Evaluating Toughness as a Parameter to Determine the Fatigue Life of Wollastonite Microfiber Reinforced High Flow Pavement Quality Concrete

Abstract

Rigid pavements are designed on the basis of flexural strength, since the concrete is brittle and supposed to show little strains post-peak stress. The stress ratio, which is the ratio of flexural stresses to flexural strength generally determines the fatigue life of the pavement. Under service load, pavements face a continuous reduction in flexural strength on account of propagating cracks, which causes fatigue damage. But the evolution of cracks in quasi-ductile concrete is different, which is somehow anticipated to depend upon the toughness of concrete. Toughness is the area under load deflection curve and indicates the energy possessed by concrete. Under repetitive loading, there is continuous reduction in strength of concrete but the total energy possessed by concrete should not vary. This paper, thus tries to find the relationship of fatigue life with stress ratio, and fatigue life with toughness and stress ratio together to check for the validity of stress ratio-fatigue life equation in case of quasi-ductile concrete. Equations have been generated for normal pavement quality concrete (PQC), flyash admixed and wollastonite microfiber reinforced PQC. Results proved that even though the toughness affects the formation of flexural stresses in any kind of concrete, stress ratio is singularly effective for finding out the fatigue life, since it reflects both toughness (through flexural stresses) and flexural strength. Quantitatively, WMF-reinforced concrete has very high fatigue life than normal PQC and flyash admixed PQC, respectively.