Self-Healing of Tensile and Shrinkage Cracks in Engineered Cementitious Composite Liquid Containing Structures

In this research, the self-healing of shrinkage and direct tension cracks in engineered cementitious composites (ECC) panels was investigated. The water leakage and self-healing of ECC elements subjected to direct tension cracking were studied under the coupled effect of sustained loading and pressurized water. The experimental program included normal concrete (NC) and ECC panels with different supplementary cementitious materials (SCM), comprising fly ash Class-F, fly ash Class-C and granulated blast furnace slag. A test setup was designed to simulate the leakage in liquid containing structures (LCS). Each panel was subjected to direct tensile loading to induce full depth cracks, and then the leakage test was carried out under sustained load and different water pressures. To consider the effect of ECC composition on the self-healing of panels exposed to loading and pressurized water, the leakage rate was continuously studied until complete sealing. Additionally, a detailed microstructural analysis was completed on full depth drilled cores, in which the samples were taken from three layers of the healed cracks in order to investigate the influence of pressurized water on the self-healing products. The results of this study highlight the advantages of using ECC in LCS and confirm a considerable effect of water pressure and SCM type on the self-healing capability of ECC. In the second phase of this research, the cracking behavior of ECC under shrinkage and temperature strains was investigated. A test setup was designed to restrain the panels against the deformation. The experimental program considered the cracking and self-healing behavior of ECC and NC panels representing a segment of LCS in the field. These panels were monitored for seven months under various environmental conditions. Following the casting, the drying shrinkage strains, hydration and ambient temperature variation, as well as cracking profiles were monitored. Also, the self-healing capability of ECC cracks was investigated under randomly natural climate exposure. The results showed that, ECC prepared with slag and fly ash-F developed higher shrinkage, causing earlier cracking generation than NC. However, in contrast to NC in which the crack widths continue to develop over time, ECCs have the potential to self-heal under harsh field conditions.