Analysis of the influence of wheat residues on gypsum composites

Gypsum is a material commonly used in construction. The growth in the consumption of this material is due to the good surface quality and the ease of molding it provides; however, owing to its limitations such as high permeability, high porosity, and low compressive strength, this material is mostly used indoors. In this context, the objective of this work was to evaluate the influence of the addition of wheat residues (0.0%; 2.5%; 5.0%; 7.5% and 10.0%) at different percentages on the physical-mechanical properties of gypsum matrix composites. For that, the wheat residues were first reduced to particles and characterized by density, ash content, lignin, and extractives analysis. Subsequently, six specimens of 40 x 40 x 160 mm dimensions, water/gypsum ratio of 0.6, and different incorporations of wheat residues were produced. After 7 days of curing, the composites were characterized by Scanning Electron Microscopy, bending, compression, humidity, density, water absorption, thermal conductivity, and sound insulation. The results showed that the composites with increasing amount of wheat fibers exhibited a decrease in their mechanical properties, though, were able to meet standard specifications. As well, a more porous surface due to the "in natura" properties of the lignocellulosic material and its water affinity, however, this porous structure, helped the composite to improve its insulating properties. Therefore, these preliminary results point to the internal usage of this product, in places where there is no contact with water.