Influence of Polypropylene Fibers on Engineering Behavior of Soil−Fly Ash Mixtures for Road Construction

Fly ash is a waste produced mostly from the burning of coal in thermal power stations, which contributes to environmental pollution. Also, a number of studies have been conducted to investigate the influence of randomly oriented fibers on the engineering behavior of coarse grained and fine grained soils. The influence of randomly oriented polypropylene fibers on the engineering behavior of soil fly ash mixtures has not been reported so as much detail as in the case of the soils. The purpose of this investigation was to identify and quantify the influence of fiber variables (content and length) on performance of fiber reinforced soilfly ash specimens. A series of laboratory unconfined compression strength tests and California bearing ratio tests were carried. Polypropylene fibers with different fiber length (6mm, 12mm and 24 mm) were used as reinforcement. Soil -fly ash specimens were compacted at maximum dry density with low percentage of reinforcement (0 to 1.50 % of weight). Four primary conclusions were obtained from this investigation. First, inclusion of randomly distributed fibers significantly improved the unconfined compressive strength of soil fly ash mixtures. Second, increase in fiber length reduced the contribution to peak compressive strength while increased the contribution to strain energy absorption capacity in all soil fly ash mixtures. Third, an optimum dosage rate of fibers was identified as 1.00 % by dry weight of soilfly ash, for all soil fly ash mixtures. Fourth, a maximum performance was achieved with fiber length of 12mm as reinforcement of soil fly ash specimens.