MEASUREMENT OF HARDENED STATE OF ASPHALT-PAVED ROAD AND DEVICE THEREOF

摘要

PURPOSE:To enable the stable traffic opening instruction by monitoring if the max. ratio between the reception voltage of supersonic waves before and after the change of the surface temperature of an asphalt pavement by the change a certain temperature becomes less than a threshold value or not. CONSTITUTION:A temperature measuring circuit 24 is installed in a probe supporting mechanism 48, and the surface temperature Ts of an asphalt pavement 30 is measured on the basis of the output of a temperature sensor 28 in contact with a road surface 32, and the temperature Ts is inputted into a control circuit 22 through an A/D converter 26. In the circuit 22, the transmission timing is controlled for a transmission circuit 14, and the reception voltage V is taken through an A/D converter 20. Further, the increase ratio H through the lapse of time between the received wave level data V1 and Vu before and after the change of the surface temperature by a certain temperature DELTAT is obtained as H=V1/Vu. The increase ratio H is compared with a previously determined threshold value 1.1, and when the value reduces less than the threshold value 1.1, the shoulder characteristic is developed on the characteristic curve determined by the temperature Ts and the reception level V, and the possibility of passing on the pavement 30 is judged.