Structure and properties of a porous wood-mineral composite based on slag-silicate binder with a finely dispersed alumosilicate additive

Introduction. The extension of the range of binders, aggregates, and fillers as well as functional additives and structural modifiers for concrete and composite materials currently allows for the production of innovative materials with enhanced mechanical, physical, and physico-chemical properties. Lightweight structural and functional materials derived from binders of different natures with fillers derived from vegetable raw materials, such as sawdust concrete, arbolite, fibrolite, or xylolite, are of particular interest. The aim of this research was to develop and investigate the properties of a wood-mineral cement-free composite material with a porous structure that has been stabilized using a finely dispersed aluminosilicate additive. Materials and methods of research. A cementfree slag-based silicate binder was utilized in the study, comprising ground blast furnace slag and a curing agent – a solution of sodium silicate (sodium liquid glass). A synthetic foam-forming agent with a finely dispersed additive (bentonite) was employed to create the porous structure of the material. Crushed softwood was used as an aggregate. A range of samples were produced, varying the composition within the following parameters: slag 330–440 kg/m3, crushed wood 120–160 kg/m3, and solution-to-slag ratio 0.5–0.7. Several samples were subjected to thermal treatment by heating in a temperature-controlled environment at 80–90 °C and at humidity of at least 90% for 6–12 hours. Samples were examined using mechanical testing methods, thermogravimetric analysis, X-ray diffractometry, porometry, and thermal conductivity measurements. Results and Discussion. A cement-free porous wood-mineral composite material (an analogue of arbolite) was obtained. It is shown that the introduction of ground blast furnace slag (330–440 kg/m3) and crushed softwood (125–160 kg/m3) into the mixture at optimal ratios of liquid glass/slag 0.7 and foaming mixture/slag 0.0035 (3.5% foaming agent + 4% bentonite) makes it possible to obtain a composite material with a density of 550–680 kg/m3, compressive strength of 1.35–3.65 MPa, an open porosity of 45–50%, and an average thermal conductivity of 0.08 W/(m·K). The heat and humidity treatment of the composite at 80–90 °C contributes to the achievement of ultimate strength within 10–12 h. The presence of a finely gel-forming additive (bentonite) with particle sizes of 1–5 m in the foaming mixture helps to stabilize the homogeneous porous structure of the composite material (spherical pore sizes less than 1 mm). Conclusion. The porous wood-mineral composite material obtained in the work can be used for the production of lightweight non-load-bearing structural elements, as a noise and thermal insulation material.