INTRODUCTION
Plant Road Connectivity is not only a key component of Plant Developmentby promoting access to economic and social services and thereby generating increased agricultural incomes and productive employment opportunities in India, it is also as a result, a key ingredient in ensuring sustainable poverty reduction. Notwithstanding the efforts made, over the years, atthe private sector, through differentprogrammer, about 40% of the Habitations in the industry are still notconnected by All-weather roads.
PROJECT OBJECTIVES
The PROJECT SCHME will permit the Up gradation (to prescribed standards) of the existing roads in those Districts where all the eligible Habitations of the designated population size have been provided all-weather road connectivity. However, it must be noted thatUpgradationis not central to the Programmed and cannot exceed 20% of the State’s allocation as long as eligible Unconnected Habitations in the State still exist. InUpgradation works, priority should be given to Through Routes of the Rural Core Network, which carry more traffic.
EXECUTION OF WORK
The relevant projects would be executed by the PIUs and completed within a period of 18 months from the date of issue of the Work order. A Work Programmed shall be obtained from the contractor for each work and approved by the PIU. Payment shall be made only after the approval of the work programmed, deployment by the Contractor of the requisite number of engineers and setting up of the Quality Control Laboratory at site. In this connection, it is clarified that:
i. The period of 18 months shall comprise 18 working months. In case the period for execution is likely to be adversely affected by monsoon or other seasonal factors, the time period for execution may be suitably determined while approving the work programmed.
ii. In respect of Hill States where the work may be executed in two stages, the above will apply separately in respect of each stage.
iii. Time period provided in the Notice Inviting Tender (NIT) and the Work Program me shall be strictly enforced. Since time is the essence of the contract, action must be taken against the contractor in cases of delay, as per the contract provisions.
DETAILS OF THE TRAINING SITE
Currently, the road construction work is in 3rd phase, each phase has got certain duration which is decided by the JSW ISPAT STEEL PVT. LTD . If the work is not completed in the scheduled time then some deduction is made in the payment of the bills to the Contractors. Still there are some places were the work is running in its 2ndor 3rd phase.
Regarding the duration of this project , this scheme was started by JSW ISPAT and was one of the six components of the logistic road. There are some industry in which this scheme has been running in a very smooth manner and are in 13thPhase.
It’sa high Priority projectinside the plant premises’ . And has plans to invest huge amount s and resources to accomplish the dream of well equipped rural Infrastructure in the coming years. We have included in this report various government statistical data in order to provide a clear picture of the work done in Roads. These data’s contains the basic standards of the road construction and bridges, geometrical designs, grade of local materials, suitable constructionconditions , and the engineers at work as far as Nagpurensures that these basic guidelines are followed in order to provide quality work.
I did mytraining under the Supervisionof KC INFRASTRUCTURES & CONSTRUCTION PVT. LTD., the Managing Director of the Firm Mr.AJAY KUSHWAHA is a very experienced and recognised personality in the field of civil engineering. He shared the intricacies of road construction with our team and also discussed the challenges involved in construction works varying from that of extremism and Irregular funding by the government.
TECHNICAL DETAILS OF THE SITE
SOIL SURVEY
For the construction and maintenance of low cost rural roads catering to relatively low volumes of traffic, local soil is not only the cheapest but also the highly versatile road material which can be used directly or after suitable processing or by modification or stabilisation by additives. It is, therefore, necessary that the needed field and laboratory investigations are carried out to scientifically evaluate the engineering properties of the various types of soils encountered adjacent to the centreline of the alignment. These investigations are needed for the evaluation of the strength of sub grade soil(s) for pavement design and to determine the type of processing that may be necessary for its use in a pavement layer. It is to be recognised that the procedures for both the field and laboratory investigations should be simple enough as would be practicable within the available resources and skills in rural areas.
FIELD INVESTIGATION DETAILS
In order to evaluate the types of sub grade soils, field investigations should be carried out along the alignment so as to collect representative soil samples wherever there is a visible change in the soil type. Even if the same soil type continues, at least 2 representative samples should be collected from each kilometre length of road alignment.
In its simplest form, the method of collecting soil samples consists in digging a pit about 1mx1mx1m. Within this pit, it should be possible to determine the depth of topsoil and the soil type(s) underneath. Generally, it is possible to get acceptable quality of soils within about 0.6m depth below the ground level, which can be used in the sub grade and even in sub base/base courses. It is necessary to collect representative soil samples for the different soil strata as visible from the test pit. Ordinarily, the depth of the pit should not be more than 1m and must not exceed 1.5m since the depth of borrow pits normally would be limited to 1.5m. It is often expedient to use a post hole/helical auger with or without the digging of pit to a certain depth. It must be ensured that the samples collected are representative of soils to be evaluated. Samples of adequate size (2 to 5kg for gradation and plasticity tests; 20kg where detailed strength tests like CBR are to be carried out). All samples should be collected in sample bags on which the location, depth of strata etc should be tagged.
VISUAL CHARACTERISTICS OF SOIL
In order to identify the broad soil types in the field without any laboratory testing, a visual classification is recommended. The following are the categories of soils visually categorized.
Gravels: These are course materials with particle size over 2.36 mm. These may have little or no fines contributing to cohesion of the material.
Murrums:These are distinctly different materials from gravels and are products of decomposition and weathering of the parent rock. The properties of these materials naturally depend on the parent rock and the process of weathering and decomposition. Visually they look like gravels except for the difference that the percent fines is relatively much higher.
Sands : These vary in texture from course to fine but exhibit no cohesion. They allow water to permeate readily through them.
Silts:These are finer than sands in texture; lighter in color compared to clays and exhibit little cohesion. Dilatency is a specific property of silts. When a lump of silty soil mixed with water is alternatively squeezed and tapped, a shiny surface makes its appearance.
Clays : These are finer than silts and are the ultimate product of weathering and decomposition of parent rock. Clay and clayey soils exhibit stickiness, high strength when dry and show no militancy. Black cotton soils and other expansive types of clays exhibit swelling and shrinkage and are characterized by a typical shrinkage pattern. A paste of clay with water when rubbed in between fingers leaves a stain which is not observed for silts.
Dry Strength (Crushing characteristics):
After removing particles larger than 380 mm sieve size, mould a part of soil to the consistency of putty, adding water if necessary. Allow the pat to dry completely by oven, sun or air drying, and then test its strength by breaking and crumbling between the fingers. This strength is a measure of the character and quantity of the colloidal fraction contained in the soil. The dry strength increases with increasing plasticity.
Toughness (Consistency near plastic limit):
After removing particles larger than the 380m m sieve size, a specimen of soil about 12mm cube in size, is moulded to the consistency of putty. If too dry, water must be added and if sticky, the specimen should be spread out in a thin layer and allowed to lose some moisture by evaporation. Then the specimen is rolled out by hand on a smooth surface or between the palms into a thread about 3mm in diameter. The thread is then folded and re-rolled repeatedly. During this manipulation the moisture content is gradually reduced and the specimen stiffens, finally loses its plasticity, and crumbles when the plastic limit is reached.
MATERIAL TESTING
The samples of locally available low grade materials should be subjected to the following laboratory tests:
i. Sieve Analysis (Particle Size Distribution).
ii. Plasticity Index.
iii. Proctor Compaction.
iv. CBR.
v. Aggregate Impact Value.
vi. Deleterious Material: In areas infested with harmful salts and containing organic matter, special tests to determine their approximate content need to be carried out, in addition to the above tests.
Proctor
This test is conducted to determine the achievable density in the field and the optimum moisture required for compaction. It is conducted in a standard Proctor apparatus. The soil sample (passing through 20 mm) is compacted in three layers giving 25 blows on each by a standard rammer (weight 2.5 kg, fall 30 cm) at five different moisture contents. From the plot between moisture content and dry density (Fig. 6), the optimum moisture content and maximum dry density are determined.
It may be pointed out here that for rural road works, the Standard Proctor Compaction (light compaction) test is relevant (as per IS : 2720 Part 7) and there is no need to go in for Modified AASHTO or heavy compaction test as per IS : 2720 Part 8, which is recommended for heavily trafficked/ highway works.
CBR
CBR as a parameter is extensively used for the design of flexible pavements in India. The test is carried out on a sample compacted at optimum moisture content to maximum dry density and soaked for 4 days. In case of stabilised soil specimen (with lime/cement), the specimen is cured for 7 days prior to 4 day soaking. The CBR of the specimen is computed from the load needed for 2.5 mm/ 5 mm penetration of a standard plunger determined from the graph between penetration and load. If required, the zero correction is applied for penetration while computing the load for 2.5 mm/ 5mm penetration.
Aggregate Impact Value
The test is done on the coarse fraction in soil-gravel or on stone and soft aggregates. The crushing produced in an AIV test apparatus by a rammer (13.5 kg) when it falls 15 times through 375 mm on the sample (Passing 12.5 mm and retained on 10 mm ISS) is determined by sieving the sample through 2.36 mm IS Sieve. The AIV of sample is expressed as percentage of the material passing through 2.36 mm IS Sieve to the weight of sample taken. A rough estimate of AIV can also be made from the moisture absorption by aggregates in 66 hrs.
GUIDELINESFOR THE USE OF LOCAL MATERIALS ON THE SITE:
1. Use of Better Granular Soil
Well-graded soils with low plasticity index values have better engineering properties and should be reserved for use as improved sub grade/ sub-base or surfacing in the case of earth roads. Such soils can be identified by their high Proctor density and low PI values.
2. Stabilization of Local Soils
A variety of techniques are available for stabilizing local soils for improving their engineering properties, but not all the techniques are applicable to all types of soils. A brief description of the stabilization mechanism and applicability of the individual techniques are given in Table 1. This may be referred to for choosing the most appropriate technique for stabilizing the soil at site. The mix proportions are generally worked out in the laboratory based on soaked CBR value.
3. Use of Naturally Occurring Low-grade Marginal Materials
Low grade marginal materials like Moorums, kankar, dandle, laterite etc where available within economic leads, should be made use of in pavement construction to the maximum extent feasible. The material may occur in a graded form or as discrete blocks or admixture with soil. The manner of using these is indicated in Table 2.
4. Use of Bricks and Overburnt Brick Metal
In alluvial plains where hard stone aggregates are normally not available within economical leads, the general specification adopted for sub-base and base courses is to provide brick soling. Either flat bricks or bricks on edge or broken brick ballast can be used depending on the thickness requirements. The bricks should be of good quality and well burnt. Before laying flat bricks or brick-on-edge, it is desirable to provide a cushion of sand above the earth subgrade.
Table 1
Mechanism and Requirements of Soil Stabilisation Techniques
Sl. No. Technique Mechanism Application
1. Mechanical stabilisation Blending missing fractions (e.g., clay with sand and sand with clay) so as to produce a mass of maximum possible density with plasticity within limits. A smooth grading similar to that given by Fuller’s grading rule is adopted to work out the proportion of the missing fractions to be blended. Sands, moorum/ gravel having missing fractions and clayey soils can be stabilised by this technique.
2. Lime stabilisation Lime in hydrated form reacts with the clay minerals in the soil to cause (i) immediate reduction in plasticity and increase in CBR because of cationic exchange, flocculation and agglomeration, which may be reversible under certain conditions, and (ii) long term chemical reaction with the clay minerals to produce cementations products which bind the soil for increased strength and stability. Medium and heavy clays having a PI of at least 10 and containing at least 15% of materials finer than 425 micron are suitable. However, some soils though containing clay fractions may not produce the long-term chemical reaction because of the presence of organic matter (> 2%), or soluble sulphate/carbonate (> 0.2%) etc. For lime stabilisation to be successful, it will be desirable to test the soil for lime reactivity. A soil whose 7-day unconfined compression strength increases by at least 3 kg/cm2 with lime treatment can be considered lime reactive.
3. Cement stabilisation The hydrated products of cement binds the soil particles, the strength developed depending on the concentration of cement and the intimacy with which the soil particles are mixed with cement. A high cement content of the order of 7-10% can produce a hard mass having a 7-day compressive strength of 20 kg/cm2 or more, and this usually goes by the term soil-cement. However, a smaller proportion of 2-3% cement can improve the CBR value to more than 25, and the material going by the term “cement-modified soil” can be advantageously used as sub-base/base for rural roads. Generally, granular soils free of high concentration of organic matter (<% or deleterious salts (sulphate and carbonate
<0.2%) are suitable. A useful rule for soil selection is that the plasticity modulus (product of PI and fraction passing 425 micron sieve) should be less than 250 and that the uniformity coefficient should be greater than 5.
4. Lime-flyash stabilisation Lime chemically reacts with the silica and aluminium in flyash to form cementations compounds, which bind the soil. Soils of medium plasticity (PI 5-20) and clayey soils not reactive to lime can be stabilised with lime and flyash.
5. Bitumen stabilisation Bitumen binds the soil particles. Clean graded sands can be stabilised by this technique.
6. Two-stage stabilisation This generally applies to heavy clays. The clay is treated with lime in the first stage to reduce plasticity and to facilitate pulverisation. In the second stage, the resulting soil is stabilised with cement, bitumen, lime or lime-flyash. Heavy clays.
Table 2
Manner of Using Soft Aggregates in Pavement Construction
Sl. No. State of Occurrence of Material Manner of using in pavement Construction Test/ Quality Requirements
1. In block or large discrete particles As water bound macadam without screenings/ filler in accordance with IRC : 19, after breaking the material into required sizes. Wet aggregate impact value (IS : 5640) not to exceed 50, 40 and 30 when used in sub-base, base and surfacing respectively.
2. Graded form without appreciable amount of soil Directly as a granular layer for sub-base/ base or surfacing. PI should be 4-9 when used as surfacing and should not exceed 6 when used in lower courses. Evaluated for strength by soaked CBR.
3. As discrete particles mixed with appreciable amount of soil such as soil-gravel mixtures. Directly as soil-gravel mix for sub-base, base or surfacing. The material should be well graded and the PI restricted as for Sl. No. 2. Evaluated by soaked CBR.
Notes on Improving the engineering properties:
(i) Improving gradation – Sieving out sizes not required and blending with missing fractions.
(ii) Reducing plasticity – Stabilisation with lime
(iii) Improving strength – Materials with appreciable soil fraction can be stabilised with lime (where PI is high), lime-flyash or cement.
Water Bound Macadam
Water Bound Macadam (WBM) is one of the most common specifications being adopted for construction of sub-base, base and surfacing courses. Broken stone, crushed slag, over burnt brick metal, laterite or kanakr of acceptable quality can be used as the coarse aggregate for WBM.
Low Cost Alternative Specifications
India is a vast country with divergent environmental conditions in different areas ranging from mountainous terrain to plain terrain and from deserts to coastal and water logged areas. Also there exists a wide range in the subgrade soil types, rainfall, traffic patterns and availability of various construction materials. Since specifications for rural road construction depend on the type of terrain and other environmental conditions, certain low-cost alternative specifications maximizing the use of local materials have been tried out on full scale on a large number of low volume roads for different sets of conditions as under:
• Plain Areas : Indo-Gangetic Plains
• Black Cotton Soil Areas
• High Rainfall Areas
• Water Logged Areas
• Hilly Areas
• Desert Areas
Long-term performance of each of the test tracks made in the above sets of conditions were evaluated and successful alternatives worked out. The various low-cost alternatives are given in Figures in Annexure 4.5 In general, 20 to 40% savings can be effected by the adoption of these low cost techniques.
Use of Waste Materials
There is a variety of waste materials which, if available close to the construction site of a rural road project, can be utilized to advantage. The various waste materials that can be incorporated in rural road works are :Flyash
in road embankments
in lime-flyashstabilized soil and in lime-flyash bound macadam
• Iron and Steel Slag
in lieu of stone aggregates in WBM
• Rice Husk Ash
in lime-rice husk ash concrete
• Recycled Concrete Aggregates
in cement concrete
in water-bound macadam (WBM)
• Other Waste Materials like quarry waste etc.
Flyash
(a) In road embankments :
A matter of environmental concern is the contamination of ground water due to heavy metal leaching which can best be prevented by providing an earth cover. The thickness of earth cover on the side slope should be in the range of 1 to 3m, depending on the height; the earth cover for embankments upto 3m height will be about 1m, which should be increased in flood-prone areas. Typical cross-sections of embankments with alternate layers of flyash and with core of flyash are given in the Rural Roads Manual. The soil cover should be considered as a part of the composite embankment for purposes of stability analysis. It must be recognized that the engineering properties of flyash being highly variable, proper testing will be necessary while dealing with any particular flyash. Typical geotechnical properties of flyash are given in the Rural Roads Manual.
The PI of soil cover should be around 5-9. In salt infested areas, chemical testing of soil will be necessary. The subgrade/ earthen shoulder material should have minimum compacted dry density of 1.75 gm/cc when tested according to IS-2720 (Part 8).
(b) In Lime-FlyashStabilised Soil
Use :In Sub-base/ Base courses
Lime-flyashstabilised layer can be used, without admixing soil.
Fly-ash :Fly-ash may be either from anthracitic coal or lignitic coal. Flyasn to be used in lime fly ash stabilisation shall conform to the requirements set forth in the Rural Roads Manual.
Lime : Should be quick lime. If pre-slaked at site, it should be used within 7 days.
Slaked Lime in airtight bags can be stored for about 3 months.
Generally, purity (by weight of CaO) should not be less than 70%.
For lower purity lime, the quantity can be proportionately increased.
Soil : Granular soils free from high concentration of organic matter or deleterious salts and sandy soils with fine silts are better suited. Normally, soils with PI 4 to 20 are suitable; proportion of particles finer than 425 micron : 15 to 25%.
Mix Properties :Should meet the following requirements:
• Provide adequate strength and durability
• Easily placed and compacted.
• Economy
Lime-flyash alone can be used, avoiding soil.
Mix proportions are designed to obtain minimum unconfined compressive strength of 1.5 MPa after 28 days curing
Ideally, lime and flyash should be mixed by weigh batching but volume batching can also be used.
Mix-in-place techniques are more economical
Soil pulverization requirements:
ISS Percent Passing
26.5 mm 100
5.6 mm 80
Mixing can be done by a Rotavator.
Temperature during construction should not be less than 10C in shade. OMC+2% is specified to compensate for loss of moisture during spreading.Not more than 60 minutes should elapse between start of moist mixing and start of compaction process. Compaction should be completed within 3 hours of mixing.
Curing : Spread moist straw or sand and sprinkle water periodically for 7 days and lay subsequent layers to prevent drying out. Alternatively, spray a cutback or emulsion @ 0.7 to 1.4 litres/m2 within 30 minutes of completion of finishing operations.
At the end of day’s work, a transverse construction joint for full depth should be made by chamfering at 30 angle.
© In Lime-Flyash Bound Macadam (LFBM)
• Coarse Aggregates : As per requirements of normal WBM
• Screenings : As per requirements of normal WBM
• Filler : A mixture of flyash, lime and moorum or sand or soil. Typical proportions of dry lime, flyash and moorum or sand or soil are :
1 : 2 : 9
Lime Flyash Moorum or sand or soil
• Provide lateral confinement by constructing shoulders in advance corresponding to compacted thickness of LFBM.
• Apply screenings as in normal WBM
• After coarse aggregates have been rolled and screenings applied, apply filler. The filler should be prepared by proper blending of lime, fly ash and sand or moorum or soil in suitable proportions. The required amount of filler material is spread uniformly over the stone metal surface. Enough quantity of water is then added while rolling so that the slurry penetrates into the voids taking care that the water used is not as profuse as in normal WBM.
• Setting and Drying : Cured for 7 days (moist). Hungry spots to be filled with screenings or binding material, lightly sprinkled with water and rolled. Only light motor vehicles could be allowed during curing. If bituminous surfacing is to be laid over the LFBM, it should be laid only after LFBM is completely dried.
5. Use of iron and steel slags in road works
Air cooled blast furnace slag and weathered steel slag can be used in place of stone aggregates to construct WBM layers and for mechanical stabilization. Granulated blast furnace slag (GBFS), which is a Pozzolanic material, can be stabilized using lime and used for construction of stabilized layers and lime-GBFS concrete base/ sub-base. Addition of a small quantity of gypsum enhances strength. GBFS can also be used in place of granular sub-base provided it meets CBR requirements. Typical characteristics of iron and steel slags are given in the Rural Roads Manual.
6. Lime-Rice Husk Ash Concrete
Rice husk is available as a waste material from rice mills where paddy is processed to obtain rice. Rice cultivation is carried out almost throughout India and rice husk is mostly burnt as a fuel. The ash obtained is thrown back to paddy fields. This ash is chemically similar to fly ash and possesses good binding characteristics in conjunction with lime and moisture. It is a Pozzolanic binder. CRRI has carried out extensive laboratory work to investigate the binder properties of lime-rice ash mixes and has recommended its use for lime rice husk ash concrete (Lime-RHA-concrete). The Lime – RHA - Concrete may be used as a sub-base / base course material in the mix proportions 1 : 2 : 9 (Lime : RHA : Sand + Coarse aggregate). If a little percentage (2 to 6 per cent) of gypsum is added the strength properties are greatly enhanced. The RHA is available freely at site in rural India and no haulage cost is involved.
7. Recycled Concrete Aggregate
Our country has a network of concrete roads built many decades ago and due to increase in traffic and axle loads, the pavements have badly cracked. The rehabilitation and maintenance is costly and time consuming. In certain areas where high quality natural aggregates are scarce, recycled concrete aggregates offer an excellent and economic opportunity. Studies on the use of recycled aggregate (properly graded and having strength greater than the concrete in which it is to be used) in cement concrete and in water bound macadam stone metal show that recycled aggregates with suitable modifications can be used again as a road pavement material in base/ sub-base and wearing courses of road pavement in place of natural aggregate for low volume roads.
8. Other Waste Materials
Many other waste materials like processed municipal waste, quarry waste, marble slurry dust, other metallic slags are available in many parts of the country. Laboratory and field studies conducted on some of these materials have indicated that such materials can be utilised for construction of lower layers of pavement and/ or embankment. However, before embarking on use of such materials, detailed characterization and design of mix through a reputed laboratory would be needed.
9. Use of Stone Aggregates
9.1 General
Stone aggregates have traditionally been used in the sub-base, base and surface courses of road pavements in India. These aggregates have to bear the stresses imposed by wheel loads on the pavement structure, and therefore should possess the following properties:
resistance to crushing
resistance to abrasive action of traffic
resistance to impact by traffic
withstand the adverse action of weather
desirable shape (cubical), permitting only very limited proportion of the undesirable flaky and elongated particles
adhesion to bitumen in the presence of water
For evaluating all of the above properties, elaborate testing facilities are needed, all of which may not always be readily available for rural road works. Based on past experience, only a few simple tests have been identified, for which, if the specified requirements are fulfilled, will ensure a satisfactory long-term performance of the aggregates. The suitability in broad terms of the aggregates obtained from different types of rocks available in different parts of the country is indicated in the IRC Rural Roads Manual. Since stone aggregates are mostly used in WBM sub-base, base and surface courses and in the bituminous surface treatments, the required proportions of stone aggregates for these types of construction only are given in subsequent paragraphs.
9.2 Stone Aggregates in WBM/ Soil-Aggregate Construction
(a) Physical Requirements
For rural road works, the physical requirements for stone aggregates need to be laid down separately for use in wearing and base courses as also in sub-base courses (WBM is generally not recommended for sub-base courses, wherein soil-aggregate mixes can be used to advantage).
• It is considered enough to evaluable the strength of stone aggregate through an AIV (Aggregate Impact Value) Test, as shown in Fig. 4.5.6 in section 4.5. The crushing produced in an AIV apparatus (which does not require any electric connection for operation) by a standard 13.5 kg rammer when it falls 15 times through 375 mm on the sample (passing 12.5 mm and retained on 10 mm ISS) is determined by sieving the sample through 2.36 mm ISS). It may be mentioned here that an estimate of AIV can also be made by a still simpler test of water absorption (water absorbed by aggregates in 66 hours). The requirements of AIV and water absorption are given below:
Use AIV less than : Water Absorption less than :
Wearing Course 30% 1.5%
Base Course 40% 3.0%
Subbase Course 50% 6.0%
• Although the proportion of flaky and elongated shapes (see Fig. 1) of aggregates should be limited, it is considered sufficient for rural road works to restrict the proportion of only flaky shaped aggregates, the flaky shaped aggregates being relatively more objectionable than the elongated ones. The requirements of Flakiness Index Value (using the standard Flakiness Gauge, Fig. 2) are given below:
Use Flakiness Index not to exceed :
Wearing/ Base Course 30%
Subbase Course 40%
(b) Grading Requirements
For determining the particle size distribution, a standard set of IS sieves is used (Fig. 3). The grading requirements of coarse aggregates are given in Table 3 while the grading requirements for screenings are given in Table 4. The grading requirements for soil-aggregates mixes are given in Annexure 4.2. The approximate quantities of coarse aggregates and screenings required for 100/75 mm compacted thickness of WBM for 10m2 areas are given in Table 5.
• Where crushed slag is used, its unit weight should not be less than 11.2 kN per m3 and the percentage of glossy material not more than 20%. The sulphur content should not be more than 2% and the chemical stability should comply with the requirements of the appendix to BS 1047.
• Where relatively softer aggregates like brick jhana, kankaretc are used, the AIV must be determined in the wet state as per IS : 5640.
• In case any bituminous treatment is not going to be taken up soon after application of creenings, a Binding/ filler material having a Plasticity Index (PI) less than 6 may be provided, for preventing ravelling. The quantity of binding material will depend on the type of screenings. Generally the quality of required for 75 mm compacted thickness of WBM will be 0.06-0.09 m310m2 and 0.08-0.10m3/m2 for 100 mm compacted thickness.
Hand-broken stone aggregates generally yield relatively more cubical shaped aggregates and therefore are preferred in WBM construction.
Table 3
Grading Requirement Of Coarse Aggregate
Grading No. Size Range IS Sieve Designation Percent by weight passing
1 90 mm to 45 mm 125 mm 100
90 mm 90-100
63 mm 25-60
45 mm 0-15
22.4 mm 0-5
2 63 mm to 45 mm 90 mm 100
63 mm 90-100
53 mm 25-75
45 mm 0-15
22.4 mm 0-5
3 53 mm to 22.4 mm 63 mm 100
53 mm 95-100
45 mm 65-90
22.4 mm 0-10
11.2 0-5
Grading Classification Size of Screenings IS Sieve Designation Percent by weight passing the IS Sieve
A 13.2 mm 13.2 mm 100
11.2 mm 95-100
5.6 mm 15-35
180 micron 0-10
B 11.2 mm 11.2 mm 100
5.6 mm 90-100
180 micron 15-35
SCREENING OF THE AGGREGATE
Classification Size Range Compacted thickness Loose Quantity Screenings
Stone Screening Crushable type such as Moorum or Gravel
Grading classification & Size For WBM Sub-base/ base course (Loose quantity) Grading classification & Size Loose Quantity
Grading 1 90 mm to
45 mm 100 mm 1.21 to
1.43 m3 Type A
13.2 mm 0.27 to
0.30 m3 Not uniform 0.30 to
0.32 m3
Grading 2 63 mm to
45 mm 75 mm 0.91 to
1.07 m3 Type A
13.2 mm 0.12 to
0.15 m3 Not uniform 0.22 to 0.24 m3
Grading 3 53 mm to
22.4 mm 75 mm 0.91 to
1.07 m3 Type B
11.2 mm 0.18 to
0.21 m3 Not uniform 0.22 to 0.24 m3
Approximate Quantities of Coarse Aggregates and Screenings required for 100/75 mm Compacted Thickness of Water Bound Macadam (WBM) Sub-base/ Base Courses for 10m2 Area .
9.3 Stone Aggregates in Bituminous Surface Treatments
(a) Physical Requirements
For each of the two types of thin bituminous surface treatments recommended for rural roads viz premix carpet and one or two coat surface dressing, it is considered sufficient to evaluate the AIV. The AIV must be restricted to a maximum of 30%. As regards shape, only the proportion of flaky particles needs to be restricted, recommending a Flakiness Index (using a Standard Flakiness Gauge) of 30%. The water absorption of the aggregates must also be restricted to 1.5%. In addition to the strength and shape tests, two more tests need to be carried out for bituminous surface treatment works viz Soundness test for evaluating the durability of aggregates and the Coating and Stripping of Bitumen Aggregate mixtures to ensure that the bitumen will not strip off the aggregates in the presence of water. In the Soundness Test, carried out as per the IS 2386 Part 3, the loss in weight must not exceed 12% when sodium sulphate solution is used and must not exceed 18% when magnesium sulphate solution is used. In the standard Bitumen Stripping Test, carried out as per IS : 6241, the extent of stripping must not be over 15%. The Water Sensitivity Test as recommended for highway works is not considered necessary for rural road works. Similarly Polished Stone Value (PSV) test is not considered necessary for rural road works.
(b) Grading Requirements
It is to be recognized that the MoRT&H specifications for Surface Dressing are basically formulated for highly trafficked highways where the sprayed bitumen can work up under the traffic to coat the cover aggregates with bitumen. For the low volume roads in rural areas the stone chipping sizes have to be selected judiciously, as laid down in Table 6. The grading requirements for various nominal sizes are given at Table 7. On the basis of extensive R&D work done abroad notably in UK & Australia on the most appropriate rates of spread of bituminous binder for surface dressing, detailed methodology is outlined in Annexure 4.2. Adopting the methodology outlined in Annexure 4.2, surface dressing may be considered both suitable and economical for Indian conditions.
In regard to the open-graded premix surfacing, no grading requirements have been specified in the MORT&H Specifications. However, the quantities of materials required for 10m2 of road surface for 20 mm premix are given in Table 8 using penetration grade bitumen and Tables 9 and 10 when bituminous emulsion is used as a binder. It may be pointed out that cost estimates show that a two-coat surface dressing is very significantly cheaper than a 20 mm open-graded premix.
Table 6
Recommended Nominal Sizes of Stone Chipping (Millimeters)
Type of Surface Approximate number of commercial vehicles with an unladon weight greater than 1.5 tonnes currently carried per day in the lane under consideration
2000-4000 1000-2000 200-1000 20-200 Less than 20
Very Hard 10 10 6 6 6
Hard 13 13 10 6 6
Normal 19+ 13 10 10 6
Soft * 19+ 13 13 10
Very Soft * * 19 13 10
Note : The size of stone chippings is related to the mid-point of each lane traffic category. Light traffic conditions may make the next smaller size of stone more appropriate.
+ Very particular care should be taken when using 19 mm chippings to ensure that no loose materials remain on the surface when the road is opened to unrestricted traffic as there is a high risk of windscreen breakage.
* Unsuitable for surface dressing
Table 7
Grading Requirements for Chips for Surface Dressing
IS Sieve Designation (mm) Cumulative percent by weight of total aggregate passing for the following nominal sizes (mm)
19 13 10 6
26.5 100 – – –
19.0 85-100 100 – –
13.2 0-40 85-100 100 –
9.5 0-7 0-40 85-100 100
6.3 – 0-7 0-35 85-100
4.75 – – 0-10 –
3.35 – – – 0-35
2.36 0-2 0-2 0-2 0-10
0.60 – – – 0-2
0.075 0-1.5 0-1.5 0-1.5 0-1.5
Minimum 65% by weight of aggregate Passing 19mm, retained 13.2mm Passing 13.2mm, retained 9.5mm Passing 9.5mm, retained 6.3mm Passing 6.3mm, retained 3.35mm
Table 8
Quantities of Materials Required for 10 m2 of Road Surface for 20 mm thick
open-graded Premix Surfacing using Penetration Bitumen for Cutback
Aggregate
(a) Nominal stone size 13.2 mm (passing 22.4 mm sieve and retained on 11.2 mm sieve) 0.18 m3
(b) Nominal stone size 11.2 mm (passing 13.2 mm sieve and retained on 5.6 mm sieve) 0.09 m3
Total 0.27 m3
Binder (quantities in terms of straight run bitumen)
(a) For 0.18 m3 of 13.2 mm nominal size stone at 52 kg bitumen per m3 9.5 kg
(b) For 0.09 m3 of 11.2 mm nominal size stone at 56 kg bitumen per m3 5.1 kg
Total 14.6 kg
Table 9
Quantities of Aggregate for 10 m2 Area
(A) Premix Carpet
(a) Coarse aggregate nominal 13.2 mm size; passing IS 22.4 mm sieve and retained on IS 11.2 mm sieve 0.18 m3
(b) Coarse aggregate nominal 11.2 mm size; passing IS 13.2 mm sieve and retained on IS 5.6 mm sieve 0.09 m3
(B) For Seal Coat
Type A : 6.7 mm size (Passing 11.2 mm and retained on 2.36 mm 0.09 m3
Type B : Passing 2.36 mm size and retained on 180 mm) 0.06 m3
Table 10
Quantities of Emulsion Binder
(A) For Premix Carpet : 20 to 23 kg
(B) For Seal Coat :
(a) for liquid seal coat (Type A) 12 to 14 g
(b) for premix coat (Type B) 10 to 12 kg
Terrain classification
Terrain classification Cross slope of the country
Plain 0-10% More than 1-10
Rolling 10-25% 1 in 10 to1 in 4
Mountainous 25-60% 1 in 4 to1 in 1.67
Steep Greater than 60% Less than1 in 1.67
Design speed for rural roads.
Design speed (km/hr)
Plain Rolling Mountainous Steep
50 40 40 35 25 20 25 20
Rural land width for Rural roads
Plain and rolling terrain Mountainous and steep terrain
Open area Built-up area Open area Built-up area
Normal Range Normal Range Normal Exceptional Normal Exceptional
15 15-25 15 15-20 12 12 12 9
The lower value of land width may be adopted where the traffic intensity is less than 100 vehicles per day and the traffic is not likely to increase due to situation like dead end, low habitation and difficult terrain conditions.
Building and control lines for rural roads
Plain and rolling terrain Mountainous and steep terrain
Open area Built-up area Open area Built-up area
Overall width between buildings lines M Overall width between control lines (m) Overall width b/w buildings line & road boundary(set-back)(m) Overall width b/w buildings line & road boundary(set-back)(m)
25/30* 35 3-5 3-5
If the land width is equal to the width b/w building line. The building lines should be set back by 2-5m from the road land boundary.
Road way width and carriage way width for rural roads.
Terrain classification Road way width (m) carriage way width (m)
Plain & rolling 7.5 3.75
Maintenance and steep 6.0 3.75
• Where the traffic intensity is less than 100 motor per day, and where the traffic is not likely to increase due to situation like dead end, low habitation and difficult terrain condition, the road width may be reduced to 6m in case of plain and rolling and carriage way width may be restricted to 3m.
• The road way width for the mountainous and steep terrain is including of parapet.
• On the horizontal curve, the road way should be increase. Corresponding to the extra width of the carriage way for curvature.
Side slope for rural roads.
Condition Slope(H:V)
Embankment in silty/sand/gravelly soil 2:1
Embankment in clay/clayey/silt or inundated condition 2 2/5: 1 to 3:1
Cutting in silty/sandy/gravelly soil 1:1 to 0.5:1
Cutting in disintegrated rock or conglomerate 0.5:1 to 0.25:1
Cutting in soft rock like shale 0.25:1 to 1/16:1
Cutting in medium rock like sand stone 1/12:1 to 1/16:1
Cutting in hard rock like quartzite,granite Near vertical
Plain terrain Rolling terrain Mountainous terrain Steep terrain
Area not affected by snow Area affected by snow Area not affected by snow Area affected by snow
Ruling min. Absolute min. Ruling min. Absolute min. Ruling min. Absolute min. Ruling min. Absolute min. Ruling min. Absolute min. Ruling min. Absolute min.
90 60 60 45 20 14 23 15 20 14 23 15
Super elevation
Super elevation to be provided on curve is calculated from the following :
e ≤ v3/225R
Where, e = super elevation in meter/meter
V = design speed in km/h
R = radius of the curve in meter
Super elevation obtained from the above expression should, be kept limited to the values:
Plain and rolling terrain / snow bound area 7%
Hilly area but not snow bound 10%
Minimum Radii of Horizontal Curve (m)
Widening at curves
Radius of curve Up to 20 20-60 Above 60
Extra widening for 3.75m wide signal 0.9 0.6 Nil
Gradient
Terrain Ruling gradient Limiting gradient exceptional gradient
Plain and rolling 3.3%
(1 in 30) 5%
(1 in 16.7) 6%
(1 in 14.3)
Mountainous & steep terrain having elevation more than 3000m above MSL 5%
(1 in 20) 6%
(1 in 16.7) 7%
(1 in 14.3)
Steep terrain having elevation more than the MSL 6%
(1 in 16.7) 7%
(1 in 14.3) 8%
(1 in 12.5)
Embankment, E/W in cutting, surface drains, shoulders, sub-grade, GSB, grave/soil-aggregate base and sub base constructions
Methodology and sequence of work
Ensured that a detailed construction methodology is submitted by contractor.
-Mechanical equipment proposed to be used.
-Sequence of various activities and schedule from start to the end of the project.
SETTING OUT
-Establish working benchmark on constructed reference pillars at 250m intervals and also at or near all cross drainage structures writ respect to the reference BM.
-Establish centre line of the carriage way by means of marker pegs and chain age boards set near the road land boundary.
-at 50m intervals for plain and rolling terrains
-at 20m intervals for hilly areas and on curves
-at 10m for sharp curves
-at 5m for hair pin bends
Earth work in cutting
-The sides of the excavated areas should be trimmed to specified slopes and the area contoured to minimize erosions and pounding, allowing natural drainage to take place.
-The cut formation which serves as sub grade should be checked for field density and if found less; the earth shall be loosened to a depth of 500mm and compared in the layers to 100% PD.
-in hilly areas cutting should be done from top to bottom. Rocks should be removed up to the formation level or 500mm below the formation level if unsuitable material are encountered.
-In rocky formation, the surface irregularities shall be corrected with granular base materials the achieve the specified profiles and levels.
-The existing shoulders shall be removed to the full width and upto sub-grade level during widening of existing pavement.
Sub grade constructions
-Ensure that the soil of sub grade is suitable.
-Compact each layer of the material in sub grade at +2% OMC to at least 1005 PD.
-If the difference between the top of the sub grade level and ground level is less than 300mmand ground does not have 100% relative compaction, loses the ground up to a level of 300mm below the sub grade, correct moisture content to =2% OMC and compact in layer to 100% PD.
-if sub grade soils have very low CBR, the same should be improved with lime or cement treatment.
-In conditions very slat concentration is in excess of 0.2%, a capillary cut off of coarse sand should be provided below the sub grade to check the upward movement of moisture from below.
-The size of the coarse material in the soil shall ordinarily not exceed 50mm when placed in sub grade.
Minimum MDD requirement
a. Embankment not subject to flooding MDD
-Ht more than 3mm ≥ 15.2 KN/m3
-Htup to 3m ≥ 14.4 KN/m b. Embankment subject to flooding ≥15.2 KN/m3
c. Sub grade/Shoulder ≥to 16.5 KN/m3
Surface Drains
-Ensure that the road side surface drains are provided strictly according to the drainage plan for the road.
-Excavate to the specified lines, levels and dimensions.
-If excavated material is found suitable, re-use it for embankment or sub grade.
-Integrate the drains to the nearest valley by providing proper gradients.
-In built up areas, ensure that water flow in the drains does not flow over the road surface.
-Provide catch water drains on stable slopes to intercept water from upper reaches.
-Provide safe outlets to natural or artificial water courses.
Shoulder Constructions
-Ensure that material should be used in suitable.
-The shoulder should be constructed in layers matching the thickness of adjoining pavement layer.
-Shoulders should be constructed to specified lines, grades and cross-sections.
-Shoulders shall be compacted to 100% PD.
-The required cross fall should be maintained at all stage of construction. Normally it is 15 more than the camber on main carriage way.
Granular sub-base Construction
-obtain materials from improved and tested sources.
-Remove all vegetation and other extraneous material.
-the materials should be spread in layers not exceeding 100mm and 225mm compacted thickness for static roller and vibratory roller respectively.
-When the sub-base material consists of a combination of material, mixing shall be done mechanically by means of rotator.
-Compaction should be carried out at ±2% OMC. Each layer shall be compacted to 100% PD.
Grading requirement for GSB
IS sieve % of wt passing IS sieve
Grading I Grading II Grading III
75mm 100 - -
53mm - 100 -
26.5mm 55-75 50-80 100
4.75mm 10-30 15-35 25-45
75mm <10 <10 <10
Grade are further classified as under
Well graded gravels-GW-% fines>5%
Poorly graded gravels-GP % fines <5%- not satisfying GW requirement.
Silty gravel GM-% fines >12%-PI < 4
Clayey gravel GM-% fines >12%-Pin > 7
Only the gravel classified as GW & GP may be suitable for use in the base course while GM & GC types are not suitable.
Sand is a coarse grained soil with more than half the courses frictional finer than 4.75mm.
Silt and clay are fine grained soil with half the total material finer than 75micron.
Grading requirements for base course
Sieve size % by mass passing IS sieve grading designation
A B C
53mm 100 - -
37.5 mm 97-100 100 -
26.5 mm - 97-100 100
19 mm 67-81 - 97-100
9.5 mm - 56-70 67-79
4.75 mm 33-47 39-53 47-59
425micron 10-19 12-21 12-21
75 micron 4-8 4-8 4-8
Construction of base course
Water bound macadam
The surface to receive WBM course should be prepared to the lines, grades and cross fall. It should be made free of dust and extraneous material.
Where the WBM is laid over a fined grained soil sub grade, it is advisable to lay a 100mm thick intervening layer of screenings or course sand.
Any existing bituminous surface over which WBM is to laid shall be completely removed.
The spreading of course aggregate shall be done from stock piles along the roadway or directly from vehicles. In no case the aggregate shall be dumped in heaps directly on the surface prepared to receive the aggregate nor shall hauling over compacted or partially compacted base be permitted.
The course aggregate shall be prepared uniformly on the prepared surface to proper profile in such quantities that would give the required thickness.
The surface should be checked with template and all high or low spots remedied.
Roll the surface with suitable road rollers till aggregates are partially compacted with sufficient void space left for application of screenings.
Rolling shall proceed from inner edge to outer edge at the super elevated portion and from the edges towards the centre in other portion. The edge should be first completed with the roller running forward and backward.
Check the profile transversely and longitudinally with templates/straight edges, correct the irregularities by loosening the surface, adding or removing the needed amount of aggregate and re-rolling until the entire surface conform to the specified camber/cross fall and grade.
Apply screening to complete it fill the interstices maintaining a slow and uniform rate, in three or more applications. The screenings should not be damp at the time of application.
Compaction check of WBM
This test is conducted to make sure that adequate quantity and composition of material have been used in the construction.
Dig a pit of 0.5m X 0.5m and take out all the WBM material from the pit. One of the test procedures given below can be used.
Test 1:-
Refill the pit with the dug material without compacting. If the pit can be filled by using not more than 65% of the dug material, it is indicative of adequate compacting and use of specified quantity of all material combined together.
Test 2:-
Separate out the portion of WBM materials passing and retained on 13.2mm and 11.2mm size sieve respectively when type A and B screenings are used.
measure the loose volumes of the two portions using cylinders of known volume and compare the combined volume with the combined specified quantities of course aggregates + screenings + binding materials.
Wet mix macadam base
• WMM shall be prepared in an approved mixing plant with mixing arrangements like pug mill or pan type mixer of concrete batching plant.
• OMC shall be determined by sand replacements method after replacing the aggregate fraction retained on 22.4mm sieve with material of 4.75mm to 22.4mm size.
• Lateral confinement of WMM should be provided by laying material in adjoining shoulders along with wet mix layer.
• No segregation of large and fine aggregate shall be allowed.
• After the mix is laid to proper thickness, grade and cross fall/camber the same shall be uniformly compacted to achieve at least 100% MDD.
Crusher run macadam base
The aggregate should be uniformly deposited on the prepared and laterally confined surface and distributed to the specified depth.
Then the material shall be blade mixed to fill depth of the layer by alternatively blading the entire layer to the centre and back to the layer of the road.
Water should be applied before and during blading, spreading and construction.
The thickness of the single compacted layer should not be more than 100mm with smooth wheel roller and 200mm with vibrator roller.
Prime coat over granular base
The granular base surface should be swept clean of dust and loose partials and where require lightly and uniformly sprinkled with water to moist the surface.
The primer should be spread uniformly using suitable bitumen pressure distributer.
A very thin layer of the coarse sand may be applied to the surface of the primer to prevent getting picked up under the wheel of the vehicles.
The surface should be allowed to cure preferably for 24 hours.
Prime coat and tack coat
Slow setting bitumen emulsion is used for prime coat whereas rapid setting bitumen emulsion is used for trace coat.
About 6-9kg’s, 9-12kg’s, & 12-15kg’s of bitumen emulsion for priming is require for 10m2 area of WBM/WMM.
About 2.5 to 3.0 kg of bitumen emulsion is required for 10m2 area of priming WBM surface for tack coat.
The surface on which tack coat is to be applied should be clean, dust free.
20mm thick premix carpet
Prepare the mix in hot mix plant. Mixing temperature of bitumen should be in the range of 1500C to 1630C and that of the aggregate 1550Cto 1630C.
The temperature at the time of the discharge of the mixture should be b/w 130-1600C.
Locate hot mix plant near the worksite.
The premix material should be spread on the road surface with rakes.
Commence rolling with 80-100KN roller beginning from the edge & progressing towards the centre.
On super elevation portion, rolling should progress from lower to upper edge.
Continue rolling operation until a smooth uniform surfaced is achieved
Seal Coat
Apply seal coat immediately after laying the bitumen coarse. The surface should be clean and free from dust.
Types A seal coat with bitumen.
Apply heated bitumen with a temperature of 150C to 163C.
Spread the stone chips immediately over the bitumen.
Commence rolling with 80-100KN as described for PMC.
Types B seal coat with bitumen.
Follow the method described for types A seal coat.
Continue rolling of the mix until the voids in the bituminous surface are completely seated.
Back filling
The back filling soil should be free from boulders, large root’s, clay lumps retaining on 75mm sieve, stone retained on 26.5mm sieve.
Back filling tranches after pipe have been laid and after jointing has hardened. On top of the pipe up to 300mm, thoroughly ram, tamp or vibrate the soil into two layers.
Carryout filling of the trench simultaneously in both side of the pipe, such that unequal pressures do not occur.
When minimum specified cushion can be provided over the pipe, encase the pipe in M 10 concrete of specific thickness.
CONCLUSION
The materials used in construction of embackment are checked according to Indian standards. The CBR test and Impact Value test are carried out on aggregates.
Construction procedure of road embackmentis studied and the culverts are observed properly.
The good control on workmanship should be kept and the proper construction procedure must be followed.
The cross drainage work is properly studied and provided.
The safety measures must be followed during construction of embackment.
please give me ppt on this topic.this ppt is on water bond maccadam road.
i will be thanking for that to you