építôanyag építôanyag  Journal of Silicate Based and Composite Materials Shear behaviour of silicate-based structural adhesives for timber dániel CSANÁDY  BME, Department of Construction Materials and Technologies  csanady.daniel@emk.bme.hu olivér FENYVESI  BME, Department of Construction Materials and Technologies  fenyvesi.oliver@emk.bme.hu Érkezett: 2021. 01. 28.  Received: 28. 01. 2021.  https://doi.org/10.14382/epitoanyag-jsbcm.2021.12 Abstract 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. Keywords: shear behaviour, adhesives for timber, timber joints Kulcsszavak: nyírószilárdsági viselkedés, faragasztó, ragasztott fakapcsolatok Dániel CSANÁDY Civil engineer k (BME 2017), PhD candidate, Department of Construction Materials and Technologi. Member of Hungarian Scientific Association of Silicate Industry. Main areas of interest: reaction to fire of building materials, development of new generation concretes and silicate binders, environmentally friendly building materials, biomimetics, thermal insulation, sound insulation, development of building materials. Dr. Olivér FENYVESI Civil engineer MSc (BME 2005), PhD (BME 2012), Specialized Engineer in Preservation of Building Heritage (BME 2017), Specialized Engineer in Corrosion (HCE 2018), assistant professor in BME, Department of Construction Materials and Technologies. Main research fields: early age shrinkage cracking in normal and lightweight concretes, fibre reinforced concretes, LWAC, building diagnostics, preservation of building heritage. Secretary of the Concrete Division and member of Stone and Aggregates Division of the Hungarian Scientific Association of Silicate Industry, member of the Hungarian Group of fib (International Federation for Structural Concrete), member of ACI (American Concrete Institute), member of the Hungarian Chamber of Engineers. 1. Research motivation e application of timber in structures has revived in recent decades, as a result of which the amount of adhesive/binder used has increased. Most of these adhesives are high environment polluting, so the present research is concerned with developing a sustainable alternative. During the technological development of the nineteenth century, timber lost its leading role in the construction industry, and modern building materials, such as concrete and steel became dominant. Due to the extensive use of natural resources and the significant demand for invested energy, the construction industry has a huge environmental footprint today. In Europe today, the construction industry responsible for around 42% of total energy consumption generates 35% of total greenhouse gas emissions. Over the past two decades, the growing awareness of policymakers and society about the depletion of natural resources and climate change has had a strong impact on the construction industry, leading to an increase in the demand for sustainable and renewable building materials [1]. Wood is the best known renewable building material. erefore, it has become important again, which has helped develop a new bond (glueing) technologies. is is well illustrated by the fact that the use of plywood in Europe almost doubled between 2007 and 2012 and is expected to increase further in the future [2] (Fig. 1). Nowadays, the sustainable lifestyle, green thinking is dominant in all areas of life. As a result, many researches have been conducted to create possible, environmentally friendly alternatives to common adhesives. More than 70% of wood products are made with some kind of glued technology [3]. Wood adhesives have a significant share of the amount of adhesive used in the world. It is of paramount importance to reduce the amount of formaldehyde-containing adhesives used, which is currently used in the largest quantities to bond fibreboard and other by-product based boards (Fig. 1). e modern adhesive industry initially used large amounts of formaldehyde in almost all adhesives, which can significantly damage the health of workers, so the development of lower formaldehyde and formaldehyde-free adhesives began. Although modern adhesives are less harmful than their predecessors, in case most of them are worth using masks and skin and eye protection. In addition, their production is energy-intensive (mostly fossil-based) and produces large amounts of waste both during production and during use, which is currently difficult to dispose or recycle [4]. Environmentally conscious adhesives were initially made from natural polymers of plants and animals, animal blood, skin, casein, starch, soybeans, dextrin, or cellulose. However, they provided a weaker bond than synthetic adhesives and had low water and fire resistance. e growing interest in biopolymers from renewable sources such as wood, corn, and cereals has encouraged the R&D sector, for example, to use biopolymers as a sustainable adhesive [6]. Inorganic adhesives can have a similarly positive effect on reducing the environmental pollution in the same way as natural-based adhesives. e laboratory research section of this article deals with such inorganic adhesives. In the next chapter, the main classes of adhesives, the most important components and basic properties of these classes are briefly described and characterised. 72 | építôanyag építôanyag  JSBCM JSBCM  2021/2  Vol. 73, No. 2