Performance in shear of reinforced concrete slabs containing recycled concrete aggregate

Concrete construction and demolition leads to the generation of a significant amount of waste and CO2 emissions, which both have a negative impact on the environment. The use of recycled aggregate concrete (RAC) is one potential way to mitigate this impact but more research is required to understand its behaviour in shear for structural applications. The objective of this research was to compare the shear behaviour of reinforced RAC slabs to reinforced concrete slabs containing non-RAC, and to compare the crack development of each specimen through the use of digital image correlation and fibre optic sensing. One way-slab specimens constructed using 5 RAC mixes (3 coarse recycled concrete aggregate mixes with up to 30 % replacement and 2 granular recycled concrete aggregate mixes with up to 20 % replacement) and a control concrete mix were tested to failure in 3 and 4 point bending. Load, displacement, distributed strain measurements, and digital images were collected throughout testing. The average peak shear forces of the RAC specimens were higher than that of the control specimens except for the specimens with the highest level of granular replacement (20 %) which had a 14 % reduction in shear capacity versus the control specimens. These specimens also exhibited shear cracking at lower loads compared to the control specimens as indicated by the digital image correlation and fibre optic measurements. Results from this research provide evidence that up to 30 % coarse recycled concrete aggregate and 10 % granular recycled aggregate may be incorporated into structural concrete mixtures without affecting the performance. However, concrete containing 20 % volumetric replacement of the natural aggregate with granular recycled concrete aggregate may require special consideration. Digital image correlation and fibre optic sensing can be used to determine the cracking behaviour of reinforced concrete specimens.