Model Experimental Investigation on the Mechanical Properties of Recycled Aggregate Concrete Curbs by Incorporating Metakaolin and Basalt Fibre

To investigate the potential of metakaolin (MK) (5%, 10%, 15%, and 20% substitution of cement mass) and basalt fibre (volume contents of 0.1%, 0.2%, and 0.3%) in recycled aggregate concrete (RAC) products, RAC’s mechanical properties were first assessed with a singular incorporation of MK. The findings demonstrated that adding 15% MK optimised the compressive strength and flexural strength of RAC (at the recycled aggregate replacement levels of 30%, 45%, and 60% by weight). An orthogonal test was conducted to investigate the synergistic effect of MK and basalt fibre (BF), with the recycled coarse aggregate (RCA) replacement rate (mass ratio of RCA to natural coarse aggregates), MK content (cement mass substitution percentage), and BF content (volume dosage) identified as the influencing parameters. The variance analysis reveals that the influence of the replacement ratio of RCA on compressive strength surpasses that of MK content, which in turn exceeds that of BF content. Conversely, as for the flexural strength, BF is substantially more effective than that of MK. A model test of RAC curbs was performed based on the ideal mix ratio suggested by the single mixing of MK and MK and BF compound mixing inside the orthogonal test. The results demonstrate that the RAC curbs, with an RCA replacement rate of 30%, display optimal mechanical properties when 15% MK and 0.2% BF are incorporated. This surpasses the performance of 15% MK alone and illustrates that the mix incorporation of MK and BF is superior to that of MK alone.