Aggregate testing lab manual

Thus, road stones should be hard enough to resist the abrasion due to traffic. When fast moving traffic fitted with pneumatic tyres move on the road, the soil particles present between the wheel and road surface causes abrasion on the road stone.

Steel tires of animal drawn vehicles, which rub against the stones, can cause considerable abrasion of the stones on the road surface.

Hence, in order to test the suitability of road stones to resist the abrasion action due to traffic, tests are carried out in the laboratory. Pounding action of these balls also exists while conducting the test. The test is considered more dependable as rubbing and pounding action simulate field conditions. What is Abrasion? It is the resistance of a material against wear, scratching or degradation is known as abrasion.

Pounding Action It is the striking action of an object on a surface for a short instant of time is called pounding action. The pounding action of these balls also exits while conducting the test. Some investigators believe this test to be more dependable as rubbing and pounding action simulate the field conditions where both abrasion and impact occur. The cylinder is then locked and rotated at the speed of rpm for a total of revolutions depending upon the gradation of aggregates.

After specified revolutions, the material is sieved through 1. This value is called Los Angeles abrasion value. A maximum value of 40 percent is allowed for WBM base course in Indian conditions. For bituminous concrete , a maximum value of 35 percent is specified.

The aggregate impact test is carried out to evaluate the resistance to impact of aggregates. Aggregates passing The material is filled in 3 layers where each layer is tamped for 25 numbers of blows see Fig Metal hammer of weight The crushed aggregate is allowed to pass through 2.

And the impact value is measured as percentage of aggregates passing sieve W2 to the total weight of the sample W1. For bituminous macadam the maximum permissible value is 35 percent. For Water bound macadam base courses the maximum permissible value defined by IRC is 40 percent. Soundness test is intended to study the resistance of aggregates to weathering action, by conducting accelerated weathering test cycles.

The Porous aggregates subjected to freezing and thawing is likely to disintegrate prematurely. To ascertain the durability of such aggregates, they are subjected to an accelerated soundness test as specified in IS: part-V. Aggregates of specified size are subjected to cycles of alternate wetting in a saturated solution of either sodium sulphate or magnesium sulphate for 16 — 18 hours and then dried in oven at to 0 C to a constant weight.

After five cycles , the loss in weight of aggregates is determined by sieving out all undersized particles and weighing. The loss in weight should not exceed 12 percent when tested with sodium sulphate and 18 percent with magnesium sulphate solution.

The particle shape of the aggregate mass is determined by the percentage of flaky and elongated particles in it. Aggregates which are flaky or elongated are detrimental to higher workability and stability of mixes.

The flakiness index is defined as the percentage by weight of aggregate particles whose least dimension is less than 0. Flakiness gauge see Fig-4 is used for this test. Test procedure had been standardized in India IS: part-I. The elongation index of an aggregate is defined as the percentage by weight of particles whose greatest dimension length is 1. This test is applicable to aggregates larger than 6.

Elongation gauge see Fig-5 is used for this test. This test is also specified in IS: Part-I. However there are no recognized limits for the elongation index. The specific gravity and water absorption of aggregates are important properties that are required for the design of concrete and bituminous mixes. The specific gravity of a solid is the ratio of its mass to that of an equal volume of distilled water at a specified temperature. Because the aggregates may contain water-permeable voids, so two measures of specific gravity of aggregates are used:.

Apparent Specific Gravity , G app , is computed on the basis of the net volume of aggregates i. Bulk Specific Gravity , G bulk , is computed on the basis of the total volume of aggregates including water permeable voids. Water Absorption: The difference between the apparent and bulk specific gravities is nothing but the water permeable voids of the aggregates. We can measure the volume of such voids by weighing the aggregates dry and in a saturated surface dry condition , with all permeable voids filled with water.

The difference of the above two is M W. M W is the weight of dry aggregates minus weight of aggregates saturated surface dry condition. The specific gravity of aggregates normally used in road construction ranges from about 2.

Water absorption values ranges from 0. This practical supplement is the how and why of the test methods and a guide to performing concrete and aggregate tests efficiently while conforming to the requirements. It aims to direct attention to factors that could affect the results of the concrete and tests. The most helpful aspect of the manual is that it often simply restates requirements of the standards in plain, simple language. The focus is to help the user perform the tests successfully and in full compliance with the published standards.

Reinforcing proper procedures and making them easier to understand encourages greater compliance, reduces operator error, and promotes accurate and repeatable test results. The idea that wisdom is knowledge shaped by practical experience goes to the heart of the gray pages. Input for topical content and information for discussion is welcomed from all industry sources. The subcommittee meets twice a year and content is created, reviewed, and curated to ensure compliance with published standards while offering pragmatic solutions to performing the tests.

The opening chapters of the manual emphasize the importance of keeping current versions of relevant standards on hand and suggestions with references for the qualification of laboratory personnel.