Estimating Potential Aggregate Interlock Load Transfer Based on Measurements of Volumetric Surface Texture of Fracture Plane

The volumetric surface texture (VST) test was developed at the University of Minnesota to provide an estimate of the load transfer potential available through aggregate interlock across a concrete fracture plane. It can also provide an estimate of the abrasion that has taken place since fracture. A study was undertaken to validate the VST concept and test procedures. The factors investigated in this study include the effects of aggregate characteristics on measured surface texture and the effects of measured surface texture on crack and undoweled joint performance, as indicated by deflection-based load transfer efficiency. Deflection, load, and crack width data were collected for both field and laboratory slabs, and VST testing was performed with companion specimens for these slabs. This study has shown that the VST test provides a means of accurately measuring surface texture so that the selection of concrete aggregates can be performed with consideration of potential aggregate interlock at cracks and undoweled joints. Performance prediction equations were developed to provide an early indication of how cracks and undoweled joints will perform before a particular aggregate size, type, gradation, or blend is used in an actual pavement.