Expanding the use and construction of concrete pavement due to its advantages over asphalt pavement has led to more consumption of ordinary Portland cement and natural aggregates for concrete production. The ability to withstand heavy traffic, lower maintenance costs and longer service life of concrete pavement to asphalt pavement are some of these advantages. Increased production of cement has led to widespread environmental pollution, such as the release of large volumes of CO2 into the atmosphere, and significant energy consumption. Also, extensive aggregates extraction for use in concrete causes loss of non-renewable resources, and higher economic costs for providing high quality aggregates. Therefore, the production of environmentally friendly concrete with recycled aggregates is considered as one of the ways to advance human societies on the path of sustainable development. In this regard, the present study has tried to investigate the possibility of using an alkali-activated binder instead of cement, recycled asphalt aggregate and crumb rubber, in concrete pavement. This type of concrete is called one-part alkali-activated slag concrete which consists of slag, pentahydrate sodium metasilicate, water, recycled asphalt aggregate, crumb rubber and natural aggregate. Due to the multiplicity of effective parameters such as the ratio of sodium metasilicate to slag, the amount of adhesive, replacement of 25, 50, 75 ,and 100 asphalt aggregates and 5, 10, 15 ,and 20% by volume with coarse aggregates and fine aggregates, respectively. Also, saving economic, time and material costs, in order to achieve the optimal mixing design based on the maximum compressive strength,the efficient method of Taguchi has been used. According to the result obtained from the Taguchi method, 25% ,and 5% were obtained for asphalt coarse aggregate and crumb rubber as the optimal replacement percentages in the optimal mixing design, respectively. Then, compressive strength tests at the ages of 7, 28 ,and 90 days, tensile and flexural strength, carbonation, freezethaw cycle and abrasion tests have been checked. In order to better understand the microscopic structure of one-part alkali-activated slag concrete under the influence of CO2 gas and freeze-thaw cycles with (SEM) and to identify the main phases of the concrete sample under the influence of CO2 gas XRD test has been performed. Also, to eva‎luate the environmentally destructive effects, the amount of CO2 emissions and energy consumption for the production of one-part alkali-activated slag concrete, made with asphalt aggregate and crumb rubber was calculated and made with cement concrete with the mentioned aggregates have been compared under the same conditions. According to the results, while the replacement of 25% and 5% of coarse asphalt aggregate and crumb rubber has led to a decrease in mechanical properties and a slight increase in the depth of CO2 penetration in concrete, but the durability of concrete against freeze-thaw cycles and abrasion has improved. Also, the amount of CO2 emission and energy consumption of alkali-activated slag concrete has been reduced by 35% and 41%, respectively, compared to cement concrete.

كياچهر بهفرنيا

مهدي ابطحي

محمد رضا افتخار، مهرداد محمد حجازي