Chloride ion permeability improvement of recycled aggregate concrete using pretreated recycled aggregates by silica fume slurry

This paper aims to investigate the effects of surface pretreatment method by soaking recycled concrete aggregates (RCAs) in silica fume slurry on mechanical and durability properties of recycled aggregate concrete (RAC). Two surface modification methods, namely RACCM and RACCD were used to improve durability of mixes. Hardened properties of the mixes were assessed in terms of compressive strength and ultrasonic pulse velocity.Water absorption, bulk electrical resistivity and rapid chloride penetration test (RCPT) and rapid chloride migration test (RCMT) were experimentally tested to characterize durability properties. In addition, Scanning Electron Microscopy (SEM) of mixes was carried out and the effect of surface modification method on the microstructure of specimens was studied. Results revealed that using pretreated recycled aggregates significantly improved durability properties of mixes especially chloride ion penetration and electrical resistivity. Moreover, SEM images showed that utilizing pretreated RCAs had a pronounce influence to improve the interface transition zone culminating in lower permeability of specimens and higher electrical resistance. The correlation results showed a strong relationship between total charge passed and electrical resistivity.