Research Progress in the Application of Calcium-based Expansive Agents as Compensation for Autogenous Shrinkage in High-strength Concrete

In this study, comprehensive investigation of the shrinkage compensation mechanisms of calcium-based expansive agents (CEAs), their effects on the properties of (ultra) high-strength concrete (HSC/UHSC), and the existing problems in applying this methodology was conducted. Analyses showed that the rational use of CEAs under certain conditions could greatly or completely inhibit the development of autogenous shrinkage of HSC/UHSC, and significantly reduce the risk of associated cracking. However, it was found that the hydration of the CEAs affected the hydration process of other binders, thereby altering the microstructure of concrete. This was in turn observed to lead to a degree of decrease in compressive strength, flexure strength and elastic modulus, and the decrease rate increasing as with the rise in proportion of CEAs. Moreover, when attempting to improve the shrinkage compensation effects, increasing the amount of CEA presented a risk of delayed expansion cracking of HSC/UHSC. Neither the expansion mechanism, expansion conditions, nor the inhibition methods have yet been fully clarified in the current stage. Lastly, newly proposed Ca-Mg composite EAs were outlined, and the research prospects of Ca-Mg composite EAs in HSC/UHSC were explored.