shall be cut down and refinished. Depressions shall be enlarged to about 8-10 cm and filled up with fresh concrete, compacted and finished. All the above operations shall be completed within 75 minutes (60 minutes in hot weather) of mixing.

6.3.4.12.

After correcting the surface for profile but just before the concrete becomes non-plastic, the surface shall be finished by belting, brooming and edging as specified.

6.3.4.13.

Where the slab is to be laid in two layers, the second layer shall be placed within 30 minutes of compaction of the lower layer.69

6.3.5. Control of concrete strength

6.3.5.1

The strength of concrete shall be ascertained either from cube or beam specimens as specified For this purpose, during the progress of work, cube/beam samples shall be cast for testing at 7 and 28 days. Sampling and testing shall be in accordance with IS: 1199 and 516 respectively. Frequency of testing shall be as indicated in Table 6.2.

6.3.5.2.

A progress chart indicating the strength values of individual sets of specimens shall be maintained. The statistical parameters, viz., mean strength and upper and lower control limits shall be calculated per set of 15 test specimens and indicated appropriately on the progress chart. These parameters and procedure for statistical analysis are explained in Chapter 8. Where the average strength of concrete shows a consistent increase or decrease from the field design strength, the mix shall be redesigned.

6.3.5.3.

Acceptance of the work shall not be based on a single test result but on statistical basis, such that the lower control limit calculated for a tolerance level of 1 in 15, for sets of 15 test results, shall not be lower than the specified minimum strength. The lower control limit is given by the mean value of the set of tests minus 1.61 times the standard deviation. The work shall be taken to meet the specification requirements when the lower control limit is above the specified strength. Where the above require-70

merits are not met with or where the quality of concrete or its compaction is suspected, the actual strength of the hardened concrete in the pavement shall be checked as set forth in Clause 6.4.

6.3.6. Joints

6.3.6.1.

All materials required for the joints, viz., tie bars, dowel bars, expansion joint filler boards and joint sealing compound shall be checked for specification requirements before their incorporation in the work. The sealing compound shall conform to IS: 1834.

6.3.6.2.

Dowel bars shall be placed parallel to each other and parallel to the surface and centre line of the pavement. The permissible tolerances in this regard shall be :

The dowel assembly shall be firmly secured in place to prevent dislocation during concreting. Bulkheads in pairs with tight fitting holes for dowels may be used for this purpose.

6.3.6.3.

All joint spaces and grooves shall conform to the specified lines and dimensions.

6.3.6.4.

During concreting special care shall be exercised at dowels and in the vicinity of joints. Care shall also be taken to ensure that joints do not cause any discontinuity in the riding surface.

6.3.6.5.

At the end of the curing period before opening to traffic, the joint grooves shall be cleaned thoroughly and sealed as specified in IRC: 57-1974. Care shall be taken to see that the sealing compound is not heated beyond the specified temperature.

6.3.7. Curing of concrete

6.3.7.1.

Curing shall commence soon after the finished pavement surface can take the weight of the wet burlap, cotton or jute mats normally employed for initial curing, without leaving71

any marks thereon. The mats shall extend beyond the pavement edges at least by 0.5 m and be constantly wetted. Initial curing shall be for 24 hours or till the concrete is hard enough to permit labour operations without damage.

6.3.7.2.

Final curing, after the removal of the mats, etc., shall be carried out by wet earth, ponding of water or other means specified. Where water is used for curing, it shall be ensured that the entire pavement surface is kept well saturated throughout the specified curing period. Where water is scarce or pavement is on a steep gradient, impervious membrane curing shall be adopted as per details specified.

6.4. Checking the Quality of Hardened Concrete

6.4.1.

Soon after the initial curing period (see Clause 6.3.7.), the surface of the hardened concrete shall be checked for surface regularity in accordance with the procedure set forth in Chapter 7. Surface irregularities beyond the permissible tolerences shall be rectified as indicated in IRC : 15-1981.

6.4.2.

Where the strength of concrete tested vide Clause 6.3.5. falls below the specified limits or where the quality of concrete or its compaction is suspected, the actual strength of the hardened concrete shall be ascertained by carrying out tests on cores cut from the hardened concrete. Frequency of testing shall be as indicated in Table 6.2. Crushing strength tests on cores shall be corrected for height—diameter ratio and age for obtaining the corresponding cube strength at 28-days in accordance with the procedure given in IRC : 15-1981. The corrected test results shall then be analysed for conformity with the specification requirements on the lines of Clause 6.3.5.

6.5. Reinforcement

6.5.1.

Reinforcing steel, where required to be provided, shall be checked for specification requirements before incorporation in the pavement. Reinforcement shall be placed as specified. Due care shall be taken to ensure that the reinforcement is not displaced during concreting operations.72

CHAPTER 7
CONTROL OF ALIGNMENT, PROFILE AND SURFACE EVENNESS

7.1. General

7.1.1.

All works shall be constructed to the specified lines, grades, cross-sections and dimensions. The objective is to achieve a well built pavement conforming to the required horizontal and vertical profile, design thickness of different pavement courses, and stipulated standards of riding quality.

7.1.2.

Given here are the procedures for checking and permissible tolerances in different cases.

7.2. Horizontal Alignment

7.2.1.

The checking of horizontal alignment shall be done with respect to the centre line of the road as shown on the plans. It involves checking the geometry of the roadway as well as edges of the various pavement layers vis-a-vis the design centre line. Horizontal alignment can be controlled properly only if the centre line.of the road has been marked in the field by means of reference pillars on both sides of the centre line located at frequent intervals along the straights and at all changes of horizontal curvature. Manner of doing so is explained in IRC: 36-1970. To ensure compliance with plans, edges of each pavement layer should be delineated with respect to the centre line before placement, with the help of pegs, strings or other tools.

7.2.2.

Except for hill roads the allowable tolerances in respect of horizontal alignment are recommended to be a follows :

For hill roads, the tolerances shall be as specified by the Engineer-in-charge.

7.3. Surface Levels of Pavement Courses

7.3.1.

Surface levels of pavement courses calculated with respect to the longitudinal and cross profiles shown on the drawings shall be checked through grid levelling/spot levelling, etc., from the subgrade upwards for each successive layer. Actual levels of the different courses shall not vary from the design levels beyond the tolerances indicated below :

7.3.2.

Care shall be taken that the negative tolerance for wearing course indicated in Clause 7.3.1. is not permitted in conjunction with the positive tolerance for base course if the thickness of the former is reduced by more than 6 mm.

7.4. Control on Layer Thickness

7.4.1.

Even though checks on surface levels of pavement courses provide an indirect control on the layer thickness, additional measures may be necessary to establish that the thickness of constructed course is in accordance with specification. These measures could be in the form of thickness blocks, or cores as may be applicable. Control on the spread of materials also provides an indirect check on the layer thickness. Whereas small deviations in thickness may be unavoidable, larger deviations would unduly vitiate the pavement designs.

7.4.2.

In general, the average thickness should not be less than the specified thickness. In addition, the spot reduction in thickness should not exceed 15 mm in the case of bituminous macadam and 6 mm in the case of asphaltic concrete and cement concrete.

7.5. Standards of Surface Evenness

7.5.1.

The criteria for surface evenness, both for longitudinal and transverse profile, have been reviewed and the latest recommendations approved by the Indian Roads Congress in August 1976 (Published in IRC: Special Publication 16:1977 “Surface76

Fig. 1. One design of template adjustable profile

Fig. 2. Another design of template with adjustable profile77

Fig. 3. Design of scratch template78

Evenness of Highway Pavements”) are indicated in Table 7.1. The various existing standards of the Indian Roads Congress are being revised on the basis of these recommendations. During construction, the surface evenness should be controlled as explained in paras 7.6. and 7.7.

7.6. Control of Transverse Profile

7.6.1.

The checking of transverse profile should commence right from the subgrade level and continued for each successive layer upto the top. Checking is done with the help of camber boards/templates, a few typical designs of which are shown in Figs. 1,2 and 3.

7.6.2.

The template in Fig. 1, has adjustable reference pods so that the template can be pre-set for any desired profile. Fig. 2, shows a template in which the bottom piece for checking is replaceable to correspond to the specified profile. These designs are meant usually for checking the profile over a single-lane width. For two-lane or multi-lane roads, generally the checking operations will require to be carried out individually for each lane. Fig. 3, depicts a design of the scratch template used for checking the regularity of the base for concrete pavements.

7.6.3.

For obtaining correct transverse profile on the finished surface of a layer, it is necessary that the spread material (before compacting/finishing) should conform to the desired profile as far as possible. Therefore, the profile of the spread material should be continuously regulated with template/camber boards (placed perpendicular to the road centre line). Normally, a set of three templates should be used in series at an interval of about 10 metres. Checking of the finished surface subsequently should be on the same lines. Additional checks may be made where visual appearance suggests an excessive variation.

7.7. Control of Longitudinal Profile

7.7.1.

The longitudinal evenness is specified in terms of the maximum permissible irregularity under a 3 metre straight-edge. Typical designs for a metallic straight-edge and measuring wedge are given in, Fig. 4. The checking of surface evenness must also commence right from the subgrade level.

7.7.2.

The procedure to be followed for making surface unevenness measurements with a straight-edge is given at Appendix 6.

7.7.3.

Straight-edge measurements are slow and rather tedious. Travelling and rolling type of straight-edges as well as other80

Note : In this design of the wedge, graduations are marked upto 15 mm. For measurements on subgrade and sub-bases, where variations are larger, a modified wedge with graduations upto 25 mm should be employed.

Fig. 4. Typical design of straight edge and wedge81

improved devices have been developed in some other countries for facilitating the work on control of surface evenness. A device available in India for this purpose is the Unevenness Indicator developed at the Central Road Research Institute. This is a travelling straightedge type of device which, when pre-set according to the specification for the surface under check, performs the following functions on being run by two workmen along the lines of measurement at a walking speed of about 5 km per hour :

1. Instantaneously indicates the size of irregularity through a pointer moving on a graduated dial, to an enlarged scale.
2. Sounds a buzzer at locations where the irregularity is in excess of the maximum permissible (as pre-set).
3. Automatically marks, through colour spray, locations where the irregularity is in excess of the premissible maximum (as pre-set).

The unit is simple to operate and is now readily available in the market. This should be used wherever possible.

7.7.4.

The criteria in columns 4 to 8.........of Table 7.1. are meant to ensure that there are not too many irregularities of a size one lower than the permissible maximum. This check is exercised by counting the related irregularities as they occur and then seeing whether there is excessive occurrence over any 300 m length. Each depression/hump is to be counted only once. Both straight-edge and Unevenness Indicator methods are amenable to exercising of this control.82

CHAPTER 8
STATISTICAL APPROACH TO QUALITY CONTROL

8.1. Statistical Quality Control

8.1.1.

It is to be appreciated that the road and runway construction, like most other construction process, has certain amount of variability inherent in the materials and methods involved. It will thus be prohibitively expensive and rather impracticable to have acceptance criteria for quality in such absolute terms as would imply the rejection of a piece of construction or a material on the basis of single sub-standard sample. Because of the inherent variability, the aim of quality control is to limit this variability as much as practicable. The acceptance criteria are thus required to be based on statistical evaluations so that they are not only realistic, but restrictive and as required by the design and performance requirements of the structure.

8.1.2.

The statistical evaluations of the quality data provide a scientific analysis of the entire production process with respect to quality. They not only point out the general trends in the quality variations but also many a time go to expose the unsuspected causes of variation and thus lead to a striking improvement in constructional quality.

8.2. Definition of Common Statistical Terms

8.2.1.

Arithmetic mean (also referred to as the average) is the sum of observations (strength results, say) divided by their number:

8.2.2.

Standard deviation is an average of the deviations of the observations from their mean. This is defined as the square root of variance which is the mean square deviation from the true

mean value. Standard deviation is given by :

A more convenient formula, as given below is, however, generally used :

8.2.3.

Co-efficient of variation is the standard deviation expressed as a percentage of the mean :

8.2.4.

Range is the difference between the largest and the smallest values of the observations in the set :

8.3.

Normal Distribution Curve and Control Limits

8.3.1.

It has been established that when values from a large number of tests are considered for any of the tests on concrete in general, and its strength in particular, they conform to the Normal Gaussion Distribution Curve, Fig. 5, the spread of which, for all practical purposes, may be taken as 3 times the standard deviation on either side of the mean value.

The value which will have only a specified number (1 in N) or percentage (p%)—termed as tolerance level—of test data falling below it, is given by x_min—(x—rj), where r is a factor dependent upon the specified tolerance level.

The values of r for various tolerance levels are given in Table 8.1.86

Fig. 5. Normal distribution curve

Conversely, for a specified minimum strength requirement x_min with a given tolerance level (and hence r), the average value x̄ for mix design strength has to be at least x̄=x_min+rj. The magnitude of standard deviation j is a function of the extent of uniformity achieved in quality of the product.

While the desired quality of the product is defined by x_min and r, the level of quality achieved is assessed from a knowledge of x̄, j and r. (x̄—rj) and (x̄ + rj) are termed as the lower control limit (L.C.L.) and the upper control limit (U.C.L.) respectively. When the stipulated specification requirements are satisfied L.C.L.⋟x_min.

8.4. Quality Control Progress Charts

8.4.1.

A quality control progress chart (see Fig. 6 for a specimen) is the progressive plot of the desired test values, e.g.,87

Fig. 6. Progress chart for strength test data

strength, against the serial number of sample tested. To obtain a general idea of the average variation in quality, the moving average of five tests which for any sample is the average of the five consecutive tests (including the sample under reference and four immediately preceding it) is also plotted on the chart. The x, U.C.L. and L.C.L. for stipulated number of samples as well as the specified x_min are also drawn. The progress chart enables seeing at a glance whether the desired quality is being achieved or not.

8.5. Illustrative Example Strength Test Data

8.5.1.

The data for the 28 day compressive strength of concrete cubes from a construction project are given in Table 8.2.88

(columns 1 and 2). The minimum specified concrete strength x_min on the project was 280 kg/sq. cm, with a tolerance level of 1 in 10 (r= 1.28).

(1) Check whether the stipulated specification requirements are being met

Tabulation of data for the calculation of various statistical parameters is shown in Table 8.2.

L.C.L. = x̄— rj = 340—1.28×40 = 288.8 kg/sq. cm
As L.C.L.>×_min the specification requirements are met.

(2) Calculate the tolerance level actually achieved for the specified concrete

Therefore the tolerance level is 1 in 15.40 (Table 8.1.).

(3) Construct a quality control progress chart with this data

The Progress Chart is shown in Fig. 6.90

8.6. Aggregate Gradation Data

Table 8.3. shows the aggregate gradation data for the project. Both the stipulated aggregate gradation required to be achieved with a confidence level corresponding to r = 2, and the results of gradation tests run on aggregate samples are shown in this table.

(1) Check whether the stipulated
specification requirements are being met

Step I. For each sieve size, calculate x̄, j, L.C.L. and U.C.L. individually.

This data is also tabulated in Table 8.3.

Fig. 7. Control chart for aggregate grading91

Step II. On a plot of the stipulated gradation zone, plot x̄. In case x̄ lies within the zone, plot L.C.L. and U.C.L., as well. If both L.C.L. and U.C.L. lie within the stipulated zone, the specification is being met. The actual plot is shown in, Fig. 7. It is seen that the specification requirements are being met, except for sieve Nos. 300 and 600 micron for which U.L.C. does not lie within the stipulated zone.94

Appendix 1

LIST OF STANDARD SPECIFICATIONS OF INDIAN ROADS CONGRESS REFERRED TO IN THE TEXT

Appendix 2

LIST OF TEST STANDARDS OF BUREAU OF INDIAN STANDARDS AND OTHER BODIES REFERRED TO IN THE TEXT

Appendix 3

CONSOLIDATED LIST OF EQUIPMENT TO BE PROVIDED IN THE STATE CENTRAL LABORATORIES

STATEMENT SHOWING THE RANGE OF ADDITIONAL EQUIPMENT PROPOSED BY SOME OF THE STATES FOR AUGMENTING THEIR CENTRAL LABORATORIES

TESTING EQUIPMENT REQUIRED FOR SETTING OF REGIONAL LABORATORY

LIST OF TESTING EQUIPMENTS REQUIRED TO BE MAINTAINED AT DIVISION/SUB DIVISION/FIELD, LEVEL

FUNCTIONS OF THE DIRECTOR QUALITY CONTROL

1. To carry out the instructions of the Engineer-in-Chief/Chief Engineer regarding policy matter, work audit, arrange seminars and training programmes, help in nomination of the staff for outside training and as directed.
2. To issue guidelines to the regional Quality Control Executive Engineers and other staff from time to time.
3. To keep in touch with the latest developments on use of new materials Quality Control methods and R & D activities in the State and elsewhere.
4. To frame and organise the training programmes for the new entrants and in-service staff
5. To analyse the reports received from the regional Quality Control Officers and issue necessary instructions to the officers concerned with the works.
6. To arrange closer association with Quality Control aspects in case of major projects for roads and bridges.

FUNCTIONS OF QUALITY CONTROL DIVISIONS

1. To provide all assistance to the field officers for compliance of the instructions contained in the Circular connected with quality control.
2. Inspection of works identified by Chief Engineer or Superintending Engineer concerned to ensure quality control.
3. To carry out tests on construction and road materials locally available and to suggest use of alternative materials.
4. To give suggestions for improving the quality at the site of work.
5. To identify the various types of building and road construction materials available in a specified area or for the execution of a particular project. While doing so the desired properties of the material and also the economic viability of their use, should be kept in view.
6. To provide testing and investigation facilities to the field officers.
7. To educate and train the technical personnel engaged at construction sites for carrying out the field tests.111

Appendix 4

SAMPLE FORMS FOR QUALITY TESTS

The samples of the suggested proformae for recording the lest results for the undermentioned items of the work.

Note : Frequency of the test to be carried out shall be as per the requirement prescribed in the handbook.

The quality control records in the prescribed proformae should be maintained in serially numbered registers, issued to personnel in charge of quality control tests on works in the same way as measurement books are issued. These registers should be presented with every third running bill. The payments of bills should thus be linked with assured quality of work.

COMPACTION CHARACTERISTICS EARTHWORK/GRAVEL/MOORUM

Q/R/2

CHARACTERSTICS OF AGGREGATE/BINDING MATERIAL/SCREENING FOR WBM, SURFACE, BASES & SUB BASE COURSES

Q/R/3

BRICK CHARACTERSTICS FOR SUB BASE AND BASE COURSE

Q/R/4

AGGREGATE CHARACTERSTICS FOR BITUMINOUS COURSES

Q/R/5

RATE OF SPREAD OF BINDER, AGGREGATE & BITUMEN CONTENT FOR BITUMINOUS WORK

Q/R/6

TEMPERATURE RECORD FOR BITUMEN WORK

Q/R/7

SURFACE EVENNESS RECORD

Q/R/8

TESTS OF COARSE AGGREGATES FOR CONCRETE

Q/R/9

TESTS OF FINE AGGREGATES FOR CONCRETE

Q/R/10

TEST ON WATER FOR CEMENT CONCRETE*

Q/R/ll

TESTS FOR CEMENT CONCRETE

Q R/12

Appendix 5

PROCEDURE FOR CERTAIN FIELD CONTROL TESTS NOT COVERED BY PUBLISHED STANDARADS

A. TRAY TEST FOR CONTROL OF RATE OF SPREAD OF BINDER

Light metal trays of about 20 cm x 20 cm and 3 cm deep previously weighed and numbered are placed at intervals along the road in the path of he binder distributor between the wheel tracks After the distributor has passed, the trays are removed one wrapped in weighed sheets of paper so that they can be handled, stocked and weighed as soon as convenient. The spacing and the number of trays can be varied to suit the circumstances of the particular site, but at least five trays shall normally be used. The tray test gives a measure of the variation in rate of spread along the road and a good approximation to the average rate of spread.

The trays shall be weighed correct to first place of decimal in gram. The maximum longitudinal distribution error shall be within ± 10 per cent of the specification.

Similarly, transverse distribution by the machine can be checked by placing a number of trays to collect the binder sprayed over each 5 cm of the width of the spray bar. The variation in transverse distribution shall not be more than ± 20 per cent from the mean (not counting the extreme 15 cm at either side of the sprayed area).

B. TRAY TEST FOR CHECK OF RATE OF SPREAD OF GRIT IN SURFACE DRESSING

The rate of spread of grit by gritters can be checked by measuring the area covered by each lorry load of known capacity.

This can also be checked by removing the chippings from small areas of the road and weighing them. A small square metal frame is laid on the new dressing and all the chippings within the enclosed area which is 10 cm square are collected and washed in solvent to remove the binder, weighed and the rate of spread is measured at points along the road at intervals of between 1 metre to 4 metre.

The transverse variation shall be less than ± 20 per cent of the

mean.

C. METHOD Of TEST FOR BINDER CONTENT FOR PAVING MIXTURES BY CENTRIFUGE

The test is intended for determination of binder content in the mix by cold solvent extraction. The mineral matter recovered from the test can be used for checking the gradation of the aggregates in the mix.

A representative sample about 500 gm is exactly weighed and placed in the bowl of the extraction apparatus and covered with commercial grade of benzene. Sufficient time (not more than 1 hour) is allowed for the solvent to disintegrate the sample before running the centrifuge.

The filter ring of the extractor is dried, weighed and then fitted around the edge of the bowl. The cover of the bowl is clamped tightly. A beaker is placed under to collect the extract.

The machine is revolved slowly and then gradually, the speed is increased to a maximum of 3600 r.p.m. The speed is maintained till the solvent ceases to flow from the drain. The machine is allowed to stop and 200 ml. of the benezene is added and the above procedure is repeated.

A number of 200 ml. solvent additions (not less than three) are used till the extract is clear and not darker than a light straw colour.

The filter ring from the bowl is removed dried in air and then in oven to constant weight at 115°C, and weighed. The fine materials that might have passed through the filter paper are collected back from the extract preferably by centrifuging. The material is washed and dried to constant weight as before. The percentage of binder in the sample is calculated as follows :

Percentage binder on the total mix

In the case of road tar which is not completely soluble in benzene, necessary correction is made on the basis of the per cent insoluble of the neat road tar in the solvent.

D. DETERMINATION OF IN-SITU DENSITY OF ASPHALTIC CARPET BY SAND POURING DEVICE

The metallic trayof the field density unit is kept on a level spot of the surface and a hole, 10cm in dia, is cut to the entire thickness of the carpet. All materials removed from the hole are carefully collected and weighed.

A known weight of drystandard sand, passing 25 and retained on 52B.S. sieve, is taken in the sand pouring cylinder. The cylinder is kept directly over the hole and the shutter of the cylinder is released without any126

jerk and closed when the hole is filled with the sand. The qauntity of the residual sand in the cylinder as well as the quantity filling the cone of the cylinder are weighed.

The in-situ density of the carpet is calculated as follows

Appendix 6

PROCEDURE FOR CHECKING SURFACE REGULATING USING A STRAIGHT-EDGE

The procedure to be followed for checking the surface regularity with a straight-edge is as follows

1. The 3-metre straight-edge may be made of steel or seasoned hard wood When made of wood, it may be 75 mm wide and 125 mm deep and its test face should preferably be shod with a metallic plate. The edge should be perfectly straight and free from warps, rots or defects of any kind.
2. Periodically, the straight-edge should be checked for its trueness with a string or a metallic master straight-edge. The straightedge should be rectified/replaced as soon as the same has lost its trueness.
3. The depressions under the straight-edge arc to be measured with a graduated wedge. The wedge should preferably be metallic but may alternatively be of seasoned hard wood. These should be graduated to read undulations upto 25 mm with a least count of at least 3 mm. Typical designs for a metallic staight-edge and measuring edge are given in Fig. 4.
4. For recording undulations in the longitudinal profile the straightedge is to be placed longitudinally parallel to the centre line of the road. Measurements along two parallel lines may normally be sufficient for a single-lane pavement and along three lines for the two-lane pavement. One additional line may be covered for each additional lane.
5. The straight-edge has limitations as regards the measurement of undulations at vertical curves. Additional templates may be made for this purpose especially if the curves are sharp.
6. The straight-edge may be placed at the starting point, wedge inserted between it and the test surface where the gap is maximum and reading taken. The edge may then be slided forward by about 1/2 length. i.e., 1.5 m, and the wedge reading repeated. This process should be continued. The straight-edge need not always be moved forward but may be moved backward and forward to record the maximum undulation existing at a location. Locations with undulations in excess of the specified magnitude should be marked on the surface.
7. A team of three persons consisting of two workmen and a supervisor and equipped with one straight edge and two graduated wedges would be required. The two workmen will operate the straight-edge while the supervisor will take measurements with the wedges and do the marking on the surface.129