Geopolymer using different size fractions of recycled brick-based mixed demolition waste

Abstract

The hike in CO₂ emission from the cement industry calls for an alternative binder to cement. On the other hand, construction and demolition waste management is a global concern. This research aims to demonstrate the complete applicability of brick-based demolition wastes in geopolymer mortar and concrete. Ground Granulated Blast Furnace Slag (GGBS) was used with brick waste to improve performance. 3 M, 4 M and 6 M NaOH were used for mortar preparation, and 6 M NaOH was used for concrete tests. The performance of the geopolymer binder and mortar was compared with the control specimen. 5 % to 20 % incorporation of demolition waste powder (DWP) with GGBS was explored to find the optimum binder combination. A 10 % incorporation for 3 M and 15 % for 4 M and 6 M was found optimum. Then, 10 % to 100 % incorporation of brick sand was studied to examine the influence of brick-based demolition waste on the fresh and hardened properties of mortar. Sand: Binder: Alkaline activator was taken 3.375: 1: 0.45 for mortar. The workability of mortar varied with the increase of brick sand content. The flexural and compressive strengths were decreased with an increase in brick sand content for all molarities of NaOH; consequently, the water absorption increased with brick sand content. The maximum mortar compressive strength of 27 MPa was found for 10 % demolished sand with a 6 M alkali concentration. However, consistent results were obtained with a 4 M concentration. Geopolymer concrete from brick-based demolition waste was prepared using 6 M NaOH. The UPV result indicates the regular quality of the concrete cube, with acceptable capillary water absorption after 24 h. However, the compressive strength of geopolymer concrete could be useful for non-structural works, and therefore, further studies with higher strength of NaOH for geopolymer concrete are recommended.