In order to make more effective use of silica fume on the improvement of the microstructure of hardened cement paste, many researchers at home and abroad have conducted more detailed studies on the optimal conditions for the application of silica fume in cement paste and concrete, including the water-cement ratio, the amount of silica fume, the selection of admixtures and other volcanic ash admixtures and their dosage.
Silica fume in cement paste and concrete applications there is an optimal water-cement ratio range, generally beyond the range, khói silic trên vữa xi măng cứng và cải thiện cấu trúc vi mô bê tông sẽ giảm.
As a researcher pointed out, ở độ tuổi 3 d hoặc 7 d in cement mortar, the water-cement ratio is less than 0.45 (tỷ lệ xi măng nước của 0.35, 0.40) of the mortar specimens containing silica fume strength decreases, while the water-cement ratio is equal to 0.45 hoặc 0.50 of the mortar specimens containing silica fume strength increases;
but at the age of 28 d hoặc 90 d in cement mortar, the water-cement ratio is less than 0.35, 0.40, 0.50 The strength of mortar specimens containing silica fume is approximately the same;
while the strength of mortar specimens containing silica fume (bất kể hàm lượng khói silic) với tỷ lệ xi măng nước bằng 0.45 thấp hơn;
khi tỷ lệ nước-xi măng bằng 0.50 and the silica fume admixture is greater than 27.5%, silica fume has a significant effect on the later strength development of the mortar.
Although silica fume (microsilica) can effectively improve the microstructure of hardened cement paste and concrete, but because of the small particle size and large specific surface area of silica fume, vì vậy hỗn hợp xi măng và bê tông trộn với khói silic, with the increase of phụ gia khói silica, nhu cầu nước tăng, and the self-shrinkage also increases. Vì vậy, the amount of silica fume is generally limited to between 5% và 10%, and high efficiency water reducing agent to adjust the water demand, đồng thời, there is a compatibility problem between cement, khói silica, phụ gia, vì thế, when using silica fume must pay attention to its application conditions.
Since the addition of silica fume in concrete may lead to self-shrinkage of concrete, and the addition of silica fume concrete is generally a special requirement of concrete, vì thế, the use of silica fume in concrete to harden the cement paste and concrete properties of the beneficial effect at the same time, must minimize the adverse effects brought about by silica fume, the most effective way to solve this problem is the addition of silica fume at the same time mixed with other volcanic ash materials or Other substances, so that they complement each other’s strengths and weaknesses to achieve better technical and economic results. Hiện tại, more research is the use of ultrafine slag and silica fume compounding, hoặc việc sử dụng tro bay và khói silic kết hợp.
Another area of silica fume application conditions are more research is the use of silane on the surface of silica fume pretreatment after mixing into the cement paste or concrete or directly silane and silica fume at the same time into the cement paste or concrete, họ có thể cải thiện khả năng làm việc của hồ xi măng tươi và bê tông, do đó cải thiện cấu trúc tế vi của hồ xi măng cứng và bê tông.
