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, silicadamp op uitgeharde cementpasta en verbetering van de microstructuur van beton zal worden verminderd.
As a researcher pointed out, op de leeftijd van 3 d of 7 d in cement mortar, the water-cement ratio is less than 0.45 (water-cementverhouding van 0.35, 0.40) of the mortar specimens containing silica fume strength decreases, while the water-cement ratio is equal to 0.45 of 0.50 of the mortar specimens containing silica fume strength increases;
but at the age of 28 d of 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 (ongeacht het gehalte aan silicafume) met een water-cementverhouding gelijk aan 0.45 is lager;
wanneer de water-cementverhouding gelijk is aan 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, dus de cementpasta en beton vermengd met silicadamp, with the increase of silica fume admixture, de waterbehoefte stijgt, and the self-shrinkage also increases. Daarom, the amount of silica fume is generally limited to between 5% en 10%, and high efficiency water reducing agent to adjust the water demand, tegelijkertijd, there is a compatibility problem between cement, silicadamp, admixtures, daarom, 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, daarom, 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. Momenteel, more research is the use of ultrafine slag and silica fume compounding, of het gebruik van vliegas en silicadamp samenstellen.
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, ze kunnen de verwerkbaarheid van verse cementpasta en beton verbeteren, waardoor de microstructuur van uitgeharde cementpasta en beton wordt verbeterd.
