Friday, June 24, 2016
How Concrete Strength Is Influenced By Water To Cement Ratio
Water to cement ratio refers to ratio related to the weight of water and the weight of cement which are the essential part of a fresh concrete mix. The stability of compacted concrete mainly relies on water to cement ratio. Cured concrete strength is based on the following two main aspects :-
1. Water to cement ratio
2. Degree of compaction
Air voids in concrete happen on the basis of the water to cement ratio. If the weight of water rises, air voids is also raised. Due to this circumstance, the concrete strength is also decreased. Solidified concrete includes about 1% of air voids. If a concrete is in a solidified condition, strength is contrarily proportionate to the water/cement ratio.
The following figure indicates that validity range of water to cement ratio is very restricted. Compressive strength will be higher, when water to cement ratio is down. The starting of the curve is based on the existing methods of compaction (that is either accomplished with vibrators or compaction by hand). If large size aggregates are applied with low water to cement ratio and greater contents of cement then it reveals deterioration of the concrete strength.
So, if there exist a low water to cement ratio in a fresh mix than as soon as the concrete is solidified, water/cement fails to keep a greater concrete strength. These conditions occur due to the formation of tensile stresses for shrinkage and creep. It results in cracking of the cement or losing bonds (that happens amid cement and aggregates) just as aggregates attempt to control the tensile stresses.
So, low water to cement ratio may cause major issues in solidification of concrete. If water to cement ratio is low in a fresh mix, then less water is available for the hydration of cement. Hence, some amount of cement paste stays un-hydrated that causes internally tension in concrete as well as feeble bond. The strength that might be established under the present situation is mainly based on the following four factors :-
1. Water to cement ratio
2. Cement to aggregate ratio
3. Maximum aggregate size
4. Physical properties of aggregates
The factors (2,3 and 4) are not so vital whereas factor (1) is the most crucial factor. Since strength of concrete is affected by the strength of mortar, bond of mortar with aggregates and coarse aggregates strength.
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