Concrete Testing

CUBE TEST

Out of many test applied to the concrete, this is the utmost important which gives an idea about all the characteristics of concrete. By this single test one judge that whether Concreting has been done properly or not. For most of the works cubical moulds of size 15 cm x 15cm x 15 cm are commonly used.

This concrete is poured in the mould and tempered properly so as not to have any voids. After 24 hours these moulds are removed and test specimens are put in water for curing.

These specimens are tested by compression testing machine after 7 days curing and 28 days curing. Load should be applied gradually at the rate of 140 kg/cm2 per minute till the Specimens fails. Load at the failure divided by area of specimen gives the compressive strength of concrete.

Normally cast four cubes for each concrete batch.

SLUMP CONE TEST

When measuring the workability and consistency of a batch of concrete, a concrete slump test must be performed for each batch of fresh concrete. Concrete admixtures affect concrete workability in unique way, and it is important to maintain a consistency between each batch.

This testing method consists of a cone with a base diameter of 200mm, a top diameter of 100mm, and a height of 300mm. The cone is placed on a smooth none absorbent surface and freshly mixed concrete is placed into the mode in three successive layers, 25 blows were applied to each layer with a bullet pointed rod 160mm in diameter 600mm long. Once filled to top (after ramming) and top struck the mode is immediately withdrawn and the slump or subsidence of the concrete measured from a straight edge held across the top of the mould. Slump is the vertical settlement of the concrete after the mode has been withdrawn. That is the different between the height of the mould and the highest point of the subsided concrete give the workability.