Investigating self-healing capacity of micro-cracked ECC with different volume of fly ash

Abstract

Crack is called the intrinsic flaw of concrete that is inevitable for concrete infrastructures during their service life. The presence of crack offer aggressive agent access to pass through, which has a direct impact on durability, therefore resulting in shortened service life. Nevertheless, the influence of crack on the durability can be greatly minimized when crack width is controlled within certain limits. Engineered Cementitious Composite (ECC) is a new class of HPFRCC micro-mechanically designed to achieve high tensile strain capacity of 3-5%, while maintaining very tight crack width. In this paper, we attempt to investigate the self-healing capacity of micro-cracked ECC by capillary water sorption test. Three ECC mix proportions with different volume of fly ash are used in this research. Before water curing the specimens are pre-loaded at 28 days so as to produce micro-cracks. The micro-cracked specimens are then cured under water for another 30 and 60 days, respectively, before water sorption test is conducted. It is found that water absorbed by cracks of the pre-loaded specimens reduces with increasing curing age, which suggests that self-healing products accumulate within the cracks over time. Subsequent ESEM observations also confirm the above findings. Most pronounced self-healing behavior is revealed for the mixture with highest fly ash content, which also shows smallest crack width. The crack width reduces with increasing volume of fly ash, denoting better capacity of crack width control. With excellent crack width control and self-healing behavior, ECC can be an ideal material for durable concrete infrastructure.