What role does limestone play in cement, Cement is mixed with a small amount of limestone can improve the early strength of cement, on the one hand is CaCO3 can accelerate clinker C3S early hydration; on the other hand is due to CaCO3 and clinker of C3A and C4AF reacted carbon aluminum acid calcium. The reaction of C4AF with CaCO3 to produce calcium aluminate. Calcium aluminate is a kind of needle like, which can enhance the early strength of cement.
In addition to the and C3A reaction of limestone in addition to the C3A and the C4AF in the clinker, the common cement with slag as the mixed material can also react with the slag, and continuously enrich the cement paste. Therefore, limestone instead of part of the slag, the strength of the cement each age are higher.
Limestone is the main component of calcium carbonate, the main chemical properties of the decomposition into calcium oxide and carbon dioxide at a higher temperature, in addition to the following some of the chemical properties.
1) anti chemical properties
In addition to acid, many of the erosive substances can not be eroded or can only slow the erosion of limestone.
2) acid traits
Limestone and all of the acid and the reaction, to form a calcium salt and release carbon dioxide, the reaction rate is determined in limestone contained impurities and their crystal size. The higher the impurity content, the larger the crystal, the smaller the reaction rate. The reaction rate of dolomite is slower than that of limestone. Method for determination of dolomite and limestone, 10% hydrochloric acid is used to produce a small amount of air bubbles on the dolomite, and the gas can be produced by the gas that can cause the clarification of the lime water to become turbid.
3) resistance to a variety of gas characteristics
Chlorine and hydrogen chloride in dry bath state and at room temperature with CaCO3, reaction is very slow, until 600 DEG C to accelerate, generating CaCl2; sulfur dioxide at room temperature under both in gaseous or liquid state of CaCO3 are no significant effect; generate Ca (NO3) and nitrogen dioxide (NO2) in 15 DEG C is CaCO3 and anti stress 2, no and CO2.