Effect of Organic Polymers on the Properties of Slag-based Geopolymers

In this paper, the effects of polyethylene glycol (PEG), polyacrylamide (PAM) and sodium polyacrylate (PAAS) on the mechanical properties of slag-based geopolymers (SG) were studied. Several characterization methods including mercury intrusion porosimetry (MIP), Fourier transform infrared spectroscopy (FT-IR) and 29Si nuclear magnetic resonance (29Si NMR) were employed to determine the pore size distribution, bonding, and the degree of [SiO4] tetrahedral polymerization of SG. The study in the mechanical characterization of SG showed that after curing for 28 days, the bending toughness coefficient of the specimen increased as much as 53.7% with the incorporation of 0.6 wt% PAAS. The MIP results showed that the larger capillary pores in SG matrix can be filled with the three organic polymers, resulting in a significant reduction in the pore size. The FT-IR results confirmed the formation of the C–O–Si bond after the incorporation of PAAS and PAM, and the 29Si NMR results indicated a reduction in the degree of [SiO4] tetrahedral polymerization and a change in the mean chain length (MCL) of [SiO4]/[AlO4] tetrahedra. From the above results, it can be concluded that the organic polymers, PAAS and PAM were involved in the formation of the network structure of SG, decreasing the degree of polymerization [SiO4] tetrahedra and increasing the MCL, thus improving the toughness of SG.