Jamshid Armaghani

Rubblization of Concrete Pavements

The Florida Department of Transportation is in the process of evaluating rubblizing concrete pavements as an effective rehabilitation technique for eliminating reflected cracks in asphalt overlays on top of concrete pavements. As part of that evaluation, a nationwide survey was performed to gather information about the practices of other departments of transportation with regard to rubblization and to determine the overall performance of rubblized sections in various states. The survey indicated that most states have a relatively small number of rubblized sections, with the exception of three states that have more than 10 sections each. The construction techniques, overlay thicknesses, and field performance varied from state to state. However, it was clear that most states are highly satisfied with rubblization as a good means for eliminating reflected cracks. Only a few states indicated problems with rubblization, mainly due to weak subgrade.

Permeability of Concrete Subjected to Cyclic Loading

The effect of microcracking development and propagation on the permeability of concrete was investigated in this study. Large numbers of single-edge-notched beams as well as unnotched beams were prepared in the laboratory and in the field from different concrete mixes and subjected to dynamic loading at various stress ratios. During the cyclic loading, stress-strain and air permeability measurements were simultaneously recorded using strain gauges and the poroscope apparatus. Obtained strain and the air permeability measurements were used to evaluate the deterioration of concrete during crack initiation and further propagation. After fatigue testing, other sets of samples were cored from the fractured beams for water permeability testing. Results from these samples were used to correlate with the air permeability as well as with the compressive strength of the beams. Findings indicated that at the first stage of cyclic loading the beam samples exhibited large strains along with a rapid deterioration in th...

American Road Map for Research for Nanotechnology-Based Concrete Materials

The mechanical behavior of concrete materials depends to a large extent on structural elements and phenomena that are effective on micro- and nanoscales. The nanomodification of concrete materials has the potential to open up new uses and classes of concrete materials, with wideranging implications for the concrete transportation infrastructure. The development of nanotechnology-based concrete materials will require a multidisciplinary approach, consisting of teams of civil engineers, chemists, physicists, and materials scientists. To help develop nanotechnology-based concrete materials, a concentrated effort was undertaken in the United States to develop a national road map for research in this area. This effort included two National Science Foundation (NSF) workshops held in August 2006 and September 2007. In addition to NSF, the Portland Cement Association, the Defense Threat Reduction Agency, the Florida Concrete and Products Association, the Army Corps of Engineers, TRB, and the International Union of Testing and Research Laboratories for Materials and Structures sponsored this effort. The road map for nanotechnology-based concrete materials charts a path beginning with current nanotechnology capabilities to advanced materials and systems. The road map details key milestones and step-by-step short-term, intermediate, and long-term courses of development that must take place to reach these key milestones. The road map also serves as a tool to identify the gap between the basic concrete materials of today and the potential of nanosystems and nanomaterials interacting in concrete nano-houses, nano-bridges, and nano-pavements. The national road map for nanotechnology-based concrete is described and discussed.

PAVEMENT ROUGHNESS DATA COLLECTION AND UTILIZATION

The Florida Department of Transportation (FDOT) is in the process of evaluating the protocols for collecting and analyzing roughness data. As part of that evaluation, a nationwide survey was performed to identify the trends and practices of various departments of transportation with regard to roughness data collection and analysis. All responding states indicated interest in obtaining the results of the survey, which was mailed to all 50 state departments of transportation. The responses show that most states are using laser-type road profilers for roughness measurements. The international roughness index (IRI) is the most widely used roughness index. Highway Performance Monitoring System (HPMS) data from different states are collected by using different equipment, and the data are collected in various wheelpaths and filtered differently. Stricter guidelines should be developed to ensure the consistency of HPMS data.

EFFECT OF MOISTURE ON MODULUS VALUES OF BASE AND SUBGRADE MATERIALS

Moisture in the base and subgrade layers of pavement can significantly decrease the modulus values of these layers. Recently, a study was performed on several Florida state roads for the purpose of evaluating the decrease in moduli of bases and subgrades due to the proximity of the water table. Dynaflect and falling weight deflectometer (FWD) tests were performed on pavement test sections throughout Florida for the purpose of backcalculation of the modulus values of the different layers. Testing was performed at different times of the year, and the water table fluctuations were recorded throughout the study. The Dynaflect and FWD deflections, water contents, depths to water table, layer thicknesses, pavement temperatures, and air temperatures were recorded on all test sections over a 5-year period. EVERCALC was used for back-calculation of modulus values on the basis of FWD tests. The Dynaflect data were also used for calculation of layer properties on the basis of a procedure developed by the Florida Department of Transportation. Both Dynaflect and FWD showed that the water table had a significant negative impact on the modulus values of the base and subgrade materials. Such results are extremely beneficial aids for establishing acceptable embankment depths so that the effects of moisture on the modulus values of pavements may be reduced.

REHABILITATION OF ELLAVILLE WEIGH STATION WITH ULTRATHIN WHITETOPPING

The Florida Department of Transportation constructed the first ultrathin whitetopping (UTW) project at the Ellaville truck weigh station on I-10 in northwest Florida. This rehabilitation project included the placement of UTW on the existing asphalt pavement, which had experienced severe rutting problems. Layer thicknesses for the UTW were 80 mm and 100 mm. The joint spacings for the UTW panels were 1.2 m and 1.6 m. High early strength concrete was used in this project. Polypropylene fibers were included in the concrete for the sections on the west side of the weight platform and plain concrete was used on the east sections. The joints on the east section were sealed with silicone sealant and the joints on the west section were left unsealed. Falling weight deflectometer tests and frequent condition surveys were performed on the projects. After 1 year of service and 1.1 million equivalent single-axle loads, the UTW shows good performance. Success and long-term performance of the UTW is highly dependent on the degree of bonding between the UTW and the asphalt base. During the study period, panels 1.2 m2 and 1.6 m2, concrete with and without fibers, sealed and unsealed joints, showed similar performance. It is predicted that the 1-year performance of the UTW at the weigh station is equivalent to 4.5 years of service at a medium traffic intersection.

Development of Florida Smoothness Specifications for Flexible Pavements

Initial pavement smoothness has been shown to improve overall pavement performance. This combined with the need to provide a comfortable ride for the driving public underscores the importance of achieving high initial pavement smoothness. The Florida Department of Transportation has developed smoothness specifications for asphalt pavements. These smoothness specifications will be used on high-speed facilities and will be based on measurements obtained with laser road profilers. The ultimate goal is to include incentive and disincentive specifications aimed at rewarding the contractor for a high-quality ride and simultaneously providing a financial deterrent to providing a poor-quality ride.

Accelerated Slab Replacement Using Self-Consolidating Concrete

A self-consolidating concrete (SCC) mix was developed to accelerate the construction of replacement slabs in concrete pavement rehabilitation projects. This work was part of a larger research project to develop an innovative process involving the use of temporary and reusable precast slabs and an SCC mix for construction of replacement slabs to reduce construction time and increase contractor production in concrete pavement rehabilitation projects. Two requirements were set for the SCC mix, high workability and flow rate without segregation, and a minimum 6-h compressive strength of 2,200 pounds per square inch [psi (15 MPa)] required by the Florida Department of Transportation (DOT). The SCC mix incorporated Grade 57 aggregate as well as a combination of admixtures, including a high range water reducer, workability retainer, water reducer and set retarder, and accelerator. Laboratory trial batches were prepared for the proposed mix and tested for workability and strength. On the basis of test results of the trial batches, the refined SCC mix was developed to achieve the high workability needed for faster concrete discharge and finish and to attain the Florida DOTs 6-h strength requirement of 2,200 psi (15 MPa) for slab replacements.

Curvilinear Behavior of Base Layer Moduli from Deflection and Seismic Methods

The reality of curvilinear relationships of stiffness versus deformation is usually neglected when moduli values from seismic methods are compared with those of deflection methods. On the basis of extensive field testing, results showed that moduli values for the base layers from deflection methods did not conform to those of seismic methods. Deflection testing techniques were signified by the falling weight deflectometer (FWD) and the Dynaflect methods. Seismic testing was carried out by use of the seismic pavement analyzer (SPA) method. The SPA test results yielded moduli values higher than those obtained from the deflection methods. Utilizing pavement parameters obtained from the SPA data, researchers determined surface deflections by use of frequency response functions of signals from the two groups of sensors used in the testing setup. Because of the types of hammers in the SPA testing, two different deflection basins were obtained at each testing point. Comparison of surface deflections from these methods indicated that deflection amplitudes from the FWD method were about 100 times higher than those obtained from the high-frequency hammer of the SPA. At certain pavement sections, deflections from the Dynaflect method were comparable to those obtained with the SPA low-frequency hammer. Accordingly, curvilinear relationships between surface deformation versus stiffness values were derived. These relationships can be used to determine moduli values at all surface deflections, including those from service loads.