Experimental study of geopolymer concrete by scanning electron microscopy (SEM) for use in marine structures

In this research, the microstructural study of geopolymer concrete based on mechanical tests and durability of concrete has been done. In this regard, one design of ordinary concrete and three designs of geopolymer (in two categories) were made. The first group of geopolymer concrete in three designs contained 0, 4 and 8% nanosilica and after selecting the optimal design (in terms of superiority of results in tests) from these three designs, the second category includes two other designs and adding 1 and 2% of polyolefin fibers were made to the optimal design (a total of 6 mixing designs). Scanning electron microscopy (SEM) imaging tests, compressive strength, modulus of elasticity and capillary water absorption at 90 days of processing age were performed on concrete samples. The results of this study indicate that the mechanical properties and durability of geopolymer concrete are superior to ordinary concrete. In the design, geopolymer concrete contained 8% nanosilica compared to the design without nanosilica). Addition of up to 2% of fibers to the geopolymer concrete composition resulted in a 7% and 23% improvement in modulus of elasticity and water permeability in concrete. SEM results indicate the production of a large volume of hydrated gels in the microstructure of geopolymer concrete compared to conventional concrete, which is due to the abundance of aluminosilicate particles in slag and nanosilica used in the composition of geopolymer concrete.