Investigation on Effect of cement Types on the cement hydration and properties of wood-cement composites manufactured from sunflower stalk (Helianthus Annuus)

In this study, the effect of type II and III Portland cement and the use of undepithed and depithed sunflower stalks particles (Helianthus Annuus) with percentages of different mixing ratio of the poplar wood particles (Populous alba) with 100:0, 75:25, 50:50, 25:75 and 0:100 respectively in the manufacturing of wood-cement composites were studied. Physical and mechanical properties of boards were measured as the effect of lignocellulosic material (sunflower stalks andpoplar wood) and Portland cement type (II and III) on the cement setting time. The results of the study showed that the lignocellulosic material reduced the hydration reaction and increased cement setting time. In this regard, sunflower stalks particles in comparison with poplar wood particles increased cement setting time intensively. The boards made from type III Portland cement had better mechanical strength and physical properties (water absorption and thickness swelling reduced) than with type II Portland cement. In comparison with poplar wood particles usage, the use of sunflower stalks particles and more amount of it caused to mechanical properties decreases and increased the water absorption and thickness swelling after 2 and 24 h water immersion. Therefore the best characteristics were obtained in boards made from 100 percent poplar wood particles. In other hands, using depithed sunflower stalks particles caused to improved the physical and mechanical characteristics. In general, it can be concluded that 25 percent of depithed sunflower stalks particles relative to poplar wood particles (relative to mass lignocellulosic materials( with type III Portland cement in the manufactured wood-cement boards has suitable physical and mechanical properties for usage of these boards in interior building applications.