Test results indicated that recycled concrete aggregate can be used as a coarse
aggregate in high calcium fly ash geopolymer concretes with the 7-day compressive strengths of 30.6
e38.4 MPa which were slightly lower than those of high calcium fly ash geopolymer concretes containing
crushed limestone. The use of high sodium hydroxide concentrations of 12 and 16 M resulted in
better performances both in strength and durability than that of 8 M.