Determination of optimum cure condition of the polymer modified mortars and investigation of mechanical properties under freeze-thaw effects

Recent years, polymers have widely used as additive materials in cement mortars thanks to developments in polymer technology. Polymer additives increase the physical and mechanical properties of the concrete. In addition, polymer additives contribute concrete for durability by increasing resistance of concrete against such as freeze-thaw cycles, acid attack and sulphate attacks. However, due to the 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, optimum cure conditions of polymer modified cement mortars are determinated by increasing mechanical and physical properties of specimens cured under different condition. For this, 3 different polymer additives (SBR (Stiren Butadien Rubber), PSBR (Polycarboxylate-Stiren Butadien Rubber), SAC (Stiren Acrylik Co-Polymer)) 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 freeze-thaw resistance is investigated. The mortars are prepared with 3 different polymers (SBR, PSBR and SAC) in 5 different ratios (0%, 5%, 10%, 15% and 20%) for freeze-thaw tests. Then, these mortars are cure with ascertained cure condition during 28 days and the mortars are exposed 3 different freeze-thaw cycles (0, 100 and 200). The end of freeze-thaw cycles, mechanical properties of mortars is 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 were reducing 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. As a result, SBR and PSBR show positive effects on properties of mortars, on the other hand, SAC shows negative effect for all conditions. Polymer modification decreases a little the compressive strength of the mortar, however increases the flexural strength and freeze-thaw resistance of the mortars importantly. After 200 freeze-thaw cycles, mortars with 15% SBR and mortars with 20% PSBR show about 45-50% increase in flexural strength according to control samples.