Nowadays, in the process of concrete preparation, silica fume is often used to replace part of the cement to improve the performance of concrete, but many partners do not know how silica fume replaces cement in the actual operation process to prepare concrete, today HSA will tell you the mixing method and amount of silica fume to replace cement.
The method and amount of silica fume blending
There are two ways to mix silica fume in concrete: one is not to reduce the amount of cement, directly use silica fume as an admixture, this method is called external mixing; the other is to reduce the amount of cement, reduce the amount of silica fume to replace, this method is called internal mixing.
Generally, the amount of silica fume blended externally is between 5% and 10%, and the mechanical properties of the concrete are higher, but it will increase the amount of cementitious materials in the concrete, making the cost higher. Silica fume blending is mainly in the case of maintaining the same water-cement ratio, with silica fume equal quality or volume of cement replacement, the amount of general between 5% and 30%, but different alternative methods have different effects on the rheological properties of concrete.
The method and impact of silica fume replacement cement
1. Silica fume equal volume replacement cement
After experiments proved that, because silica fume contains a large number of SiO2 crystals, smooth surface, has a good lubricating effect, so in the water reducing agent saturation dosing conditions, silica fume equal volume replacement cement, will cause the plastic viscosity of concrete mortar and the relative yield stress is reduced, with the increase in the replacement rate, the two parameters at the same time gradually reduced.
2. Silica fume equal mass replacement of cement
When silica fume replaces cement by equal mass, because the density of silica fume is smaller than that of cement, the solid phase volume of the cementitious material increases by equal mass, and at the same time, the own water volume in the concrete mortar decreases greatly, but the dispersion of the cementitious material is low, and then the yield stress of concrete mortar increases greatly while the plastic viscosity remains unchanged. decreases and the yield stress increases significantly.
It can be seen that the main methods of replacing cement with silica fume are equal volume replacement and equal mass replacement, but the effects of the two replacement methods are very different, and the specific amount of silica fume also affects the rheological properties of the concrete mortar after replacing cement. In general, in order to determine the performance of concrete, it is necessary to determine through experiments whether silica fume is equal volume substitution or equal mass substitution of cement, as well as the specific amount of admixture.
Therefore, regarding how to replace cement with silica fume, we should choose equal mass replacement or equal volume replacement according to the actual project needs, but no matter which replacement method, it is inseparable from high quality and high grade of silica fume. HSA has been a global supplier of high-quality silica fume since 2001. We have established long-term and stable cooperation with many concrete construction companies around the world to provide our customers with high-quality silica fume with different contents and different uses, fully satisfying all kinds of concrete project needs.
If you have any needs for concrete, please feel free to contact us!