Bio-Based Chitin for Cement Pastes: From Surface Interactions to Mechanical Performance

Chitin, a bio-based polymer derived from crustacean shells, has attracted growing interest as a sustainable additive for cementitious materials due to its biodegradability and reactive hydroxyl and acetamide functional groups. In this study, chitin extracted from blue crab shells was incorporated into cement paste at 0, 1, 2, and 3 wt.% of cement to investigate its effects on mechanical performance, moisture sorption, and microstructural evolution. The extracted chitin was characterized by Fourier Transform Infrared Spectroscopy, X-ray Diffraction, Thermogravimetric Analysis, and Scanning Electron Microscopy. Cement pastes were evaluated using compressive strength testing, Dynamic Vapor Sorption (DVS), the Guggenheim–Anderson–de Boer (GAB) adsorption model, and SEM observations. The incorporation of 3 wt.% chitin increased the compressive strength by 56.8% compared with the reference paste. DVS and GAB analyses revealed enhanced water adsorption and an increase in accessible adsorption sites with increasing chitin content. SEM observations indicated a progressively denser and more homogeneous microstructure, accompanied by a reduction in visible porosity, as the chitin content increased. These findings suggest that chitin promotes favorable physicochemical interactions within the hydrated cement matrix, resulting in improved microstructural compactness and mechanical performance, highlighting its potential as a sustainable bio-based polymer for cement-based materials.