Investigation of mechanical behavior of the polymer modified mortars under different cure conditionsand high temperature effect

Polymers getting cheaper and popular nowadays by developing polymer technology have been started to find widely using area in structural application. Polymer additives enhance physical and mechanical properties of the concrete. In addition, polymer additives contribute concrete for durability by increasing resistance of concrete against such as acid attack, freeze-thaw cycles and sulphate attacks. In addition, it is supposed to contribute to concrete by melting under high temperature against detrimental effects like spalling. However, due to fact that polymers needs dry condition for its polymerization and concrete needs wet condition for its hydration occurs important problem for these composites. This study was constituted from two main parts. In the first part of the study, the optimum cure conditions of polymer modified cement mortars are determined by investigating mechanical and physical properties of specimens cured under different condition. For this objective, 3 different polymer additives (MAD (Modified Acrylic Dispersion), PU (Polyurethane),SBR (Stiren Butadien Rubber)) are added to mortars in five different ratios (0% (reference), 5%, 10%, 15% and 20%) by cement mass. Then, these polymers are cured under 3 different conditions (1. Cure condition: Watering twice a day, 2. Cure condition: 16 hours in the water-8 hours out, 3. Cure condition: One day in the water-one day out) during 28 days, and the mechanical properties of mortars is investigated. In the second part of the study, the mortars are cured under the cure condition ascertained in first section during 28 days and high temperature resistance is investigated. The mortars are prepared with 3 different polymers (SBR, MAD and PU) in 5 different ratios (0%, 5%, 10%, 15% and 20%) for high temperature tests. Then, these mortars are cure with ascertained cure condition during 28 days and the mortars are exposed 4 different temperatures (21 °C, 100 °C, 200 °C and 250 °C). Changes in mechanical properties of mortars exposed to stated temperatures for an hour are investigated. Besides, water absorption, depth of penetration of water under pressure, specific mass and petrographic properties of mortars are investigated for observing changes in physical properties of polymer modified mortars. The most important results found from the study are summarized; when considering the physical properties, polymer additives reduced water absorption and depth of penetration of water under pressure of mortars dramatically. In the first part of the study, it is investigated that mechanical properties of polymer modified mortars decreased while increasing its water curing. According to this result, the optimum cure condition is determined as 1. Cure Condition. In general, polymer modification decreases a little the compressive strength of the mortar, however increases the flexural strength and high temperature resistance of the mortars importantly. As a result, SBR and MAD have positive effects on properties of mortars, on the other hand, PU shows negative effects for all conditions. The mortars modified with SBR polymer show the best performance for the highest temperature (250 °C). For the highest temperature, when SBR is used in 15% additive ratio, the flexural strengths (42%), deflections (15%) and compressive strengths (21%) of the samples increase according to control sample.