Pyrolysis mechanism of natural fiber in cement-based composites at high temperatures

Abstract

• A new method for fibre–matrix separation was developed; • The chemical composition change of the natural fibres in the cementitious matrix at different temperatures were investigated; • The main pyrolysis gas components of natural fibres at high temperatures were analyzed; • The pyrolysis kinetic parameters of natural fibres were determined based on the pyrolysis kinetic methods. The mechanism of pyrolysis of natural fibres in cementitious composites at high temperature has been investigated based on a new developed separation method. The influence of cementitious environment on the pyrolysis of natural fibres was revealed by examining the chemical composition, morphological changes and kinetic parameters of pyrolysis of natural fibres at different temperatures. The experimental results show that natural fibres are more susceptible to pyrolysis under high temperature conditions when embedded in a cementitious base. The fibre pyrolysis process can be considered to be through shrinkage, microfibre separation, fracture and eventually partial mass conversion into gas escape. Furthermore, the complex cementitious environment causes the crystallinity index ( CrI ) and crystallinity percentage ( % Cr 1 ) of natural fibres to decrease and then increase at elevated temperatures, which is different from the phenomena observed in a normothermic cementitious environment or under high temperature conditions alone. This work is of assistance and relevance to the evaluation of the durability of natural fibre reinforced cementitious composites at high temperature.