Valorization of Recycled Aggregate in Concrete and Mortar

Abstract

In this study, the influences of partial replacements of sand by fine recycled aggregate (RA), and replacement of cement by very fine RA, on the mechanical behaviour and the microstructure changes of mortar were investigated. An experimental program was carried out for producing mortar incorporated with large volumes of RA of various particle sizes. Using the two-step method, five mixtures were made for each part of study (part 1: only aggregate less than 630µm, and part 2: 360µm were replaced by natural aggregate NA), starting by a mix with 100 % of RA, and then 75%, 50%, 25% and 0%. Prism samples were molded in (4*4*16 cm) for mechanical testing (flexure and compression). The results obtained showed that it is possible to use the fine RA to give mixes with compressive strength and flexure strength close to the control mix. Moreover, the use of super-plasticizer leads to a significant increase for both strengths. In the case of the replacement of cement with the very fine RA and in order to obtain green cement, both compressive and flexure strengths are closer to the control mix, which is consistent with microstructure investigations.