养护环境对掺有氧化镁膨胀剂的应变硬化水泥基复合材料裂缝自愈合的影响

Effect of Curing Condition on Self-healing of Strain-Hardening Cement-Based Composite Crack Incorporating MgO Expansive Agent

用四点弯曲试验对掺有氧化镁膨胀剂(MEA)的应变硬化水泥基复合材料(SHCC)试件(SHCC-MEA)加载诱导产生裂缝,通过在不同养护时间测量其裂缝宽度以及毛细吸水量,研究了干燥(RH 50%)、水雾(RH 95%)、水(Tap water)以及饱和氢氧化钙溶液(Sat. Ca(OH)2) 4种养护环境对其裂缝自愈合的影响,并通过电子显微镜和能谱仪(SEM-EDS)对愈合产物进行微观分析。结果表明,氧化镁膨胀剂的加入有效提高了SHCC裂缝愈合能力,在水雾环境下有明显效果;水分是裂缝自愈合过程中必不可少的条件,即使掺有氧化镁膨胀剂,干燥环境下的愈合效果依然很差;相比于对照组,饱和氢氧化钙溶液环境下的SHCC-MEA试验组的裂缝愈合效果不理想。

A four-point test was utilized to induce cracks in the strain-hardening cement-based composite(SHCC) specimen(SHCC-MEA) with MgO expansive agent(MEA). The crack width and capillary water absorption at different curing time were measured. The effect of curing condition on the self-healing abilities of SHCC-MEA cracks was investigated. The microstructure of healing products was analyzed by scanning electron microscopy-energy dispersive spectrometry. The pre-cracked specimens were exposed to different curing conditions(i.e., dry(RH 50%), water fog(RH 95%), tap water and saturated Ca(OH)2 solution). The results indicate that the addition of MgO expansive agent can improve the healing ability of SHCC crack effectively, and it has an effect on the water fog condition. Water is essential in the process of crack self-healing, even if the expansive agent is involved, the healing effect in the dry condition is still poor. Compared to the control group, the SHCC-MEA test group in the curing condition of saturated Ca(OH)2 solution has an unsatisfactory crack healing effect.