Effects of rubber aggregates from grinded used tyres on the concrete resistance to cracking

In practice, pavements or slabs are subjected to wide range of length changes during their service life. In case of cement-based materials, their length changes due to shrinkage and/or temperature variations induce tensile stress which can result in cracking detrimental for durability. Generally, aggravating circumstances are observed due to the length change restraint. This contribution focuses on experimental results of tests performed on rubberized concrete produced by partly replacing natural sand (0-4 mm) by rubber aggregates up to 40% by volume. The rubber aggregates are obtained by grinding of used tyres. Effect of rubber aggregate on brittleness index (BI) and on damage evolution was investigated by conducting three-point bending tests on notched beam. Results of these tests confirmed that the both BI and damage decrease with the increase of rubber aggregate content in the concrete. Acoustic emission (AE) technique was applied to detect damage mechanism in concrete by analyzing AE parameters. The Elastic Quality Index (EQI) was adopted to take into account two mutually exclusive properties which govern the sensitivity to cracking, namely strain capacity and tensile strength. Results obtained from the tests performed at 20 degrees C, 40 degrees C and 70 degrees C showed that rubberized concrete exhibits EQI values within acceptable limits for the design of cement-based pavements. (C) 2011 Elsevier Ltd. All rights reserved.