Impact of Sulfuric Acid Attack in Portland Cement Mortar Mixtures with Chitosan Addition

Abstract

This paper investigates the impact of chitosan addition on mortar performance during sulfuric acid attack. Twenty-four mortars were prepared using Brazilian portland cements, varying traces, and chitosan dosages ranging from 0% to 3%. Mortar expansion tests were performed to evaluate sulfuric acid attack resistance. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) were performed to evaluate the morphology, XDR was performed to confirm the FTIR results. Chemical structure and bending (3 points) and compressive tests were conducted to evaluate mechanical properties. The study demonstrated that mechanical properties as well the sulfuric acid-attack resistance are sensitive to the biopolymer incorporation, with noticeable effects even at low concentrations, 1% chitosan improves bending strength for CP V-ARI and CP V-ARI-RS in trace A, but decreases it for all cements in trace B, an outcome reflected in SEM images. FTIR results reveal lower levels of gypsum and ettringite formation in mortars with added biopolymer, except for CP V-ARI-RS. Tests on mortar expansion demonstrate that chitosan enhances sulfuric acid attack resistance by reducing mortar expansion by up to 60%. The degradation of cement-based materials due to sulfuric acid-attack is a significant issue, as it leads to the formation of expansive products that progressively weaken concrete structures and increase its vulnerability to penetration by other substances. This research aims to investigate the impact of incorporating chitosan, a biopolymer, into mortar prisms in terms of sulfuric acid resistance. The study examines changes in mechanical properties, alterations in material structure, and the performance of mortars with and without chitosan when exposed to sulfuric acid attack. Findings indicate that both mechanical properties and resistance against sulfuric acid deterioration are influenced by the addition of biopolymer and chitosan enhances protection from sulfuric acid attack by reducing mortar expansion. This research has application on concrete structures subject to sulfate attacks present on soil and water. So, reservoirs, sewage treatment plants and pipes are some of the practical applications of this study.