# Influence of Polymer Types on the Mechanical Properties of Polymer-Modified Cement Mortars
## 1 Introduction  
It is known that adding a polymeric compound to a cementitious material can improve the material properties such as strength, durability, and interfacial bond between the newly applied material and the existing substrate [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12]. Therefore, incorporating polymers in patch repair cement mortars is common for better repair work of various reinforced concrete (RC) structures, including bridges, dams, high-rise buildings, pavements, and marine concrete structures [13; 14; 15; 16; 17; 18; 19; 20; 21]. There exist a few representative types of polymers, including acrylate polymers (AC), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), and ethylene-vinyl acetate (EVA), all of which are utilized in the repair or surface treatment of RC structures. Many experimental studies were conducted to investigate the effect of different polymer types on the mechanical properties and durability of polymer-modified cement mortars (PCMs) [1; 2; 3; 4; 5; 6; 7; 8; 9]. [PERSON] and [PERSON] [1] studied the effects of different SBR replacement ratios (by weight) on the concrete strength measured at three, seven, and 28 days. Furthermore, they reported that the 1% replacement showed a higher strength compared to the 3%, 5%, and 8% replacements. [PERSON] and [PERSON] [1] also confirmed a significant reduction in the measured strength of the sample with 8% SBR replacement. These results are consistent with those reported by [PERSON] [2]. [PERSON] [2] reported that the SBR replacement ratio should be less than 5% to improve the mechanical properties of PCM. [PERSON] et al. [3] stated that the strength of the epoxy-modified cement mortar could be reduced when the epoxy replacement ratio was higher than 10%, based on an experimental study focusing on the strength properties of cement mortars. [PERSON] and [PERSON] [4] investigated the effect of environmental conditions on the adhesive strength and deformation of various PCMs and confirmed that the constant laboratory conditions were preferred to outside exposure when demonstrating the effects of testvariables. [PERSON] et al. (2020) recently conducted an experimental study to clarify the effects of three different polymers (SBR, styrene-acrylic ester (SAE), and polyacrylic ester (PAE)) on the mechanical properties and durability performance of PCMs, and they concluded that PCMs with SBR exhibited better performance when compared to PCMs with SAE or PAE, in terms of strength, weight loss, and chloride ion penetration resistance. [PERSON] et al. (2020) compared two PCMs containing epoxy emulsion and acrylic emulsion, and they reported that the PCM using epoxy emulsion showed better performance in terms of strength and durability. [PERSON] et al. (2020) conducted an extensive experimental study to compare two different polymers (SBR and acrylics) through measurements of strength, durability, and bond strength. The authors concluded that the bond strength of PCMs containing SBR was generally higher than that of PCM containing acrylics. By contrast, [PERSON] et al. (2020) stated that no significant differences were observed between PCMs and conventional cement mortar in terms of mechanical properties and penetration resistance, based on test results and comparisons. [PERSON] (2019) reported that water-to-cement ratios (0.38 to 0.47) did not show a significant influence on the adhesion between the PCM and substrate concrete. A few case studies also confirmed that the application of PCMs to structural members can bring a positive effect to the structural performance of repaired RC structures ([PERSON] et al., 2019; [PERSON] et al., 2020; [PERSON] et al., 2020). [PERSON] et al. (2020) studied the possibility of using PCMs containing an organic film-forming re-dispersive polymeric powder produced in Pakistan for repairing cracks that occurred on the surface of RC beams. The authors reported that the repaired specimens showed an equivalent or higher load-carrying capacity under the same load condition.