Mechanical and transport properties of recycled aggregate concrete modified with limestone powder

Abstract

In this work, the mechanical and transport properties of recycled aggregate concrete (RAC) modified with limestone powder were studied. The results indicate that replacing 10 wt% cement with limestone substantially improves the compressive strength of RAC. A better resistance to chloride and water ingress can also be achieved owing to the decreased pore connectivity. The initial sorptivity is found to increase linearly with increasing permeable voids content. Mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) analyses demonstrate that adding limestone leads to a refinement of pore structure and densification of both bulk paste and interfacial transition zone, respectively. X-ray diffraction (XRD) patterns suggest that incorporation of limestone prevents the transformation from ettringite (AFt) to monosulfate (AFm), thus increasing the total volume of hydration products. Thermogravimetry and differential scanning calorimetry (TG/DSC) analyses confirm an improved hydration process in RAC containing limestone, explaining for the enhanced mechanical and transport properties.