Properties of metakaolin-high calcium fly ash geopolymer concrete containing recycled aggregate from crushed concrete specimens

This study aims to investigate the effects of metakaolin (MK) on the properties of a fly ash-based geopolymer concrete containing 100% recycled coarse aggregate from crushed specimens of laboratory. The MK was used as a partial replacement for high calcium fly ash (HCF) in geopolymer binders. The results showed that geopolymer concrete with MK has better strength, porosity, water absorption, and acid resistance. Increasing the use of MK leads to higher strengths in both natural and recycled aggregate geopolymer concrete. Furthermore, the high calcium fly ash blended with MK geopolymer concrete containing recycled aggregate is suitable for environment friendly construction and is comparable in terms of mechanical performance to a normal geopolymer concrete made with natural aggregate.