Effect of Sulfate Attack and Carbonation in Graphene Oxide–Reinforced Concrete Containing Recycled Concrete Aggregate

Abstract

Sulfate attack and accelerated carbonation tests were conducted on five concrete mixes made with 50% recycled concrete aggregate (RCA) and 30% fly ash (FA) blended with 70% ordinary portland cement (OPC). The graphene oxide (GO) and graphene oxide ball-milled (GObm) added in the concrete mixes varied by 0.05% and 0.1% by weight of binders. The 28-day cured specimens of the mixes were exposed to sodium sulfate solution and accelerated carbonation chamber under a controlled environment. The change in mass increased but the residual compressive strength reduced with progressing exposure to sulfate solution. The carbonation depth decreased with an increase in graphene oxide inclusion in the mixes but with increasing exposure to CO2, the carbonation depth increased. The X-ray diffraction analysis (XRD) was conducted on samples after 28-day exposure to sulfate solution to confirm the delayed ettringite formation and gypsums. The thermogravimetric analysis (TGA) was performed on 28-day exposure to accelerated carbonation in order to understand the variation in the degradation process. The porosity and pore size distribution for the mixes with GO and GObm addition showed lesser porous compared to the mix without graphene oxide, which was confirmed from the mercury intrusion porosimeter (MIP) analysis conducted on 28-day cured specimens.