3.4 Flexural strength of fiber cement flat sheets In accordance with ASTM C1185 and ASTMc1186. natural fiber cement flat sheets mixed with 5%, 10% and 15% of coconut coir and oil palm fibers by weight of Portland cement were tested to deter mine the flexural strengths, as shown in Fig 7 The mix proportion with 15% of cellulose fiber was difficult for casting a flat sheet.
the results shows that the flexural strength of both fiber cement flat sheets with the fiber ratio of 10-15% had similar flexural strengths exceeding 4 MPa(or 40 kglcm in accordance with the ASTM c1186 standard. In addition, compared to previous researches l 121,24l, the results are similar and consis- tent: ratios between 2% and 5% for both coconut coir fiber and oil palm fiber yielded the standardized flexural strength, in the case of roof sheets not manufactured by extrusion process with pressure.