Feasibility of Roller Compacted Geopolymer Concrete Containing Recycle Concrete Aggregate

In this research, the feasibility of roller compacted geopolymer concrete (RCGPC) containing 100% recycle concrete aggregate (RCA) was investigated. Mechanical characteristics of the RCA-RCGPC composite were evaluated using a compressive strength test, and semi-circular beam test. The effects of different curing conditions (time and temperature) on compressive strength were also assessed. The durability of the material was studied using the freeze-thawing test. Microstructure and morphology investigations were also performed using X-ray diffraction (XRD). Throughout the experimentation, class F (low calcium) fly ash was used. The mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as an alkali activator. It was observed from the test results that, RCA-RCGPC has a high optimum moisture content, which was due to the higher absorption capacity of RCA. By using 8 M concentration of NaOH, Na2SiO3 to NaOH ratio of 1 by mass and 15% fly ash content, 60 degrees C accelerated curing method yielded satisfactory unconfined compressive strength (UCS), semicircular bending beam (SCB) strength and durability were also found to be promising using 100% RCA aggregate. XRD analysis had also proven the formation of new chemical bonds or geopolymeric compounds in the newly formed RCA-RCGPC composite. Based on the test results, this material could be a cost-effective and durable solution to the construction of pavement structures.