Influence of the moisture state of recycled fine aggregate on the impermeability of concrete

The impermeability of recycled fine aggregate concrete (RFAC) with different contents of recycled fine aggregate (RFA) was tested according to the standard test method of ASTM C1202. The moisture states of RFA were controlled at air-dried (AD), oven-dried (OD) and saturated surface-dried (SSD) states. Both the interfacial structure and the pore structure of RFAC were analyzed. Research results show that, for the same total water-cement (TWC) ratio and the same content of RFA, the interfacial transition region of RFAC became denser by increasing the moisture amount of RFA from oven-dried, air-dried to a saturated surface-dried state; meanwhile, the density and porosity of hardened cement paste (HCP) improved as well, which resulted in the higher impermeability of RFAC. Whereas by contrast, for the same moisture state and by increasing the RFA content, both the interfacial transition region and the property of the interface structure of RFAC became weaker. Also, the decreasing density and porosity of HCP resulted in lower impermeability of RFAC.