## 3 Results and Discussion
### Mortar Characterization  
The water/binder ratio and the proportion of the inputs used were maintained for all treatments, in order to obtain a more precise analysis, with only the proportion of fibers in relation to the amount of cement varying, as reported by some authors [16]. Some researchers ([9] and [30]) maintained the amount in mass of the mortar elements for the analyzed treatments, varying only the number of fibers in relation to the mass of cement, thus obtaining a better evaluation between the mixtures and the treated fibers. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Treatments** & **I\({}_{200}\)** & **I\({}_{\text{AM}}\)** & **CI (\%)** \\ \hline Natural & 5540 & 2850 & 48.56 \\ Ca(OH)\({}_{2}\) & 6340 & 2870 & 54.73 \\ NaOH & 8080 & 2730 & 66.21 \\ KOH & 5750 & 2900 & 49.57 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Segal Crystallinity Index for corn straw fiber. Figure 5: XRD results for corn straw fibers. Figure 6 indicates the slump flow test results for the mortars containing different types of fiber. Among all treatments, the one that presented the best results regarding workability for mortar coating was the one treated with NaOH at a proportion of 2.5%, since its horizontal spread was within the limits of 260 \(\pm\) 5 mm, as already cited by [42; 43] and recommended by NBR 13276 [44]. The loss of workability with the use of fibers in mortars has already been widely highlighted by other authors. For practical applications and the adoption of natural fibers in mortars, it is important to be concerned about the loss of workability caused by these materials. In this type of application, it is important to use superplasticizers in mortars, improving the workability parameters of the material. In addition, care must be taken not to form points of fiber agglomeration within the matrix, which can weaken the composite. This will be assessed based on the mechanical properties described below. Figure 7 shows the results of the density of cementitious composites in the hardened state. In general, there is a reduction in the weight of the mixture when natural fibers are used for making mortars [9; 15; 45]. However, it is observed that this reduction, in relation to the reference mortar, was only with the natural fibers in the proportion of 5% and those treated with NaOH, resulting in a lighter composite. In contrast, the treatments with KOH and Ca(OH)\({}_{2}\) resulted in an increase in density. Some authors [46] state that the increase in density is related to the impact of the treatment on the surface area of the fibers, causing an improvement in the adhesion between the fiber and the matrix. As highlighted by the previous results, the treatment with KOH degraded the lignocellulosic structure of the fiber, reducing its mechanical parameters. In contrast, the degradation of the fiber improved the adhesion of the material with the cementitious matrix, resulting in the density results observed in Figure 7.  
Figure 6: Consistency of mortars containing corn straw fibers. Natural fibers absorb a high water content, due to their hydrophilic characteristic [9; 47]. This characteristic directly impacts the mechanical strength of mortars [7], since the water that should be available for cement hydration is absorbed by the fiber. Figure 8 presents the data obtained for water absorption in the specimens in the hardened state, while Figure 9 presents the porosity results. The mortars made with treated fibers obtained lower water absorption values compared to natural fibers. About porosity, [48] highlights that this is a parameter little discussed in fibers that underwent alkaline treatments. This happens because, in general, the porosity and water absorption are related to the mechanical behavior, so that the lower the porosity, the higher the strength of the material. However, in cement composites with lignocellulosic fibers, this logic is not valid.