Investigation of Potential Concrete Tie Rail Seat Deterioration Mechanisms: Cavitation Erosion and Hydraulic Pressure Cracking

Rail seat deterioration (RSD) is the most critical problem with concrete tie performance on North American freight railroads. Currently, the causes and mechanics of RSD are not sufficiently understood, limiting effective approaches to RSD mitigation and prevention. Past research and field experience with concrete ties identified five concrete deterioration mechanisms that may occur during RSD: abrasion, crushing, freeze-thaw cracking, cavitation erosion, and hydraulic pressure cracking. Currently, little empirical evidence exists to substantiate theories on cavitation erosion and hydraulic pressure cracking. A set of laboratory experiments has been developed to isolate cavitation erosion and hydraulic pressure cracking from the other potential mechanisms to challenge the theory that conditions exist in concrete tie track for these two mechanisms to contribute to RSD. The authors have instrumented submerged, unreinforced concrete specimens with a pressure transducer to measure the hydraulic pressure between the tie pad and the concrete rail seat during loading. Preliminary results relevant to hydraulic pressure cracking suggest that the magnitude of the applied load and the tie pad geometry significantly influence both the water pressure pulse magnitude and the pressure dissipation rate with subsequent load cycles. The results of these laboratory experiments will guide the development of effective methods for mitigating RSD, with the goal of reducing the life-cycle cost of concrete-tie track.