Influence of expansive agent and curing method on the mechanical and drying deformation properties of Engineered Cementitious Composites (ECC)

Aimed at reducing drying shrinkage of Engineered Cementitious Composites (ECC) and uncovering the significance of curing method as to ECC with additives, twenty groups of specimens were designed and tested in this paper. Influence of expansive agent, curing method (dry curing, standard humid curing, and 3d/7d early-water-curing composited with later-dry-curing), and curing age on the compressive strength, uniaxial tension properties, free and restrained drying deformation properties of ECC were comprehensively studied. The results indicate that the addition of expansive agent reduces the compressive strength of ECC, and the early strength is relatively low followed by a gradual development. Besides, sufficient long-term curing guarantees the strength development of ECC with expansive agent mixed. Both high tensile strength 7.16 MPa and ductility 4.77% can be obtained by early sufficient curing and later dry environment, respectively. With increasing the content of the expansive agent, the tensile cracks become finer and even invisible. The mixed expansive agent ensures the quantity of potential ettringite while an appropriate curing method contributes to the formation of it. It reduces drying shrinkage, offsets other kinds of shrinkage, and transforms the stress state of restrained ECC from shrinkage to expansion, reducing the risk of cracking. Evaluating the deformation of ECC with expansive agent under different curing conditions is necessary to avoid harmful expansive deformation, especially when it is restrained. The study provides credible and valuable experimental data and suggestions for facilitating the application of ECC with the characteristic of low drying shrinkage in practice.