3. Aggregate abrasion value test: Hardness or resistance to wear is an important property of concrete. It is possible to cause wear by abrasion, i.e., by rubbing of a foreign material against the stone under test or by attrition of stone particles against one another. Three tests are in common use to test aggregate for its abrasion resistance – (1) Deval attrition test (2) Dorry abrasion test & (3) Los Angeles test.
CHAPTER – 3
STRENGTH OF CONCRETE
Strength of concrete is its resistance to rupture. It may be measured in a number of ways, such as, strength in compression, in tension, in shear or in flexure. All these indicate strength with reference to a particular method of testing.
For a given cement and acceptable aggregates, the strength that may be developed by workable, properly placed mixture of cement, aggregate and water (under the same mixing, curing and testing conditions ) is influenced by:
(a) Ratio of cement to mixing water
(b) Ratio of cement to aggregate
(c) Grading, surface texture, shape, strength and stiffness of aggregate particles
(d) Maximum size of aggregate
3.1 Compressive strength
The compressive strength of concrete is one of the most important and useful properties of concrete . In most structural applications concrete is employed primarily to resist compressive stresses. In those cases where strength in tension or in shear is of primary importance, the compressive strength is frequently used as a measure of these properties. Therefore, the concrete making properties of various ingredients of mix are usually measured in terms of the compressive strength. Compressive strength is also used as a qualitative measure for other properties of hardened concrete. The usual test employs a cylindrical specimen of height equal to twice the diameter, moist-cured for 28 days and then subjected to slow (“static”) loading at a specified rate until rupture occurs.