Using calcium formate skillfully to solve the problem of setting and hardening of cement

The early strength growth of cement is fast, and the later strength growth is slow. If the temperature and humidity are suitable, its strength can still increase slowly after several years or more than ten years. Today we will talk about clever use of calcium formate to solve the problem of setting and hardening of cement.

Setting time is one of the important performance indexes of cement

(1) The hydration of cement progresses from the surface to the inside gradually. With the continuation of time, the degree of hydration of cement is continuously increasing, and the hydration products are also continuously increasing and filling the capillary pores, so that the porosity of the capillary pores decreases and the porosity of the gel pores increases accordingly.

Calcium formate can increase the concentration of Ca²⁺ in the liquid phase and accelerate the dissolution rate of calcium silicate. And the effect of the same ion will accelerate the crystallization, increase the solid proportion in the mortar, which is beneficial to the formation of cement stone structure.

Through the analysis and judgment of its appearance, fineness, formate content, solubility in cold water, etc., the dispersibility and viscosity strength of calcium formate in mortar were studied. The performance comparison of calcium formate products and the bonding strength in plaster mortar were tested and compared.

(2) Temperature has a significant effect on the setting and hardening of cement. When the temperature increases, the hydration reaction accelerates, and the strength of the cement increases faster. When the temperature decreases, hydration slows down and the strength increases slowly. When the temperature is lower than 5 ℃, hydration hardening is greatly slowed down. When the temperature is lower than 0 ℃, the hydration reaction basically stops. At the same time, because the temperature is lower than 0 ℃, when the water freezes, it will also destroy the cement stone structure.

In cold weather, the effect of calcium formate is even more pronounced. Calcium formate is a newly developed low-temperature early-strength accelerator in China, and the physical properties of calcium formate are relatively stable at room temperature and not easy to agglomerate. It is more suitable for application in mortar.

(3) Cement stones in a humid environment can maintain sufficient moisture for hydration and coagulation hardening, and the generated hydrates further fill the capillary pores to promote the strength development of the cement stones. Measures to maintain the temperature and humidity of the environment to increase the strength of the cement stone are called curing. When determining the strength of cement, it must be cured to the specified age in the specified standard temperature and humidity environment.

Calcium formate early strength agent is a concrete early strength agent with wide application range and good effect. A large number of experimental studies have proved that the use of calcium formate early strength agent has a significant effect on shortening the setting time of concrete and improving early strength, and can also effectively prevent freezing damage of concrete under low temperature conditions. At the same time, its low price and wide source also make calcium formate early strength agent favored.