Study on the microstructure of metakaolin-based geopolymer enhanced by polyacrylate

Abstract

In order to explore the microscopic mechanism of the remarkable improvement of the organic polymer on the mechanical properties of the geopolymer, fourier transform infrared spectroscopy, 29 Si nuclear magnetic resonance, scanning electron microscope and molecular imprinted polymer were used to investigate the effects of polyacrylate (PAAS) on the microstructure of the metakaolin-based geopolymer (MKG). The load-deflection curves were also tested to confirm the toughing effect. The results show that the organic polymer can modify the structure of the geopolymer at the molecular scale and submicroscopic scale. At the molecular scale, SiOC bonds formed in MKG after the incorporation of PAAS and the polymerization degree of [SiO 4 ] tetrahedra reduced resulting in the mean chain length of [SiO 4 ]/[AlO 4 ] tetrahedra change. At the submicroscopic scale, the MKG became denser after adding PAAS because PAAS could fill the cracks and capillary pores of MKG. Also, PAAS formed a film with an interconnected network structure, which interpenetrated to geopolymer. The loaddeflection curves confirmed increase by 50% in the flexural toughness coefficient of the MKG with the incorporation of 0.8 wt% PAAS.