氧化镁膨胀剂对混凝土早期裂缝自愈合性能的影响

Self-healing Behavior of Early Concrete Cracks Incorporating Magnesium Oxide Expansive Agent

对比分析了2种型号的氧化镁膨胀剂在5%及10%掺量(质量分数,下同)下对混凝土早期裂缝自愈合性能的影响,对混凝土的限制膨胀率、裂缝形态、裂缝宽度变化及抗压强度恢复率进行了试验分析.结果表明:氧化镁膨胀剂活性越高、掺量越大,混凝土的限制膨胀率越大,在相同龄期条件下,相同初始宽度的混凝土裂缝自愈合效果越好;氧化镁膨胀剂对初始宽度为0.40mm及以下的早期裂缝有较好的愈合效果,对初始宽度超过0.40mm的裂缝愈合效果相对较差;掺氧化镁膨胀剂的混凝土试件7,28d抗压强度恢复率较空白组均得到显著提高,提高幅度约为55%~68%.

The influence of two kinds of magnesium oxide expansive agent on self-healing behavior of early concrete cracks under content of 5%and 10%(by mass,the same below)was compared and analyzed.The restrained expansion rate,crack morphology,crack width variation and recovery rate of compressive strength were tested.Results show that the higher the reactivity and the more the content of the magnesium oxide expansive agent,the higher the restrained expansion rate,and the better the self-healing behavior of concrete cracks with the same initial width.In these experiments,magnesium oxide expansive agent has better self-healing effect on early cracks with smaller initial width(less than 0.40 mm),while the effect shows a significant reduction when initial width grows beyond 0.40 mm.What is more,the 7,28 d compressive strength recovery rate of the specimens mixed with magnesium oxide expansive agent will be significantly improved by 55%68%compared with the control group.