Effect Of Several Salts On Early Age Autogenous Shrinkage And Cracking Resistance Of Concrete

In cold regions of our country, in order to extend the construction period or increase the early strength of concrete to prevent the frost of concrete early, people often add salts to concrete as early strength agent and antifreeze. The early strength agent and antifreeze’s main component are often sulfate, nitrate, nitrite and chloride and other salts and calcium formate, calcium acetate, triethanolamine and other organic matter or organic salts. The real project showed early strength agent and antifreeze improve the concrete early strength and frost effects, but also accelerate cracking of concrete.This work mainly investigates the effect of calcium nitrate, calcium nitrite, calcium acetate and sodium thiocyanate on the early-age autogenous shrinkage and cracking resistance of concrete under the water-cement ratio which is 0.3~0.4 in order to provide guidance for the practical application of salt additive in concrete engineering. The study under the water-cement ratio and dosage used in the test found that:When the content of calcium nitrate is high the early-age autogenous shrinkage and cracking is improved. There is no significant effect to the early-age autogenous shrinkage and cracking resistance when the content of calcium nitrate is small. The incorporation of calcium nitrite improves the early-age autogenous shrinkage of concrete and reduces early-age cracking resistance of concrete. The content of calcium acetate is lower than1.0%, the early-age autogenous shrinkage and cracking resistance have little change. The content of calcium acetate is higher than 1.0%, the early-age autogenous shrinkage and cracking have a significant increase. When the water-cement ratio is large, the early-age autogenous shrinkage of concrete reduces at the second time and then increases with the increasing of the content of sodium thiocyanate.