Enhancing hydration and internal curing in cementitious mixes: The impact of pre-treated milkweed fibres

This study investigates the internal curing effects of milkweed fibres (MW) in Portland cement mixes, exploring various dosage levels and pre-treatment methods. The study first assessed the impact of MW fibres on the effective water-to-cement (w/c) ratio through rheological measurements, enabling accurate comparisons of samples with identical effective w/c ratios. Both MW fibre pre-treatments and dosages were found to impact the effective w/c ratio in the mixes, leading to the categorization of MW fibre-incorporated samples into three groups based on their effective w/c ratio. In the subsequent phase, the internal curing effect and hydration characteristics of cementitious mixes were evaluated with varying dosages of MW fibres. Optimal internal curing performance was achieved with 0.1% pre-treated MW fibres compared to 0.2%, resulting in up to a 17% improvement in the degree of hydration compared to the reference sample with the same effective w/c ratio. This showed the adverse effect of higher percentage due to the reduction in the free water availability and higher leaching of extractives, which further intensified the hindrance of the hydration process. Furthermore, microstructure analyses, including TGA/DTG, XRD, and SEM-EDS, of cementitious mixes incorporating MW fibres confirmed that the inclusion of 0.1% hybrid and hydrothermally-treated MW fibres resulted in a higher formation of hydration products. This is achieved by providing an adequate amount of free water for the initial reaction of cement hydration and entrained water in the lumen for the subsequent internal curing. These findings show the effectiveness and suitability of using pre-treated MW fibres for internal curing applications, as validated by the comprehensive analyses conducted in this study.