Title : Biomass-enhanced lightweight concrete for sustainable construction - advancing towards carbon neutrality in the built environment
Abstract:
Concrete technology faces a significant sustainability challenge in reducing its high carbon emissions, as over 8% of global carbon production comes from cement manufacturing. The study reported here aims to provide an alternative for reducing resource consumption of aggregates and cement by i) introducing biomass waste from wood manufacturing as aggregate replacement and ii) using wood ash as a supplementary cementitious material. The biomass waste in the form of wood chips is optimized in its shape in order to allow for a complete replacement of lightweight aggregates. Three different wood species were used in the present experimental study. In order to minimize moisture uptake from fresh concrete as well as to optimize the shape of the initially cubic, elongated wood chips, various coating materials were considered, namely, wood ash, ground bottom ash, and cement. Moreover, different cover thicknesses (one, two, and three layers of cover) were analysed. Investigated aggregate fractions include 2/4 mm and 4/8 mm. Physical properties of uncoated and coated wood chips (grain size distribution, shape, water absorption) were tested for all wood and coating type combinations. Furthermore, relevant fresh concrete properties (fresh density, temperature, slump) as well as hardened concrete properties (compressive strength, density, and thermal conductivity) were investigated for all investigated combinations. It was found that the three-layered coating of wood chips leads to the most beneficial results in terms of water absorption, particularly for the larger fraction, as in this case, the wood chips approach the ideal round shape. Even though the cement coating absorbed the least amount of water, it was found that coating made of wood ash and ground bottom ash deliver acceptable levels of performance. Both fresh and hardened concrete properties of concrete with wood chips and supplementary cementitious material were comparable to or better than those for standard lightweight aggregates.
