Crack usually occurs in the flexural beam. The crack occurs because of the
characteristic of concrete that’s has low tensile strength. To reduce the crack,
addition fiber into concrete would be a solution to this problem. Because of the
characteristic of fiber has a good tensile strength, this research will study the
flexural strength of reinforce concrete using polypropylene as an admixture.
At this research tested 36 cylinders with diameter 15cm and height 30 cm, where
tested the compression, splitting tensile tested at 7,14,28 days and modulus of
elasticity tested at 14 and 28 days. The flexural strength of the beam tested 2 sample
of reinforce concrete beam with diameter width:15 cm, height:25 cm, and length:
260 cm with effective length 230 cm, tested at 28 days. The beam used longitudinal
steel bar at compressive area with diameter of bar 12mm and steel bar at tension
area with diameter of bar 10 mm and by using shear reinforcement with diameter
8mm.
The experimental result shows that compression tested at 7, 14, and 28day of
concrete age, where the ordinary concrete: 9.302 MPa, 10.491 MPa, 11.132 MPa
and pp fiber concrete: 10.197 MPa, 13.648 MPa, 13.852 MPa. and splitting tensile:
3.865 MPa, 3.158 MPa, 3.510 MPa and with pp fiber: 3.845 MPa, 3.665 MPa, 4.390
MPa. The average value of modulus elasticity tested at 14 and 28 days, the ordinary
concrete: 11642.57 MPa, 18811.06 MPa, and the pp fiber concrete: 17590.23MPa,
19902.04 MPa. The maximum load of the normal beam is 74.334 KN greater
1.408%, than polypropylene fiber where 73.302 KN. The crack at the surface of
ordinary concrete beam is reduced when compared with the fiber concrete beam