The effect of shallowness, temperature and humidity for the maturation process
The fineness has a very significant influence on the ripening process. The finer the grains, in the same volume of cement, there is a greater area of cement-water contact, and therefore a larger area, where the reaction takes place simultaneously. This intensifies the hydration process, and thus it influences the increase of self-insulation as well as the acceleration of the bonding process and faster increase in the strength of the product. The cements are of the higher class, and in turn rapidly hardening, the more shallow they are, as a rule. However, you have to remember, that at the specific surface < 1700 cm² / g very low hydration occurs, and at > 4500 a large shrinkage is formed.
The increase in temperature affects the cement setting process like all other chemical reactions. Higher temperature accelerates, and a lower one delays this process. Approximately it can be assumed, that in practice any temperature difference of the order of 12 to 15 ° C it is twice as fast or by 50% delays the binding process.
The reaction completely disappears in the presence of frozen water. We can assume, that the water is free, freezes in the concrete mix at -1 do -3°C, and in the gel at -5 do -70°C, which depends on the size of the individual pores, the smaller the pores, the lower the freezing point of the water.
However, the influence of temperature on the strength of the grout, and thus the concrete, is more complicated. It must be emphasized, that the lower the temperature, but positive, in the first period of maturation, the greater amount of cement will chemically react with water, which will have a positive effect on the final strength of the grout and concrete, already matured at a normal temperature of ≥ 10 ° C.
Humidity is so important, that in the environment of low humidity, water evaporates quickly from the mixture of grout or concrete and there may not be enough water for the proper course of the setting. It is then said to be overdrying. Elements made of such concrete are fragile, weak and with increased contraction. The higher the ambient humidity and the longer it is kept, all the better for the setting process and the technical properties of the product. In fact, in the exposed concrete element, there is a hydrodynamic equilibrium between its moisture, and the relative humidity of the surrounding air.