Experimental Study of the Chemical Deformation of Metakaolin Based Geopolymer

Chemical deformation is an important material property which influences the autogenous deformation of the materials. While geopolymer is emerging as an eco-friendly alternative to ordinary Portland cement (OPC), few studies have been conducted on the chemical deformation of this material. In this paper, the chemical deformation of a metakaolin (MK) based geopolymer is studied. Unlike OPC paste which exhibits monotonous chemical shrinkage, metakaolin-based geopolymers can show chemical shrinkage and chemical expansion at different stages of curing. X-ray diffraction (XRD) and Fourier transform Infrared Spectrophotometer (FTIR) tests were conducted to characterize the geopolymer paste cured at different ages in order to explain the mechanisms of different chemical deformation behaviors. It was confirmed that the early age chemical shrinkage was mainly due to the dissolving of MK, where the density of MK plays an important role. The chemical expansion taking place in the second stage was mainly associated with the formation of Al-rich products. The chemical shrinkage in the late age was related to the formation of Si-rich products in literature, but this finding was not confirmed in this study. The understanding of chemical deformation of geopolymers is helpful to explain the autogenous deformation of geopolymers.