工程水泥基复合材料自愈合过程与产物

Selfhealing Processes and Products of Engineered Cementitious Composites Materials

摘要:

借助环境扫描电镜(ESEM)对纤维表面以及15,30,50 μm不同宽度裂缝自愈合产物的生长过程进行了连续观察,结合EDS(energy dispersive spectroscopy)、TEM(transmission electron microscopy,透射电镜)、XRD(Xray diffraction)及FTIR(fourier transform infrared spectroscopy)等先进研究手段,对工程水泥基复合材料(ECC)裂缝自愈合产物的化学特性进行了分析.结果表明,体系中水泥基材料的进一步水化及CSH凝胶和CaCO3晶体的生成是裂缝自愈合的主要原因.宽度15 μm裂缝的自愈合产物主要为CSH凝胶;宽度30 μm裂缝的自愈合产物主要为CSH凝胶和CaCO3;观察周期内,宽度50 μm形成的自愈合产物量无法填满裂缝.从微观层次上看,宽度30 μm以下的裂缝几乎都能完全自愈合.同时,ECC材料中的PVA(聚乙烯醇)纤维有亲水特性,为自愈合产物的形成提供了成核点,有助于ECC材料自愈合产物的形成和生长.

Abstract:

The growth processes of selfhealing products on 15 μm,30 μm,and 50 μm cracks as well as on fiber surfaces were displayed by means of ESEM.The chemical characterizations of healing products were reported by applying many advanced research technologies such as EDS,TEM,XRD and FTIR.These results suggest that further hydration of cementitious materials and the formation of CSH gel and CaCO3 crystals are the main reasons for the selfhealing phenomena.CSH is the main selfhealing product for crack widths of 15 μm,and CSH and CaCO3are the main selfhealing products for crack widths of 30 μm.Selfhealing products couldn’t fill in the crack widths of 50 μm within observation period.At the microlevel,cracks below 30 μm in width can be almost totally healed.Meanwhile,PVA fibers with hydrophilic nature in ECC provide nucleation sites for healing products that may aid in the selfhealing of ECC.