Mechanical and durability properties of one-part alkali-activated slag concrete containing recycled asphalt pavement aggregate Arezoo Dadkhah Tehrani Ardkh73@gamil.com September 21, 2020 Department of Civil Engineering Degree: M.Sc Language: Farsi Isfahan University of Technology, Isfahan 84156-83111, Iran Kiachehr Behfarnia kia@iut.ac.ir The growing need of societies for construction has increased the importance of building materials. Cause of this, concrete, having the suitable properties, is one of the most widely used building materials. The supply of concrete ingredients such as cement and aggregates has many destructive environmental effects. Extraction of aggregates destroys the natural environment and causes the loss of non-renewable resources, on the other hand by producing Portland cement, greenhouse gases are emitted and causes global warming. Concrete made from Portland cement is vulnerable to some environmental invasive factors such as acids, sulfates, gases, chlorides, seawater, freeze-thaw cycles. In some cases these invasive factors lead to concrete destruction and, ultimately, structural failure. In order to solve these problems, the use of recycled aggregates and cement replacement binders seem to be a logical solution for sustainable development. In the present research, an attempt has been made to produce and study green concrete using recycled asphalt aggregates, slag and alkali activator. In the concrete mix design, slag, pentahydrate sodium metasilicate and recycled asphalt aggregates were used. In all design, by keeping the water/binder ratio and the amount of binder in 1 m3 of concrete constant, the effect of replacing recycled asphalt aggregates instead of natural aggregates on the mechanical properties and durability of concrete in magnesium sulfate and the freeze-thaw cycle have been studied.25, 50, 75 and 100% recycled asphalt aggregates have been replaced instead of natural aggregates. In order to study the mechanical properties, compressive strength tests at the ages of 7, 28, 90 and 120 days and tensile and flexural strength tests at the age of 28 days were performed. To evaluate the durability of alkali-activated slag concrete, changes in compressive strength, volume and mass in 5% magnesium sulfate solution at the ages of 60, 90 and 150 days and changes in compressive strength, volume and mass under 100, 200 and 300 cycles of freeze- thaw have been checked. The experimental results indicates that a increase in the percentage of replaced recycled materials instead of natural materials, caused 3-6% decrease in slump and 2-11% decrease in specific gravity. Increasing the percentage of recycled asphalt aggregates in the mix design reduces the compressive strength by 8 to 17%. It also reduces tensile and flexural strength by 1 to 11% and 1 to 7%, respectively. By examining the samples placed in the invasive environment of magnesium sulfate at the age of 150 days, 0.19 to 1.16% decrease in mass, 1.67 to 2.94 increase in volume and 5 to 16% decrease in compressive strength have been reported. Volume change of the samples exposed to the freeze-thaw cycles is about 0.33% of the initial volume, which can be ignored. By increasing the percentage of replaced recycled asphalt aggregate, the mass of the samples placed in this environment has increased and at the end of 300 freeze-thaw cycles the maximum mass change of these samples have been 0.7%. Increasing the replacement percentage of recycled asphalt aggregates has a negative effect on samples subjected to freeze-thaw cycle. For example, in all freeze-thaw cycles, by replacing 25% of the natural aggregates by recycled aggregates, the compressive strength has been reduced by 19 to 38. Keywords: One-part alkali-activated slag concrete, pentahydrate sodium metasilicate, Slag, Recycled asphalt aggregate, Magnesium sulfate, Freeze-thaw cycle.