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 characterization of a styrene–butadiene modified mortar
Abstract Polymer-modified mortars (PMCs) are used in the construction industry as tile adhesives or frontage coatings. This way of modifying classical mortars improves practical use and adhesion properties. However, the influence of the polymer phase on the durability and the mechanical properties of the modified mortars are still unknown. Three-point bending and compression tests were carried out on PMCs and classical mortar beams. The tests were made under strain control in order to reach the softening part of the stress–strain curve. The compression tests show the influence of polymer content on elastic characteristics, mechanical resistance and strain at rupture. Three-point bending tests reveal the PMC behavior in tension and the damage evolution is monitored by the loss of stiffness. Finally, scanning electron microscopy shows the polymer distribution in the composites.
Development of polymer films by the coalescence of polymer particles in powdered and aqueous polymer-modified mortars
Abstract This paper evaluates and compares the coalescence of polymer particles (continuous polymer films formation) in powdered polymer-modified mortars (PPMMs) and aqueous polymer-modified mortars (APMMs). Polymer-modified mortars (PMMs) using various redispersible polymer powders (powdered cement modifiers) and polymer dispersions (aqueous cement modifiers) were prepared by varying the polymer–cement ratio (P/C) and were tested for the characterization of polymer films using a scanning electron microscope (SEM) after curing for 28 days. It is concluded from the test results that mortar constituents of unmodified mortar (UMM) are loosely joined with each other due to the absence of polymer films, thus having a structure with comparatively lower mechanical and durability characteristics. By contrast, mortar constituents in PPMMs and APMMs are compactly joined with each other due to the presence of interweaving polymer films, thereby forming a monolithic structure with improved mechanical and durability characteristics. However, the results make obvious the poor coalescence of polymer particles or development of inferior quality polymers films in PPMMs as compared to that observed in APMMs. Moreover, PPMMs show less uniform distribution of polymer films as compared to that in APMMs. Different powdered cement modifiers have different film-forming capabilities. However, such difference is hardly recognized in aqueous cement modifiers. The polymer films in PPMMs and APMMs may acquire different structures. They may appear as mesh-like, thread-like, rugged, dense or fibrous with fine or rough surfaces. Development of coherent polymer films is not well pronounced at a P/C of 5% in PPMMs, whereas sometimes coherent polymer films are observed at a P/C of 5% in APMMs. At a P/C of 10% or more, fully developed, coherent polymer films are observed in both PPMMs and APMMs.