Properties Of Polymer-modified Mortars Research Articles

Effect of high-temperature on polymer-modified mortars using the plastic waste of polyethylene as reinforcement

This study aimed to investigate the influence of plastic waste of polyethylene (PWP) particles as reinforcements on the properties of polymer-modified mortars (PMMs) at high temperatures. Sulphate-resistant cement-based mortars with up to 8% PWP, obtained through extrusion of plastic caps, were elaborated. All of the residual compressive strength (RCS), mass loss, porosity, density, theoretical intrinsic permeability and capillary absorption at 20 °C, 140 °C, 250 °C and 350 °C were studied after cooling. Comparisons of PMMs with the control mortar highlighted the influence of PWP with a rate below 6% in improving RCS. Mass loss was negligible and density of PMMs reduced with increasing PWP rates and temperature evolution. Water-accessible porosity had no impact on the cementitious matrix and theoretical permeability was proportional to RCS and showed a small increase at 350 °C. Capillary-water absorption tests revealed very limited degradation of the PMMs pore network at 350 °C when blended with PWP and XRD and SEM analyses revealed a reduction in cracking in the cementitious paste and no chemical interaction of PWP with temperature increase.

Properties of Polymer-Modified Mortar Using Silane as an Integral Additive

Abstract In the present paper, the addition of silane to improve the properties of mortar was experimentally investigated. The morphology and microstructure of mortar were investigated by using both scanning electron microscopy (SEM) and polarizing microscopy (PM). The results show that silane significantly alters the microstructure of mortar, reduces the crystallization, restricts the degree of hydration of cement-based materials, and decreases micro-voids. As a result, silane effectively improves the chemical and carbonation resistance, as well as the chloride and water penetration resistance of mortar. Results also indicate that the consistency of mortar was improved but the compressive strength of the mortar was decreased. Specifically, silane would also be beneficial to the bridging cracking function to resist crack propagation.

Properties of VA/E/MMA Terpolymer Powder-Modified Mortars

This study is to examine and clarify the quality of polymer-modified mortars using a VA/E/MMA terpolymer powder as compared with polymer-modified mortars using a VAE copolymer powder. Polymer-modified mortars using general commercial redispersible polymer powders are prepared with various polymer-cement ratios, and tested for flexural and compressive strengths, tensile strength, water absorption, chloride ion penetration, carbonation and pore size distribution by mercury porosimetry. Overall, the properties of polymer-modified mortars using a VA/E/MMA terpolymer powder were superior to those of polymer-modified mortars using a VAE copolymer powder. And VA/E/MMA terpolymer powder-modified mortars showed significantly improved mechanical properties and durability in comparison with unmodified mortar. It is concluded from the test results that the modification of cement mortar with redispersible polymer powder improves the properties of unmodified mortar, and VA/E/MMA terpolymer powder has higher quality than VAE copolymer powder.

Influence of Coagulation of Polymer Dispersion on the Properties of Polymer-Modified Mortar

The coagulation process of polymer dispersion in cement-based materials is different from that of the pure polymer dispersion during drying and film formation. This process is influenced by the various ions released from cement hydration and the interaction between polymer and cement grain in the water. This paper focuses on the coagulation of polymer dispersion during cement hydrating and the influence on the performances e.g. water absorption, flexural and compressive strength and bonding strength of cement mortar. Commercial anionic styrene-acrylate polymer dispersion was investigated in the coagulation process in the polymer-modified cement paste with polymer to cement ratio (p/c) from 5% to 20% and water to cement ratio of 0.3. The amount of coagulated polymer particles was measured by testing the solid content of the supernatant of the diluted polymer-modified cement paste for a period of time. The calorimetric property was measured by TAM AIR calorimeter. Water absorption and mechanical properties of the modified mortar were also measured according to the China standard. The result showed that the polymer dispersion mixing with cement was found to be coagulated in the very early stage under the low polymer to cement ratio, and the quantity of the polymer particles remained in the liquid is quite low within few minutes during this fast coagulation process. The fast coagulation process undermines the influence of polymer dispersion on the cement hydration and the heat evolution. But it has negative impact on the mechanical properties and water resistance. Adding of surfactant into the polymer dispersion extends the coagulation process and improves these performances.

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Microstructure and mechanical properties of polymer-modified mortars

The influence of the addition of polymer in mortars is investigated with special emphasis on the microstructure and mechanical properties of hardened materials. The presence of polymer in the mortars causes an increase of both the setting time of the cement and the porosity in hardened materials. The observation of these composites by scanning electron microscopy shows the formation of a continuous film of polymer within the matrix for a polymer/cement ratio of 10%. Therefore, the presence of polymer provides a structure where bicontinuous phases of polymer and cement hydrates are intertwined. This leads to a better resistance to acid attack and improves the adhesion between the cement paste and aggregates in mortars. The mechanical properties of composite mortars decrease with the addition of polymer due to the increase of porosity. L’influence de l’addition de polymère dans un mortier est caractérisée en s’intéressant particulièrement à la microstructure et aux propriétés mécaniques des matériaux durcis. La présence de polymère dans le mortier entraîne l’augmentation du temps de prise du ciment et du taux de porosité dans les matériaux durcis. L’observation de ces échantillons par microscopie électronique à balayage permet de mettre en évidence la formation d’un film continu de polymère dans la matrice pour des rapports polymère/ciment de 10% dans les mortiers. La présence de polymère permet donc d’obtenir une structure bicontinue où les phases de polymère et d’hydrates de ciment sont entremêlées. Cela entraîne une meilleure résistance aux attaques acides et une amélioration de l’adhésion entre la pâte de ciment et les granulats dans les mortiers. Les propriétés mécaniques des mortiers composites diminuent avec l’addition de polymère en raison de l’augmentation du taux de porosité.

Properties of polymer-modified mortars using epoxy and acrylic emulsions

Water based polymer systems are often used for improvement in the properties of plain cement mortar or concrete. Presently, latexes of a single or combinations of polymers like polyvinyl acetate, copolymers of vinyl acetate–ethylene, styrene–butadiene, styrene–acrylic, and acrylic and styrene butadiene rubber emulsions are generally used. One of the limitations of these polymer systems is that they may re-emulsify in humid alkaline conditions. To overcome this problem, an epoxy emulsion based polymer system has been developed. In this paper the properties of the cement mortar modified with this newly developed epoxy emulsion are compared with those of the acrylic-modified mortar. The results showed that the mortars with the newly developed system have superior strength properties and better resistance to the penetration of chloride ions and carbon dioxide.

Influence of water-cement ratio and cement content on the properties of polymer-modified mortars

The compressive strength of modified and unmodified mortars depends on water-cement ratio and, to a lesser extent, on the cement content of the mortars. The flexural strength of unmodified mortars responds only slightly to modification of water-cement ratio or cement content. With polymer modification of the mortars, the influence of the variation is increased. There is only a minor influence of water-cement ratio and cement content on the adhesion strength of the modified mortars on concrete slabs. Only in wet conditions is there an additional effect at high cement contents and lower water-cement ratios. Shrinkage and water absorption are a function of water-cement ratio and cement content.