Cement has a rapid early strength gain and a slow late strength gain. If the temperature and humidity are suitable, its strength can still slowly increase after a few years or more than ten years. Calcium formate can be used to solve the problem of cement setting and hardening.
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Setting time is one of the important performance indicators of cement
Hydration of cement starts from the surface and gradually progresses deeper into the interior. Over time, the degree of hydration of cement continues to increase, and the hydration products also continue to increase and fill the capillaries, reducing the porosity of the capillaries and correspondingly increasing the porosity of the gel pores.
Calcium formate can increase the concentration of Ca2+ in the liquid phase, which accelerates the dissolution of calcium silicate. In addition, the same ion effect will accelerate crystallisation, increase the proportion of solid phase in the mortar, and facilitate the formation of cement stone structure.
The dispersibility and adhesive strength of calcium formate in mortar were studied by analysing its appearance, fineness, formate content and solubility in cold water. Tests were carried out to compare the performance of calcium formate products and their bond strength in plastering mortars.
Temperature
Temperature has a significant effect on the setting and hardening of cement. When the temperature rises, the hydration reaction accelerates and the strength of the cement increases more quickly; when the temperature drops, the hydration reaction slows down and the strength increases more slowly. When the temperature is below 5°C, the hydration and hardening process slows down significantly. When the temperature falls below 0°C, the hydration reaction basically stops. At the same time, because the temperature is below 0°C, when water freezes, it can also damage 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, and its physical properties are relatively stable at room temperature, making it less prone to agglomeration and more suitable for use in mortar.
Humidity
Cement paste in a humid environment can maintain sufficient moisture for hydration and condensation hardening. The hydration products further fill the capillaries and promote the strength development of the cement paste. Maintaining the temperature and humidity of the environment and measures to continuously increase the strength of the cement paste are called curing. When determining the strength of cement, it must be cured in a specified standard temperature and humidity environment until the specified age.
Calcium formate early strength agent is a concrete early strength agent with a wide range of applications and good results. 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 concrete frost damage under low temperature conditions.
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As the saying goes, “the expert looks at the door, the layman looks at the crowd”, the early strength of cement grows fast, the later strength grows slowly, if the temperature and humidity are appropriate, its strength can still grow slowly in a few years or ten years. Let’s talk about the use of calcium formate to solve the problem of cement setting and hardening.
Setting time is one of the important performance indexes of cement
(1) The hydration of cement is carried out gradually from the surface to the interior. With the continuation of time, the hydration degree of cement is increasing, and the hydration products are also increasing and filling the capillary pores, which reduces the porosity of the capillary pores and correspondingly increases the porosity of the gel pores.
Calcium formate can increase the concentration of Ca 2+ in the liquid phase, accelerate the dissolution rate of calcium silicate, and the co-ionic effect will accelerate the crystallization, increase the proportion of solid phase in the mortar, which is conducive to the formation of cement stone structure.
The dispersion and viscosity of calcium formate in mortar were studied by analyzing its appearance, fineness, formate content and solubility in cold water. The properties of calcium formate products and the bond strength in plastering mortar were tested and compared.
temperature
(2) Temperature has a significant effect on the setting and hardening of cement. When the temperature increases, the hydration reaction is accelerated, and the cement strength increases faster. When the temperature decreases, hydration slows down and the strength increases slowly. When the temperature is below 5℃, the hydration hardening is greatly slowed down. When the temperature is below 0℃, the hydration reaction basically stops. At the same time, due to the temperature below 0 ° C, when the water freezes, it will destroy the cement stone structure.
At low temperatures, the effect of calcium formate is even more pronounced. Calcium formate is a new low temperature and early strength coagulant developed in China, and the physical properties of calcium formate are relatively stable at room temperature, not easy to agglomerate, more suitable for application in mortar.
humidness
(3) The cement stone in a humid environment can maintain enough water for hydration and condensation and hardening, and the generated hydration will further fill the pores and promote the strength of the cement stone. The measures to maintain the temperature and humidity of the environment, so that the strength of cement stone continues to grow, are called maintenance. When determining the strength of cement, it must be cured to the specified age in the specified standard temperature and humidity environment.
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Post time: Jun-04-