Study on properties of PB-g-PS latex-modified cement mortars
The PB-g-PS latex was used to modify cement mortar, and the weight ratios of polybutadiene to styrene ranged from 70/30, 50/50 to 30/70. In the constant water-cement ratio of 0.5, and curing 24h at 20°C, RH90% air followed by 27d at 20°Cwater. This study examines the effects of weight ratios polybutadiene to styrene and the polymer-cement ratios on the flow, compressive and flexural strength and water absorption rate of PB-g-PS latex modified cement mortar. The experimental results show that the flow of modified mortar is increased with increasing polymer-cement ratios and decreasing weight ratios of polybutadiene to styrene, PB-g-PS latex can markedly reduce capillary water absorption rate. The minimum is 1.33Kg/m2. PB-g-PS latex can marked influences much on the mechanical properties of modified mortars. The compressive of the polymer modified mortar decreased, and the flexural strength of polymer modified mortar decreased as well. Overview on, PB-g-PS latex can be incorporated into cement mortars as cement modifier.
Mechanical behaviour of polymer modified mortars
Abstract We investigate the mechanical behaviour of a mortar and five polymer (latex styrene–butadiene) modified mortars (PMMs) with different polymer contents. The mechanical characterisation of the materials is based on compression and three-point bending tests. As expected, compression tests reveal a decrease of the PMMs rigidity and compressive strength for increasing polymer content. On the contrary, three-point bending tests show an increase of the flexural strength from a polymer-to-cement weight ratio higher or equal to 10 wt.%. After some considerations on material porosity and cement hydration, we establish that the main cause of the PMMs flexural strength increase is the latex percolation into a continuous network. Finally, analysis on damage initiation and material rigidity seems to indicate that latex addition limits skin and inner material micro-cracking due to sample drying out.
The AC response of polymer-coated mortar specimens
Abstract Polymeric coatings are widely used for the repair of reinforced concrete. In this paper, the influence of coatings on the permeability was studied using alternating current impedance spectroscopy (ACIS). Two types of polymer coatings [styrene–butadiene rubber latex (SBR) and chlorinated polyvinyl chloride solution (CPVC)] were used. The AC impedance spectra of the polymer-coated mortar specimens displayed a semicircle at the high-frequency range, and the diameter of the semicircle indicated the permeability of the coatings. It was also found that the thickness of coatings had different effects on the impedance spectrum, depending on the type of coating. Comparison of the impedance spectra of the coated mortar specimens before and after the chloride migration test demonstrated that the SBR was suitable for repairing chloride-contaminated concrete because the resistance of the coating increased after the migration test. However, the CPVC was not suitable for repairing because the resistance of the coating was enormously reduced after the migration test.