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This study reports on the self-healing capability of a strain-hardening fiber reinforced geopolymer composite, named Engineered Geopolymer Composite (EGC). EGC specimens were first uniaxially loaded to a tensile strain of 1%. The cracked specimens were then subjected to three different conditioning regimes: air curing, water curing, and no curing (i.e. reloading right after the preloading). Stiffness reduction was measured for each series by comparing the initial stiffness of intact specimens and the residual stiffness of the cracked specimens. In the water-cured specimens, white precipitates were observed in microcracks formed by preloading. Experimental results of the series showed significant stiffness recovery for low stress levels in the range of 0.5 – 1.0 MPa. Self-healing products observed by using a scanning electron microscope were mostly angular, stone-like substance. An analysis of energy dispersive spectroscopy showed that the healing products were relatively rich in silicon (Si) and aluminium (Al) and had lower concentration of calcium (Ca), compared to the geopolymer matrix phase. This implies that main product of EGC self-healing is unlikely to be either calcite (CaCO3) or salt deposits such as Na2CO3, but rather a formation of some aluminosilicate compounds. This study provides a baseline for further investigations into the development of geopolymer composites with robust self-healing. 

This paper aims to clarify the influence of different types of fly ash on the mechanical properties and self-healing behavior of Engineered Cementitious Composite (ECC). Five types of fly ash with different chemical and physical properties were used in ECC mixtures. The fly ash to cement ratio was fixed at 3.0. The compressive and uniaxial tensile tests were conducted to evaluate the influence of fly ash type on mechanical properties. The permeability test was used to assess self-healing behavior of ECCs with different types of fly ash. The microtopography and chemical characteristics of the self-healing products in the crack were observed and examined by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The fly ash with relatively higher calcium content and smaller particle size was found conducive to a higher compressive strength. The lower combined Al2O3 and CaO content of this fly ash, however, was found to enhance the tensile strain capacity. Furthermore, high calcium fly ash accelerates the self-healing process of ECC for the same pre-damaged level. The self-healing product was a mixed CaCO3/C-S-H system with the CaCO3 as the main ingredient. 

This paper considers the requirements of construction materials to support civil infrastructure resiliency and sustainability. Relevant properties of a re engineered ductile concrete, named Engineered Cementitious Composite (ECC), are reviewed under this framework. Based on a growing body of experimental data, it is suggested that the tensile and compressive ductility, the damage tolerance and tight crack width characteristics, and the self-healing functionality of ECC provides the foundation of a materials technological platform that contributes to structural durability and resiliency. The technology is undergoing a transition from laboratory studies to full-scale field applications. The state-of-the art of ECC technology is illustrated with highlights of an application in bridge deck retrofit aimed at enhancing infrastructure sustainability, and an application in a new building design aimed at enhancing building resiliency under earthquake loading.