Sodium hydroxide-free geopolymer binder for prestressed concrete applications

Abstract

Geopolymer is a sustainable binding material which can be produced from industrial by-products, such as fly ash and ground granulated blast furnace slag. Despite having higher mechanical strengths and durability properties than conventional ordinary Portland cement (OPC) concrete, geopolymer concrete has not been widely used in structural grade concrete, so far. The safety hazards in mixing and handling of concrete due to the use of liquid sodium hydroxide in geopolymer binder is one of the barriers to the adaptation of geopolymer in the concrete industry. This study aims to use sodium hydroxide-free one-part geopolymer binder for structural concrete applications, such as prestressed concrete beams. In this study, the mechanical and serviceability properties of grade 50 MPa geopolymer concrete cured at ambient temperature are investigated and compared against same grade OPC concrete. The effects of tensile strength of concrete in load–deflection behaviours of prestressed concrete beams of different spans and sizes are investigated using finite element analysis for short-term and long-term durations. This study finds that geopolymer concrete has around 27% higher indirect-tensile and flexural strengths than OPC concrete of same strength grade which contributes to geopolymer prestressed concrete beams to withstand around 20% higher first-crack load than OPC concrete beams of same span. In addition, geopolymer prestressed concrete beams show a relatively smaller loss in prestressing stress which results in a smaller loss in flexural capacity of beams over the service life of the structure.