Experimental study of modulus of elasticity of Alkali-activated concrete based on XRF and SEM tests

In this research, firstly, three mix designs of alkali-activated concrete containing 92, 96, and 100% blast furnace slag and 8, 4, and 0% nano-silica were made. After performing the compressive strength and modulus of elasticity tests and choosing one design as the optimal design in terms of superior mechanical properties, by adding 1 and 2% polyolefin fibers to the optimal design, two more designs of alkali-activated concrete were made. All concrete samples were subjected to compressive strength and modulus of elasticity, XRF and SEM tests. The results of the tests exhibited superiority in mechanical and microstructural properties of the alkali-activated concrete compared to normal concrete at all processing ages. At the processing age of 90 days (as the best age in performance due to the progress of the chemical process), following the compressive strength test, the lowest (49.94 MPa) and the highest (66.36 MPa) compressive strength values ​​were obtained, respectively, for design 1 including Normal concrete and design 4 including alkai-activated concrete containing 8% nanosilica. At the same processing age, the lowest (32.44 GPa) and the highest (42.51 GPa) modulus of elasticity were achieved in design 1 and 6 of the alkali-activated concrete containing 8% nano-silica and 2% polyolefin fibers, respectively. At this age, addition of 8% nano-silica and 2% fibers in the alkali-activated concrete of design 6 resulted in a decrease of 22.49% in the compressive strength and an improvement of 7.05% in the modulus of elasticity.