Microstructure and Modified Mechanism of Core-Shell Structure Latex Modified Cement Mortars

摘要

The PB-g-PS core-shell structure latex was used to modify cement mortar, and the weight ratios of polybutadiene to styrene ranged from 70/30, 50/50 to 30/70. Polymer-modified mortars (PMMs) using three kind different core-shell ratios latex were prepared by varying the polymer-cement ratio (P/C). In the fixed flow of 175 ± 5mm, and curing 24h at 20℃,RH90% air, and followed using two curing methods(6d immersed in 20 ℃ water followed by 21d at 20℃, RH 65% or 27d at 20℃water).The polymer modified mortar structure was studied by SEM. The microstructure analysis showed that mortar constituents of unmodified mortar (UMM) are loosely joined with each other due to the absence of polymer. By contrast, mortar constituents in PMMs are compactly joined with each other due to the presence of interweaving polymer films and dispersing of polymer particles in the matrix of modified-mortars, thereby forming a monolithic structure. The PMMs may acquire different structures. They may appear as branch-like, band-like, cone-shaped particles, the tasset bundle-shaped particles, closely packed polymer particles, and the different morphology of polymer film. Overview on, the modified mechanism of PMMs are that polymer forming film, dispersing of polymer particles in the matrix of modified-mortars, polymer film and polymer particles deforming, which are beneficial for improving properties of modified-mortars.