The purpose of this research was to compare the rutting, cracking, and development of roughness of two asphalt overlay types commonly used in northern Utah and to evaluate how well the Mechanistic-Empirical Pavement Design Guide (MEPDG) can predict the observed results. AC-10 and PG 64-34 asphalt overlay materials were paved in a checkerboard pattern at a test site on State Route 30 near Logan, Utah, and observed for 3 years at 6-month intervals. Primary data included rutting, cracking, and roughness. At the conclusion of the 3-year evaluation period, rut depths were 0.08 in. deeper, on average, in the AC-10 overlay compared to the PG 64-34 overlay. Fatigue cracking in the PG 64-34 overlay exceeded that in the AC-10 overlay by 0.11 percent, on average. The measured roughness of the PG 64-34 overlay was greater by 24 in./mile, on average, than the AC-10 overlay. In summary, although the AC-10 product exhibited more rutting than the PG 64-34 product, the latter exhibited more fatigue cracking and greater roughness than the former. Although the MEPDG predictions for rutting are within the range of observed rut depths, the MEPDG overestimated the AC-10 rut depth while underestimating the PG 64-34 rut depth. Furthermore, the apparent inability of the MEPDG to predict amounts of longitudinal, fatigue, and transverse cracking comparable to measured values is concerning; the MEPDG predicted negligible cracking for both overlay types for the duration of the 3-year analysis period. While the MEPDG cracking models appear to be unsuitable for predicting cracking at this site, the MEPDG predictions for roughness are shown to be within the range of observed values. Given the findings of this study, the researchers recommend that Utah Department of Transportation (UDOT) engineers consider specifying the AC-10 asphalt overlay product for pavement treatments in conditions similar to those evaluated in this investigation. Even though the MEPDG predictions of rutting and roughness were generally correct, the researchers recommend that such predicted values be used as general predictions only. Further evaluation of these models, as well as the MEPDG models for longitudinal, fatigue, and transverse cracking, should be completed before the MEPDG is fully adopted by UDOT.

The objective of this research was to assess the condition of four decommissioned bridge decks treated with waterproofing membranes and asphalt overlays following the completion of their service lives. Large samples were cut from each of the bridge decks immediately prior to demolition and taken to the Brigham Young University Highway Materials Laboratory, where extensive sampling and testing was performed. Methods used to evaluate the condition of the bridge deck samples included visual inspection, hammer sounding, Schmidt rebound hammer testing, resistivity testing, half-cell potential testing, linear polarization testing, cover depth measurement, and chloride concentration measurement. The samples were removed from four concrete bridge decks along the Interstate 15 corridor in Provo, Utah. One bridge deck was constructed in 1937, two were constructed in 1964, and one was constructed in 1984. Each of the bridge decks was constructed using conventional cast-in-place methods. With the exception of the 1984 bridge deck, which had epoxy-coated rebar, all of the bridge decks were reinforced with black bar. A waterproofing membrane was installed on each of the bridge decks in 1984, meaning each waterproofing membrane had been in service for 26 or 27 years at the time of sampling. With the exception of one of the bridges, which was in good condition after 26 years of service, each of the bridge decks sampled had successfully served for at least 46 years. Aside from asphalt maintenance, no rehabilitation was needed on any of the bridge decks following installation of the waterproofing membranes. Without the application of the waterproofing membranes, the chloride concentrations in the bridge decks likely would have been much higher. Additional exposure to chloride ions from deicing salts would have quickly increased the chloride concentration in the concrete above critical levels, which would have led to significant corrosion and bridge deck deterioration, prematurely. While the application of membranes as a bridge deck maintenance procedure has mostly been replaced by the use of epoxy-based polymer overlays, many bridge decks protected with membrane systems are still in service today. The research findings suggest that application of waterproofing membranes and asphalt overlays in a timely manner, before the accumulation of excessive amounts of chlorides within a deck, can be an effective approach for concrete bridge deck preservation.

Research was performed to analyze the performance of the crack, seat, and overlay (CS&O) roadway rehabilitation technique in the Central Coast and Northern regions of California. This technique was evaluated through literature review to determine the state of practice and their conclusions. California highway sections rehabilitated using CS&O were selected for evaluation based on age and location. Pavement distresses and traffic data for these sections were collected and analyzed. Prior to beginning analysis this data was checked for errors, outliers, and omissions. The analysis consisted of checking the data for correlations among distresses and regions. The focus of this research is to develop performance prediction models for pavement distresses in CS&O sections. Using data collected from Caltrans’ Pavement Condition Reporting Software, performance models were developed based on dependent (distress) variables: alligator cracking, transverse cracking, longitudinal cracking, and International Roughness Index (IRI). And independent (explanatory) variables: age, traffic in the form of equivalent single axle load (ESAL), thickness of hot mix asphalt (HMA), thickness of Portland Cement Concrete (PCC), and cumulative traffic in the form of cumulative ESAL. Prediction models were then analyzed for preciseness and sensitivity to the variables included in each model.

The objectives of this research were to 1) compile a synthesis of information about polyester polymer concrete (PPC) from the literature; 2) conduct a scanning tour to observe PPC construction, inspect in-service PPC overlays, and discuss topics related to PPC; 3) revise the existing Utah Department of Transportation (UDOT) PPC specification; 4) document a PPC field demonstration project; and 5) perform laboratory characterization of the material properties of field-mixed PPC. The scope of the research included a scanning tour, field testing, and laboratory experimentation. The objectives of the scanning tour included observation of a PPC overlay placement, inspection of existing overlays, and discussion of selected topics related to PPC. The scanning tour comprised a 3-day visit to California. Items related to material properties, mixture and overlay design, laboratory testing, and construction and field testing were investigated. Several recommendations relevant to Utah bridge deck preservation practice were developed based on the findings and then incorporated into a revised UDOT PPC specification. The objective of the field testing was to evaluate specific aspects of construction, quality assurance, and performance of PPC overlays on concrete bridge decks. The scope of the project included testing of a PPC test section overlay and three PPC bridge deck overlays during and after construction. Hardness tests were performed on the test section placements, and hardness, skid resistance, impact-echo, impedance, and resin content determination tests were performed on each of the bridge deck overlays. The field testing yielded valuable information about PPC overlays. Recommendations regarding hardness testing, skid resistance testing, patching, and surface preparation were developed based on the findings. The objectives of the laboratory experimentation were to characterize several material properties of field-mixed PPC sampled from actual bridge deck overlay placements in Utah and compare them to properties of laboratory-mixed PPC reported in the literature. Laboratory testing was conducted on a typical PPC mixture. Properties that were measured include density, modulus of elasticity, coefficient of thermal expansion, hardness, unconfined compressive strength, splitting tensile strength, rapid chloride permeability, and resin content. Measured properties were consistent with typical ranges cited in the literature.

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