Water-cement ratio means the ratio between the weight of water to the weight of cement used when preparing concrete mix, and plays an important role in developing the strength of concrete. The water-cement ratio is also responsible for the porosity of the hardened cement paste. Water cement ratio is stated as the amount of water used to the significant amount of cement in the mixture by weight for proper workability. A minimum water-cement ratio of about 0.3 by weight is
necessary to ensure that the water comes into contact with all the cement particles, which assures complete hydration of the cement paste.
Problems Caused by High Water-Cement Ratio?
Concrete with a higher water-cement ratio is also more susceptible to cracking and shrinkage. Shrinkage leads to micro-cracks, which are zones of weakness. Once the fresh concrete is placed, excess water is squeezed out of the paste by the weight of the aggregate and the cement paste itself. When there is a large excess of water, that water bleeds out onto the surface. The micro channels and passages that were created inside the concrete to allow that water to flow become weak zones and micro-cracks. For higher strength concrete, lower ratios are used, along with a plasticizer to increase flowability. Good concrete
results from good mix design and a low water-cement ratio is just one part of a good mix design.
By/or: Dillon Murray
Quality Control Director