Studies on performance enhancement of recycled aggregate by incorporating bio and nano materials

This paper investigates the modification effect of nanosilica and ureolytic/non-ureolytic bacteria at the interfacial transition zone (ITZ) of RA and recycled aggregate concrete (RAC).The improved RA showed reduction in water absorption (43% in non-ureolytic bacteria, 64% in ureolytic bacteria and 21% in nano modified RA) and increase in specific gravity (∼29% in non-ureolytic bacteria, 30% in ureolytic bacteria and 18% in nano modified RA). The studies also proved that properties of RA and RAC on the macroscale were highly improved by the soaking approach than the direct mixing approach. ITZ studies were carried out using Field Emission Scanning Electron Microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDX) analysis, which revealed that, biogenic calcite and nano mediated accelerated hydration products densified both the ITZs (old and new), leading to substantial improvement in macroproperties of RAC. Thus, the proposed modification techniques, seems promising for the performance enhancement of recycled aggregate.