It is mainly based on the design requirements to determine the mixing method of silica powder, the optimal mixing amount of silica powder, the optimal mixing amount of water reducing agent and the adjustment of sand and gravel materials, while the others are carried out according to the ordinary concrete design method.
1. The method of mixing silica powder: There are generally two methods for silica powder in concrete: one is internal mixing, and the other is external mixing, both of which must be used in conjunction with a water reducing agent. The internal mixing method often uses silica powder instead of cement and is divided into equal replacement and partial equal replacement. The equal replacement is the silica powder content to replace the equal cement, and the partial replacement is 1 kg silica powder instead of 1 to 3 kg cement. As a research, the general mixing amount is 5% to 30%, and the water-cement ratio generally remains unchanged: while the external mixing method refers to the addition of silica powder to the concrete like an admixture, and the amount of cement does not decrease, the mixing amount is generally 5% ~10%, the mechanical properties of the concrete obtained by the general admixture method are much higher, but the amount of cementing material in the concrete is increased.
2. The optimum amount of silica powder: Too little silica powder in the concrete will not improve the performance of the concrete much, but if the amount is too much, the concrete will be too sticky and difficult to construct, and the shrinkage will be large and the frost resistance will be poor. Therefore, when adding silicon powder, the optimal dosage should be found to obtain the best results. Under normal circumstances, the effect is more satisfactory if the dosage is less than 10%. The appropriate amount of silica powder is generally selected according to the silica powder, the type of cement and the nature of the aggregate, such as 3, 5, 7, 10%, etc., and the concrete specimen is formed, and the R-SF (strength -The silicon powder content) curve is determined. It is worth noting that the price of silica powder is relatively high, and the technical and economic indicators should also be considered when determining the optimum amount of silica powder.
3. The optimal amount of water-reducing agent: When using silica powder in concrete, if you want to keep the same fluidity without adding a water-reducing agent, you must increase the water consumption, increase the water-cement ratio, and increase the strength of concrete with silica powder. It can't go up, which is the reason why silica powder has not been popularized in concrete in the past. The water-cement ratio of silica powder and water-reducing agent mixed with silica powder remains , that is, the water consumption does not increase, and the same fluidity as the concrete without silica powder can be achieved, and the strength of the silica powder concrete is greatly improved. In general, naphthalene-based superplasticizers, such as Jian1, H, DH3, FDN, NF, N2B, etc., are generally used in the country. The mixing amount is generally within 1% of the amount of glue. Sometimes in order to reduce the water-cement ratio, mix To make super- high-strength concrete, the amount of water-reduci ng agent can reach 2% to 3%.