Long-term shrinkage and mechanical properties of fully recycled aggregate concrete: Testing and modelling

To advance the research on recycled concrete (RC), recycled coarse aggregate (RCA), recycled fine aggregate (RFA) and recycled powder (RP) were used in preparing fully recycled aggregate concrete (FRAC), which lead to more comprehensive usage in the recycling of concrete waste. Recycled aggregates were studied as types of aggregate combinations instead of partial substitutes, and four aggregate combinations were designed with the use of natural and recycled aggregates in this study. The effects of different aggregate combinations on the longterm mechanical and shrinkage properties of concrete were examined. Furthermore, the effects of using RP on the properties of FRAC were studied. The results showed that using fully recycled aggregate (FRA) combinations had negative effects on the long-term mechanical and shrinkage properties of concrete, which were consistent with previous research on recycled concrete. However, the effect caused by FRA combination were found to be higher than the sum of that caused by fully recycled coarse aggregate and fully recycled fine aggregate combination. Moreover, RP decreased the mechanical properties of FRAC by 5%-17% whereas the shrinkage strain of FRAC in 180 days were decreased by 3%-13% with the increase of RP content from 10% to 30%. A long-term shrinkage model suitable for FRAC was derived by adding modification coefficients for aggregate combinations and RP contents to the current models.

Automated summary

This study investigated the effects of different aggregate combinations on the long-term mechanical and shrinkage properties of fully recycled aggregate concrete (FRAC). It was found that using fully recycled aggregate combinations had negative effects on the concrete properties, and the effect caused by fully recycled aggregate combination was higher than the sum of the effects caused by fully recycled coarse aggregate and fully recycled fine aggregate combination. Additionally, the study examined the impact of recycled powder (RP) on FRAC properties and found that RP content affected the mechanical properties and shrinkage strain of FRAC.