Engineering Properties of Geopolymer Aggregate Concrete

This paper reports a novel methodology to manufacture geopolymer coarse aggregate (GPA) using low calcium fly ash. The developed methodology is outlined together with a systematic experimental study undertaken to examine a viable manufacturing process for GPA production and the consideration of key mechanical properties and durability characteristics of GPA concrete up to 90 days. GPA with a dry compressive strength in excess of 50 MPa can be manufactured using a solid cylindrical mould with compression applied using a cylindrical piston. The key mechanical properties investigated for GPA concrete demonstrate a good correlation with the compressive strength to conventional crushed aggregate concrete. Concrete with mean compressive strength up to 37 MPa can be produced using the innovative GPA concrete. The GPA concrete demonstrates low water and air permeability indicating that the material is a high-quality concrete with a dense pore structure. Overall, GPA investigated in this research shows potential as a lightweight coarse aggregate in portland cement concrete, with the significant additional benefit of addressing and reducing the environmental impact of fly ash from coal fired power generation.