Effects of varying mixing sequences on the compressive and flexural strength of concrete with recycled concrete aggregates.

The need for sustainable development has given rise to the use of recycled concrete aggregate as substitute to natural aggregates in mixing concrete. This study involved using several mixing techniques to improve the quality of concrete produced using recycled aggregates. Also, recycled aggregates used varied between saturated-surface-dry and air-dried. The quality of concrete was tested by compressive and flexural strength. Experiments conducted in relation to this study was divided into four phases: 1) Making and Curing of Virgin Concrete, 2) Crushing and Obtaining Recycled Concrete Aggregates (RCA), 3) Making of New Concrete with Recycled Concrete Aggregates using Varying Mixing Sequences, 4) Testing of Concrete Cylinders and Beams with Recycled Aggregates. The behavior of concrete using recycled aggregates in response to the different mixing procedures and the difference in moisture content of the RCA were determined and carefully analyzed. After conducting the experiment, and after analyzing the results gathered, the researchers have come to a conclusion that varying the mixing sequence can improve the quality of concrete. Double mixing improved the compressive strength by up to 42.74%. Covering the recycled aggregate with cement paste increased the strength. Also air-dried aggregates are better than saturated-surface-dry aggregates due to the fact that air-dried aggregates have open pores which the cement paste can penetrate thus having better bond. Flexural strength results, however, showed no clear pattern