Repeated falling weight deflectometer (FWD) tests were conducted at three sites. The tests were conducted at regular intervals for 2 to 3 consecutive days per location, and also done during different seasons in order that the widest possible range of temperatures could be obtained. The influence of cracks on temperature correction was also investigated. Temperature correction equations for deflection and moduli were developed so that users could be allowed to input their own reference temperatures. For all test pads, only the W1 and W2 deflections were found to be significantly affected by temperature. Comparisons with other reported temperature correction equations showed close agreement for deflection, but not for moduli. Tests were also run on cracked locations. Temperature did not affect the response of the cracked pavement as much as it did the intact pavement. Due to the different temperature-dependent characteristics of intact and cracked locations, the equations developed from the intact locations may not be used on cracked locations.

The dynamic cone penetrometer (DCP) is one of the lowest-cost alternatives for characterization of pavement layer qualities. In addition, it is fairly easy to collect and analyze data with the DCP. The DCP is not popular in the pavement engineering community, partly because of the lack of a solid correlation between DCP results and modulus values. More than 60 DCP tests have been conducted on two test pavements used for accelerated pavement testing to assess the validities of empirical equations proposed in previous literature to compute layer moduli from data obtained with the DCP. The effect of the test procedure on the DCP test values was studied, and the moduli obtained with the DCP were compared with those obtained by falling weight deflectometer (FWD)-multidepth deflectometer (MDD) and laboratory tests. It was found that the values obtained with the DCP are dependent on the test procedure, which affects the results by at least 10 percent. If there is an asphalt concrete layer, it is preferable to conduct DCP tests through a drilled hole. A sample size of 6 is recommended for routine characterization of base and subgrade layers, because this number would achieve 95 percent confidence and an error of estimate of less than 20 percent. The moduli obtained by using the DCP and the adopted equations yielded results compatible with those obtained from FWD-MDD tests. Those equations have been recommended to the Texas Department of Transportation for further evaluation and use in routine analysis. The laboratory-determined subgrade moduli were only slightly higher than those from DCP and FWD-MDD tests. No correction factor is required for the moduli backcalculated from FWD data to match the moduli obtained in the laboratory.

The purpose of this paper is to present the effectiveness of in-situ instrumentation on diagnosing the pavement layer conditions under full-scale accelerated traffic loading. The test section is an in-service pavement (US281) in Jacksboro, Texas. Multi-Depth Deflectometers (MDDs) are used to measure both permanent deformations and transient deflections, caused by accelerated traffic loading and Falling Weight Deflectometer (FWD) tests. Four different FWD loads of 25, 40, 52, and 67 kN were applied in close proximity to the MDDs at various traffic loading intervals to determine pavement conditions. It was found that the majority of rutting occurred in the newly recycled asphalt mix. The aged (> 40 years) underlying base and subgrade layers contributed less than 30% to overall rutting. Only the top recycled asphalt layer underwent notable deterioration due to traffic loading. Up to 1.5 million axle repetitions, the test pad responded to FWD load almost linearly, not only over the whole pavement system but also within individual layers. However, under higher FWD loads, the percentage of total deflection contributed by the subgrade increased.

The Dynamic Cone Penetrometer (DCP) is one of the least expensive testing devices able to characterize base and subgrade properties. To fully use the DCP in pavement evaluation, an empirical relationship between DCP penetration rate and layer modulus is required. However, the literature on this correlation is limited. This study incorporates a total of 198 DCP and Falling Weight Deflectometer (FWD) tests done over 8 years on various types of highways (Interstate Highway, US, and Farm-to-Market). The computer program MODULUS was employed to backcalculate the layer moduli from the FWD results to build a correlation with DCP results. A comparison was made with the widely-used model by Powell et al. (1984). It is found that the difference between the two models decreases as the Penetration Rate (PR) increases. For a PR of less than 10 mm/blow, the difference between these two models was over 10%. The difference is only about 1.7 % when the PR is 80 mm/blow. Without knowing the true moduli, it is impossible to tell which equation is better. The correlation developed here provides another option and allows researchers to recognize the range of variability.