矿物掺合料对低水胶比混凝土干缩和自收缩的影响

Effect of mineral admixtures on drying and autogenous shrinkage of concrete with low water-to-binder ratio

研究了粉煤灰(0%、10%、30%、50%)、矿粉(0%、10%、30%、50%)以及硅灰(0%、10%、20%)对水胶比为0.24的低水胶比混凝土干缩和自收缩性能的影响规律,并采用双曲线函数的收缩表达式对试验结果进行拟合,定量化地揭示了矿物掺合料对收缩随时间发展趋势的影响,分析了干缩与自收缩的关系.结果表明:粉煤灰有利于减少低水胶比混凝土的干缩,矿粉次之,硅灰略增大混凝土的干缩;粉煤灰有利于减少低水胶比混凝土的自收缩值,矿粉增大了自收缩,硅灰非常明显地增大混凝土自收缩;低水胶比混凝土的自收缩在所测试的干缩中占有很大的比重,而且随着粉煤灰、矿粉和硅灰掺量的增加所占的比重均逐渐增大.

The influences of fly ash with replacement percentages of 0%, 10%, 30% and 50%, ground granulated blast-furnace slag with replacement percentages of 0%, 10%, 30% and 50% and silica fume with replacement percentages of 0%, 10% and 20% on the drying and autogenous shrinkage of mortar in super high strength concrete with water-to-binder ratio of 0. 24 were studied. By analyzing the shrinkage curves fitted from the experimental data for the concrete mixtures with different mineral admixtures using hyperbolic expression, the influences of mineral admixtures on the time-dependent shrinkage behavior and the relationship between drying and autogenous shrinkage were investigated. The results indicate that both fly ash and slag obviously decrease the drying shrinkage of the concrete with low water-to-binder ratio, while silica fume increases the drying shrinkage a little. On the other hand, while the autogenous shrinkage is reduced with the addition of fly ash, it increases with the addition of slag or silica fume. The results also show that the proportion of autogenous shrinkage to the drying shrinkage of the concrete with low water-to-binder ratio is remarkable and may further increase with the content of fly ash, slag or silica fume.