خواص بتن تازه با میکروسیلیس و دوام بتن

Properties of fresh concrete with microsilica Microsilica :
جايگزين نمودن Microsilica  Replacing microsilica with cement increases the rate of hydration and due to the high flowability of this material, the mixture becomes sticky and requires more water for proper flow. Due to the adverse effect of increasing the water-cement ratio on the durability of concrete, it is usually necessary to increase the flowability of such mixtures by using a lubricant or superplasticizer. Also, replacing some of this material with cement reduces the tendency to water-drop and separation of the mixture. Fresh concrete mixture that has not yet fully set is susceptible to surface cracking caused by the shrinkage of the concrete paste. This phenomenon is more acute in hot weather conditions, when the rate of evaporation from the surface of the concrete exceeds the amount of water transferred from the inside of the concrete to its surface. Therefore, since the water-drop phenomenon is very low in concrete, there are many reports of the sensitivity of this type of concrete to cracking caused by shrinkage of the paste. Therefore, in the case of this type of concrete, after pouring and compacting it, water evaporation from the concrete surface must be prevented immediately. Microsilica .

. Microsilica The effect of microsilica on concrete durability :
. Microsilica  The use of microsilica in concrete leads to the creation of a structure with smaller pores, which reduces permeability. On the other hand, the elimination of the phenomenon of water loss causes better cohesion in the transition zone of cement paste and aggregate, and as a result, increases the strength of concrete. In addition, replacing some of this material instead of cement due to the increase in the electrical resistance of concrete reduces the permeability against chloride ion penetration. It should be noted that the use of this material in environments exposed to magnesium sulfate does not perform well. In research, a replacement amount of 7-12 percent. Instead of cement has had favorable results. A very important point about the use of this material is that it must be completely mixed before use. The slurry must be completely smooth and free of adhering particles. For this purpose, it is necessary to use a mechanical mixer with high speed. The adhesion of these materials to each other, due to their high porosity, acts as active silica in the reaction with alkalis and causes damage due to the silica-alkali reaction. Microsilica . Microsilica .