چكيده انگليسي :
Concrete is the second most widely used material in the world after water. One of the most important areas of concrete consumption is pavement, which is used to construct highways, airports, roads, industrial areas, and other types of flooring. Due to the longer life and lower maintenance costs of concrete pavements, engineers in different communities have considered this type of pavement.
Ordinary Portland cement is used as the main binder in concrete, which has caused many environmental problems. The cement industry has seriously destroyed natural mines by extracting raw materials emitting 5% of greenhouse gases and consuming more than 10% of the world's total energy consumption. Research has also shown that 1 ton of cement production produces approximately 1 ton of carbon dioxide. Aggregate is one of the main components of concrete, which makes up about 75% of the volume of concrete. Lack of natural aggregates, high production costs, and environmental resource degradation are other problems of human societies. Therefore, in the present study, to pay attention to eco-design approaches, reduce energy consumption, produce less carbon dioxide and preserve the environment, waste and recycled materials have been used instead of non-renewable sources. In this study, one-part alkali-activated slag binder was used instead of Portland cement, and recycled asphalt aggregates were used instead of natural aggregates. In other words, a kind of green concrete has been produced and studied. At the beginning of this research, the Taguchi laboratory design method was used due to the diversity of effective parameters, time savings, material consumption, and economic costs. The most important issue was achieving the optimum mixing design based on maximum compressive strength. According to the optimum mixing design obtained by the Taguchi method, binder 400 kg / m3, replacement of 25% recycled asphalt aggregate, water to binder ratio of 0.49, and sodium metasilicate to slag ratio of 0.18 were considered for the optimal mixing design. In this research, considering the optimum mixing design of alkali-activated concrete, the control mixing design of alkali-activated concrete, and the control mixing design of cement concrete, on the fabricated samples of compressive strength, tensile strength, flexural strength, slump, the specific mass of fresh concrete, setting time, freeze and thaw cycle, abrasion resistance, water absorption, impermeability, carbonation, thermal conductivity determination, X-ray diffraction (XRD) and electron microscopy (SEM) imaging have been performed and their results have been studied. Based on the obtained results, 25% replacement of recycled asphalt aggregate has reduced some mechanical properties and durability of concrete, including compressive strength, flexural strength, tensile strength, abrasion resistance, resistance to freeze and thaw cycles, and increased thermal conductivity of concrete. However, the replacement of recycled asphalt aggregate has improved the CO2 penetration depth in the carbonation test and the water absorption and permeability of the concrete. Simultaneous use of one-part alkali-activated slag binder instead of cement binder and replacement of 25% recycled asphalt aggregate with natural aggregate in pavement concrete has reduced CO2 emissions by 42% and reduced energy consumption by 29% compared to ordinary Portland cement concrete.
