To improve the resistance of recycled aggregate concrete (RAC) to the internal steel corrosion by the pre-treatment of aggregate

Abstract

The present study proposes to improve the performance of recycled aggregate concrete (RAC) subjected to the internal steel corrosion by conducting the pre-treatment on recycled aggregate (RA). A sulfoaluminate cement (SAC) slurry and a diluted water glass (WG) solution were taken for the RA pre-treatment, respectively. Test results show that the RAC as modified by both the two RA treatments presented a better resistance to the steel corrosion as accelerated by the chloride ingress and the direct current (DC) power simutaneously. The corrosion of steel bars embedded in the modified RAC was found to be postponed, moreover, the width development of the cracks induced by the steel corrosion on the concrete surface was retarded, compared to the reference RAC. Microscopic measurements showed that the microhardness of the new ITZ formed between the new cement mortar and the treated RA by both two techniques was improved, moreover, the new ITZ presented a sandwich-like structure by using the SAC-treated RA. Likely due to the more significant enhancement in the new ITZ, the improvement in RAC’s resistance to the internal steel corrosion was more significant with the SAC treatment than with the WG treatment. Also considering the potential risk of a large early-age shrinkage caused by the high alkaline content introduced by the WG treatment, to pre-treat RA with the SAC slurry was suggested to be more beneficial than that with the WG solution to extend the service life of the reinforced RAC structures serving in severe environments with high risks of steel bar corrosion.