Comparative Study between Microstructure of a Novel Durable Concrete and Normal Concrete Subjected to Harsh Environments

Abstract

Degradation of concrete members exposed to aggressive sulphuric acid environments is a key durability issue that affects the life cycle performance and maintenance costs of vital civil infrastructures [1]. Groundwater, chemical waste, sulphur bearing compounds in backfill, acid rain in industrial zones and biogenic acid in sewage systems are the main sources of sulphuric acid affecting concrete structures. In this research, microstructures of a novel acid resistant concrete (ARC) and a type of conventional concrete (CC), as the reference, have been studied in the laboratory subjected to accelerated testing. For this purpose, ARC and CC, were immersed in 7% (by volume) sulphuric acid solution. Mechanical properties of both concretes as well as their microstructures were examined after 28 days of curing and then after two, four and eight weeks of exposure to acid. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Xray diffraction (XRD) and X-ray mapping (XRM) were employed to analyse the microstructure of concretes before and after exposure to acidic environment. The results of this analysis revealed interesting facts about the mechanism of sulphur penetration in both concrete samples. In addition, they showed differences in the crack locations and propagation patterns and in interfacial transition zones (ITZ) of concretes, particularly after acid exposure. These changes of microstructures, as was proved in experimental tests, could significantly contribute to changing the ductility of the concretes in modulus of rupture (MOR) test.

Towards Eco-Flowable Concrete Production

“…The elemental analyses of these four plastic particles are reported in Figure 4. Samples were X-ray mapped using a JEOL JXA-8600 super probe SEM with an "AMPTEK" EDS silicon drift detector [20]. SEM allows greater magnification, resolution, and depth-of-field than those of an optical microscope.…”