Microstructural and Durability Assessment of Various Concrete Types Under Different Chemical Environments

The research investigates the microstructural analyses and durability performances of a geopolymer concrete (GPC), two different engineered cementitious concretes (ECC), and an ordinary Portland cement concrete (NC) under 3.5% seawater (SW), 5% magnesium sulfate (MS), and 5% sulfuric acid (SA) environments. The nanosilica (NS) and F-type fly ash incorporated GPC specimen was activated using a mixture of sodium silicate and sodium hydroxide solution with a sodium silicate/hydroxide ratio of 2.5. The low-calcium (LCFA-ECC) and high-calcium (HCFA-ECC) fly ash-based ECC specimens were produced, and the NC was also cast for comparison. The durability performances of concretes were assessed by visual inspections, weight changes, and compressive strength tests, and microstructures of the chemically exposed specimens were compared to that of the unexposed specimens by Scanning Electron Microscopy (SEM) micrographs. The results showed that LCFA-ECC samples showed the best performance, while NC samples performed the worst performance against all chemical attacks. The GPC specimens showed a better durability performance than HCFA-ECC specimens under SW and MS attacks, while HCFA-ECC specimens exhibited better chemical resistance against SA attack. SEM images confirmed that sulfuric acid is the most hazardous environment since increased dosage of sulfates was observed on the surfaces, interfacial transition zone (ITZ), and polyvinyl alcohol (PVA) fibers.