Abstract
This study investigated the compressive and tensile strength of concrete made with recycled concrete aggregate gathered from demolition sites. 30% of both coarse and fine normal aggregate was replaced by recycled aggregate. The concrete was produced by the normal or the two-stage production method, in which coarse aggregate is first placed in a mold, and then grout injected via a pipe to fill the voids between the coarse aggregate. At water-cement ratios of 0.55 a compressive strength of about 20 N/mm2 (2.9 ksi) was obtained for both normal and recycled aggregate concrete, produced by both the normal and the two-stage production method. However, the two-stage production method resulted in a slightly lower tensile strength than the regular production method. These results suggest that recycled aggregate can be used for concrete structures.