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This is the Project on Design of Rigid Pavement. Here you will get an idea of how (Design of Rigid Pavement) takes place. What are the important aspects to keep in mind while (Design of Rigid Pavement) takes place.What are the materials used in Design of Rigid Pavement? What are the tests that are done while (Design of Rigid Pavement) takes place.

Contents

Methodology

  1. Introduction (Design of Rigid Pavement)
  2. Highway Alignment & Surveys (Design of Rigid Pavement)
  3. Highway Materials (Design of Rigid Pavement)
  4. Design (Design of Rigid Pavement)
  5. Machinery & Pavement Construction (Design of Rigid Pavement)
  6. Failures & Maintenance (Design of Rigid Pavement)
  7. Miscellaneous (Design of Rigid Pavement)

Methodology (Design of Rigid Pavement)

1) Data Assimilation: (Design of Rigid Pavement)

Data for this report was assimilated from N.H.A.I &M.P.P.W.D, Nirman Bhavan, Bhopal which includes following:

a) Traffic Volume Count &

b) Relevant IS & IRC codes

2) Soil Sampling & Testing: (Design of Rigid Pavement)

Soil was sampled somewhere from N.H. 86 which was found to be Black Cotton Soil. The C.B.R of this soil was less than 8, hence not in accordance with the provision as per clause no. 5.7.3.6 of IRC 58:2011.

Therefore, another soil of C.B.R>8 was procured.

3) Material Procurement: (Design of Rigid Pavement)

Fly ash was procured from H.E.G Limited Mandideep. Cement(J.K. OPC 43 grade) was procured from UIT-RGPV, Bhopal and rest of the material was available at Q.A.Q.C Lab, S.P.C.L., Vallabh Bhavan Extension Project, Bhopal.

4) Design:

Thickness design, Dowel bars & Tie bars designs were prepared.

5) Material Testing:

Testing of cement, fine aggregate & coarse aggregate were performed at Q.A.Q.C Lab, S.P.C.L, Vallabh Bhavan Extension Project, Bhopal.

6) Trial Mix:

8 trials were done for M 40. 

Introduction (Design of Rigid Pavement)

1.1 History (Design of Rigid Pavement)

It is widely believed that the origin of concrete pavements began in 1894 in Bellefontaine, Ohio, U,S.A, which is still in use but according to Blanchard's American Highway Engineers' Handbook of 1919, cement concrete pavement was prepared in Scotland in 1879, however the pavement could not last long.

In the early part of 20th century many concrete roads were constructed across the globe, It is probably in 1917 the dowel bars were used for the first time in the concrete roads of Virginia in USA. During this period many different configurations of slab cross sections, types of joints and reinforcement patterns for rigid pavements emerged.

Design of Continuously Reinforced Concrete Pavements (CRCP) was introduced to eliminate joint stresses in the mid-1950s, which soon became very popular.

Concrete pavement technology is continuously evolving and today the much of the emphasis is given to the use of eco-friendly construction materials in the pavement concrete and durability aspects of concrete roads. In 1980s cement was partially decontrolled due to which modernization of the cement industry and capacity enhancement took place. As a resuit of this, the interest in cement concrete pavement was revived in the late 1980s. It is because of this, the indigenous effort on the pavement concrete technology was almost non-existent and there was hardly any research in the field of pavement concrete technology in India

1.2 Importance of Rigid Pavement (Design of Rigid Pavement)

a) It helps in the development of agriculture of the area.

b) It helps in the development of natural resources of area.

c) It provides facilities of transporting rural produce such as vegetables, fruits etc in very short time to the cities and the farmers get better price for their produce, which helps in improving the economic conditions of the rural areas.

d) It helps in the development of Industry and promotes regional specialization.

e) It helps in the development of the commerce of the area.

f) It helps in medical, education and sanitation facilities.

g) It helps in better fire and police protection.

h) It increases the mail facilities.

i) It is essential in the case of national defense.

j) It helps in saving vehicle operation cost from 15 to 40 %.

1.3 Pavement: (Design of Rigid Pavement)

Pavement may be defined as a relatively stable layer or crust constructed over the natural soil. The main function of pavement is to support and distribute the heavy wheel loads of vehicles over a wide area of the underlying sub grade soil and permitting the deformation with in elastic or allowable range

1.3.1 Types of pavement: (Design of Rigid Pavement)

a) Flexible Pavement: Pavement structure that maintains intimate contact with and distributes loads to the sub grade and depends on aggregate interlock, particle friction, and cohesion for stability.

b) Rigid pavement: Pavement that will provide high bending resistance and distribute loads to the foundation over a comparatively large area.

Design of Rigid Pavement
                                                                             Fig 1. Design of Rigid Pavement

1.3.3 Components of Pavement: (Design of Rigid Pavement)

a) Soil sub grade: (Design of Rigid Pavement)

The soil sub grade is a layer of natural soil prepared to receive the other layers of the pavement The loads on the pavements are ultimately taken by the soil sub grade and dispersed to the earth mass below. The sub grade should possess the following properties:-

i) Strength

ii) Drainage

ill) Ease of compaction

iv) Permanency of compaction etc.

The strength properties of the sub grade can be evaluated by any of the following tests:-

i) California bearing ratio test

ii) California resistance value test.

iii) Plate bearing test.

iv) Triaxial shear test.

b) Sub base course: (Design of Rigid Pavement)

It is a layer of selected granular soil, stabilized soil or gravels, boulders, broken stones, bricks etc. The main purpose of providing sub base layer is to permit the building of relatively thick pavement at a low cost. The sub base course usually is provided for any one or more purposes:

i) To increase the structural support for the base and surface courses.

ii) To improve drainage.

iii) To eliminate frost heave and salt heave.

iv) To prevent the base and surface courses from the ill effect of poor qualities of the under lying soil.

c) Base course: (Design of Rigid Pavement)

It is a foundation layer, designed for its structural stability. It is provided for the following purposes

i) To prevent the pumping in fine grained soils.

ii) To protect soils susceptible to frost action.

iii) To check the volume changes of the sub grade on highly active soils.

iv) To form a working surface on silts and clay.

v) To provide leveling course on rough shaped formation.

vi) To increase the structural stability.

d) Wearing course: (Design of Rigid Pavement)

It is that component of pavement with which the wheels of vehicles are in actual contact. The main purpose of wearing course is to provide smooth and dense riding surface that resists the pressure exerted by tyres. It also resists the wear and tear due to traffic. It also offers resistance to the infiltration of surface water into the base or sub base layer. The wearing course also adds appreciable strength to the entire pavement surface. 

Design of Rigid Pavement
                                                                                                  Fig 2. Design of Rigid Pavement

Highway Alignment & Surveys (Design of Rigid Pavement)

2.1 Planning Surveys: (Design of Rigid Pavement)

Before taking any decision for the development or new construction, certain factual data is collected which is known as planning surveys. The planning surveys include the detailed studies of the following factors:

a) Economic studies: (Design of Rigid Pavement)

To estimate the economic feasibility of the proposed highway following data are collected

i) Details of population and its distribution in each area i.e. village, town, city etc

ii) Trend of population growth.

iii) Area wise statistics of agriculture and industrial produce.

iv) Agriculture and industrial development.

v) Per capita income in the area.

vi) Existing facilities of education, recreation, means of communication etc.

b) Financial studies: (Design of Rigid Pavement)

Under this head following information are collected:

i) Sources of income in the area and estimated revenue from taxation on road transport.

ii) Living standard of the people in the area.

iii) Sources from which funds can be collected such as toll tax, vehicle registration, local levies etc.

iv) Future trends in financial aspects.

c) Road use or traffic studies: (Design of Rigid Pavement)

Under this head following information are collected

i) Traffic volume in vehicles per day, peak hourly traffic and annual average traffic etc.

ii) Traffic flow pattern.

iii) Origin and destination studies.

iv) Accidents and their causes, their cost analysis etc.

v) Future trend of traffic pattern and volume.

vi) Mass transportation facilities.

d) Technical or Engineering studies: (Design of Rigid Pavement)

Under this head following data are collected

i) Topographic survey of the area.

ii) Soil type survey of the area.

iii) Location and classification of the existing roads in the area.

iv) Road life studies.

v) Problems relating to drainage, construction and maintenance.

vi) Traffic studies origin and destination studies

2.2 Highway Alignment (Design of Rigid Pavement)

The position or layout of the centre line of the highway on the ground is called the alignment. The horizontal alignment includes the straight path and curves. A new road should be aligned very carefully as faulty or improper alignment may result in one or more of the following disadvantages:

a) Increase in construction cost.

b) Increase in maintenance cost.

c) Increase in vehicle operation cost.

d) Increase in accident rates.

2.2.1 Requirements of ideal alignment: (Design of Rigid Pavement)

The basic requirement of an ideal alignment between two terminal station are as follows:

a) Short: It is desirable to have shortest alignment between two terminal stations. A straight alignment would be shortest. However practical constraints may cause deviations from the shortest path.

b) Easy: The alignment should be easy to construct and maintain the road with minimum problems. It should be easy for the operation of vehicles with easy gradients and curves.

c) Safe: The alignment should be safe for construction and maintenance from the view point of stability of noted hill slopes, embankment and cut slopes and foundation of embankments. It should also be safe for traffic operation with safe geometric features.

d) Economical: An road alignment is called economical if the total cost including initial cost, maintenance cost and operation cost is minimum. 

The alignment should be such that it offers maximum utility by serving maximum population and products.

2.3 Engineering Surveys: (Design of Rigid Pavement)

Before finalising the alignment of a highway, the engineering surveys must be carried out. The surveys may be collected in four stages as follows:

a) Map study: (Design of Rigid Pavement)

In this study if the topographical map of the area is available, the likely routes of the road may be marked on it. The probable alignment can be located on the map from the following available details:-

i) Avoidable points, such as ponds, valleys, lakes etc.

ii) Possibility of crossing through a mountain pass.

ili) Approximate location of a bridge site for crossing the river, avoiding bends etc.

iv) Two stations are situated at higher level and the other on lower level etc.

b) Reconnaissance Survey: (Design of Rigid Pavement)

The main objective of this survey is to examine the general characteristics of the area for determining the most feasible route or routes for further detailed investigations. The data collected should be adequate to examine feasibility of all the different routes. The reconnaissance survey may be conducted in the following sequence:-

i) Study of topographical survey sheets, agricultural soil and meteorological maps and aerial photographs if available.

ii) Aerial reconnaissance where necessary and feasible.

ii) Ground reconnaissance.

c) Preliminary Survey: (Design of Rigid Pavement)

This survey is relatively large scale instrument survey, conducted for the purpose of collecting all physical information which affects the proposed location of a new highway. Information collected for this survey are as follows:

i) The highest subsoil water level, the variation between the maximum and minimum and the nature and extent of inundation if any.

ii) The character of embankment foundation including the presence of any unstable strata, poor drainage or marshy areas etc.

iii) Any particular construction problem of the area as sub terrain flow, high level water storage, resulting in steep hydraulic gradient across the alignment.

iv) In cut section nature of rock, defects of rocks etc. should also be considered.

d) Final Location Survey: (Design of Rigid Pavement)

This survey is carried out to lay the final centre line of the road in the field based on the alignment selected in the design office and to collect necessary data for the preparation of working drawings. 

Highway Materials (Design of Rigid Pavement)

3.1 Soil (Design of Rigid Pavement)

The term soil is defined as an unconsolidated material, composed of solid particles produced by the disintegration of rocks by the action of water frost, temperature, pressure or by plant or animal life.The characteristics of soil grains depend on size, shape, surface texture, chemical composition and electrical surface charges. Moisture and dry density influence the engineering behavior of a soil mass. Sub-grade soil is an integral part of a road pavement structure as it provides the support to the pavement from beneath. Therefore this soil should possess sufficient strength and stability under adverse climatic and loading conditions. Soil used as a highway material should possess the following properties:-

a) Stability

b) Incompressibility

c) Good drainage

d) Ease in compaction

e) Minimum volume change

f) Permanency of strength

Design of Rigid Pavement
                                                                                    Fig 3. Design of Rigid Pavement

3.1.1 Evaluation of Soil Strength (Design of Rigid Pavement)

a) Bearing Power: (Design of Rigid Pavement)

It is determined with the help of plate bearing test, using plates varying from 75 cm to 30 cm in diameter. For pavement design usually 75 cm diameter plate is used while for building 30 cm diameter plate is used. The plate bearing test originally was developed to find out modulus of sub-grade reaction.

b) Penetration Resistance of soil: (Design of Rigid Pavement)

The penetration test can be performed in the laboratory or in situ. They can be considered as small scale bearing tests in which the ratio of penetration to the size of the loaded area is much greater than in bearing tests.  For penetration tests, Calfiornia bearing ratio test and cone penetration tests are commonly known tests.

3.1.2 California Bearing Ratio Test: (Design of Rigid Pavement)

C.B.R may be defined as the ratio of the test load required to force a cylindrical plunger of 19.355 sq.cm cross sectional area into the soil mass at the rate of 0.25 cm/min to the load required for corresponding penetration of the plunger into a standard sample of crushed stone, the later load is known as the standard load.

Design of Rigid Pavement

                                                                    Video. Design of Rigid Pavement

3.2 Aggregate (Design of Rigid Pavement)

Aggregates form the major portion of pavement structure and they form the prime materials used in pavement construction. Aggregates have to bear the wheel load of the vehicles and they also have to resist wear due to abrasive action of traffic. 

These are used in pavement construction in cement, concrete, bituminous concrete and other bituminous constructions and also as granular base course underlying the superior pavement layers.

3.2.1 Properties (Design of Rigid Pavement)

a) Strength: The aggregate used should be sufficiently strong to withstand the stresses to traffic wheel loads. The strength of coarse aggregate is determined by aggregate crushing test.

b) Hardness: The aggregate used in the surface courses are subjected to constant abrasion due to moving vehicles. The mutual rubbing of stones also causes wear in the aggregates. This action of mutual rubbing of stones is known as attrition. The hardness of aggregates is tested by abrasion test.

c) Toughness: Aggregates in pavements are also subjected to impact due to moving wheel loads. It is determined by impact test

d) Durability: Aggregates used in pavements have to withstand the adverse action of weather such as physical and chemical actions of rain and ground water and effects of atmosphere etc. lt is determined by soundness test.

e) Shape of aggregate: For cement concrete pavements more than 45% of flaky and elongated particles should not be used. For such pavements rounded aggregate should be preferred due to better workability for the same proportion of cement paste and water cement ratio.

3.2.2 Aggregate Tests (Design of Rigid Pavement)

a) Crushing Test: The strength of coarse aggregate may be assessed by aggregate crushing test. The aggregate crushing value provides a relative measure of resistance to crushing under gradually applied compressive load. The apparatus for the standard test consists of a steel cylinder 12.5 cm diameter with a base plate and plunger, compression testing machines, cylindrical measure of diameter 11.5 cm and height 18 cm, tamping rod and sieves.

The aggregate crushing value for good quality aggregate to be used in base course shall not exceed 45% and the value for surface course shall be less than 30%

b) Abrasion Test: Abrasion test are carried out to test the hardness property of stones and to decide whether they are suitable for the different road construction. The apparatus used for abrasion tests are Los Angeles Abrasion Testing Machine, Deval Abrasion Testing Machine and Dorry Abrasion Testing Machine.

c) Impact Test: A test designed to evaluate the toughness of stone or the resistance of the aggregates to fracture under repeated impacts is called impact test. The aggregate impact value indicates a relative measure of resistance of aggregate to impact, which has different effect than the resistance to gradually increasing compressive stress. 

The apparatus used is Aggregate Impact Testing Machine.

The aggregate impact value should not normally exceed 30% for aggregate to be used in wearing course of pavements. The maximum permissible value is 35% for bituminous macadam e and 40% for water bound macadam base courses

d) Soundness Test: Soundness test indicates the resistance to disintegration of aggregate is determined by using saturated solution of sodium sulfate or magnesium sulfate.

e) Shape Test: The particle shape of aggregate mass is determined by the percentages of flaky and elongated particles contained in it and by its angularity. 

The evaluation of shape of the particles is made in terms of flakiness index, elongation index and angularity number.

i) Flakiness Index: The flakiness index of aggregate is the percentage by weight of aggregate particles whose least dimension or thickness is less than 3/5th or 0.6 of their mean dimension. It is applicable to sizes larger than 6.3 mm. It is desirable that the flakiness index of aggregates used in road construction is less than 15% and normally does not exceed 25%.

ii) Elongation Index: The percentage by weight of particles whose greatest dimension or length is greater than 1.8 times their mean dimension. It is not applicable for sizes smaller than 6.3 mm. Actually no limit for elongation index is fixed, but it should not exceed more than 10 to 15%.

ii) Angularity Number: Angularity number measures the voids in excess of 33%. Higher the number, more angular the aggregate The degree of packing of particles of single sized aggregates depends on the shape and angularity of aggregate. It is defined as 67- percentage solid volume. For road construction it should not exceed 11 i.e. it should remain between 0 to 11. 

f) Specific gravity and Water absorption tests: The specific gravity of an aggregate is considered to a measure of the quality or strength of the material. Low specific gravity specifies a weaker stone. The specific gravity test also helps identifying the stone specimen.

Stone having higher water absorption value are porous and thus weak.

The specific gravity of rocks vary from 2.6 to 2.9. Rock specimens having more than 0.6% water absorption are considered unsatisfactory unless found acceptable based on strength tests.

3.3 Ordinary Portland Cement (Design of Rigid Pavement)

The Ordinary Portland Cement (OPC) comes in three grades, 33 grade, 43 grade and 53 grade. If the 28 days strength is not less than 43 N/sq. mm, it is called 43 grade cement.

3.3.1 Tests (Design of Rigid Pavement)

3.3.1.1 Field Tests (Design of Rigid Pavement)

a) Color: The color of cement should be uniform. It should be typically grey color with a light greenish shade.

b) Physical Properties: The cement should feel smooth when touched or rubbed in between fingers.

c) Float Check: If a small quantity of cement is thrown in a bucket of water, it should sink and not float.

d) Presence of lumps: The cement must be free of lumps. Lumps are formed by water absorption from the atmosphere.

3.3.1.2 Laboratory Tests (Design of Rigid Pavement)

a) Fineness Test: This test is carried out to check proper grinding of cement. Finer cement offers a greater surface area for hydration and hence faster development of strength. It may be determined either by sieve test or by permeability apparatus test. 

In sieve test, the residue on sieve when weighed should not be more than 10% of original weight. 

In permeability test the specific surface of cement should not be less than 2250 sq. cm/g.

b) Consistency Test: The purpose of this test is to determine the percentage of water required for preparing cement paste for other tests. 

It is determined using Vicat Apparatus.

The Vicat plunger having 10 mm diameter and 50 mm length should penetrate to a depth of 33 to 35 mm from the top of the mould.

c) Setting Time Test:

i) Initial Setting Time: It is regarded as the time elapsed between the moment that water is added to the cement, to the time at the paste starts losing its plasticity. 

It is determined using Vicat apparatus. The needle should penetrate upto about 5 mm measured from bottom of mould. 

It is 30 minutes for mxing and handling operations.

ii) Final Setting Time: It is the time elapsed between the moment the water is added to the cement, and the time the paste completely loses its plasticity and attains sufficient firmness to resist certain pressure. 

It is determined using Vicat apparatus. The time at which the needle makes an impression on test block but the collar fails to do so.

It is 10 hours for placing, compacting and finishing.

d) Soundness Test: The purpose of this test is to detect the presence of uncombined lime and cement. It is important that the cement after setting should not undergo any appreciable change of volume. 

It is determined using Le Chatelier's apparatus.

The difference between initial and final measurements should not exceed 10 mm.

3.4 Water (Design of Rigid Pavement)

This is the least expensive but most important ingredient of concrete. It should be clean and free from harmful impurities such as oil, alkali, acid etc. in general the water which is fit for drinking should be used for concrete. Water is an important ingredient of concrete as it actively participates in the chemical reaction with cement. 

The pH value of water for making concrete should lie between 6 to 8 and should free from organic matter. 

A particular source of water is suitable for concrete making or not, is to make concrete with this water and compare its 7 days and 28 days strength with companion cubes made with distilled water. If the compressive strength is up to 90%, the source of water may be accepted.

The initial setting time of test block made with cement and water proposed to be used shall not differ by ±30 minutes from the initial setting time of the test block made with same cement and distilled water.

3.5 Fly Ash (Design of Rigid Pavement)

The fly ash is fairly divided residue which results from the combustion of ground or powdered bituminous coal or sub-bituminous coal and transported by flue gases of boilers. It is a byproduct of many thermal power stations. 

The fly ash resembles a pozzolana i.e. a substance which although not cemetitious itself contains constituents which combine with lime to form a material having cementing properties. Normally, it contains some unburnt carbon. It is acidic in nature and its main constituents are silica, aluminium oxide and ferrous oxide.

It imparts the following properties to the concrete:-

i) It produces the cement aggregate reaction.

ii) It slows heat evolution.

iii) It greatly improves water tightness of concrete.

iv) It permits easier placing and finishing because of improvement in plasticity and cohesiveness of concrete.

v) It improves the strength of concrete.

vi) It results either in small reduction or no change in the quantity of mixing water required per cubic metre of concrete for a given consistency or a slump.

3.6 Reinforcement (Design of Rigid Pavement)

The steel reinforcement is generally in the form of round bars of mild steel or HYSD bars. The diameter of bars may vary from 8 mm to 40 mm. Sometimes the square bars or twisted bars or ribbed tor steel are used for road slabs and such other constructions the reinforcement may also consist of sheets of rolled steel of suitable thickness. The hybrid which is a steel lath may also be used as steel reinforcement.

3.7 Admixture (Design of Rigid Pavement)

A material other than cement, water and aggregates added in concrete to improve its certain qualities or change physical property in its fresh or hardened stage is an admixture. 

It is widely used because of the following advantages:-

a) Adjusting the final setting time of concrete.

b) Higher early and ultimate strength.

c) Higher slump and self leveling concrete.

d) Increasing durability of concrete.

e) Lesser w/c ratio.

f) Reducing quantity of cement.

g) Reduction in permeability of concrete.

h) Time saving in terms of repair and maintenance.

Depending upon a respective activity in the concrete mix, admixture can be classified as:

a) Accelerators

b) Air entraining admixtures

c) Plasticizers

d) Super plasticizers

e) Retarders 

Design (Design of Rigid Pavement)

4.1 Traffic Volume Study (Design of Rigid Pavement)

Traffic volume may be defined as the number of vehicles crossing a selected section of road per unit time at any suitable selected period. Traffic volume is used as a quantity measure of traffic volume that is how many vehicles of what type and from which direction have passed a definite section of the road per hour.

Uses of traffic volume studies:-

a) It gives the idea of relative importance of road and helps in deciding the priority for expansion and improvement of the existing roads.

b) It is useful in planning the traffic control and operation of the existing roads and also for planning and designing new roads.

c) This study can be used for the analysis of traffic pattern of roads.

d) It is useful for the structural and geometric designs of the pavement and computing road users capacity.

e) Turning movement studies are used in the design of intersections, planning of signal timings, channelization and other controls etc.

Machinery & Pavement Construction (Design of Rigid Pavement)

5.1 Machinery (Design of Rigid Pavement)

With the help of machines many complicated and gigantic works can be done economically in shorter duration. Hence the knowledge of machinery is essential for the pavement construction.

5.1.1 Clearing the Site (Design of Rigid Pavement)

For site clearance generally following machinery can be used:-

a) Dozer: A dozer is a machine used for earth moving work. It is one of the most important machines used on all types of earth work projects. They are mounted on tractors primarily it is a pushing unit.

Dozers can be used for following purposes:-

i) To clear site, tress and stumps.

ii) To construct and maintain access and haul roads through rocky terrain etc.

iii) To move earth up to a distance of 100 m.

iv) Helping trucks out of the pit and towing damaged vehicles.

v) Backfilling trenches and spreading material.

b) Rooter or Ripper: It is a machine mounted on wheels and towed by a tractor. It has one or two teeth which are driven into the ground to loosen it and pull out roots. It is used to fell trees.

c) Tractors: Tractors are multipurpose self propeller machine. Its size and weight varies from light models used for agricultural purposes to heavy models crawler units equipped with special rigs used for earth moving work. Their primary purpose is to push or pull loads.

d) Scrapers: It is a digging and carrying unit which picks up the earth after scrapping the ground, and transporting it to site. After discharging material, it spreads the same over the desired area. It consists essentially of a large scoop with a cutting edge. The scoop is a bucket container of steel known as bowl or body.

5.1.2 Formation of Sub-grade: (Design of Rigid Pavement)

a) Tractor: Already discussed previously.

b) Dozer: Already discussed previously.

c) Grader: It is primarily used for shaping a sub-grade, constructing earth roads and spreading loose materials. Sometimes it may also be used for mixing gravel and slope trimming. 

It mainly consist of an angled blade 3 to 4 m long and can swivel through 360 degrees, lowered or raised to suit the soil condition.

d) Shovel: These are primarily used to excavate earth and load it into hauling units such as trucks or tractor pulling wagons or in conveyor belt etc. These can be used to excavate all types of soil except hard rocks without prior loosening. These are available in different sizes ranging from 0.3, 04, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 cubic metre capacities.

e) Drag Line: It is a machine of shovel family, It is given this name because of its prominent operation of excavation, by dragging the bucket against the material to be dug instead of digging. The bucket which is the main digging tool is loosely attached to the boom through cables.

f) Cam Shell: It is also a machine of shovel family, its front end is essentially a plain boom with a specially designed bucket, loosely attached at the end through cables, The bucket consist of tool sheels hinged at the top. At the end of the bucket either sharp teeth or sharp edge is provided.

g) Rollers: After spreading the material, the rolling operation is commenced. A Tandem or Pneumatic roller of 6 to 9 tons is used. To prevent addition of mix of material to roller wheels the same is kept damp with water. The rolling is done until there is no further movement of material.

h) Trucks: Already discussed previously.

5.1.3 Laying of Concrete (Design of Rigid Pavement)

a) Batching Plant: For major project works the material such as coarse and fine aggregate, cement etc. are used by weight in concrete mix. For better quality control, materials are weighed with the help of automatic machines known as batching plant.

b) Mixer: For proper mixing of different constituents of cement concrete, mixers are used. They can be classified into two categories:-

i) Batch Mixer

ii) Continuous Mixer

Further mixers can be classified as:

i) Tilting mixer

ii) Non tilting mixer

iii) Open pan mixer

c) Hauling Units: Mixed concrete can be brought to site by using

i) Pans

ii) Borrows

iii) Dumper or lorries

d) Compaction: Concrete can be compacted by hand tempers. For this work, different types of vibrators can be used such as

i) Surface vibrator

ii) Internal Vibrator

e) Finisher: After proper compaction surface can be finished giving proper grade and camber by hard wooden floats or by machines.

5.2 Procedure of Pavement Construction (Design of Rigid Pavement)

Step-I: Scarifying existing bituminous surface to a depth of 50 mm by mechanical means.

Step-II: Construction of sub-grade of selected soil having CBR> 8 (as IRC 58:2011). Grading it to required slope & camber and compacting using vibratory roller of 80 to 100 KN static weight.

STEP-III: Providing crushed stone aggregate, depositing on a prepared surface by hauling vehicles, spreading and mixing with a motor grader, watering an compacting with a vibratory roller to form a layer of sub-base.

STEP-IV : Construction of dry lean cement concrete sub-base over a prepared sub-grade with coarse and fine aggregate conforming to IS: 383, the size of coarse aggregate not exceeding 25 mm, aggregate cement ratio not to exceed 15:1, proper aggregate gradation is done. Cement content should not be less than 150 kg/ cum, optimum moisture content to be determined during trial length construction, concrete strength not to be less than 10 MPa at 7 days.

STEP-V: Cement Concrete Pavement (Construction of un-reinforced, dowel jointed, plain cement concrete pavement M-40 grade concrete over a prepared sub base with cement, coarse and fine aggregate conforming to IS 383, maximum size of coarse aggregate not exceeding 25 mm, mixed in a batching and mixing plant as per approved mix design, transported to site, laid with a fixed form or slip form paver.

Failure & Maintenance (Design of Rigid Pavement)

6.1 Failure in Concrete Pavements (Design of Rigid Pavement)

a) Scaling of Cement Concrete: Due to excessive vibration given to mix (cement mortar comes to the top during construction and thus with use, the cement mortar gets abraded exposing the aggregate of the mix).

b) Shrinkage Cracks: During the curing operation of cement concrete pavement immediately after the construction, the shrinkage cracks normally develop.

c) Spalling of Joints: Sometimes when pre-formed filler materials are placed during casting of pavement slabs, the placement is somehow dislocated and and filler is thus placed at an angle. Thus this form an overhang of a concrete layer on the top side and the joint later on shows excessive cracking and subsidence.

d) Warping Cracks: If the joints are not well designed to accommodate the warping of slabs at edges, this result in development of excessive stresses due to warping and the slab develops cracking at the edges in an irregular pattern.

Hinge joints are generally provided for reliving the slabs of warping stresses.

e) Mud Pumping: It is recognized when the soil slurry ejects out through the joints and cracks of cement concrete pavement caused by the downward movement of slab under the heavy wheel load.

Factors which cause mud pumping are:

i) Extent of slab deflection

ii) Type of sub grade soil

iii) Amount of free water

iv) Warping Stress

v) Mud Pumping

6.2 Maintenance/Repairs (Design of Rigid Pavement)

a) corrective Methods: (Design of Rigid Pavement)

i) Full-depth repairs: Full-depth repairs fix, cracked slabs and joint deterioration by removing at least a portion of the existing slab and replacing it with new concrete. Maintains the structural Integrity of the existing slab and pavement. It is also appropriate for shattered slabs, corner breaks and some low-severity durability problems.

ii) Partial-depth repairs: Partial-depth repairs correct surface distress and joint/crack deterioration in the upper third of concrete slab. In this process the deteriorated layer is removed then cleaned and the new concrete is placed.

iii) Cracking and seating: This technique is used prior to placing an asphalt or concrete overlay to control reflective cracking in the overlay. It is used to re-establish support between the sub base and the slab where there may be voids.

b) Preventative Techniques (Design of Rigid Pavement)

i) Joint and crack resealing: Minimizing the infiltration of surface water thus reducing sub grade softening and slows pumping and erosion of subbase or subgrade fines. It also helps in minimizing incompressible material into joint system thus reducing potential or spalling and blowups.

ii) Retrofitting concrete shoulders: Retrofitting concrete shoulders adds a tied concrete shoulder to an existing pavement.

iii) Retrofitting edge drains: Adding a longitudinal drainage system to a pavement aids in the rapid removal of water and may prevent pumping, faulting, and durability distress from developing.

c) Corrective-and-preventative techniques (Design of Rigid Pavement)

i) Diamond grinding: Diamond grinding improves a pavement ride by creating a smooth, uniform profile by removing faulting, slab warping, studded tyre wear, and patching unevenness.

ii) Dowel-bar retro fitting: Dowel-bar retrofit increases the load transfer efficiency at transverse cracks and joints in pavements by linking the slabs together so that the load is distributed evenly across the joint. Improving the load transfer increases the pavement's structural capacity and reduces the potential for faulting.

iii) Slab undersealing: Slab undersealing is a means to stabilize existing pavement slabs by filling small voids beneath the slab and base or base and sub base. Several grouts have been trialed and portland cement grout was found to produce best results.

iv) Cross stitching: Cross-stitching is used to repair longitudinal cracks that are in a fair condition. It increases load transfer at the crack by adding steel reinforcement to restrict widening of the crack. 

v) Grooving: Grooving restores skid resistance to concrete pavements.

Miscellaneous (Design of Rigid Pavement)

7.1 Factors affecting stability of pavement (Design of Rigid Pavement)

a) Traffic factors: These include the character and volume of traffic which will use the pavement.

b) Moisture factors: These represent change of moisture content of the subgrade due to any of the conditions of precipitation, capillarity and irrigation in the area etc.

c) Climatic factors: These factors represent the effect of temperature changes such as frost penetration etc.

d) Soil factors: These factors represent the effect of the condition of natural foundation soil in cuta under shallow embankments or soil used in embankment immediately underlying subgrade surface.

e) Stress distribution factors: These factors represent the function of pavement and base for transmitting the load of the subgrade.

7.1.1 Traffic capacity studies (Design of Rigid Pavement)

a) Traffic volume: The number of vehicles moving in a specified direction on a given road way that pass a given point or cross section during specified unit of time is known as traffic volume. It is expressed as vehicles per hour or per day.

b) Traffic density: The number of vehicles occupying a unit length usually a kilometer lane of a road way at a given instant is known as traffic density.

c) Traffic capacity: The maximum numbers of vehicles on a road that can pass a given point in one hour is known as flow and have the same units.

7.2 Elements of Highway Embankment (Design of Rigid Pavement)

a) Height of embankment: The height of embankment depends upon the desired grade line of the highway and topography of the area. Sometimes it is also governed by the stability of foundation specially when the soil is weak usually it is taken 0.6 m.

b) Fill Material: For highway embankment, generally granular soils are preferred, clay and silt is less desirable while organic soils are unsuitable. From economic considerations generally best locally available soil should be used.

c) Settlement: All earthwork settle after their construction due to any of the following reasons:-

i) Due to consolidation

ii) Due to settlement of foundation

ii) Due to settlement of fill

iv) Due to settlement of foundation and fill both.

d) Stability of foundation: When the foundation of embankment is weak, it should be fully investigated, more specially for high embankments.

e) Stability of side slopes: To eliminate the possibility of embankment failure under adverse moisture or other conditions the side slopes should be stable. IRC has recommended the following side slopes for embankments

i) Height of embankment upon 60 cm, slope 1 in 4

ii) For heights above 60 cm, natural slope or 1 in 2 which ever is flatter.

7.3 Drainage (Design of Rigid Pavement)

Since increase in moisture reduces the bearing power of the soil , the stability of highway is reduced. Thus to maintain the stability highway drainage is essential. The process of removing and controlling the excess surface and subsoil water within the right of way is known as highway drainage.

7.3.1 Mode of damages caused by water: (Design of Rigid Pavement)

a) Earthen and water bound macadam roads are damaged by softening the road surface.

b) Washing out the unprotected top surface, erosion of side slopes, side drains and forming gullies etc.

c) Softening of sub grade soil and decreasing its bearing capacity.

d) Softening of soil along the highway causes land slide.

7.3.2 Requirement of highway drainage system: (Design of Rigid Pavement)

a) The surface water from the carriage way and shoulders should be drained off effectively and as soon as possible without allowing it to percolate to the sub-grade.

b) The surface water from the adjoining land should not be allowed to enter the road.

c) The side drains should have sufficient capacity and longitudinal slope to discharge maximum surface water collected in the region.

d) The flow of surface water along the slopes or across the road should be allowed to erode them or form ruts.

e) The seeping water or seepage and other sources of under ground water such as capillary rise water etc. should be drained off as earliest by subsurface drainage system otherwise it will reduce the bearing power of the sub-grade.

7.4 Camber (Design of Rigid Pavement)

Camber is the slope provided in the transverse direction of the road to drain off the rain water from the road surface. Usually camber is provided in the straight roads by raising the centre of the carriage way with respect to the edges forming highest point at the centre.

7.4.1 Types of Camber: (Design of Rigid Pavement)

a) Barrel Camber: It consists of continuous curve either parabolic or elliptical. In this type of camber the shape of the surface is flat at the middle and steeper towards the edge. This type of camber is preferred for fast moving vehicles as they have to cross the central or crown line frequently during overtaking operations.

b) Slope Camber: This type of camber consist of two straight slopes joining at the centre. This type of camber is provided in relatively impervious pavement surfaces such as cement concrete pavements.

c) Composite Camber: This type of camber consist of two straight slopes with parabolic portion at the centre. This type of camber is preferred for slow moving vehicles such as bullock drawn iron tyred carts.

7.5 Joint filler and Sealer: (Design of Rigid Pavement)

Joints form the weakest plane in the concrete pavement and can allow infiltration of rain water and ingress of stone grits. The infiltration of water may damage the subgrade and the ingress of stone grit reduces the effective width of the joint causing faults like spalling of the joint.

7.5.1 Filler material: (Design of Rigid Pavement)

a) Properties (Design of Rigid Pavement)

i) Compressibility: The filler material should be compressible and elastic. As per IRC recommendations the joint filler materials should be of such that it could be compressed to 50% of its original thickness by the application of pressure.

ii) Elasticity: The filler material should be quite elastic. As per IRC the material should at least recover 70% of its original thickness after the release of applied load after one hour at the end of third application of load.

iii) Durability: It should be quite durable.

b) Materials used: (Design of Rigid Pavement)

i) Soft wood

ii) Impregnated fibre board

iii) Cork or cork bound with bitumen

iv) Coir fibre

7.5.2 Joint sealer: (Design of Rigid Pavement)

a) Properties:

i) Adhesion to cement concrete edges

ii) Extensibility without fracture

ii) Resistance to infiltration of rain water, ingress of grit

v) Durability

b) Materials used:

i) Bitumen

ii) Rubber bitumen

This was all the information I could give you on the topic Design of Rigid Pavement.

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