• Energy Research

Using fine recycled concrete aggregates (FRCA) in concrete manufacturing points towards achieving sustainability in recycled aggregate valorisation. The higher absorption and amount of hardened cement paste of FRCA may impair concrete performance. One of the most influenced properties is drying shrinkage; this is because of the extra cement paste content and higher porosity and deformability of FRCA when compared to natural sand. Thus, the influence of FRCA on shrinkage appears to depend on the quality of FRCA and how its absorption is considered during mix design. In this study, the influence of FRCA mineralogy and quality on drying shrinkage is evaluated, also considering the compensation of FRCA absorption rates. In addition, the feasibility of different models to predict the ultimate shrinkage is also analysed. The quality of FRCA and the compensation of water absorption cause different effects on concrete according to the property evaluated. The storage of water inside the FRCA particles causes no influence (or even a beneficial influence) on the shrinkage of concretes. Models used to estimate the drying shrinkage show they are still reliable with the use of FRCA.

The building sector’s sustainability requires construction and demolition waste (CDW) to contribute to the circular economy. Among the CDW, recycled concrete aggregates (RA) have been mainly studied to replace natural aggregates. Still, the approval of their use in regulations and standards is slower. Some barriers to the adoption of RA are related to the durability of recycled aggregate concrete (RAC). However, their physical and mechanical properties have been extensively studied. The durability risks associated with sulfate attacks have been solved for conventional concrete. However, sulfate attack on recycled concrete still raises numerous unsolved questions. In this literature review, the experience of sulfate attack on RAC is compiled and analyzed using a compressive framework highlighting the most relevant aspects of the new matrix in RAC and the old matrix of RA to support its relevance to the damaging sulfate process. Suggestions for further research are presented to understand the full extent of this issue and contribute to incorporating and extending recycled aggregates into existing regulations.