Water reducing agent is an admixture that can be added before or during the mixing process to reduce or greatly reduce the water used for mixing concrete. Adding water-reducing agent to concrete can effectively improve the workability and fluidity of concrete, improve the structure of concrete, and increase the strength. A large amount of cement can be saved while maintaining the strength of concrete.
Therefore, the water reducing agent has become an indispensable admixture for the preparation of commercial concrete. Seeing that the water-reducing agent can improve the strength and save a lot of cement, the construction personnel mistakenly believe that when preparing the commercial concrete and using the water-reducing agent, the higher the water-reducing rate is, the better, and even the higher the requirements are when preparing low-grade concrete. Water reduction rate。
Under normal circumstances, as the water reduction rate increases, the strength of concrete will become higher and higher. For concrete with high water cement, the reduction in water consumption will reduce the drying shrinkage of the concrete, which is of course very beneficial to increase the strength of the concrete and reduce the shrinkage and cracking of the concrete. However, the current design of concrete construction generally has a low water-to-binder ratio. Since auto-shrinkage cannot be ignored, if the water consumption is greatly reduced, the internal drying shrinkage of the concrete will increase, thereby increasing the auto-shrinkage of concrete.
In addition, the preparation of commercial concrete is generally mixed with retarder, because the hydration is slow, the concrete does not set for a long time, and the concrete surface loses water seriously, which increases the risk of concrete shrinkage and cracking.
Of course, some people think that we can prevent concrete from drying and shrinking by watering and curing, but the very low water glue is denser than concrete, and the water seldom can penetrate into the concrete, and it is difficult to achieve the purpose of supplementing water shortage.
When selecting admixtures in concrete, the type of cement and the characteristics of other components should be considered at the same time, and different types of water-reducing agents should be selected according to different purposes. When selecting, we should consider both the economy and the quality stability of the water-reducing agent.
If you encounter the problem of the incompatibility of cement and admixtures, you must eliminate the relevant factors through experiments, select the appropriate type of water-reducing agent, analyze the quality of the cement, determine the appropriate dosage, and the influence of the concrete mix ratio. When several admixtures are used in combination, attention should be paid to the compatibility between varieties and their influence on concrete performance. Tests should be carried out before use.
For example, polycarboxylic acid-based high-performance water-reducing agents and naphthalene-based water-reducing agents should not be used in combination . With the development and application of concrete admixtures, the weaknesses of “low strength, self-weight, and high brittleness” existing in the project have been overcome, and the continuity of project construction has been ensured, the construction period has been greatly shortened, and the fluid concrete technology and The development of new pumping and pouring technology has accelerated the development of commercial concrete.
The development of commercial concrete has brought great economic and environmental benefits to the construction industry in China, and has further promoted the development of the construction industry and the improvement of construction technology.