Early Water Damage Evaluation For Highway Asphalt Pavement By Ground Penetrating Radar

In recent years, with freeway traffic mileage increase, more and more early distress isfound in asphalt pavement. Moisture damage is one of the important kinds. Currentnondestructive testing methods are hard to evaluate early moisture damage due to theconcealment of it. It is high effective, nondestructive, continuous monitoring that The groundpenetrating radar technology (GPR) provides an on-time, scientific approach to monitor andanalyze the early moisture damage.The test based on the domestic research of ground penetrating radar and water damagetechniques, though using high frequency radar (2GHz) to corresponding theoretical researchand field testing for asphalt pavement internal damage. A Fortran program using2D-FDTDfinite-difference method is coded and applied to simulate the damage of Surface course、middle course and base course course constructed by asphalt mixture; Also, a C++source filewas edited to standardize oscillogram obtained by2G high frequency radar.；Through on-sitedetection of300core samples corresponding to the position of laboratory tests, to establish aquantitative relationship between radar waveforms inverse peak amplitude and porosity；using2GHz ground penetrating radar for HeFei-LiuAn-YeJi of Anhui Expressway thicknesstesting site and analyzing its road thickness uniformity; through laboratory CPN tests fordifferent porosity, asphalt pavement, compare ruts trends analysis in the surface layer andmiddle course；though Dynamic Water Pressure for different porosity test on asphalt, makingcomparative analysis in the surface layer and middle layer of the core sample splittingstrength and CPN rut depth.Theoretical analysis and laboratory test results show that can better detect the asphaltpavement voids exist in different locations through the radar waveforms and the inverse peakamplitude and asphalt mixture inside the cavity size is positively correlated and with theinterior loosely degree of asphalt mixture the inverse relationship; radar waveforms inversepeak amplitude and asphalt porosity (void) there is a linear relationship: Y=-347.11x+622.53;the establishment of a radar waveforms inverse peak amplitude ratio and Porosity of AsphaltMixture (empty) linear relationship: Y=-0.0186x+0.0376;2G radar can ensure high accuracy(error <2%) of the continuous detection of the thickness of the asphalt pavement; throughCPN experimental study found, the porosity(>5%) of the specimens average CPN value isless than11%the porosity(<5%); though splitting test results, the porosity(>5%) of thespecimens splitting7.8%strength than the porosity (<5%); By dynamic water pressure testresults, porosity (>5%) asphalt loss16.3%strength after dynamic water pressure; the strength of the (>5%) asphalt after dynamic water pressure test less than10.4%of the porosity(>5%)asphalt; After dynamic water pressure test, CPN rut depth of the surface layer increases15.3%and the middle layer increases10.2%,after dynamic water pressure test,surface layerof the CPN rut depth increases more evident than in the middle layer; also observed thatdynamic water pressure flushing of the internal asphalt mix asphalt peeling occurs, theasphalt mortar occurring migration phenomenon.Through these studies, forming radar detection-analysis of radar waveforms-establishing waveforms with asphalt pavement surface porosity relationship-relationshipbetween different porosity and water damage-the development influencing of differentporosity for water damage-other diseases, such as the relationship between the porosity,water damage and rutting. For high frequency (2GHz) ground penetrating radar better appliedto the detection of asphalt pavement, estimating asphalt early water damage, and other aspectsof other diseases, such as porosity and rutting provides a new research idea.