USE OF FIBROUS CONCRETE FOR ROADS CULVERTS AND PENSTOCKS

Abstract

Fibrous concrete is a composite material made of cement, fine and coarse aggregates with random dis-continuous discrete fibres. Plain cement concrete possesses a very low tensile strength, limited ductility and little resis-tance to cracking. Internal micro-cracks are inherently present in the concrete and due to its poor tensile strength, the cracks propagate with the application of 1 oad. In fibrous concrete, the fibres tend to arrest these cracks thereby increasing the tensile strength of the composite. Fibrous concrete possesses improved properties like compressive strength, flexural strength, impact strength and fatigue resistance. In the present investigation improvements in the properties like compressive strength, modulus of elasti-city and flexural, strength due to addition of fibre has been studied. Two full scale simply supported culvert slabs, one in conventional Reinforced cement concrete and the other in Steel Fibre Reinforced Concrete (Rein-forced cement concrete with fibres) were cast and tested to study their load deflection behaviour, crack widths, first crack load and load at the permissible crack width, (iv) crack pattern etc. Three pipes, first in reinforced cement concrete, second in reinforced cement concrete with fibres and the third in steel fibre reinforced concrete were cast and tested under hydrostatic pressure to study their hoop stress strain behaviour and leakage. It is found from these studies that fibrous concrete possesses improved properties like compressive strength, modulus of elasticity, flexural strength and load carrying capacity over the conventionally used Rein-forced Cement Concrete. The applications of the composite matrix to pavement slabs, culverts and penstock pipes for microhydel power station have been established. Smaller crack widths and deflections; and higher load carrying capacity of the structural elements made of the composite matrix provide a versatile material for structural applications.