FLEXURAL FATIGUE ANALYSIS OF FERRO- FIBROCRE TE PAVEMENTS

Abstract

It is well known that plain cement concrete (PCC) fails due to formation of micro cracks in initial stage and their subsequent propagation. So it has a limited resistance to impact and fatigue loading. Due to the above reasons the addition of fibres and wire mashes are used to reinforce the concrete to enhance the structural behaviour of the composite construction. Composite properties related to flexural fatigue performance of FFC are described for use in load carrying structural members. Concrete pavements in the highways are subjected to millions of cycles of repeated axle loads from trucks and automobiles. Concrete structures supporting dynamics machines are also subjected to hundreds of millions of load cycles involving complicated stress states. The present investigation, therefore, planed to study the flexural fatigue analysis of ferro-fibrocrete pavements for different stress levels by two-parameter of Weibull distribution. The fatigue life of FFC specimens is found to improve with the number of mesh layers, fibre concentration, aspect ratio and type of fibre used. From the test results, the increase in compressive strength is 50%, static flexural strength is 66% of FFC as compared to the PCC. From the fatigue tests, the test results are presented as S- N relationships with maximum fatigue stress expressed as a percentage of ultimate strength of FFC (i.e. stress level, S) under static loading and number of cycles to failure N. The two-million cycle endurance limit for PCC is found to be 62% and for FFC is found to be 69% corresponding to static flexural strength. The recent research has established the performance and economics of ferro- fibrocrete. Study shows that when composite material are used in pavement construction in place of plain or conventionally reinforced concrete section, the thickness requirement is appreciably reduced and life expectancy is more. The Ferro-fibro combination in the matrix helped in maintaining the crack tightly closed due to crack arrest properties. The life expectancy is more then 7 times with compared to PCC and cost ratio is found to be more than 2.92 with compared to PCC. When the structure is subjected to repeated load during its service life, the design should be based on its fatigue loading.