# Agricultural Residues of Lignocellulosic Materials in Cement Composites
## 3 Results and Discussion
These findings are due to the low density of these lignocellulosic materials that resulted in a weak fibre-matrix interface, thus causing lower mechanical resistance. Nevertheless, these panels could still be used as sealing systems without structural load. To use these structurally loaded panels, new production variables must be evaluated, such as lower percentages of reinforcement material depending on the proportional density and the geometric and chemical characteristics. In Figures 2 and 3, to investigate the surface morphology of the fillers, we collected SEM images of the fracture surface before and after the ageing accelerated process. Image supervised classification (ISC) was performed to classify the percentages of the three studied classes: I--voids; II--lignocellulosic materials; and III--matrix of the same images. Figures 2 and 3 show the SEM analysis of the fibre-matrix interface of the composites. Regardless of the lignocellulosic material type, the fracture surfaces of the composites showed large cracks and boundaries between the lignocellulosic material and the matrix. Moreover, numerous fibre pull-outs and voids were observed on the surfaces, thus indicating the poor interfacial adhesion between the components. Because of the elongated nature of strands, some difficulties are expected in mixing the lignocellulosic materials with cement, thus potentially leading to incomplete coating/wetting of the particles with cement [9] and void formation. The presence of voids is considered the most critical defect affecting a composite's mechanical properties [54]. Voids prevent the load from being effectively transferred to the particles from the matrix, thus leading to debonding of the particles of lignocellulosic materials and to low mechanical properties of the composites. The physical-mechanical properties of cementitious composites are directly associated with the adhesion of fibres with the matrix [14]. The lower MOR and MOE values (Table 3) observed may be associated with the loss of adhesion of the fibres with the matrix (Figures 2 and 3). Thus, the SEM results were consistent with the mechanical results. The surface of sugarcane composite was smoother than the surfaces of the other lignocellulosic composites. Figure 2 and Table 3 show that sugarcane and eucalyptus had higher adhesion with the matrix. In these composites, the fracture surface showed a highly homogenous texture, suggesting good dispersion and compatibility, although some voids and protruding lignocellulosic particles were observed in the fracture surfaces. The presence of voids caused by the movement of the fibres of the lignocellulosic materials resulted in an increased water absorption capacity. Figure 2: Scanning electron microscopy (SEM) images and image supervised classification (ISC) of the evaluated lignocellulosic materials before and after the accelerated ageing process. Figures 2 and 3 show the consequences of the accelerated ageing process on the microstructures of the composites. Degradation of the fibres was observed after the accelerated ageing tests. According to [PERSON] [55], the principal factors that promote material degradation under weathering are moisture, sunlight, and heat. The accelerated ageing test evaluated two of these factors (moisture and heat) [56]. The adhesion of the lignocellulosic material in the fibre-matrix interface exposed to the accelerated ageing process was also observed. The accelerated ageing test evaluated two of these factors (moisture and heat) [56]. ageing process was lower than that before the exposure. We observed damage at the interface as a result of the accelerated ageing process, thus causing variations in the volume of the fibres. Similar results have been found by [PERSON] et al. [14]. In addition, according to [PERSON] et al. [56], this degradation of the fibres and variation in the volume may directly influence the performance of the composites, because the fibres are responsible for supporting the mechanical load imposed on the composite material.