Assessment of properties of recycled concrete by means of a highly fractioned factorial design of experiment

The study presented in this paper has been carried out using a highly fractional factorial experimental design. This design allows the analysis of a greater number of factors and levels with a reduced number of mixes. In the state of art of recycled concrete the studies have been carried out varying the level of one factor while the rest remained fixed. However an excessive number of factors or levels are not considered. This highly simplified test program was designed in order to make the number of tests viable whilst guaranteeing the reliability of the conclusions. The concrete has been produced by substituting the natural coarse aggregates for recycled aggregates from construction and demolition waste, which is mainly composed of concrete. In this research some factors that have not been analyzed in previous studies, such as the granular structure of the concrete or the replacement criteria, have been studied. The properties of recycled concrete analyzed were: density, absorption, compressive strength, elastic modulus and penetration of water under pressure. The concrete was made with dry recycled aggregate. The percentage of replacement of the recycled aggregate did not affect the compressive strength since the water/cement rate remained constant. However the elastic modulus is affected by the percentage of replacement when it exceeds 50%. (C) 2011 Elsevier Ltd. All rights reserved.