Silicon power influence on concrete physical properties
Add silicon power into concrete, can change some of the important physical performance of concrete, can meet the requirements of some certain peculiarities. Fume particles can fill the pores of relative large cement particles, to reduce the volume of the pores, but the silicon power large specific surface area is greater impact on the workability.
Thus, the general water consumption to be increased with the silicon power content increased. But in order to maintain the same liquidity while adding silicon power are generally required to add superplasticizer.
Improve the workability, under the circumstances of concrete water-cement ratio [W / (C + SF)] is lower, adding silicon power to increase the cohesiveness. In order to get the same workability with the concrete not add silicon power, generally need to increase 50mm slump, but in the cases of the cement consumption is less than 300kg / m 3, silicon power can improve its cohesiveness.
Reduce bleeding and segregation, because of the very high specific surface area of silicon power, many of the free water in the fresh concrete silicon power particles are bound, can greatly reduce the secretion of water. Silicon power can improve the performance of concrete segregation. When larger slump, vibration time is relatively long, silicon power concrete segregation is not easy.
Plastic shrinkage, plastic shrinkage cracking of concrete is because of the concrete surface tensile stress exceeds the early tensile strength of concrete. Such tensile stress is caused by moisture movement of the concrete surface. When the silicon power concrete significantly reduce the secretion of water, the risk of plastic shrinkage cracking is increased, especially in the high evaporation rate (for example, in the case of high wind, low humidity and high temperature). Plastic shrinkage cracking can occur after pouring. Plastering until the concrete begins to solidify, occurs mostly in the concrete close to the initial setting. In order to prevent the plastic cracking, the concrete must be covered to prevent the rapid evaporation of the surface covering the available sacks or plastic film or the curing agent, or to reduce evaporation in the spray method, can retard evaporation, some special admixtures also used to reduce the plasticity danger of cracking in many countries.
Setting time, the setting time of the silicon power concrete compared to the same strength concrete which not add silicon power often have a slight increase. In the case of no superplasticizer may be delayed, especially in case of high content of silicon power. When add silicon power to improve strength, depending on the variety of additives have different effects on setting time, some shortening 1to 2h, and some did not increase significantly, and some delay 1 to 2h. As the silicon power is higher than the surface area, under the circumstances of the same dose of the cited case of the gas generating agent, the containing gas is reduce, despite the use of superplasticizer.
Reduce the heat of hydration and temperature rise, use cement replace of silicon power can reduce the temperature rise and the heat of hydration. Metal powder supplier once had tested silicon power substitution is 0, 10%, 30% of the cement hydration heat. Heat peaks are slightly earlier than doped silicon power cement, but the total heat release are below not add silicon power, seven days total heat release in the substitution is 10% and 30%, respectively, decreased by 29% and 19 %. The amount of cement is 540kg / m 3 and 10% silicon power replace of cement with high strength concrete, the adiabatic temperature rise can doped 9% than not added.
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