Durability performance of raw bamboo anchors under hygrothermal, saline and alkaline conditions

The natural biomass material bamboo can be utilized to replace conventional steel anchors in support works with guaranteed safety and environmental benefits. However, the durability of bamboo is vulnerable to various environmental factors in practical engineering applications. While there is little understanding of how these factors affect the durability of bamboo. Therefore, the effects of typical influencing factors, including hygrothermal, saline and alkaline conditions as well as various grouting materials, on the physical and mechanical properties of bamboo were investigated in this study via tensile tests. The stress-strain curves and tensile failure modes of bamboo under different conditions were analyzed, and the microstructure of bamboo subjected to hygrothermal and alkaline environments was observed. Results showed that the moisture content of the specimens increased with rising water temperature and extended immersion time, with a corresponding decrease in tensile strength. After 24 h of immersion in NaOH and Na 2 SO 4 solutions, the tensile strength of the specimens decreased by 73% and 14%, respectively. Both NaOH solution and silicate cement-based grout resulted in a tensile fracture mode of neat fiber breakage. Magnesium phosphate cement-based grout had low alkalinity and exhibited superior compatibility with raw bamboo anchors. The stress-strain curves exhibited greater fluctuation and dispersion under elevated temperatures and prolonged water immersion. Strongly alkaline environments increased specimen brittleness and reduced fracture strain. Both high temperatures and alkaline conditions caused deformation of bamboo thin-walled cells, while alkaline agents further degraded specimen strength by dissolving hemicellulose and lignin in the bamboo matrix.