Biodeterioration of gypsum pineapple fibre composites subjected to accelerated humid and fungal ageing

Abstract

The sensitivity of bio-based materials to moisture and biological agents limits their use in tropical regions. This study evaluates the durability of gypsum-based composites reinforced with pineapple leaf fibres, subjected to accelerated ageing in a humid atmosphere saturated at 91% RH and in a fungal environment on Sabouraud medium (pH 5.6). A D-optimal design was used to analyse the combined effects of fibre volume fraction, conditioning time, and type of ageing medium on six properties: mass gain, density, volumetric deformation, flexural strength, and modulus of elasticity. Increasing fibre content promotes water absorption, with mass gains of up to 12% in humid conditions and 70% in a fungal environment, associated with notable mechanical degradation (elastic modulus reduced by up to 30% and hardness by up to 25% after six months). Antagonistic effects were observed: at low content ($$\:<$$1 ), fibres maintain internal cohesion, while at high content and longer durations, hyphae and spore penetration at the fibre-gypsum interface weakens the matrix. Polynomial models ($$\:{R}^{2}>$$ 0.90) reliably predict property variations and support optimisation of fibre dosage. Microscopic analyses confirmed these alterations and provide a framework for optimising the use of gypsum–fibre composites in humid or tropical environments.