Development of Fly Ash- and Slag-Based Geopolymer Concrete with Calcium Carbonate or Microsilica

Geopolymer is a cementitious material known for its environmental benefits and characteristics comparable to those of conventional ordinary portland cement. Geopolymer concrete (GPC) is a relatively new construction material that is yet to be regulated by standards due to the high variability in the mix design. This paper thoroughly investigates the mechanical, chemical, and durability properties of three types of GPC in an attempt to improve mix designs. In Type I, four concrete mixes were synthesized with high binder content (43%) and 3%-6% microsilica. In Type II, four concrete mixes were made with moderate binder content (20%) and 0%-6% calcium carbonate. In Type III, one mix was designed with low binder content (15%). High compressive strength (71.6MPa) was achieved by the M1 mix of Type I. Type II and III mixes showed strengths superior to those of comparable mixes from previous studies. It was found that Type I mixes were more prone to microcracking than mixes with a lower binder content, resulting in poor durability performances. Type II and III mixes performed similarly in the durability tests, which was mainly due to their similar binder contents. It was shown that microsilica and calcium carbonate could be added to GPC mixes without a significant impact on durability performance. (C) 2018 American Society of Civil Engineers.