لخّصلي

Concrete Concrete is a mixture of stone and sand held together by a hardened paste of hydraulic cement and water.The required strength and properties of concrete can be obtained by careful selection of its ingredients, correct grading of ingredients, accurate water additions and adopting a good workmanship in mixing, transportation, placing, compaction, finishing, and curing of concrete in the construction work.

Concrete
Concrete is a mixture of stone and sand held together by a hardened paste of hydraulic
cement and water. When the ingredients are thoroughly mixed they make a plastic mass
which can be cast or moulded into a predetermined size and shape. When the cement
paste hardens the concrete becomes very hard like a rock. It has great durability and has
the ability to carry high loads especially in compression.
The required strength and properties of concrete can be obtained by careful selection of
its ingredients, correct grading of ingredients, accurate water additions and adopting a
good workmanship in mixing, transportation, placing, compaction, finishing, and curing
of concrete in the construction work.
The main ingredients of concrete are cement, coarse aggregate (i.e. screenings, gravel,
etc.), fine aggregate (i.e. sand), chemical admixtures (if necessary) and fibrous materials
(as necessary). Aggregates in concrete constitute by far the bulk of the mass. Acceptable
concretes usually have proportions within the following ranges (by volume):
Water 15% to 20%
Cement 7% to 17%
Aggregate (coarse and fine) 78% to 63%
Paste (water + cement) 22% to 37%
Typical characteristics which are desirable to be achieved in the body of a concrete mix
include adequate compressive strength, uniformity of mixing, freedom from internal
defects such as voids and cracks, high modulus of elasticity and dynamic poisson's ratio
and correct positioning of reinforcing steel bars, freedom of reinforcing bars from
corrosion, correct positioning of pipes in the concrete structures, uniformity of
distribution of fibres in the fibre concrete, freedom from any foreign inclusions,
uniformity of thickness and grouting ducts for post tensioned concrete and adequacy of
covering depth over the reinforcements.