Evaluation of an experimental mix proportion study and production of concrete using fine recycled aggregate

This paper deals with the investigation of an experimental mix design method and production of recycled concrete incorporating fine recycled aggregate (FRA) from mixed construction and demolition waste. During the experimental mix design process the recycled concrete workability was measured using Graffs flow table instead of using slump test. The concrete were designed considering two FRA proportions (20% and 40%) and two levels of flowability (355 +/- 5 mm e 405 +/- 5 mm). The application of this method shows the influence of aggregate/ cement ratio, cement content, water/cement ratio on the compressive strength, and the mix design nomograms were achieved for the well-established concrete relationships. From these nomograms a validation study was performed evaluating the compressive strength, splitting tensile strength and modulus of elasticity for concretes with w/c ratios of 0.45 and 0.65. The results pointed out the FRA physical properties such as higher water absorption; surface roughness and shape irregularly; and lower specific density can be overcome when using the proposed mix design method that deals with all these parameters in an experimental basis. Also, the recycled concrete compressive strength, splitting tensile strength and modulus of elasticity results decrease for the highest flowability level studied (405 mm) due to the lowest aggregate/cement ratio and the increase for the mixtures with the highest proportion of FRA (40%) due to the highest cement content.