Recycling of Brick Aggregate Concrete as Coarse Aggregate

Abstract

An extensive investigation was carried out for recycling of demolished brick aggregate concrete as coarse aggregate. For this, demolished concrete blocks were collected from 33 different building sites of different ages and broken into pieces as coarse aggregate. Owing to the lack of availability of stone aggregate in Bangladesh, most of the old structures are constructed with brick chips as coarse aggregate, therefore the recycled aggregate investigated in this study is different from the recycled aggregate investigated in other countries which are mostly made of stone chips. The properties of recycled aggregate, such as specific gravity, absorption capacity, and abrasion were tested. More than 700 cylinder concrete specimens of diameter 150 mm and height 300 mm were made with water-to-cement ratios of 0.45 and 0.55. Concrete specimens were tested at 7, 14, and 28 days for compressive strength, tensile strength, and Young’s modulus. The results are compared with virgin brick aggregate. Extended study was also conducted on partial replacement (10–50%) of virgin brick aggregate with recycled brick aggregate. Also, in-situ strength of an old structure has been compared with the compressive strength of recycled aggregate concrete made with the recycled aggregate collected from the same structure. Based on this investigation, it is revealed that recycled brick aggregate can be used as coarse aggregate for making concrete of strength 20.7 to 31.0 MPa. For the same mix design, the recycled aggregate concrete produces almost similar strength compared with the virgin first class brick aggregate concrete commonly used in Bangladesh. However, relatively better performance of recycled aggregate concrete is found for W/C = 0.45. No significant change in compressive strength of concrete is found for up to 50% replacement of virgin aggregate by recycled aggregate. By recycling, it is possible to make concrete with more strength compared with the in-situ strength of concrete of old structures.