Gabriel Bazi

PERFORMANCE OF COLD IN-PLACE RECYCLING IN NEVADA

In light of the increasing cost of hot-mix asphalt (HMA) mixtures and the limited availability of good materials, cold in-place recycling (CIR) offers an attractive alternative for rehabilitating asphalt pavements. Because of its limited performance history and the unavailability of a standard mix-design procedure, the use of CIR mixtures has been limited to low-and medium-volume roads. For more than a decade, many highway agencies have experimented with or used CIR mixtures and reported numerous successes. The Nevada Department of Transportation (NDOT) is currently using CIR on low- and medium-volume roads. The CIR layer is treated as a stabilized base course followed by a thin HMA overlay. As part of this program, NDOT developed a mix-design procedure based on the Hveem mix-design method to establish the optimum moisture and emulsion contents. The design procedure evaluates the moisture sensitivity of the CIR mixture and determines the need for lime treatment of the CIR mix. The basic concept of the mix design is to assess the ability of the CIR process in providing a flexible and stable mix that can withstand the combined action of traffic loads and environment. The designed CIR mixtures were implemented on three field projects and showed excellent performance, which led NDOT to construct additional CIR projects.

Seasonal Effects on a Low-Volume Road Flexible Pavement

Alaskas Parks Highway is a 323-mi, asphalt-paved, predominantly two-lane, low-volume roadway that links the states two largest cities (Anchorage and Fairbanks). The effects of thawing on this low-volume roadway pavement were assessed, and seasonal adjustment factors for the different pavement layers were developed. Falling weight deflectometer (FWD) testing was carried out weekly during springtime at three temperature data probe sites. The purpose of the FWD tests was to monitor the pavement structural conditions and moduli variations during the spring thaw and recovery periods. When the pavement began to thaw, how quickly thawing progressed, and whether the pavement returned to an equilibrium summertime state were also determined. Observations indicated that profound changes in backcalculated modulus values could occur within 1 week of thaw onset. In addition, moduli were used to develop modular ratios for the subgrade and base course layers. Results showed that while thawing, the subgrade and base course layers reached about 30% to 40% and 50% to 70%, respectively, of their summertime reference moduli. These ratios were lower than those currently used in Alaskan pavement design. Additional testing should be conducted to verify the proposed seasonal adjustment factors. Surface moduli values, calculated and plotted without the need for the pavement layer thicknesses, are useful in instantly identifying whether partial thawing has occurred.

Analysis of R/C decks in multi-cell box girder bridges under rational wheel load distributions

This paper presents the results of a finite element (FE) study on the analysis of reinforced concrete decks in multi-cell box girder bridges under wheel loading. The deck bending moments were investigated for typical multi-cell box girder bridges with various overhang widths and girder spacings. A parametric study related to the tyre pressure distribution showed that a single uniform tyre pressure distribution produces maximum moment effects in reinforced concrete (R/C) decks. The FE analysis showed that the AASHTO LRFD and Standard Specifications methods overestimated the overhang transverse negative bending moments for overhang widths between 105 cm (3.5 ft) and 165 cm (5.5 ft) and the transverse positive bending moment for girder spacings between 3 m (10 ft) and 4.2 m (14 ft). It is concluded that the overestimated moments in the bridge specifications are due to the specified effective width.

Finite element modelling of the rolling resistance due to pavement deformation

ABSTRACT Rolling resistance is defined as the energy lost when the vehicle tyre rolls over a pavement surface. The pavement surface texture, roughness and deformation are shown to influence rolling resistance to varying degrees. Several recent studies have focused on determining the vehicle rolling resistance primarily based on pavement surface characteristics without quantifying the effect of pavement elastic deformations on this parameter. This paper focuses on isolating the pavement structure-induced component of the rolling resistance by performing finite element (FE) modelling on flexible and rigid pavement structures using the ABAQUS software under a moving wheel load. The structure-induced rolling resistance (SRR) was shown to be significant for flexible pavements with thin structures and weak support, and relatively insignificant for rigid pavements and thick flexible pavements at low temperature. Due to the complexity of the FE analyses, a reliable procedure was developed for predicting the SRR for in-service pavements using falling weight deflectometer data. Quantifying the effect of SRR can lead to the construction of pavement structures with lower rolling resistance, which in turn will reduce the fuel consumption and the carbon footprint of the roadway network.

Integrating Data Collection Optimization into Pavement Management Systems

This paper describes a method for using location data to optimize the routing of pavement data collection vehicles. In much of the developed world, pavement testing is performed on a regular basis; the pavement testing data, in turn, serves as input to Pavement Management Systems. Currently, in the United States of America, state departments of transportation plan this data collection work by providing the list of roads that must be tested and then leave the routing of the vehicles to the equipment operators who typically execute the work in an ad hoc manner. This study presents the processes required to code the list of roads for testing, select appropriate hotels in the region of testing, and apply a Traveling Salesman Problem with Hotel Stops model to derive a route. Applying the processes to a case study shows significant cost savings associated with this method of roadway testing, as opposed to the current ad hoc methods.