Brief description of Water Cement Ratio and Abrams' law
Duff Abrams is the developer of a formula that is called as Abrams law. It states that for a specified set of concreting materials, the strength of the concrete is exclusively based on the relative quantity of water relative to the cement. Alternatively stated, the strength refers to a function of the water to cement ratio (w/c) where w denotes the mass of water and c denotes the mass of cement.
Abrams’ law stands for a special case of a general rule prepared experimentally by Feret. The formula is represented as follow:-
S denotes strength of concrete
K denotes a constant
c,w & a denote volume of cement, water & air correspondingly
Although, in many times, w/cm is applied and cm signifies the mass of cementing materials, that conains the portland cement along with any additional cementing materials like fly ash, slag cement, or silica fume.
Unwantedly, if there is high water content, the cement paste will be dissolved (the adhesive of concrete) and the volume of resultant concrete will be raised. If water content is decreased, the following benefits can be obtained:
- Higher compressive and flexural strength
- Lesser permeability and greater water tightness
- Improved stability and resistance to weathering
- Superior bond among concrete and reinforcement
- Lowered drying shrinkage and cracking
- Less volume change from wetting and drying
If there is less water, the quality of the concrete will be superior assuming the mixture can still be solidified correctly.
If lesser amounts of water are mixed, mixture will turn to stiffer. Stiffer mixtures are easily arranged with vibration. So, consolidation by vibration enhances the quality of concrete.
With the reduction in water content of concrete, the w/cm is also decrease and it results in increasing strength and stiffness, and reduction in creep. The drying shrinkage and related risk for cracking will also be decreased. The concrete will obtain a lesser permeability or higher water tightness that will improve it resistance strength against weathering and the action of aggressive chemicals. With the reduction of water in cementitious materials ratio, the bond amid the concrete and embedded steel reinforcement is also increased.