Effects of Polypropylene Fiber Content on Strength and Workability Properties of Concrete

Abstract

Low tensile strength of plain concrete is due to the inherent presence of microcracks due to drying shrinkage occurrences or other causes of volume changes in concrete. The addition of a proper amount of fibers to concrete would act as crack arrester thus improves its static or dynamic properties. In this paper, the concrete with different amount of polypropylene fiber was investigating to find out the fibers effect on its fresh and mature properties. A plain concrete mix (reference mix) prepared for comparison purposes. Nine concrete mixes were prepared with different fiber volume fraction (FVF) ranging from 0.06% to 2.16%. It has been found out that the fiber content of the concrete mix will increase compressive, splitting, and flexural strengths of the concrete at the age of 28 days. The strengths increased and reached their maximum value at a corresponding (FVF) of about 0.36%. In comparison with the reference mix, the increase in the maximum compressive strength was about 18%, while the increase in maximum splitting tensile strength was about 16% and the increase in flexural strength was about 14%. When the fiber content increased beyond the mentioned 0.36% volume fraction: The concrete strengths started to decrease due to high volume fiber interface with the cohesiveness of the concrete matrix causing difficulty in concrete compaction with lowering its workability. At fiber (FVF) of 0.96%, the concrete slump value became zero. Thus, forced vibration needed for the compaction. For each mature concrete mix density and water absorption percentage were measured. It has been noticed that with an increase of fiber dosage in the concrete mix its density will decrease leading to contrarily an increase in the water absorption percentage. This was due to an increase in air void in the concrete due to the reduction in the workability of the concrete.