Complete triaxial stress–strain curves for geopolymer

• As a new material, stress–strain data geopolymer is limited in the literature.
• We present this data under triaxial conditions which is new.
• We show geopolymer is very similar to normal concrete.
• This will be very reassuring to the engineers who would like to use geopolymer.
• The model is useful for incorporating geopolymer in finite element modelling.

Geopolymer is an emerging alternative to Portland cement and is made from fly ash – a waste stream from coal power stations. As a relatively new material, many mechanical properties of geopolymer are still unexplored. In this paper, the stress–strain characteristics of geopolymer under various levels of confining stresses have been studied. Based on triaxial laboratory tests, the relationships between axial-stress and axial-strain, as well as lateral-strain under active lateral confinement, have been developed for high- and low-strength geopolymers (85 MPa and 28 MPa). Tests were performed under a range of confining pressures from 0 to 35 MPa. Based on this work, a constitutive model describing the complete stress–strain behaviour of geopolymer is proposed. The model developed for the constitutive behaviour of geopolymer has many similarities to Portland cement binder; however, differences do exist namely in the form of increased stiffness or reduced ductility in geopolymer compared to Portland cement binder.