Post Date:5,Sep,2022

The effect of water reducing agent on shrinkage cracking of commercial concrete:

A water reducing agent is an admixture that can be added during the concrete mixing process to significantly reduce or greatly reduce the concrete mixing water, improve the fluidity of the concrete, and increase the strength of the concrete. Practice has proved that after adding water reducer to concrete, if there is no need to increase the strength, the amount of cement can be greatly reduced, and the compactness of concrete can be improved. Therefore, water reducing agent is an indispensable additive material in commercial concrete.

In order to further improve the economic benefits of commercial concrete, concrete manufacturers like to use water reducing agents with high water reducing properties to improve the strength of concrete or greatly reduce the amount of cement and reduce production costs. In fact, this is a major misunderstanding. Although water reduction is beneficial to improve the compressive strength of concrete, excessive water reduction will also adversely affect the flexural strength of concrete. Although a proper amount of water reduction is beneficial to reduce the shrinkage rate of concrete, it must be noted that when designing the concrete mix ratio, the water-reducing function of adding a water-reducing agent has been taken into account, and the water-binder ratio is generally designed to be low. Water consumption will increase the drying shrinkage of concrete and increase the shrinkage rate of concrete.

Although the compressive strength of commercial concrete does not decrease when the cement content is greatly reduced, the tensile strength decreases with the decrease of the volume of hardened cement stone in the concrete. Due to the reduction of the amount of cement, the concrete cement slurry layer is too thin, and more micro-cracks will occur in the concrete. Of course, the micro-cracks have little effect on the compressive strength of the concrete, but the influence on the tensile strength and other properties of the concrete cannot be underestimated. The substantial reduction of cementitious materials will also affect the elastic modulus and creep of concrete, making concrete more prone to cracking.

To sum up, when producing commercial concrete, the concrete water reduction rate and the amount of cementitious materials must be fully considered, and no limitless water reduction or excessive reduction of cementitious materials is allowed.