James A Crovetti

Deflection-Based Analysis Techniques for Jointed Concrete Pavement Systems

Techniques are presented that are based on the dense-liquid foundation model for analyzing deflection data obtained at center slab, slab edge, and slab corner positions to provide indications of the quality and uniformity of support beneath jointed concrete slabs. Deflections obtained at central slab positions are used to quantify a baseline foundation k-value for each slab tested. Edge and corner deflection data are used to establish the foundation edge and corner k-values of each slab. Adjustments for slab size and temperature curling during testing are discussed. Slab support ratios are determined on a slab-by-slab basis using the ratio of edge and corner k-values to center-of-slab k-values, ke/ki, and ke/ki. When nonuniform support exists, the foundation support ratio will typically be less than 0.75. Example and field results are provided to illustrate the analysis techniques and the interpretations necessary to distinguish between poor support due to slab curling or foundation voids.

Comparative Analysis of Field Permeability Testing of Compacted Hot-Mix Asphalt Pavements: Using Air and Water Permeameters

The in-place permeability of asphalt pavements has been the focus of recent research as investigators try to establish links between pavement permeability and performance. Previous research concluded that pavements with in-place air voids exceeding 8% to 10% may be considered as excessively permeable, and it is generally accepted that excessively permeable pavements are more prone to oxidation and stripping of the asphalt binder, as well as more susceptible to freeze-thaw degradation. As the use of the Superpave® design procedures has increased, numerous questions have arisen regarding the effect of certain mix design parameters on the in-place density and permeability of compacted asphalt pavements. A recent investigation into this issue has generated the need for reliable test methods and equipment that can be used to assess the field permeability of in-place pavements. Results of field permeability tests conducted on newly constructed asphalt pavements by using both water and air permeameters are prese...

Analysis of Load Pulse Durations for Marquette Interchange Instrumentation Project

The loading frequency is an important input for determining the stiffness of asphalt materials on the basis of their dynamic modulus data. This stiffness relationship is used in the Mechanistic–Empirical Pavement Design Guide (MEPDG) to calculate a pavements structural response to loading. This response—typically maximum horizontal strain and vertical pressure—is then used to estimate the number of load repetitions to failure. The Marquette Interchange Perpetual Pavement Instrumentation Project is a research effort carried out by the Transportation Research Center at Marquette University. The project implemented different pavement sensors to provide researchers with a complete set of pavement response data for calibration of local design variables and to provide insight into the structural behavior of a perpetual pavement opened to live urban freeway traffic. An analysis of the strain and pressure data recorded from the project was conducted to measure the length of strain and pressure pulse durations. The load pulse durations for each axle were then analyzed and compared with models contained in the MEPDG software. The analysis showed that the models may broadly fit actual load durations, but the surrounding assumptions may not be adequate for all axle and load configurations.

Construction and Performance of Fly Ash-Stabilized Cold In-Place Recycled Asphalt Pavement in Wisconsin

Cold in-place recycling (CIR) is a common rehabilitation practice used in Wisconsin to improve the ride quality and structural capacity of deteriorated asphalt pavements. In recent years, increased emphasis has been placed on incorporating stabilizers into the CIR materials to improve the structural capacity of the CIR base layer. This improvement can serve to increase the performance life of the completed pavement or to allow for a reduced hot-mix asphalt (HMA) surface thickness. The city of Mequon, Wisconsin, included asphalt emulsion and fly ash CIR stabilization over a portion of its CIR projects in 1997. Presented are the findings relating to the constructability of the fly ash–stabilized CIR pavement as well as performance trends for the CIR pavements based on distress and deflection testing results. CIR is a common rehabilitation practice used in Wisconsin to improve the ride quality and structural capacity of deteriorated asphalt pavements. In one type of CIR application, existing HMA layers are pulverized, graded, and compacted, then used as a base layer for a new HMA surface. The pulverization process is completed to provide uniformity of support to the HMA surface and to significantly reduce or eliminate the occurrence of reflection cracking of the HMA surface. In most CIR applications, pulverization is completed through the full thickness of the existing HMA layers, as well as through the top 25 to 50 mm of aggregate base. Penetration into unbound aggregate base materials aids in cooling of the bits on the pulverizer mandrel. After pulverization, graders typically are used to spread the materials to the desired width and shape. Compaction is achieved by using vibrating steel drum and pneumatic-tire rollers. The moisture content of the CIR materials is adjusted, as necessary, by surface spraying from a water tanker truck.

USING A ROAD SURFACE ANALYZER TO EXPLAIN NOISE CHARACTERISTICS OF PORTLAND CEMENT CONCRETE PAVEMENT SURFACE TEXTURE

Uniformly spaced, transverse-tined portland cement concrete (PCC) pavements have been in extensive use in the United States since the early 1970s. Recent research by the Wisconsin Department of Transportation (WisDOT) and FHWA has led to an interim guideline for randomization of the tining pattern, with spacings varying from 10 to 40 mm and 50 percent of the spacings at or below 25 mm. At least five states have experimented with this random pattern. A six-state research study, funded by WisDOT and FHWA, was completed in 2000 by Marquette University and the HNTB Corporation. This study investigated 57 different PCC pavement textures, including a wide range of transverse and longitudinal tining patterns. One goal was to explain noise differences within and between various textures as well as to document noise and texture differences. The laser-based road surface analyzer (ROSAN), developed cooperatively by the Turner Fairbanks Research Center and private industry, was utilized for surface textural measurements. Before the advent of laser-based texture measurement devices, large studies of this type would have relied on manual volumetric (sand patch) measurements to quantify surface textural differences, making virtually impossible the determination of reasons for differences in noise characteristics of various textures. The use of ROSAN is described, tools developed to analyze textural variations and noise characteristics of tined pavement surfaces are presented, and correlations between ROSAN outputs and other variables, including noise level and sand patch measurements, are provided. Examples of simple and more subtle causes of noise discrepancies on random transverse tined PCC pavements are presented by use of ROSAN outputs. A great variation in surface texture, including tine spacing, width, and depth, was found among different PCC pavement sections constructed to identical tining specifications. Significant variations were also noted within any given test section in all states. A low correlation between ROSAN estimated texture depth and noise was observed. A more significant correlation between depth and width of tining was observed with use of ROSAN outputs. Recommendations include the need for quality control of tine depth, the need for a wet pavement accident study to determine tining depth requirements, and the development of an improved measurement device for measuring longitudinally tined PCC pavements.

Construction and Performance of Alternative Concrete Pavement Designs in Wisconsin

The design and performance of concrete pavement test sections constructed in Wisconsin in the summer of 1997 to validate the constructability and potential cost-effectiveness of alternative concrete pavement designs incorporating variable dowel strategies and slab thicknesses are described. To reduce the number of dowel bars across the transverse joints and remain consistent with dowel bar installation equipment currently used within the state, four alternative dowel patterns were examined. Test sections were constructed with alternative dowel materials including fiber-reinforced polymer (FRP) composite dowels, solid stainless steel dowels, and hollow core mortar-filled stainless steel dowels as well as a variable slab thickness. Postconstruction monitoring including deflection testing, joint distress surveys, and ride quality surveys have been done. Observed joint distress including minor spalling, chipping, and fraying is mainly due to joint saw cut operations. No transverse joint faulting or slab cracking has been observed. Deflection testing to date indicated general uniformity of foundation support in all test sections. Deflection testing has also been done across transverse joints to quantify deflection load transfer efficiency. Joint tests in the fall of 1997 and 1998 indicated reduced load transfer efficiencies in all test sections compared with control sections, most notably in the FRP composite dowel test sections and the placement alternative with three dowels in each wheelpath. Ride quality surveys indicated general uniformity among sections.

Assessing impact of bus traffic on pavement maintenance costs: City of Los Angeles

Engineers for the city of Los Angeles have observed that lanes carrying Mass Transit Authority (MTA) bus traffic deteriorate at a faster rate than similar lanes without bus traffic. The increased rate of deterioration results in greater maintenance costs in these lanes. To properly apportion the increased maintenance costs, city engineers need an objective method for quantifying the impact of MTA bus traffic. Multiple evaluation techniques are presented that may be used to quantify the effect of buses in terms of increased deterioration rates and greater rehabilitation costs. State-of-the-art techniques that use the results of deflection testing and pavement condition surveys are presented. Data collection procedures, methods for condition and structural analyses, and life-cycle costing procedures are provided. A case study that uses data collected from the city is presented. This study indicates an average yearly additional maintenance cost of

NOISE AND TEXTURE ON PCC PAVEMENTS - RESULTS OF A MULTI-STATE STUDY

800 per lane-mile caused by MTA bus traffic, excluding associated costs for curb and gutter or maintenance hole adjustments.