DURABILITY OF STEEL FIBRE REINFORCED CONCRETE

Abstract

Plain concrete possesses a very low tensile strength, limited ductility and little resistance to cracking. Internal micro-cracks are inherently present in the concrete, and its poor tensile strength is due to the propagation of such cracks, eventually leading to brittle fracture of the concrete. To overcome these flaws, short, closely spaced and uniformly dispersed steel fibres are added to concrete to obtain a composite material called Steel Fibre Reinforced Concrete (SFRC). With the growing interest in the use of SFRC for various applications, a need has arisen to make clear their durability characteristics. Durability of structures has become very important parameter in our country off late which is evident from the revised edition of IS: 456-2000, due to increasing pollution level in the environment. Concrete is susceptible to attack by sulphuric acid produced from either sewage or sulphur dioxide present in the atmosphere of industrial cities. This attack is due to the high alkalinity of Portland cement concrete, which can be attacked by other acids as well. Sulphuric acid is particularly corrosive due to the sulphate ion participating in sulphate attack, in addition to the dissolution caused by the hydrogen ion. The aim of this investigation is to study the durability of SFRC with different fibre concentrations under the varying concentration of sulphuric acid to simulate the effect of sulphur oxides. The durability of material is a physical phenomenon difficult to quantify by any one parameter and hence physical properties like the weight loss, the water absorption and the compressive strength have all been investigated. The general trend found in all these cases is the progressive increase of weight. loss, water absorption and the reduction in compressive strength with the decay of the material. A relation between the physical properties and the concentration of the sulphuric acid solution and the immersion period for SFRC has been established.