Enhancing cement composite interface with waterglass modification on bamboo fiber: A viable and effective approach

Cement and cement-based composites are known for their high compressive strength but are often lacking in toughness, making them susceptible to cracking when subjected to external loads. The incorporation of bamboo fiber (BF) into cement-based composites holds promise for enhancing tensile strength and overall durability. However, a significant challenge lies in achieving a strong interfacial bond between BFs and the cement matrix. In this study, a viable and effective surface modification approach for BF has been developed. Waterglass, as an economical inorganic modifier, can be grafted with hydroxyl groups on fiber surface after hydrolysis and condensation. Simultaneously, the alkaline properties and silicate-containing characteristics of waterglass facilitate its participation in cement hydration, acting as a coupling agent to establish a robust fiber-matrix interface. To confirm the successful modification of BF with waterglass, FTIR, NMR, and XPS spectra were used to examine the chemical structure of BFs. Due to the denser bonding achieved between the fiber and cement matrix, the composites exhibit improved toughness with superior flexural strength (10.1 MPa) and splitting tensile strength (3.7 MPa). The addition of bamboo fibers also mitigates shrinkage in cement mortar, enhancing the volume stability of cement-based materials. Notably, waterglass modification led to a reduction in the hydrophilicity of BF and enhanced the compatibility between the fiber and the matrix, which further improved the overall durability of the composites, including their resistance to capillary water absorption, freezing, and carbonization.