Abstract:
This research investigates the development of green base material from recycled concrete mixed with fly ash geopolymer for sustainable infrastructure. The studied influence factors included RCA/FA ratio, liquid alkaline content (L), sodium silicate (NS)/sodium hydroxide (NH) ratio, and curing time. The unconfined compressive strength (UCS) test and scanning electron microscope (SEM) test were used to evaluate the engineering and microstructure properties of the specimen. The maximum dry unit weight of RCA-FA geopolymer specimens increased as FA replacement increased. It was due to the filler effect of FA, leading to the improvement of unit weight. However, For FA higher than 20, the maximum dry unit weight of RCA-FA geopolymer specimens decreased with FA replacement. It may be due to the lower specific gravity of FA. The optimum ingredient of RCA-FA geopolymer specimens is at L content of RCA/FA of 90/100, optimum liquid content (OLC), NS/NH of 50/50, 60/40, 70/30, and 80/20, which meet the 7-day UCS requirement of pavement base material for the low-volume road. There is one ingredient for high-volume road, which is at L content of OLC, NS/NH of 60/40, and RCA/FA of 90/100. The outcome of this research will enable RCA as a replacement virgin aggregate material and FA geopolymer as an alternative low-carbon cementitious material replaced to Portland cement for the pavement base material.