Influence of acetic acid treatment on microstructure of interfacial transition zone and performance of recycled aggregate concrete

Utilization of acetic acid treatment to enhance the quality of recycled aggregate (RA) has exhibited environmentally friendly and cost-effective method. This study aims to investigate the effect of acetic acid treatment on the change of microstructure properties and performance of recycled aggregate concrete (RAC). The treatment process involved treating low -quality RA with acetic acid, followed by removal of the old attached mortar by mechanical rubbing. The experimental investigation was conducted in three parts. First, the physical properties, including the water absorption, specific gravity, and bulk density of acetic acid treated RA, were determined. Then, the mercury intrusion porosimetry (MIP), Vickers microhardness, and scanning electron microscopy (SEM) tests were conducted to study the effect of acetic acid treatment on the microproperties of RAC. In addition, the compressive strength, splitting tensile strength, and chloride ion penetration resistance of the RAC prepared with treated RA were evaluated. The results showed that the interfacial transition zone (ITZ) Vickers microhardness increased, while the total pore volume of RAC and the width of the new ITZ decreased when the treated RA was used. The effects of acetic acid treatment on the microproperties of RAC were in agreement with the results of macroproperties. Compared to natural aggregate concrete (NAC), there was only a 6.2 % reduction in compressive strength when 50 % treated RA was incorporated. The effect of acetic acid treatment on the performance of RAC was more pronounced on RAC prepared with a low W/C ratio than a high W/C ratio. Based on the findings, the study holds significant potential in promoting the wider use of higher replacement percentage of natural aggregate (NA) with low -quality RA in durable and sustainable concrete construction.