矿物掺合料对MgO膨胀剂膨胀性能的影响及其机理

Effect of mineral admixtures on expansion properties of MgO expansion agent and its mechanism

MgO膨胀剂具有良好的膨胀稳定性,与混凝土收缩相匹配,可以有效抑制混凝土收缩裂缝的产生。研究了矿物掺合料对MgO膨胀剂膨胀性能的影响及其机理。通过对不同配合比的8%MgO膨胀剂混凝土进行抗压强度、抗折强度和限制膨胀率的测试,探究了矿物掺合料对混凝土性能的影响。试验结果表明:随着粉煤灰掺量的增加,混凝土的抗压强度和抗折强度降低,而矿渣对其强度影响不明显。混凝土在水中养护的膨胀过程可以分为潜伏诱导期、快速膨胀期、缓慢膨胀期和稳定期。矿物掺合料的加入降低了MgO膨胀剂的膨胀效果,且掺量越高,影响越大,其中粉煤灰的影响更为显著。膨胀是由于MgO反应生成的Mg(OH)2晶体填充孔隙所致,矿物掺合料通过降低MgO反应程度和增加孔隙率来减少膨胀现象。矿渣的活性较高,对MgO反应的阻碍较小。

MgO expansion agent has good expansion stability,which matches with concrete shrinkage and can effectively inhibit the formation of concrete shrinkage cracks.The effect of mineral admixtures on the expansion properties of MgO expander and its mechanism were studied.By testing the compressive strength,flexural strength and limited expansion rate of 8%MgO expansion agent concrete with different proportions,the influence of mineral admixture on the performance of concrete was investigated.The experimental results show that with the increase of fly ash content,the compressive strength and flexural strength of concrete decrease,but the slag has no obvious effect on its strength.The expansion process of concrete curing in water can be divided into latent induction period,rapid expansion period,slow expansion period and stable period.The addition of mineral admixture reduces the expansion effect of MgO expansion agent,and the higher the dosage,the greater the effect,among which the fly ash is more significant.The expansion is caused by the filling of pores by the Mg(OH)2 crystals generated by the MgO reaction.The mineral admixtures reduce the expansion by reducing the degree of MgO reaction and increasing the porosity.The slag has higher activity and less obstacle to MgO reaction.