Strategies for improving physical-mechanical performance and dimensional stabilisation of fibre cement

• Ano de defesa: 2024
• Autor(a) principal: Fioroni, Carlos Alexandre
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Accelerated carbonation; Carbonatação acelerada; Cellulose pulp; Drying shrinkage; Hornificação; Hornification; Polpa de celulose; Retração por secagem; Silanes; Silanos; Sol-gel
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/74/74133/tde-23042025-083942/

This study aimed to perform treatments on cellulose pulps used as reinforcement in fibre cement and fibre cement treatments as strategies to improve fibre cements physical-mechanical performance and dimensional stability. These properties of fibre cement are linked to the needs of fibre cement industries to produce their products with quality and compliance with performance standards. Fibre cement-based products, mostly roofing elements and flat boards, can present defects such as cracks, warping and delamination due to low mechanical performance and high dimensional variation when exposed to moisture variation. Commercial cellulose pulps from unbleached pine, bleached pine, bleached eucalyptus, and bamboo pulp obtained by the organosolv process were subjected to treatments to modify the water retention capacity. The cellulose pulp treatments studied were hornification to collapse the cellulose pulp fibre lumen and reduce water retention capacity, application of a commercial silane-based emulsion Dowsil™ IE-6683 to reduce hydrophilic character, and sol-gel treatment based on tetraethylorthosilicate (TEOS) or triethoxyoctylsilane (TEOS) as a coupling agent and hexadecyltrimethoxysilane (HDTMS) as water-repellent agent due its long alkyl chains. The treated cellulose pulps were used as reinforcement in the moulding of flat boards in the laboratory for performance evaluation. Immersion of the fibre cement in a commercial silane-based emulsion Dowsil™ IE-6683 and thermal curing with accelerated carbonation were applied to treat the composite. The results showed that the cellulose pulps treated with silane-based emulsion and sol-gel treated cellulose pulps had a hydrophobic character, obtaining contact angles greater than 90° in sheets moulded with these pulps. The use of 10% by mass of these treated pulps as reinforcement in the fibre cement presented up to 20% less dimensional variation of the fibre cement when compared to the fibre cement produced with the untreated cellulose pulps. However, the fibre cement reinforced with the treated cellulose pulps presented a loss of up to 35% in flexural strength. Thermal curing with accelerated carbonation of the fibre cement conferred an increase in flexural strength of up to 65% compared to fibre cement cured only in thermal curing (without accelerated carbonation). Although fibre cement reinforced with sol-gel-treated cellulose pulps decreased the flexural strength performance, this fibre cement presented a 30% better flexural strength performance when associated with thermal curing with accelerated carbonation compared to fibre cement only cured in thermal curing. The dimensional variation of fibre cement reinforced with sol-gel-treated cellulose pulps was also reduced with thermal curing with accelerated carbonation, obtaining a performance of up to 0.9 mm/m of variation. It is also noteworthy that accelerated carbonation provided CO2 capture in the early ages of fibre cement in up to 108 g of CO2 per kg of fibre cement, thus contributing to obtaining a more sustainable composite by reducing the carbon footprint in its production chain.