Engineered cementitious composites are a special type of fiber-reinforced cementitious composites that exhibit pseudo strain-hardening behavior and high tensile strain capacity while using a moderate amount of fibers. Due to the high structural performance and high durability of these composites, the use of them in infrastructures will be a big step towards sustainable development. But as these composites are typically manufactured with high amounts of conventional Portland cement and due to the high energy consumption and adverse environmental effects of cement production, the credibility of moving towards sustainable development in this technology has been reduced to some extent. In this study, by replacing all Portland cement with alkali-activated slag and using polypropylene fibers, different types of engineered cementitious composites with lower environmental impact were produced and their properties were investigated. Although in the production of alkali-activated slag by using powdered and solid alkali solids (one-part alkali-activated slag) rather than the alkaline solution, generally the physical and mechanical properties of the alkali-activated slag are deteriorated, this method removes problems of using the alkaline solution. In one-part alkali-activated slag technology, by mixing solid alkali activating powder with slag, in the resulting compound chemical reactions begin only by adding water, such as in Portland cement technology. This similarity in manufacturing will increase the commercial capability of alkali-activated slag. In the first stage of this study, the effects of two different types of sodium metasilicate (anhydrous and pentahydrate) as solid alkali activator on the properties of One-Part alkali-activated slag mortars are compared. At this stage, using 0.08 alkali activator to slag ratio affords the highest compressive strength and using 0.12 alkali activator to slag ratio, provides the fastest compressive strength growth. In the second stage of the research, by altering the initial ratios of raw materials, including slag, sodium metasilicate pentahydrate, microsilica, water, high range water reducer, fine silica sand and polypropylene fibers, various types of strain-hardening alkali-activated slag were produced. The specimens were heat cured at 60°C for 24 hours then their mechanical properties were studied. Also, the effects of type of curing were studied by investigating the mechanical properties of specimens at ages 7 and 28 days which cured under plastic coating and stored at laboratory temperature. In this study, different types of strain-hardening alkali-active slag with moderate compressive strength and modulus of elasticity and high tensile strain capacity or with high compressive strength and modulus of elasticity and desired tensile strain capacity were produced. Due to the problems of uniaxial tensile test of cementitious materials, as the third stage of the research, a new method for indirect obtaining of tensile behavior and compressive modulus of elasticity of these composites was proposed. In this method, firstly the surface deformation of the specimens in the four-point bending test is investigated with a digital image correlation (DIC) software and the curvature throughout the bending beam is studied during the loading steps. By using a suitable model for compressive and tensile behavior of composites and solving the moment and force equilibriums in bending cross-section using the results of four-point bending test (ultimate load moment) and the calculated bending curvature (at the ultimate load moment), tensile strength and strain capacity and compressive modulus of elasticity of the composite are estimated. The results of this new method were compared with two other indirect methods (JCI standard method and UM method) and differences were studied. key words: Engineered Cementitious Composites (ECCs), One-Part Alkali-Activated Slag, Indirect Method to Obtain Stress-Strain Response, Digital Image Correlation (DIC), Bending Curvature, Polypropylene Fibers.