Early Detection of Joint Distress in Portland Cement Concrete Pavements.

摘要

INDOT (as well as several surrounding states) have observed that certain concrete pavements may show a susceptibility to joint deterioration. Unfortunately, by the time that this joint deterioration is observed it is often too late and costly partial depth repairs are needed. The deterioration is generally occurring in the joint behind the backer rod and joint sealant; as such, it is difficult to detect even if one is standing directly above the joint. This project investigated the use of electrical resistivity and ground penetrating radar as two techniques to detect premature joint deterioration. The thought process was that if the joint deterioration is determined at an early stage, low cost corrective actions can be taken to extend the life of the concrete. The electrical response was measured for mortars subjected to a temperature cycle from 23 °C to ?35 °C, with varying degrees of saturation, and varying salt concentrations. The resistivity increased as the degree of saturation was reduced due to the reduction in the volume of the conductive medium and increase in tortuosity. Changes in resistivity were detected when cracking occurred in the sample. The magnitude of these changes was similar to that detected using changes in the ultrasonic wave speed. Ground penetrating radar (GPR) was used effectively to detect fluid accumulation in the saw?cut joint behind the joint sealant. The typical GPR waveforms are however difficult and time consuming to interpret. A signal processing approach called, referred to as the CID, was used to obtain a single number that reflects the potential for fluid in the joint. Scalar waveform features and the computed CID can be used to estimate which joints may contain fluid thereby providing insights into which joint sealant sections may need to be repaired or when a sufficient number of joints may contain fluid suggesting a larger joint maintenance effort be performed to seal the joints or the concrete. 17.