Shear behaviour of silicate-based structural adhesives for timber

In timber structures, many joints are constructed with polymer adhesives and industrial timber by-products also contain polymer resins in huge amount. Majority of these adhesives are artificial polymers with big environmental footprints and lots of them have a negative effect on human health. Some natural or silicate-based adhesives are available in the construction industry, but their heat or water resistance are poor. Some of these types of adhesives have evolved but compounds contain some artificial polymer, and the heat resistance is worse than silicate-based in general. In this article, water-resistance and heat resistance have been investigated in the case of silicate-based binders. In order to be a benchmark, a PVA based industrial timber adhesive (as reference) was also tested. The shear strength of the bonded joints was tested and compared under wet and hot conditions. Reference silicate-based binder was modified with other silicate, acids or alkalines. The effect of modifiers on the solubility of binders was also investigated. As a result it was stated, that reference binder has a higher strength under normal conditions, but the modified silicate binders have better performance under wet and hot conditions. The modifiers can increase the shear strength, ductility, and water-resistance without decreasing the heat resistance and also makes the material quality more uniform. The silicate binders make a rough bond surface, which can pass the forces effectively between the components of specimens.