Table 2 shows that the panel with 9 % untreated coconut fiber has the highest compressive strength (43.8 MPa). The lowest compressive strength is given by the cement panel with 9 % treated coconut fiber (24.5 MPa).
Generally, untreated coconut fiber gives higher compressive strength for the cement panel as compared with treated coconut fiber. However, cement panel with 3 % untreated coconut fiber gives low compressive strength (33.7 MPa).
In this case, even though adding fiber contributes to increasing strength, the strength does not increase linearly with increasing fiber content. The congestion or clustering of fiber may lead to reduce bonding between coconut fiber and cement.