Characteristics or properties of cement concrete

CHARACTERISTICS / PROPERTIES OF CEMENT CONCRETE

1. Homogeneity

Mixing of concrete is done thoroughly so as to produce homogeneity.

2. Work ability

It is defined as the ease with which concrete can be compacted fully without segregation and bleeding. Work ability depends on the quantity of water and aggregates used.

3. Segregation

Segregation means separation of coarser particles from the mix. It results in non homogeneity of the concrete mix. Segregation results in honeycombing and decrease in density and ultimately loss of strength of hardened concrete. To avoid segregation, the concrete should not be thrown from a height.

4. Bleeding

Bleeding refers to the appearance of water along with cement particles on the surface of freshly laid concrete on compaction. [Compaction of the concrete is done either by ramming or vibrating.] Bleeding occurs due to excessive compaction or excess water present in the mix. Bleeding causes formation of pores in the concrete, making it weak. Bleeding should be avoided by controlling quantity of water, providing finer grading of fine aggregate and performing suitable optimum compaction.

5. Compressive Strength

Concrete should have high compressive strength, so that it can resist the heavy loads of the structures.

6. Tensile Strength

Concrete is weak in tensile strength. Therefore, steel reinforcement is provided in it to withstand the tensile stress.

7. Reinforced Cement Concrete (R.C.C.)

Concrete is weak in tension. Hence, steel reinforcement is provided to take up the tensile stresses. This is known as Reinforced Cement Concrete (R.C.C.).

8. Minimum Shrinkage

On hardening, the concrete should exhibit minimum shrinkage due to loss of water.

9. Density:

Concrete must be adequately dense.

10. Process of Hardening

Concrete hardens with age. The process of hardening should continue for a long time after the concrete attains sufficient strength.

11. Hardness and Resistance to Abrasion

Concrete should form a hard surface and provide enough resistance to abrasion.

12. Durability

Durability of concrete refers to its resistance to deterioration due to weathering (temperature or rain), fire, chemical attack, etc.

13. Free from Corrosion

Concrete should be free from corrosion. Porous-concrete leads to the corrosion of steel reinforcement.

14. Porosity

Concrete should not be porous. Porosity is caused in the concrete due to the presence of voids formed during and after its placing.

15. Impermeability or Water Tightness

Impermeability is the resistance of the concrete to the flow of water through the pore-spaces in it. Concrete should have sufficient Impermeability or Water Tightness, so that the moisture does not flow inside the structure and corrode the steel. Corrosion of steel causes the structure to fail. Concrete is made water-tight by using Hydro-phobic Cement.

16. Good Finish

Concrete should provide the required good finish to the structure.

17. Dimensional Changes

In concrete, dimensional changes are caused due to shrinkage of concrete, thermal changes, elasticity and creep in concrete. The dimensional changes may induce certain stresses in the concrete leading to its cracking.