Analyses on the Expansion of Large Mock-Ups and Laboratory Specimens Exposed to ASR and DEF

As laboratory studies of internal swelling reactions are usually performed on small-size samples, the results of these studies are not able to reproduce the real condition to which the massive concrete structures are submitted. The expansion data for two groups of specimens subject to aggregate-silica reaction (ASR) and delayed ettringite formation (DEF) are recalled in this study, including large mock-up blocks and core samples extracted from the block after 200 days of exposure. Each investigated case exposed the samples to the same conservation conditions. The objective of this study is (i) to analyze the experimental expansion data of laboratory specimens and large mock-ups exposed to ASR and DEF; (ii) to correlate the behaviour of real-scale massive structures with the residual expansion of core samples; and (iii) the final goal is to provide recommendations for predicting the long-term expansion of massive concrete structures based on residual strain analysis. The possible reasons for explaining the inconsistent expansion of specimens at multi-scales are proposed in this study, from the perspectives of differences in moisture degree, leaching degree of alkalis/calcium, temperature gradient, the occurrence of microcracks due to the high-speed action of the drill, and the restraint from the end support. The restraint effect induced by concrete self-weight and metal support is believed to be the main reason leading to the different behaviour of specimens at multi-scales. Calculations of the swelling stress and predictions of expansion are performed in this study, considering the restraint effect in constitutive equations that are coupled to a damage model.