High temperature degradation mechanism, mechanical properties and constitutive model of reed straw reinforced brick aggregate concrete

Abstract

The application of natural plant fibers in concrete promotes the sustainable development of green buildings, but its high temperature resistance is an important factor that must be considered in practical engineering applications. In this study, the high-temperature degradation mechanism of brick aggregate reed straw concrete (BARSC) was analyzed by simultaneous thermal analysis, X-ray diffraction and scanning electron microscopy, the mechanical properties of concrete before and after high temperature were tested, an axially compressed constitutive model was established, and a life cycle assessment of its production process was conducted. The results show that: At 20 ℃-500 ℃, cracks appear in the reed-matrix ITZ due to moisture evaporation, dehydration and decomposition of C-S-H gel, and shrinkage, pyrolysis and carbonization of reed straw. At 500 ℃-900 ℃, due to the phase change and expansion of SiO_2, the transformation of reed straw into ash and the decomposition of CaCO₃, the concrete becomes sparse and porous, the brick-matrix ITZ bond fails, and the structural integrity is lost. Reed straw increases the tensile strength of BARSC by a maximum of approximately 28.6 %. For every 1 % increase in reed straw content, the carbon emissions of concrete are reduced by 4.21 kg/m³. The combination of brick aggregates and reed straw makes comprehensive use of industrial and agricultural waste, providing a new method for carbon emission reduction and solid waste recycling in the construction industry.