Improvement in flexural strength of Portland cement by lamellar structured montmorillonite

Abstract

Montmorillonite (Mt) was treated by wet grinding (i.e., WGMt) and lamellar structured Mt was obtained. And it was used to promote the flexural strength of Portland cement (PC). WGMt-PC system was designed, and the addition ratio of WGMt was chosen as 0%, 0.5%, 1%, 1.5% and 2%. Flexural and compressive strength of WGMt-PC mortars at 1, 3 and 28 d were measured, and the related mechanism was analyzed by hydration heat, TG-DTG, XRD, 29Si NMR, MIP and SEM in details. Results exhibited that lamellar structured Mt with D50 = 360 nm was obtained via wet-grinding process. Moreover, WGMt augmented the flexural strength of PC notably in the early period; 2% WGMt increased the 1 d flexural strength by 28.6%, and 3 d strength was also augmented significantly. One reason was that lamellar structured WGMt induced the formation of hydrates in the two-dimensional direction and made the shape and arrangement more regular. The other reason was that the filling effect of WGMt refined the pore structure. Such results confirmed that WGMt could be used to improve the flexural performance of PC at the early age.