Production of Self Compacting Concrete using Recycled Brick Aggregate

Abstract

Sustainability is a pressing concern in construction, especially with dwindling material resources. Bricks are frequently used in construction works in Bangladesh as coarse aggregate, and recycling of this concrete after demolition of buildings provides a sustainable solution. This study investigates the fresh and hardened properties of self-compacting concrete (SCC) incorporating recycled brick aggregate (RBA) as coarse aggregate as well as fine aggregate. To understand the possibility and challenges for making SCC using RBA, ten different mixes were designed using RBA of maximum size of aggregate as 15 mm and 20 mm. Natural-river sand and recycled fine aggregate were used as fine aggregate. As binder CEM Type I and blended cement with fly ash, slag, and silica fume were used. The water-cement ratio and sand-to-aggregate ratio were 0.35 and 0.50 respectively; while admixture dosage was adjusted based on the flow ability of concrete. A total of 150 cylindrical specimens were casted. Compressive strength tests were conducted at 7, 14, 28, and 90 days respectively. The obtained results demonstrated that RBA can be utilized to make SCC that satisfies both fresh and hardened properties when combined with either natural or recycled brick aggregate as fine aggregate. Notably, partial replacement of cement with fly ash and slag only, significantly improved fresh properties, while on the other hand, adding silica fume improved resistance to segregation, in certain situations, this came at the expense of decreased flow characteristics. The flow diameters were within the range of 500 - 700 mm and for certain cases V-funnel test results were varied from 6-12 seconds. Cases with recycled sand as fine aggregate showed a tendency of less flow ability compared to the cases made with natural sand cases. On the other hand, the cases with natural sand and fly ash and slag as partial replacement of cement yielded minimal strength in comparison to the cases made with recycled brick aggregate as fine aggregate. The compressive strength is increased significantly when silica fume was added. By using RBA as coarse aggregate and fine aggregate and adding silica fume, it is possible to make SCC of compressive strength 42 MPa.