ABSTRACT
Compressive strength of hardened concretes made with both coarse and fine recycled aggregates was studied as a function of compressive strength of original concretes from which the recycled aggregates were derived. It was found that based on equal slump, the water requirement of concrete made with both coarse and fine aggregates was 14 percent higher than that of control concretes made with natural sand and gravel. Based on equal water-cement ratios the reduction in compressive strength of recycled concretes was an average of 30 percent. However, the water-cement ratio of such concretes was very difficult to control because common standard testing methods for determining when fine recycled aggregate is in a saturated and surface-dry condition are inappropriate and highly inaccurate. As a consequence of the findings, it cannot be recommended to attempt to produce quality concrete with fine aggregate which is derived from crushed concrete.
