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Transportation Engineering 1

by Garikapati Rambabu
Type: PracticalInstitute: Sai TIRUMALA NVR ENGINEERING college Course: B.Tech Specialization: Civil EngineeringDownloads: 1Views: 14Uploaded: 2 months agoAdd to Favourite

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Transportation Engineering 1 by Garikapati Rambabu

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Garikapati Rambabu
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Transportation Engineering Lab Manual 1.0 General Aggregates form a major part of the pavement structure and it is one of the primary materials used in pavement construction. Aggregates have to bear load stresses and abrasive action caused by movement of vehicles on the roadways and runways. They should also be water and weather resistant. Aggregate are used in construction of pavement surfaces, be it cement concrete, bituminous concrete or water bound macadam. Aggregate also serve as granular base course layers underneath superior pavements. Thus the properties of the aggregates are of considerable significance to highway engineers. Key Characteristics of Road Aggregates: The Desirable properties of road aggregates, which are generally studied by laboratory testing, are shown in Table 1.1. Table 1.1 Characteristics of road aggregates Property Indicator Strength Crushing Hardness Abrasion Toughness Durability Adhesion with Bitumen Specific Gravity Impact Soundness Flakiness, Elongation and Angularity Number Stripping Density Porosity Water Absorption Shape Factor Tests to determine the properties of aggregates: The tests that are to be performed to know the quality of aggregates for usage in pavement construction are listed below: 1. Aggregate Crushing Value 2. Aggregate Impact Value 3. Los Angeles Abrasion Value 4. Shape Tests (Flakiness Index, Elongation Index and Angularity Number) 5. Benkleman Beam and MERLIN Cycle 6. Gradation of Aggregates, Specific Gravity and Water absorption Standards for Testing of Aggregates: Indian standard codes giving guidelines in the field of aggregate testing are given in Table 1.2. 1
Transportation Engineering Lab Manual Table 1.2 IS codes on aggregate testing S No Name of the Test Test Method 1 Aggregate Crushing Value IS: 2386 – part 4 2 Aggregate Impact Value IS: 2386 – part 4 3 Loss Angels Abrasion Value Test IS: 2386 – part 4 4 Shape Tests (Flakiness Index, Elongation Index) IS: 2386 – part 1 5 Gradation of Aggregate IS: 2386 – Part 1 6 Specific Gravity, Water absorption and Bulk Density for aggregates IS: 2386 – part 3 2
Transportation Engineering Lab Manual Exp No 1: Aggregate Crushing Value Test The strength of coarse aggregates is determined by aggregates crushing test. The aggregate crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load. To achieve a high quality of pavement, aggregate possessing low aggregate crushing value should be preferred. Apparatus The apparatus for the standard aggregate crushing value test consists of the following: 1. Steel cylinder with open ends and internal diameter 15.2 cm, square base plate, plunger having a piston of diameter 15 cm, with a hole provided across the stem of the plunger so that a rod could be inserted for lifting or placing the plunger in the cylinder. 2. Cylindrical measure having internal diameter of 11.5 cm and height 18 cm. 3. Steel tamping rod with one rounded end, having a diameter of 1.6 cm and length 45 to 60 cm. 4. Balance of capacity 3 kg with accuracy upto 1 g and IS sieve of sizes 12.5 mm, 10mm and 2.36 mm for sieving the aggregates. 5. Compression testing machine capable of applying load of 40 tonnes, at a uniform rate of loading of 4 tonne per minute. Procedure 1. The aggregate passing 12.5 mm sieve and retained on 10 mm IS sieve is selected for standard test. The aggregate is dried by heating at a temperature 1000 C to 1100 C for a period of 4 hours, and then is tested after cooling to room temperature. 2. The cylindrical measure is filled by the test sample of aggregate in three layers of approximately equal depth, each layer being tamped 25 times by the rounded end of the tamping rod. 3. The surface of the aggregates is levelled ant the cylindrical measure is weighed. 4. The aggregates are transferred from cylindrical measure to the steel cylinder resting on the base plate in three layers, each layer being subjected to 25 blows and the surface is levelled. 5. On top of the sample in the cylinder, plunger is inserted so that it rests on the surface in level position. Load is applied at a uniform rate of 4 tonnes per minute until the total load is 40 tonnes and then load is released. 3
Transportation Engineering Lab Manual The crushed aggregates are removed from the cylinder and sieved on a 2.36 mm 6. IS sieve and the material which passes through the sieve is weighed. Observations and Calculations Empty weight of cylindrical measure, Wc= g Table 1.3 Observation table for aggregate crushing value test S. No Trail Number Details 1 2 Average Weight of aggregate sample in the 1 cylindrical measure, W1 g (excluding empty wt of cylindrical measure) 2 3 Weight of crushed aggregates after passing through 2.36 mm sieve, W2 g W  Aggregate Crushing Value:  2  100   W1  Result Aggregate crushing value = % (Rounded to the nearest whole number) Specifications Indian Roads Congress (IRC) and BIS have specified that the aggregate crushing value of the coarse aggregates used for base layer should not exceed 45%. For aggregates used in surface courses, the aggregate crushing value shall not exceed 30%. Applications The aggregate crushing value is an indirect measure of crushing strength of aggregates. Low aggregate crushing value indicates strong aggregates, as the crushed fraction is low. The aggregates used for the surface course of pavements should be strong enough to withstand the high stresses due to wheel loads, including the steel tyres of loaded bullockcarts. As the stresses at the base and sub-base courses are low, aggregates with lesser crushing strength can be used in the lower layers of the pavement. 4

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