It’s a new type of early accelerator at low temperature. Its molecular formula is C2H2CaO4,which is white or yellowish flowing powder. In dry mortar products, calcium formate is mainly used in tile adhesive, cement-based plastering mortar, repairing mortar, waterproof mortar and other products. In order to improve the early strength, high aluminum cement is usually added to the mortar as a coagulant, and antifreeze is needed to be added in the low temperature environment. Calcium formate has dual functions, which can not only accelerate the hardening speed of cement, improve the early strength, but also avoid the problem of slow setting speed under winter construction or low temperature and humidity conditions, so that the cement products can be put into use as soon as possible to improve the strength, especially the contribution of calcium formate to the early strength.
In summer the dosage of calcium formate is usually 0.3%~0.7% of the cement. While in winter the dosage should increase with the decrease of temperature, about 0.5%~1.0%. Calcium formate dosage should not be too high, otherwise it will lead to cracking.
In the past, calcium chloride was widely used as coagulant in China. But calcium chloride has the function of corroding steel bras and chloride free accelerators are being developed at home and abroad. Calcium formate is one of them. Calcium formate can accelerate the hydration of tricalcium silicate (C3S) in cement and increase the early strength of cement mortar. The influence of calcium formate on cement mortar and concrete depends on the content of tricalcium silicate in cement. If the content of tricalcium silicate in cement is low, the strengthening effect of calcium formate will be good.
Because portlant cement is often used in dry mortar, it is characterized by low early strength and high later strength. In order to improve its early strength, it is very beneficial to add a proper amount of calcium formate into the product. Calcium formate, as a kind of coagulant, can not be used as antifreeze alone in winter. Only when calcium formate and antifreeze are used together, can it achieve good antifreeze effect and improve early strength.