Comparison of increasing the thickness of the concrete slab by increasing the compressive strength of the concrete slab in determining the fatigue life of rigid pavements

چکیده مقاله

In this paper, by applying a certain and heavy load due to a dual wheel on a concrete rigid pavement located on a weak subgrade, according to Portland Cement Association ,we calculated the maximum stress on the edge of the concrete slab with different thicknesses and compressive strengths and after that, we calculated stress ratios and  finally fatigue life of the pavement in different cases; after determining relations and charts of the number of allowable repetitions in front of the concrete compressive strength and the thickness of the concrete slab and comparing them with each other ,it was found that on the one hand, the rigid concrete pavements subject to high stresses which are located on weak subgrades, neither with conventional thicknesses nor by the compressive strengths ,the concrete is able to withstand fatigue due to heavy traffic on main roads, highways and freeways as with the highest conventional compressive strength implemented and the maximum thickness resulting in the lowest proportion of high tension under the PCA ,the highest number of allowable repetitions of pavement will be acceptable only for byroads ,and on the other hand, an exponential relationship exists between the number of allowable repetitions and each indicator of the compressive strength of the slab concrete and the slab thickness alone as an independent variable, with the exception that the number of allowable repetitions is more sensitive to the slab thickness and its changes is more severe against thickness variations. Also, the graph of logarithmic values of the number of allowable repetitions versus each variables of concrete compressive strength and the thickness of the concrete slab both are polynomial functions with the difference that the logarithmic graph of the number of allowable repetitions in terms of thickness of the concrete slab has higher concavity and more slowing rate.

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