Effect of Addition of Fibres on Mechanical and Durability Properties of No-Fines Concrete

Abstract

The aim of this research work is to study the effect of addition of fibers on various mechanical and durability properties of no-fines concrete. No-Fines concrete (NFC) was first prepared and then the modifications in mechanical and durability properties were studied by adding different types of fibres in the form of Polypropylene fibre (NFC-P), Jute fibre (NFC-J) and Steel fiber (NFC-S). Polypropylene fibers of 12 mm length were used at a volume fraction of 0.2% whereas jute fibers of 15 mm length were used at a volume fraction of 0.1%. Hooked end steel fibers with aspect ratio of 66.67 were used at a volume fraction of 1%. Results show that hooked end steel fiber and jute fiber had a considerable effect on mechanical properties of no-fines concrete while polypropylene fibers gave a slight increase to the compressive strength, split tensile strength and flexural strength in comparison to the no-fines concrete. Steel fibres enhance the mechanical properties significantly with 190% increase in Compressive Strength, 20% increase in Split Tensile Strength and 142% increase in Flexural Strength. Results for mechanical properties of NFC-J were on a higher side as compared to NFC-P and controlled no-fines concrete but on a lower side when compared to NFC-S. This is due to the lower elastic modulus and strength of polypropylene fibers than jute fibers and steel fibers. Therefore in can be said that addition of steel fibres in NFC gives the best mechanical properties. With the addition of all types of fibres, the permeability decreases but with a small amount. The permeability of NFC-P, NFC-J and NFC-S is decreased by 13.67%, 17.49% and 8.19% from control sample. The addition of fibres does not affect the abrasion resistance of NFC by a significant margin. The results show that steel fiber is best for increasing the properties of no-fines concrete without much decrease in permeability. The primary purpose of no-fines concrete is to pass water through it. This water can corrode the steel fibres easily. Therefore steel fibres are not much preferred. Jute fibres also provides good strength to no-fines concrete without much decrease in permeability and abrasion resistance. Hence they can be utilized effectively. Also they are cheaper than steel and polypropylene fibres.