Devising Test Method for Measuring Spot Deformation Resistance of Asphalt Mixture under Railroad Crossties

초록

Research for application of asphalt concrete pavement under the railroad track has been under progress in Korea. The asphalt mixture to be used under the crosstie (sleeper) of railroad tracks should be strong enough against the spot-deforming stress which appeared to be similar to bearing stress. The rutting of highway asphalt pavement is induced by compressive and shear stresses, but the primary stress under the crossties in railroad is due to the vertical compression. Most of the current methods for evaluating rut resistance of highway pavement use a pressure wheel, slowly tracking on top of the asphalt mixture slab to induce vertical deformation (depression) in a form of rut. However, since the deforming mechanism of the pavement under railroad crosstie and temperature environment are different from those of roadway pavement, a test protocol to measure deformation resistance for railroad pavement should be devised in a different concept. The normal wheel tracking test for roadway asphalt mixture was modified as by placing wooden sticks in between asphalt slab and steel plate as simulated crossties. The vertical depth of mixture deformation underneath the simulated crossties was measured using the normal wheel tracking system. The objective of this study is to evaluate feasibility of the modified wheel tracking protocol for measuring deformation resistance of asphalt mixture for railroad pavement. The test concept evaluated in this study was found to show reasonable results for railroad pavement environment.