Fiber cement boards modified with styrene-acrylic copolymer: An approach to address dimensional stability and cellulose fiber preservation

The performance of polymers such as acrylics, styrene-acrylics, styrene-butadiene, ethylene vinyl acetate, type added in cementitious composites are well reported in the literature to boost properties in the fresh mortar stage as workability, anti-bleeding, and hard stage as deformation, adhesion strength, crack bridging, cohesion, durability and reduced water uptake. Polymer treatment was performed in fiber cement boards by adding 5% w/w (dry basis) of styrene-acrylic copolymer aiming to investigate the impact on the mechanical and physical properties at initial curing period (28 days) and after the 200 soak and drying ageing cycles. Dimensional stability at 28 days and the cellulose fiber/cement interface transition zone were assessed by scanning electron microscopy combined with dispersive energy X-ray spectroscopy (EDS). These experiments confirmed that the water absorption value in polymer modified cement boards was reduced by 50% after the ageing cycles when compared to the unmodified boards. Additionally, improvements on board's rigidity with reduction of modulus of elasticity (MOE) values up to 40% and 15% reduction of board shrinkage was noticed, enhancing boards dimensional stability and preventing fibers from the mineralization process by keeping the cellulose fiber adhered on the cementitious matrix, providing a dense and cohesive fiber-cement interface transition zone after the ageing cycles. This achievement can open important fields of application for the reinforcement of flat panels.

Automated summary

Studies show that adding styrene-acrylic copolymer to fiber cement boards leads to improved properties such as reduced water absorption, increased rigidity, decreased shrinkage, and enhanced stability of the fiber-cement interface transition zone. This modification prevents fiber mineralization, contributing to the overall dimensional stability of the boards, which could open up new applications in reinforcement of flat panels.