FLEXURAL BEHAVIOR OF REINFORCED CONCRETE BEAMS USING SYNTHETIC AGGREGATES PRODUCED FROM CONCRETE WASTE POWDER IN VIETNAM

The use of recycled aggregates from construction and demolition waste (CDW) in concrete mixes is widely practiced in developed countries. To promote the recycling of CDW, using recycled aggregates in the construction field needs to be more widely studied. However, there are still limitations in recycling powder waste generated from the crushing process of CDW. In this study, a type of artificial aggregate called synthetic aggregates (SA), made from waste concrete recycled fine powder (WFC), is used as recycled coarse aggregates (RCA) in concrete mixes. Reinforced concrete (RC) beams were made with five different SA contents (0%, 25%, 50%, 75%, and 100%) for the replacement of natural coarse aggregates (NCA). The 4-point bending test was used to analyze the bending behavior of reinforced SA-concrete (CSA) beams with reference to equivalent conventional concrete (CC), such as cracking load, ultimate load, maximum deflection, failure mode, and ultimate flexural strength. The results showed that there was no significant difference in the ultimate load of CSA beams compared to CC beams (2.42-4.41%). However, the first cracking loads of CSA beams reduced significantly by 28% and 49% when the SA contents were at 75% and 100%. Furthermore, as the number of flexural cracks increased, the mid-span deflection of the CSA beams also increased with the SA content, indicating a decrease in the stiffness of the beam. These results may serve as recommendations for the design of flexural CSA beam members in Vietnam.