Performance evaluation of loadbearing compressed fully recycled aggregate concrete bricks

Due to rapid expansion of infrastructure around the world, many countries are facing severe shortage of natural resources. Further, environmental issues originating from Construction and Demolition (C&D) waste are becoming a concern for society. Recycling of C&D waste is one of the most viable options that can help to reduce the burden on natural resources as well as provide an eco-friendly and sustainable solution. Recycled Concrete Aggregates (RCAs) obtained by recycling of C&D waste have been used in the production of Recycled Aggregate Concrete (RAC). In this study, the effect of RCAs on compressive strength and durability performance of loadbearing concrete bricks manufactured by Compression Casting Technique (CCT) is investigated. The concrete bricks were prepared using different mixes containing 100% RCAs using ratios of coarse-to-fine aggregates i.e., 60:40 and 70:30. For comparison, Natural Aggregates Concrete (NAC) and burnt-clay bricks were also tested. They were tested in compression and durability tests such as water absorption (WA), cycling ponding test in acidic and brine solution, efflorescence and drying shrinkage were conducted. The results showed that RAC bricks satisfied the density, WA and compressive strength requirements specified in ASTM standards. Compared to burnt-clay bricks, density and compressive strength of RAC bricks were higher (20.7–30.5% & 11.2–25.2%, respectively) while WA was less (34.4–68.5%). The RAC bricks performed better than NAC under 5% sulfuric acid and supersaturated brine solutions. The drop in compressive strength for RAC bricks after 4 cycles of immersion in acidic solution for 28 days was negligible. An increase of 21% in compressive strength of RAC bricks with 60:40 ratio of RCAs, and 10% cement was achieved after 4 cycles of immersion in the supersaturated brine solution for 56 days. The RAC bricks were more susceptible to drying shrinkage due to their porous nature. No efflorescence problem was observed in both RAC and NAC bricks. This study concluded that masonry units made using 100% RCAs fulfill performance criteria specified in international standards are structurally viable and are an eco-friendly solution. The commercial use of RAC bricks will have a significant positive impact on the environment and ensure sustainable development in construction industry.