# Agricultural Residues of Lignocellulosic Materials in Cement Composites
## 3 Results and Discussion
The values obtained for the density of the composites in this study were between 0.984 (banana pseudostem) and 1.267 g/cm\({}^{3}\) (coffee husk). The Bison Wood-Cement Board [40] determines the density of cement-based panels in the range of 1.250 g/cm\({}^{3}\), when the panels are produced with wood particles. The density of the panel is dependent on the compaction of the material, pressing pressure, particle size, and the density of the raw material and the binding agent [41]. The variability in density was dependent on the combination of raw materials and their compaction, owing to the presence of particle-particle bonding, because the pressure and the cement ratio were constant for all panels [42]. Density is an important property because it correlates with many properties of the composite material, such as thermal and mechanical characteristics. A relationship between density and porosity is observed in composites: the higher the density, the lower the porosity. Porosity results from the formation of air-filled cavities inside an otherwise continuous material, and it is often unavoidable in composites. Porosity develops during the mixing and consolidation of two different material parts: plant fibre composites typically contain a relatively high porosity, which may influence the properties and performance of the composites [43]. The panels produced with banana pseudostem had the lowest values of density and the highest values of porosity--findings associated with fibres with longer lengths and higher slimmess index values. Coffee husk panels had the lowest porosity values, the lowest slimmess index, and the highest density among the panels. Therefore, fibres with longer lengths are less able to interact with the matrix, thus causing more empty spaces in the composite, because of the difficulties in coverage and mixture with cement and fibre/matrix interactions. However, these values are also influenced by the chemical composition of the material (Table 1). Higher amounts of holocellulose and intermediate values of extracts, such as coffee husk, influence the connection with the matrix and the curing of the cement, thus resulting in panels with higher densities and lower porosity values. Coconut shell panels, despite having the lowest extract values, had the lowest density among the panels, possibly because of the lower amount of holocellulose and the geometry of the reinforcement material. Similar findings were observed for sugarcane bagasse. Although sugarcane had the highest amount of extract, which affects the curing of panels [6; 11], owing to the association with the geometry of the fibres, these panels showed the highest density \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Density** & **Porosity** & **Water** & **Water** & **Thickness** & **Thickness** \\  & **g/cm\({}^{3}\)** & **(\%)** & **Absorption** & **Absorption** & **Swelling 2 h (\%)** & **Swelling 24 h (\%)** \\ \hline Eucalyptus & 1.18 bc (0.068) & 74.2 bc (2.073) & 15.700 bc (0.991) & 16.467 ab (0.977) & 2.267 b (0.246) & 6.467 b (0.458) \\ \hline Sugar cane & 1.17 abc (0.082) & 78.5 bc (8.512) & 5.200 a (0.678) & 10.800 a (1.355) & 1.067 a(0.789) & 5.300 b (0.965) \\ \hline Banana & 1.00 ab (0.022) & 87.5 c (2.110) & 26.034 d (0.805) & 27.834 c (0.228) & 1.834 ab (0.186) \\ \hline Coconut shell & 0.98 a (0.082) & 62.8 ab (5.100) & 21.867 cd (5.410) & 23.567 bc (5.339) & 1.900 ab (0.365) & 3.367 a (0.688) \\ \hline Coffee husk & 1.27 c (0.079) & 52.5 a (9.702) & 12.567 ab (0.024) & 13.400 a (2.027) & 1.267 ab (0.117) & 2.134 a (0.360) \\ \hline \(p\) value & 0.0024 & 0.000 & 0.000 & 0.0001 & 0.034 & 0.000 \\ \hline CV (\%) & 6.31 & 8.92 & 17.46 & 14.44 & 25.50 & 13.71 \\ \hline \multicolumn{7}{c}{Averages followed by the same letter in the column present statistical equality by the Tukey test at a 5\% significance.} \\ \multicolumn{7}{c}{The values in parentheses are the standard deviation. CV: coefficient of variation.} \\ \end{tabular}
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