矿粉、高钙灰及脱硫石膏对水泥收缩性能的影响

Effect of Grinded Blast Furnace Slag High-Calcium Fly Ash and Desulfurized Gypsum on Shrinkage Performance of Cement Mortars

研究了50.0%(质量分数,下同)矿粉和高钙粉煤灰等量替代水泥对水泥净浆早期自收缩性能的影响及水泥砂浆的长期干燥收缩性能和初始开裂敏感性.结果表明,在水泥-矿物材料体系中,自收缩与矿物材料的水化活性成正相关性,用50.0%的矿粉和高钙粉煤灰替代水泥后,水泥浆体的自收缩率随着矿物材料活性的降低而降低;硫酸盐激发材料既具有增加水化程度和提高化学收缩的作用,又具有增加AFt量和产生膨胀的作用,因而对水泥浆体的自收缩影响不大;掺50.0%矿粉及1.0%元明粉可显著提高干燥收缩;脱硫石膏和煅烧脱硫石膏按照一定比例复合能显著降低干燥收缩;初始开裂时间、自收缩与矿物材料水化活性的相关性较大,自收缩越高则其开裂敏感性越大,早强措施增加开裂风险;采用矿物材料尤其是采用低活性矿物材料替代水泥可使水泥水化减缓,自收缩和干燥收缩减少,开裂敏感性降低.

Effects sum and sodium cation shrinkage of slag, high-calcium fly ash, desulfurized gypsum, calcined desulfurized gypsulfate on early age autogenous shrinkage of cement pastes, long terms of desicand initial cracking sensitivity of cement mortar are researched. The results indicate that there are relationships between autogenous shrinkage and hydration activity of materials in cement-mineral system. The autogenous shrinkage of cement sample is higher than that of 50% （by mass） of slag or high-calcium fly ash samples. The autogenous shrinkage decreases a- long with the decreasing of hydration activity of minerals. Because of enhanced hydration degree, the chemical shrinkage, amount of AFt and the expansion, the sulfate active material affects the autogenous shrinkage a little. 50% （by mass） of slag increases the desiccation shrinkage clearly duo to slag urge pastes to eduction and lose more water at early age. 1% （by mass） of NazSO4 increases the desiccation shrinkage duo to its early reinforcing and more water.consumption for hydration. Both the slag and Na2SO1 accelerate the volume of pastes to shrinkage due to the inner desiccation. Mixing of desulfurized gypsum and calcined desulfurized gypsum in certain mixture can decrease the desiccation shrinkage significantly. The initial cracking time relates with the autogenous shrinkage and hydration activity. The more the autogenous shrinkage, the higher is the sensitivity of initial cracking. Reinforced process for cement enhances the risk of cracking usually. Replaced some of cement with equal amount of mineral material, especially the minerals with low activity, hydrating course prolongs, autogenous shrinkage and desiccation shrinkage decrease and crack-resisting performance of mortar would be improved.