4. Conclusions
The results indicate that recycled concrete aggregate can be
used as a coarse aggregate in high calcium fly ash geopolymer
concrete. The obtained strengths and durability were slightly lower
than those containing crushed limestone. However, geopolymer
concrete containing recycled concrete aggregate still possessed
sufficiently high compressive strength of 30.6e38.4 MPa or
approximately 76e93% of the same geopolymer concretes containing
crushed limestone.
Sodium hydroxide solution of 12 M was an optimum concentration
for the fabrication of high calcium fly ash geopolymer
concrete in terms of compressive strength, splitting tensile
strength, flexural strength, and surface abrasion resistance. While,
both 12 and 16 M gave geopolymer concretes with good water
absorption, volume of permeable void, rate of sorptivity, chloride
penetration depth, and weight loss from sulfuric acid solution.