The Influence Of Calcium Nitrate On The Compressive Strength Of Concrete Exposed To Freezing Weather

Based on ACI 306R-88, the minimum temperature necessary for maintaining concretehydration and strength gaining is 50C. If the atmosphere weather becomes lower than 50Csome preserve measurements should be taken in order to prevent decrease in the rate ofhydration and to prevent fresh concrete from freezing. Most of the cold weather livingcountries spend annually plenty of money in order to facilitate concrete placing in the coldweather and to extend the construction season. It has been tried to carry out the behavior of fresh and hardened concrete contained calcium nitrate at different curing temperatures below freezing temperature of water and compare the results with the both control samples and real Erzurum winter conditions. For this reason, calcium nitrate is used at level of 6% by weightof cement dosage in the mixes. After casting, one group of concrete samples were cured in the different deepfreezes at -5,-10,-15,-200C for 7, and then that same samples were cured inwater for 28 days. With usage of calcium nitrate in the mixes, compressive strength of concrete increased between 96-297% at -50C, -100C, -150C and -200C, when compared tomixes without antifreeze admixtures that 7 days only freezer cured and 28 days water curedafter 7 days freezer cured, respectively. The results showed that it is possible to use calciumnitrate as an antifreeze admixture in concrete placing process in cold weather concreting

Investigation of physical and mechanical properties of mortars produced by polymer coated perlite aggregate

With its low unit weight, expanded perlite (EP) offers significant advantages in heat and sound insulation in the construction sector. However, due to its high-water absorption capacity, EP affects the physical and mechanical properties of concrete negatively. Therefore, it is aimed to reduce water absorption by coating the EP with polymer and thus to improve its mechanical and physical properties. In this study, mortar production was carried out by replacing coated and uncoated EP with CEN reference sand at 0%, 20%, 40%, 60%, and 80% respectively. The effective water/cement ratio of all produced mortar samples was determined to be 0.6. For coated and uncoated EP aggregate mortar series, unit weight, compressive strength, bending tensile strength, water absorption, ultrasonic pulse velocity (UPV), and thermal conductivity coefficient were determined. The results showed that the unit weight of the mortar samples decreased as the amount of EP increased, but their physical and mechanical properties also changed. Mortar samples with better thermal insulation properties were obtained with decreasing thermal conductivity values. The polymer coating of EP improved physical and mechanical properties. Especially in the 80% substituted EP series, the thermal conductivity decreased from 1.20 to a coefficient of 0.91 W/mK. © 202