Jo Sias Daniel

Performance characteristics of plant produced high RAP mixtures

The main focus of this study was to obtain plant produced Reclaimed Asphalt Pavement (RAP) mixtures, to document the mixture production parameters and to evaluate the degree of blending between the virgin and RAP binders. The effect of mixture production parameters on the performance (in terms of stiffness, cracking, rutting, and moisture susceptibility) and workability of the mixtures was evaluated. Eighteen plant produced mixtures were obtained from three locations in the Northeast United States. RAP contents (zero to 40%) were varied and softer binders were used. The data and analysis illustrated that the degree of blending between RAP and virgin binders is a function of production parameters. The stiffness of the mixtures increased as the percentage of RAP increased, but not when the discharge temperatures of the mixtures were inconsistent. The cracking resistance was reduced as the percentage of RAP increased. The rutting and moisture damage resistance improved as the percentage of RAP in the mixtures increased. Finally, reheating the mixtures in the laboratory caused a significant increase in the stiffness of the mixtures.

Mechanistic and Volumetric Properties of Asphalt Mixtures with Recycled Asphalt Pavement

This research examines how the addition of recycled asphalt pavement (RAP) changes the volumetric and mechanistic properties of asphalt mixtures. A Superpave® 19-mm mixture containing 0% RAP was the control for evaluating properties of mixes containing 15%, 25%, and 40% RAP. Two types of RAP were evaluated: a processed RAP and an unprocessed RAP (grindings). Testing included dynamic modulus in tension and compression, creep compliance in compression, and creep flow in compression. Dynamic modulus and creep compliance master curves were constructed with the use of the time-temperature superposition principle to describe the behavior of each mix over a range of temperatures. The voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) of the RAP mixtures increased at the 25% and 40% levels, and there was also an influence of preheating time on the volumetric properties. The dynamic modulus of the processed RAP mixtures increased from the control to 15% RAP level, but the 25% and 40% RAP mixtures...

Validating the Fatigue Endurance Limit for Hot Mix Asphalt

This report presents the findings of research performed to investigate the existence of a fatigue endurance limit for hot mix asphalt (HMA) mixtures, the effect of HMA mixture characteristics on the endurance limit, and the potential for the limits incorporation in structural design methods for flexible pavements. The report describes the research performed and includes proposed standard practices using various experimental and analytical procedures for determining the endurance limit of HMA mixtures. Thus, the report will be of immediate interest to materials and structural design engineers in state highway agencies and engineers in the HMA construction industry.

EFFECTS OF AGING ON VISCOELASTIC PROPERTIES OF ASPHALT-AGGREGATE MIXTURES

The effects of aging on asphalt-aggregate mixtures is a topic that has been gaining attention in recent years. Of special interest is how the fatigue performance of asphalt concrete mixtures changes with time because of changing material properties. The fatigue performance of a mixture is related to its viscoelastic material properties. An investigation of the effects of aging on viscoelastic properties of an asphalt-aggregate mixture, such as creep compliance, relaxation modulus, dynamic modulus, and phase angle, is discussed in this paper. The framework for including the effect of aging in an existing uniaxial constitutive model is established, and the applicability of Schapery’s elastic-viscoelastic correspondence principle to aged mixtures is validated.

Can More Reclaimed Asphalt Pavement Be Added? Study of Extracted Binder Properties from Plant-Produced Mixtures with up to 25% Reclaimed Asphalt Pavement

Results of a study conducted by the New Hampshire Department of Transportation (NHDOT) in cooperation with three local paving contractors are presented. Plant-produced hot-mix asphalt (HMA) mixtures containing reclaimed asphalt pavement (RAP) percentages from 0% to 25% were obtained from seven different batch plants. Twenty-eight mixtures were sampled and sent to the binder testing laboratories at NHDOT and Pike Industries, Inc. The virgin binders were also sampled and sent for binder testing. Binders were extracted and recovered from all of the mixtures and were tested to determine the performance grade (PG) binder grade and critical cracking temperature. The effect of the RAP at various percentages on binder properties was evaluated. High-end PGs were found to remain the same or increase only one grade for the mixtures tested. Low-end PGs also remained the same or bumped only one grade, and the critical cracking temperatures changed by only a few degrees for the mixtures examined in this study. Results of this study led to a change in the implementation of the new NHDOT specification in regard to the use of recycled asphalt binder in HMA.

Method for Evaluating Implications of Climate Change for Design and Performance of Flexible Pavements

A method to assess the impacts of forecasted climate change on pavement deterioration is presented. Traditional methods of pavement design use historic climate data and assume that climate is stationary with time. Climate change challenges this assumption of stationarity (i.e., natural driving forces of engineering have a variability described by a time-invariant probability density function). Therefore, the use of historic climate data is insufficient for the prediction of climate conditions. The focus is on the preparation and the use of climate model data sets as inputs to the Mechanistic–Empirical Pavement Design Guide (MEPDG) model to simulate flexible pavement performance and deterioration over time. The method is illustrated with a case study that uses future climate model temperature data from three North American Regional Climate Change Assessment Program scenarios at four sites across New England. Pavement distress predicted with future temperature scenarios is compared with that from MEPDG temperature data. Application of the method demonstrates the importance of matching the overlapping periods before using climate forecast output in the MEPDG. Although the simulated impact of future temperature changes on pavement performance was negligible for alligator cracking at the four study sites, asphalt concrete rutting differences were great enough to warrant additional consideration and to suggest that climate change and variability in future climate scenarios could affect pavement design and evaluation. The proposed method can be used to evaluate the impact of other climate variables alone or in combination. The method also can readily use new climate model output and be adapted for new downscaling methods.

Evaluation of the effects of hot mix asphalt density on mixture fatigue performance, rutting performance and MEPDG distress predictions

The purpose of this study was to evaluate the effect of density on the fatigue cracking and rutting performance of hot mix asphalt mixtures. Two plant produced Superpave mixtures, 9.5 and 12.5 mm, were utilised to fabricate specimens to target density levels of 88, 91, 94 and 97% of the theoretical maximum specific gravity. The specimens were used to evaluate the mixture stiffness in the asphalt mixture performance test device, fatigue cracking characteristics utilising the beam fatigue test and the overlay test-based fatigue cracking analysis and rutting potential using the asphalt pavement analyser and the flow number test. Additionally, the mechanistic-empirical pavement design guide (MEPDG) distress prediction equations were used to predict the mixture performance as function of density. Overall, the testing analysis and MEPDG predictions indicated that higher density specimens yielded improved fatigue and rutting performance.

Evaluating Recycled Asphalt Pavement Mixtures with Mechanistic–Empirical Pavement Design Guide Level 3 Analysis

The main objective of this study is to assess the sensitivity of the predicted performance of recycled asphalt pavement (RAP) mixtures to the assumed binder grade. That is achieved with the Mechanistic-Empirical Pavement Design Guide (MEPDG) software to predict the performance of a specific flexible pavement structure with a RAP-modified hot-mix asphalt surface layer. Different design runs are conducted for which all the pavement properties and conditions are held constant except the properties of the surface layer. Specifically, a near-full factorial experiment is performed in which RAP content and effective binder PG grade are the main variables. Comparison of the predicted performance of the various runs reveals important findings on the extent and manner in which those two properties affect pavement distresses and performance. The influence of the assumed PG binder grade on the RAP mixtures, particularly the high-temperature grade, has a significant effect on the predicted amount of thermal cracking a...

A comprehensive evaluation of the fatigue behaviour of plant-produced RAP mixtures

In this study, the fatigue performance of 12 plant-produced mixtures from New Hampshire and Vermont that contain reclaimed asphalt pavement (RAP) contents of 0–40% by total weight of mixture was evaluated. The mixture tests included dynamic modulus, uniaxial fatigue, beam fatigue, and overlay tests. Also, the simplified viscoelastic continuum damage (S-VECD) model failure criterion, called the GR method, was applied and input to the linear viscoelastic pavement analysis for critical distresses (LVECD) programme to predict the fatigue behaviour of the tested mixtures on thin and thick asphalt pavement structures. In order to explain the observed fatigue behaviour, the performance grades (PGs) of the binders that were extracted and recovered from the mixtures were determined. In general, the addition of RAP resulted in an increase in the stiffness of the materials. The magnitude of the impact of higher RAP percentages varied with each set of mixtures. The S-VECD model and beam fatigue test data showed a loss of fatigue resistance for high-percentage RAP mixtures in most of the cases. The overlay tester results showed clear drops in performance at higher RAP contents. The impact of lowering the PG of the virgin binder to compensate for higher levels of RAP also was studied. Lowering the PG led to improvement in the fatigue properties and was found to be a convenient practice. The changes in the measured properties also appeared to be a function of mix design variables that included the stiffness of the RAP, asphalt content, and production parameters such as silo storage times. In some cases, the effects of these factors outweighed the impact of the RAP level or PG of the virgin binder in the mixtures.

Low-temperature properties of plant-produced RAP mixtures in the Northeast

The impact of reclaimed asphalt pavement (RAP) materials on pavement performance is an important topic of study in the industry due to environmental and cost benefits. The primary concern for increasing allowable RAP percentages in hot mix asphalt relates to the presence of aged materials, which may embrittle the mixture and decrease cracking resistance. Low-temperature cracking is a major distress in cold temperature climates, such as the Northeastern United States. Currently, there are several procedures to analyse low-temperature performance of asphalt binders and mixtures. However, these methods use different starting (initial) temperatures and cooling rates that may not represent actual field temperatures and cooling rates. This paper presents the results of a study on low-temperature performance of plant-produced RAP mixtures. Eighteen mixtures from three states were tested with varying RAP contents (0–40%) and different virgin binder grades. The objectives of the study were to: (1) evaluate the impact of cooling rate and starting temperature on the critical cracking temperature of RAP materials; (2) evaluate the impact of RAP content on the low-temperature properties of mixtures; (3) evaluate the benefit of using softer virgin binder grades to mitigate the impact of the aged RAP binder in the mixture; and (4) to compare the low-temperature cracking properties determined from different mixture and binder tests. Based on the results, warmer starting temperatures and faster cooling rates result in warmer critical cracking temperatures for all mixtures. Through use of the uniaxial thermal stress strain test, it was found that the addition of RAP alters fracture behaviour from ductile failure towards a brittle failure. Based on results from the indirect tensile test, tensile strength increases with RAP content. However, due to a faster-building thermal stress, warmer critical cracking temperatures result. It was also determined that degree of blending may impact the effectiveness of using softer binder grades at higher RAP percentages to improve low temperature cracking resistance. The data also show that analysis procedure and test protocols can have a profound effect on critical cracking temperature. The conclusions presented reinforce the need for more accurate representation of RAP materials, and careful selection of analysis parameters.