Zeolite to improve strength-shrinkage performance of high-strength engineered cementitious composite

Abstract

Engineered cementitious composite (ECC) is a class of high-performance material because it displays strain hardening by multiple crack formation under tension. This unique property makes ECC an ideal constructional binding mortar or repairing material particularly for concrete cracks in existing structures. However, a major issue of ECC is the high shrinkage, which creates differential shrinkage and extra tensile stress that adversely affects its durability. To mitigate shrinkage, a novel way of using zeolite as an internal curing agent without sacrificing the strength of ECC is herein advocated. Zeolite is structurally porous that can trap water and act as a water reservoir to increase internal relative humidity (IRH). In this paper, the shrinkage, IRH and compressive strength of ECC containing 15% (18%), 20% (24%), and 30% (36%) of zeolite replacing quartz sand by weight (and by volume) is studied experimentally. Test results indicate that the 28-day total shrinkage of ECC decreases with the zeolite replacement ratio. From the shrinkage-to-strength ratio, it shows that ECC with 30% zeolite yields the lowest shrinkage per compressive strength, and hence the optimal ratio for quartz sand replacement in this study. With the beneficial effect observed, zeolite replacement ratio greater than 30% (36%) is recommended for future study on shrinkage reduction of ECC.