Influence of High Temperatures on the Mechanical Properties of Wood Bio-Concretes

Abstract

The use of wood wastes in the production of bio-concrete shows high potential for the development of sustainable civil construction, since this material, in addition to having low density, increases the energy efficiency of buildings in terms of thermal insulation. However, a concern arising from the production of bio-concretes with high amounts of plant biomass is how this material behaves when subjected to high temperatures. Therefore, this work aims to evaluate the influence of high temperatures on the mechanical properties of wood bio-concretes. The mixtures were produced with wood shavings volumetric fractions of 40, 50 and 60% and cementitious matrix composed of a combination of cement, fly ash and metakaolin. Uniaxial compression tests and scanning electron microscopy (SEM) were performed, with bio-concrete at age of 28 days, at room temperature (reference) and after exposure to temperatures of 100, 150, 200 and 250 °C. The density and compressive strength of the bio-concrete gradually decreased with increasing biomass content. Up to 200 °C, reductions in strength and densities less than 19% and 13%, respectively, were observed. At 250 °C, reductions of compressive strength reached 87%. Analysis performed by SEM showed an increase in the number of cracks in the wood-cementitious matrix interface and wood degradation by increasing the temperature.

Fire reaction properties of bio‐based aggregates used in thermally insulated building components

“…After considering the importance of applying treatments on residues to produce cement composites 35 due to chemical incompatibilities as well as a reduction in properties such as MHRR and EHC, the residues were previously treated. In order to evaluate the microstructure of treated bio‐aggregates, before and after MLCC tests, analyses by SEM were performed.…”

“…The water absorption of the bio-aggregates was determined by reproducing the mixing conditions simulating the composite production process, with the same mixing time. 35 To obtain the moisture content of the bio-aggregates, the specifications of the ABNT NBR 9939 (2011) 37 standard were followed. For this analysis, three samples weighing 50 g each were placed in an oven at 100 C until mass was constant.…”

“…Finally, the samples were dried in an oven at 100°C until mass was constant. The water absorption of the bio‐aggregates was determined by reproducing the mixing conditions simulating the composite production process, with the same mixing time 35 . To obtain the moisture content of the bio‐aggregates, the specifications of the ABNT NBR 9939 (2011) 37 standard were followed.…”

“…Given the problem of chemical incompatibility between extractives present in lignocellulosic materials and cementitious materials, 33 it was necessary to carry out a treatment in the three wastes studied. From studies of treatments already carried out with wood particles, 34,35 the alkaline treatment in calcium hydroxide solution at a concentration of 1.85 g/L of water was chosen. The alkaline treatment with calcium hydroxide causes a carbonation phenomenon on the surface of the particles, causing a physical–chemical change in the fibres structure that modifies the binding properties of the material, in addition to extracting soluble substances (extractives) from the bio‐aggregates.…”

Caracterização reológica de pastas ternárias para o desenvolvimento de bioconcretos leves de casca de arroz

“…A escolha da matriz desta pesquisa visou substituir o cimento Portland por materiais cimentícios suplementares (SCM) para mitigar a pegada de carbono do bioconcreto, conforme realizado por CALDAS et al [9]. O teor de 45% de cimento foi utilizado baseando-se no desempenho mecânico observado por AGUIAR et al [32] e CALDAS et al [9] que produziram bioconcretos de madeira com 40% e 50% de cimento, respectivamente, Quanto ao teor de cinza volante, foi fixado a 30% seguindo as recomendações de AGUIAR et al [32] e consequentemente, a fração mássica de cinza de casca de arroz foi de 25%. Foi verificado nos estudos de LIMA e IWAKIRI [33] que até 30% de CCA podem ser empregado em bioconcretos de casca de arroz sem perda da resistência à compressão.…”