Post Date:27,Nov,2023

Retarder is a commonly used admixture in engineering construction. Its main function is to effectively delay the occurrence of the heat peak of cement hydration, which is beneficial to the long transportation distance, high ambient temperature and other conditions of concrete, cement mortar and other building materials. Maintain plasticity under conditions, thereby improving the quality of concrete pouring; when affected by other special circumstances such as weather or construction schedule requirements, a retarder also needs to be added, which can improve the working performance of the concrete, extend the cement setting time, and also reduce construction cracks. How to choose the appropriate type and dosage of retarder to affect the performance of cement concrete is a question worthy of study.

1.Effect on Clotting Time

After adding retarder, the initial and final setting time of concrete are significantly prolonged. Different retarders have different effects on concrete setting time at the same dosage, and different retarders have different retarding effects on concrete. A good retarder should have a good retarding effect when its dosage is small. An ideal retarder should prolong the initial setting time of concrete and reduce the final setting time. That is to say, the initial and final setting interval of concrete should be shortened as much as possible.

 2.Effect on the workability of the mixture

In engineering practice, in order to adapt to transportation and meet construction requirements, retarder is often added to concrete to improve the workability of the concrete mixture and reduce slump loss over time. The addition of retarder significantly improves the uniformity and stability of the mixture, maintains plasticity for a longer period of time, improves the quality of concrete construction, and effectively prevents cracks caused by early shrinkage of concrete.

3.Effect on concrete strength

The addition of retarder can fully hydrate the cement particles, which is beneficial to increase the strength of concrete in the middle and late stages. Since some retarders also have a certain water-reducing function, within the appropriate dosage range, if the dosage is larger, the water-cement ratio of the concrete mixture will be smaller, which will help the strength development of concrete. In actual projects, due to the excessive dosage of retarder, the concrete may not set for a long time, and the concrete strength may not meet the design requirements during project acceptance. Therefore, we must pay attention to the selection of retarder varieties and strictly control the dosage of retarder. At the same time, we must also fully consider the matching and adaptability between retarder and concrete raw materials.