Sharif University of Technology Sharif Journal of Civil Engineering 2676-4768 37.2 3.2 2021 11 22 INVESTIGATING THE EFFECT OF SODIUM HYDROXIDE ADDITIVE ON STRENGTH PROPERTIES AND DURABILITY OF SELF-COMPACTING CONCRETE WITH SULFATE AGGREGATES IN SULFATE ENVIRONMENT INVESTIGATING THE EFFECT OF SODIUM HYDROXIDE ADDITIVE ON STRENGTH PROPERTIES AND DURABILITY OF SELF-COMPACTING CONCRETE WITH SULFATE AGGREGATES IN SULFATE ENVIRONMENT 3 14 22326 10.24200/j30.2021.55938.2811 FA H. Abtahi D‌e‌p‌t. o‌f C‌i‌v‌i‌l E‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g S‌h‌i‌r‌a‌z B‌r‌a‌n‌c‌h, I‌s‌l‌a‌m‌i‌c A‌z‌a‌d U‌n‌i‌v‌e‌r‌s‌i‌t‌y A. Hajiani Boushehrian D‌e‌p‌t. o‌f C‌i‌v‌i‌l E‌n‌g‌i‌n‌e‌e‌r‌i‌n‌g S‌h‌i‌r‌a‌z B‌r‌a‌n‌c‌h, I‌s‌l‌a‌m‌i‌c A‌z‌a‌d U‌n‌i‌v‌e‌r‌s‌i‌t‌y Journal Article 2020 07 11 Self-Compacting Concrete (SCC) is used even in the complex shapes and can pass through the densest reinforcement without requiring the means of vibration, that is to say, it is recommended that concrete be used in major projects. It uses superplasticizer and stabilizers to significantly increase the ease and rate of flow. Degradation and serious damage of concrete structures triggered by sulfate attack have been widely reported in the saline soil or salty-lake areas all over the world. Sulfate has been claimed to be one of the common corrosive sources in the environments such as soil, groundwater, lakes, or rivers. Many studies revealed that sulfates in the pore solutions could react with cement composition or hydration products to form new phases. Concrete aggregates can include healthy and unhealthy gravel and sand grains. In this study, the effect of unwell aggregates disposed to expand reaction in a simulated destructive environment on the strength and durability of samples is investigated at different ages for compression, tensile and bending samples of self-compacting concrete. Unhealthy materials extract from the exploited gravel and sand mines, which have an impurity rate of more than the allowable value of 0.4% according to Issue 9 of the Iran National Building Code. Sodium hydroxide with three different percentages (2%, 2/5%, 3%) of water weight is used to prevent the destructive effects of sulfate environment. According to a review of past studies and review of similar topics, self-compacting concrete was used instead of concrete. Also, in this study, the aggregate sulfate is used in self-compacting concrete. Therefore, the mechanical properties and durability of self-compacting concrete in sulfate environments were investigated. The results of the study show that the addition of sodium hydroxide to the sulfate aggregate in 7 days for self-compacted concrete sample increases the tensile strength up to 84.15% and reduces the permeability and water absorption up to 21.87 and 16.67, respectively. Self-Compacting Concrete (SCC) is used even in the complex shapes and can pass through the densest reinforcement without requiring the means of vibration, that is to say, it is recommended that concrete be used in major projects. It uses superplasticizer and stabilizers to significantly increase the ease and rate of flow. Degradation and serious damage of concrete structures triggered by sulfate attack have been widely reported in the saline soil or salty-lake areas all over the world. Sulfate has been claimed to be one of the common corrosive sources in the environments such as soil, groundwater, lakes, or rivers. Many studies revealed that sulfates in the pore solutions could react with cement composition or hydration products to form new phases. Concrete aggregates can include healthy and unhealthy gravel and sand grains. In this study, the effect of unwell aggregates disposed to expand reaction in a simulated destructive environment on the strength and durability of samples is investigated at different ages for compression, tensile and bending samples of self-compacting concrete. Unhealthy materials extract from the exploited gravel and sand mines, which have an impurity rate of more than the allowable value of 0.4% according to Issue 9 of the Iran National Building Code. Sodium hydroxide with three different percentages (2%, 2/5%, 3%) of water weight is used to prevent the destructive effects of sulfate environment. According to a review of past studies and review of similar topics, self-compacting concrete was used instead of concrete. Also, in this study, the aggregate sulfate is used in self-compacting concrete. Therefore, the mechanical properties and durability of self-compacting concrete in sulfate environments were investigated. The results of the study show that the addition of sodium hydroxide to the sulfate aggregate in 7 days for self-compacted concrete sample increases the tensile strength up to 84.15% and reduces the permeability and water absorption up to 21.87 and 16.67, respectively. https://sjce.journals.sharif.edu/article_22326_8ad6e09b6463122150bcac2b585e9db4.pdf