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The traffic speed deflectometer (TSD) is a device used to evaluate the pavement's structural condition. Measurements obtained from the TSD are affected by noise, which can make it hard to interpret test results. The main objective of this paper is to develop a denoising methodology to use with TSD measurements and improve pavement structural evaluation. The denoising methodology comprises a computational algorithm to identify significant features in a high-dimensional vector of observations containing white Gaussian noise. The algorithm minimizes the classification error of features in the wavelet transform domain by adaptively selecting the level at which to control the false discovery rate. When tested in a simulation study, the results of the proposed algorithm compared favorably with other state-of-the-art methods. The proposed methodology was then successfully used with TSD measurements to identify possible weak joints in a jointed concrete pavement overlaid with an asphalt layer and to calculate asphalt layer modulus values. Repeated measurements were used to validate that the denoised measurements more accurately represent the structural condition than raw measurements. [ABSTRACT FROM AUTHOR]

Compacted sand concrete is being researched for potential usage in road construction because of the overexploitation of quarry gravels and the risk of a shortage in gravel resources in many countries throughout the world. This paper describes the steps followed to validate the use of such material from the proportioning to the performed mechanical tests (compressive strength, indirect tensile strength, flexural strength, and Young's modulus). This study also describes the development of an economic test setup to test the fatigue properties of compacted sand concrete. The developed machine produced repeatable results and was able to generate the fatigue curves for a conventional concrete mixture and three different compacted sand concrete mixtures. Two of the tested sand concrete mixtures were made using crushed sand from two different quarries, whereas the third one was made using a mixture of crushed sand and desert sand. The encouraging fatigue results, as well as the acceptable initial construction costs, validate the use of compacted sand concrete in pavements. [ABSTRACT FROM AUTHOR]

One of the 12 instrumented sections of the Virginia Smart Road was used to compare measured vertical compressive stress and measured transverse horizontal strain under the hot-mix asphalt (HMA) layer induced by a 25.8 kN (5.8 kip) single tire and a 39.5 kN (8.9 kip) set of dual tires to those calculated using layered linear elastic theory. The pavement section is composed of 38 mm (1.5 in.) HMA wearing surface, 150 mm (6 in.) of HMA base mix, 75 mm (3 in.) of asphalt stabilized open graded drainage layer, 150 mm (6 in.) of cement stabilized aggregate layer, and 175 mm (7 in.) of unbound aggregate base. The subgrade is a fill material composed mainly of rocks. Measured stresses were obtained using pressure cells embedded in the pavement during construction. Horizontal transverse strain was measured using H-type strain gauges that were also embedded during construction. Temperature in the pavement layers was measured using embedded T-type thermocouples. Theoretically calculated stresses and strains were obtained using software based on the layered-elastic theory (Kenpave, Bisar 3.0, Elsym5, and Everstress 5.0). In addition, two finite-element approaches were used. Results indicated that the layered elastic theory overestimates pavement responses at low and intermediate temperatures, but significantly underestimates the pavement responses to vehicular loading at high temperatures. [ABSTRACT FROM AUTHOR]

The objective of this study was twofold: (1) quantify the benefits of a specially designed geocomposite membrane [a low modulus polyvinyl chloride (PVC) layer sandwiched between two nonwoven geotextiles] to act as a moisture barrier in flexible pavement systems; and (2) quantitatively measure the moisture content of unbound granular materials nondestructively. The geocomposite membrane was installed over half the length of a pavement test section at the Virginia Smart Road, while the other half of the test section consisted of the same design without the interlayer system. An air-coupled ground penetrating radar (GPR) system with 1 GHz center frequency was used to monitor and detect the presence of moisture within the pavement system over different periods of time corresponding to different levels of water accumulation. Results of GPR data analysis indicated that the use of the geocomposite membrane reduced water infiltration to the aggregate base layer by as much as 30% when measurements were performed after rain. It was also found that the moisture content underneath the interlayer was almost constant and therefore independent of the amount of rainwater, which is the primary source of moisture in pavement systems that have a low water table. The impact of moisture in the granular layers was investigated using the results of a deflection monitoring program. The results indicate that the area with the geocomposite membrane always showed less deflection than the area without the interlayer. The study recommends that any pavement drainage layer must be backed by an impermeable interface, given that the water table is low. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar has been used successfully to predict layer thicknesses in flexible pavements. Currently, a time-domain method is used to measure the two-way travel time between reflections from which the layer thickness is predicted. In this method, the dielectric constants are assumed to be real and are calculated from simplified equations. This paper presents a new method to measure layer thicknesses in flexible pavements. The method is based on predicting the reflected frequency spectrum through a multiple reflection model. The dielectric constants of the materials are assumed to be constant over the entire frequency range of the radar system, although dielectric and conduction losses are considered in the model. An optimization procedure is used by first calculating the reflected frequency spectrum using several values for the thicknesses and the complex dielectric constants, then choosing the solution with the minimum root-mean-square error between the predicted and measured frequency spectrums. The method was used in three pavement sections with known layer thicknesses. A percentage error of less than 3.6% was found between the measured and predicted values. [ABSTRACT FROM AUTHOR]

Abstract: Compacted sand concrete is being researched for potential usage in road construction because of shortage in gravel resources in many countries. However, one of the problems for this material with such application is shrinkage cracking. This paper presents the results of the unrestrained shrinkage test performed on three different compacted sand concrete mixes. Two existing shrinkage prediction models, namely the ACI 209 and the CEB 90, were used to fit the measured shrinkage data. The CEB 90 model with an application of a correction factor was found to perform well with compacted sand concrete. Based on the results of the shrinkage tests, joint spacing between compacted sand concrete slabs was calculated. [Copyright &y& Elsevier]