Effect of pozzolan slurries on recycled aggregate concrete: Mechanical and durability performance

Disposal of construction and demolition wastes (C&DW) has been deemed as a major concern all over the world due to their disposal crisis that often adversely affect the environment. Several efforts are being made to recycle and manage such wastes for using them in the different building materials production. Using recycled concrete aggregate (RCA) as a partial or full substitution for normal aggregate (NA) in cement concrete is becoming a desirable solution to handle the huge amount of (C&DW). However, RCA possesses relatively higher porosity due to the adhered mortar, which often impedes its application in the construction industries. This paper proposes an economic and environmental approach to optimize the recycled aggregate concrete (RAC) performance. Outcomes showed that the modified RAC exhibited better mechanical strength and higher chloride ion migration resistance than untreated RAC. Compared with normal concrete (NAC), the loss in compressive strength was between 4.5 and 18%, flexural strength 3-18.5%, and elastic modulus 8-22% for the modified RAC at 28-days age. The numerical simulation model to analyze the chloride migration process for the treated RAC showed a good convention with the experimental test results. X-mu CT images demonstrated that the untreated RCA sample has larger pores and air voids than the treated RCA samples. The proposed strengthening technique improved the micro-structure of the ITZ for RAC, making it denser and reduced the micro-cracks when compared with the untreated RAC. This technique provides the possibility to use 100% RCA in concrete and address the long-term environmental, waste disposal, and economic goals. (C) 2020 Published by Elsevier Ltd.

Automated summary

The paper proposes an economic and environmental approach to optimize the performance of recycled aggregate concrete, showing that the modified concrete exhibited better mechanical strength and higher chloride ion migration resistance. Compared with untreated concrete, the loss in compressive strength for the modified concrete was small, indicating the possibility of using 100% recycled aggregate in concrete to address waste disposal and economic goals.