Application of SEM and XRD in the Microstructure Analysis of Fiber-Reinforced Concrete Corroded by Salt Solution

Abstract

In order to study the damage law of salt solution erosion on the microstructure of concrete, the dry wet alternation method was used to conduct salt solution corrosion tests on the samples. The corrosion characteristics and mechanisms were analyzed from macroscopic experiments such as corrosion results, relative dynamic elastic modulus, and mass loss rate; Then, SEM and XRD were used to further demonstrate and explain the corrosion mechanism from a microscopic perspective. The conclusion drawn from the analysis: The observation and analysis of the erosion products and SEM and XRD microscopic characteristics of fiber-reinforced concrete indicate that in the initial state without erosion, the sample contains original cracks and pores, and the fibers are tightly bound to the cement slurry. Under the acceleration of dry wet cycles, sulfate erosion is mainly gypsum type erosion and ettringite type erosion, and the erosion products are columnar and needle shaped distribution of ettringite and gypsum crystals; In the later stage of erosion, the surface concrete deteriorates severely, the cement slurry gradually falls off, the internal pores increase, and cracks increase, resulting in partial separation of fibers from the cement slurry. At this time, the fibers rely on their own tensile strength to play a role in toughening and crack resistance.