Effect of alkaline pre-treatment and chemical additives on the performance of wood cement panels manufactured from sunflower stems

Abstract

This research was performed to investigate the NaOH pre-treatment, chemical additives, and their combined effects on the properties of wood cement panels produced with sunflower stems. The experimental panels were produced with a target density of 1200 kg/m3, a wood/cement ratio of 1:3 and a dimension of 500 mm × 500 mm x 10 mm using the treated/untreated sunflower stem particles as a partial replacement of poplar wood and various chemical additives (CaCl2, AlCl3, MgCl3). The physical, mechanical, thermal, and morphological properties of sunflower stem-based cement panels were evaluated and compared with traditional wood cement panels. In general, the highest mechanical properties were obtained from the panels produced by using the CaCl2 additive and a mixture of pre-treated sunflower stems (40%) and aspen poplar (60%). The panels containing 100% sunflower stem particles-treated with NaOH reached mechanical properties above the minimum standard requirements when CaCl2 was added. The panels’ water resistance, dimensional stability, and mechanical performance were remarkably enhanced by the NaOH pre-treatment of sunflower stems and the chemical additives. Moreover, the addition of sunflower stems led to a marked decrease in the thermal conductivity of the panels. TGA results demonstrated that the sunflower stem adversely affected the cement hydration reaction, whereas the chemical additives and the pre-treatment improved it. In addition, the combined effect of NaOH pre-treatment and chemical additives resulted in more portlandite content in the WCPs compared to their separate use. The SEM observations revealed that the NaOH pre-treatment of sunflower stems and the chemical additives contributed to promoting cement hydration products. It was also observed that the honeycomb structure of sunflower stem pith was crushed and deformed due to the high pressure applied in the manufacture of WCPs.