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Gainesville, FL, United States

Ping W.,Florida State University | Sheng B.,Florida State University | Ling C.-C.,Florida State University | Dietrich B.,05 Suwannee Street | Horhota D.,007 Northeast 39th Avenue
Transportation Research Record | Year: 2010

The resilient modulus of pavement subgrade materials is an essential parameter for mechanistically based flexible pavement design procedures. "Base clearance" is defined as the clearance between the groundwater level and the pavement base layer within a pavement system. A high pavement moisture content, which is strongly influenced by the base clearance, causes detrimental effects on the resilient modulus of pavement subgrades. The determination of a pavement base clearance is one of the most important steps toward setting up grade lines in a roadway design. This paper presents an experimental study to evaluate the effects of base clearance on the resilient modulus of pavement subgrades. Full-scale dynamic pavement tests were conducted in test pits to simulate vehicle dynamic impact on field pavements. The level of base clearance was adjusted by raising or lowering the water level within the pavement layer in the pit. Ten types of Florida subgrade material were tested at different base clearances for this study. The dynamic plate load test results were compared with the resilient modulus obtained from the laboratory triaxial test by using layer theory. The differences between the resilient modulus from the laboratory test and the plate load test were typically about 20%. Resilient modulus measured from the laboratory triaxial test could be used to predict the resilient deformation of the pavement subgrade layers. The experimental results showed that, at lower base clearances, the high pavement moisture content caused a significant reduction of the resilient modulus of pavement subgrade layers. The resilient modulus of subgrade materials decreases with the decrease of base clearance.

Nam B.H.,University of Central Florida | Behring Z.R.,District 4 | Kim J.,Center for Advanced Infrastructure and Transportation | Chopra M.,University of Central Florida | And 2 more authors.
Journal of Testing and Evaluation | Year: 2015

Recycled concrete aggregate (RCA) is often used as a replacement for virgin aggregate in road foundations (base course), embankments, hot-mix asphalt, and Portland cement concrete. However, the use of RCA in exfiltration drainage systems, such as French drains, is still uncommon. The primary concerns with using RCA as drainage media are excessive fines and calcite precipitation that can cause a reduction in permeability performance. This study investigates the potential benefits of RCA as drainage material. This paper presents and discusses: (1) the results of a nationwide survey on current practices and policies, (2) physical and chemical properties, (3) effective fine-removing methods, (4) re-cementation potential, (4) permeability (under varied fine content), and (5) long-term drainage performance of RCA as drainage material. Test results indicate that RCA No. 4 gradation does not restrict the flow of water, but the RCA fines being generated during aggregate handling process (e.g., stockpiling, placing and transporting) may cause clogging buildup over time. Copyright © 2014 ASTM International.

Zaabar I.,Michigan State University | Chatti K.,Michigan State University | Lee H.S.,007 Northeast 39th Avenue | Lajnef N.,Michigan State University
Transportation Research Record | Year: 2014

A new backcalculation program, DYNABACK-VE, was used to back-calculate pavement layer properties with Held data. DYNABACK-VE used a time domain viscoelastic dynamic solution (ViscoWave-II) as a forward routine and a genetic algorithm for backcalculation analysis. The genetic algorithm search method was selected because it had a high potential for converging efficiently to a global solution. The forward solution used continuous integral transforms (Laplace and Hankel) that were more appropriate for transient, nonperiodic signals in the time domain. The algorithm was implemented in C++ and coded for parallel processing with multithreading for achieving better computational efficiency. Field falling weight deflectometer load and deflection sensor time histories from three sites (Waverly Road near Lansing, Michigan, and two long-term pavement performance sections) were used for validation. The backcalculuted asphalt concrete modulus master curves were compared with those obtained from laboratory testing. Very good agreement was obtained. The new algorithm was capable of backcalculating reliably the master curve of the asphalt concrete layer (four sigmoidal Coefficients and two time-temperature shift factors), the elastic moduli for the unbound base or subbase and subgrade materials, and the modulus of stiff layer and the depth to stiff layer, if present. The advantage of the new solution is that it can analyze the response of pavement systems in the lime domain and can therefore accommodate time-dependent layer properties and incorporate wave propagation. Also, because the backcalculation is performed in the time domain, the algorithm Is not sensitive to truncation in the deflection time histories. This is a significant Improvement to the state of the art, since truncation of deflection time histories has prevented frequency domain backcalculation solutions from being successful when measured field data are used.

Bekoe P.A.,University of Florida | Tia M.,University of Florida | Bergin M.J.,007 Northeast 39th Avenue
Transportation Research Record | Year: 2010

This study evaluated the feasibility of using concrete containing recycled concrete aggregate (RCA) in concrete pavement application. Concrete containing 0%, 25%, and 50% RCA was produced in the laboratory and properties vital to the performance of concrete pavement were evaluated. Results from the laboratory testing program indicate that the compressive strength and elastic modulus are reduced slightly as the percentage of RCA increases. The flexural strength, splitting tensile strength, and coefficient of thermal expansion are about the same for concrete containing virgin aggregate and RCA. The free shrinkage increases slightly as the percentage of RCA increases. With the measured properties, a finite element analysis was performed to determine how the concretes containing the different amounts of RCA would perform if they were used in a typical concrete pavement in Florida. Analysis from the finite element model determined the maximum stresses under critical temperature and load conditions. Potential performance of the pavements was evaluated based on the computed maximum stress to flexural strength ratio. The maximum stress to flexural strength ratio in the pavement was found to stay about the same as the percentage of RCA increases. This indicates that RCA can be used in concrete pavement without affecting its performance.

Nash T.,007 Northeast 39th Avenue | Sholar G.,007 Northeast 39th Avenue | Page G.,King of Asphalt Consulting | Musselman J.,007 Northeast 39th Avenue
Transportation Research Record | Year: 2012

This study examined the long-term performance and life span of mixture designs with a high percentage of reclaimed asphalt pavement (RAP) (≥30%) used on higher-tonnage (>5,000 tons) projects. The pavement performance of mixtures containing high RAP percentages and mixtures containing no RAP was compared for the period 1991 to 1999. The pavements analyzed contained a lower structural layer that contained RAP and an upper layer that contained either an open-graded or dense-graded non-RAP friction course. Several databases were consulted to obtain the necessary information regarding tonnage, mixture designs, percentage of RAP, project information, traffic volumes, pavement performance, and life span. A trend showing that the time needed for the pavement to reach a deficient state decreased as the percentage of RAP increased was evident when the data were examined without accounting for the volume of traffic. When traffic volume was accounted for and projects ≥5,000 tons were isolated, a trend of decreasing performance with increasing amounts of RAP was seen. However, in the range analyzed (30% to 50% RAP), all mixtures containing RAP performed better than the mixtures containing no RAP. Consideration of the type of non-RAP friction course placed over the RAP mixtures showed that as the amount of RAP increased, pavement performance decreased at the same rate, regardless of the type of friction course. Although this trend may be correct, the implication that RAP mixtures overlaid with an open-graded friction course have a longer life span than RAP mixtures overlaid with a dense-graded friction course may be the result of factors that are not correctly reflected in this data set.

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