Risk evaluation for recycled aggregate according to deleterious impurity content considering deconstruction scenarios and production methods

Recycled aggregate (RA) obtained from demolished concrete waste (CW) is beneficial owing to its applicability in recycled aggregate concrete (RAC). However, in designing RAC mix proportions, various impurities in the RA that can adversely affect the properties of the concrete, should be considered. Current RA production focuses on the physical quality of the RA without consideration of the impurities present. To improve the stable production and use of RAC, the amounts of deleterious impurities present and their effects on the concrete mix should be estimated. In this study, the risk associated with the presence of impurities in RA was defined as including the amount of impurity residue in the RA and the effects of impurities on RAC properties Both impurity types and RA production methods were considered in assessing risk for five building demolition scenarios. To quantify the risk, the amount of demolished building waste was estimated, the amount of CW was predicted, the RA ratio was calculated from the predicted amount of CW, and impurity sorting levels were investigated for nine methods of RA production. The impurity residue ratio per unit RA was estimated for each demolition scenario, RA production method, and RA quality level considered. A risk model is proposed in this paper that can be used to estimate the risk of RA adversely affecting RAC performance using information on the demolition scenario and the RA production method.