Effect of water-based acrylic copolymer on void systems of cementitious repair mortar

Abstract

Recent literature has found excessive air content as a drawback in the polymer-modified cement mortars. Excessive air content has an adverse impact on the compressive strength of polymer-modified, cement-based mortars. Entrapped air voids in the cement based mortars are typically classified greater than 1 mm in diameter. In contrast to these voids, the entrained air voids (<1 mm) are identified as fine voiding systems in the cement matrix. Modification of cement-based mortars through polymers commonly leads an increase in entrapped air voids volume. This increase developed a concern of reducing the compressive strength of the polymer-modified mortars. Therefore, the objective of this article is to assess this concern by introducing a new composition of Styrene acrylic copolymers. An anti-foaming agent is introduced in this proposed copolymer in order to reduce the entrapped air voids. Quantitative image analysis is run as a well-known technique in Petrographic methods. The entrapped air volume is assessed in the samples that are modified with different polymer dosages of Portland cement within 0 to 20 0–20 wt% range. The effect of adding Styrene Acrylic on the compressive, tensile, bonding, and flexural strength are assessed within 0–20 wt% ratio of Portland cement. Quantification of air void contents reveal a decreasing trend through the entrapped air voids for samples with higher dosage of the copolymer (optimizing in dosage of 15%). This reduction in the entrapped air voids is further strengthens by the results of mechanical analyses. According to these obtained results, an inverse correlation is found between the porosity and the mechanical property of the polymer-modified mortars. Keywords: Air voiding, Styrene, Image analyses, Repair mortar, Mechanical strength