RESEARCH on oven-dry wood. For the cement hydration, proper amount of water is of high importance, to obtain boards that can properly harden. The total water demand required for WWCB during the industrial production can be divided into:
• the moisture to reach the saturation •
• •
point of the used wood (30 % of the dry oven mass); the outer surface area of the wood wool strands (depending on the dimensions of the wood wool strands); the water demand required to let cement fully react (25 % of the mass of cement); the water demand to cover the surface of the cement particles.
Reducing carbon footprint
Next, the hydration kinetics of cements were studied and the retardation of sugars on cements with varying aluminate and CaSO4 contents are evaluated, providing new insights into the retardation mechanism. Based on the acquired knowledge, efficient utilization of binders through approaches including particle packing, modified mixing procedures and implementation of supplementary materials is investigated, leading to new WWCB with increased mechanical and thermal properties and reduced environmental footprints.
The use of alkali-activated binders is then studied to fully replace cement, based on the understanding of the alkaline degradation mechanism of wood and reaction mechanisms, which result in the development of a hybrid binder with a reduced carbon footprint of up to 60 % compared to the use of cement as binder and a significant reduction in costs.
Purifying the air
An orientated study is then performed on increasing the functionality of the boards by implementation of photocatalysis based on the fundamental insights in the surface morphology. Thus, the material was investigated to become an
air purifying material, adding an additional feature to this almost century old product. It was found that WWCBs had good support properties that allowed the use of very low quantity of TiO2, while realizing a high degradation rate (> 95 %). This increases not only the indoor air quality, but also makes the application of TiO2 for air purification also more cost efficient. This extraordinary performance was related to the high surface area while maintaining a high mass transfer due to the open surface structure. The TiO2 particles were homogeneously coated on a wider surface, allowing a greater efficiency, and thus higher degradation amount. Moreover, no intermediate compounds (NO2) were produced from the degradation of NOx.
Modelling and optimizing the sound absorption
The main application of WWCB is as a ceiling material because of its sound absorption properties. Hence, a study is performed to characterise the acoustic properties of WWCB manufactured with different strand widths, densities and board thicknesses. Using an impedance tube and optimized impedance models it was found that the acoustic performance of WWCB could be accurately predicted. This enabled more inside into the sound absorption properties and allowed to specify regions of density, strand widths, thickness and even multilayer configurations in which the sound absorption was the highest.
23 | INNOVATIVE MATERIALS 4 2019