Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords:strain; MMLS3; temperature; frequency; accelerated pavement testing; hot mix asphalt. Includes bibliographical references (p.71-72).

The focus of the study was to evaluate the effect of placing hydrated lime on the surface of asphalt concrete pavement. The study assesses the influence of hydrated lime on both the peak surface temperature as well as the temperature profile of the pavement with depth. The amount of lime that would yield the optimal temperature reductions without placing excess ineffective material was selected. To address the aforementioned goal, eight Superpave mix samples were prepared in the lab and compacted at the design compaction temperature to achieve a relatively consistent percent of air voids. All samples were compacted using a vibratory compactor to simulate real field construction procedures and conditions. To examine the effect of hydrated lime, surface temperatures as well as with-depth temperature measurements were made with an infrared camera, and thermocouples buried into the pavement, respectively. The same tests were performed at a field site with a newly laid down pavement. To minimize variables, the field Hot Mix Asphalt (HMA) pavement was of the same design as that used to prepare the lab samples. The effect of temperature on the mechanical properties of HMA mixtures used in Ontario; namely Superpave SP12.5FC2 PG64-28, SP12.5FC2 PG70-28, SP19.0, and Stone Mastic Asphalt (SMA), was assessed. The mechanical properties studied include rutting susceptibility, fatigue resistance, and resilient modulus. Thirty two samples were prepared in the laboratory and compacted at the design compaction temperature and percent air voids. For each mix, two samples were used to test rutting susceptibility, three samples were used to test fatigue resistance, and three samples were used to test the resilient modulus of the mixes. With regards to rutting, the samples were tested in the Asphalt Pavement Analyzer (APA) at four different temperatures in order to give a complete rutting versus temperature profile. Three samples of each mix were tested to measure the resilient modulus at different temperatures using the Nottingham Asphalt Tester (NAT). Lastly, the fatigue resistance for each mix was assessed in the NAT with each of the three samples tested at a different strain to provide a complete picture of the mix behaviour when subjected to fatigue. The stiffness characteristics of the newly laid down in-situ pavement was determined using the Light Weight Deflectometer (LWD). Results indicate that placing 100g/m^2 of hydrated lime on the surface of the hot mix asphalt pavement was the optimum surface treatment while avoiding the placement of excess ineffective material. This level of surface treatment led to temperature reductions that significantly improved the mechanical properties of asphalt concrete. Using the increased resilient modulus, consistent with the temperature reductions, it was shown, by carrying out an analysis using KENLAYER, that the design life of a pavement could be increased from approximately 25 to 33 years, from 20 to 30 years and from 12 to 20 years corresponding to cool, intermediate and hot weather conditions, respectively. / Thesis / Master of Applied Science (MASc)

Resilient moduli of different surface mixes placed at the Virginia Smart Road were determined. Testing was performed on Field cores (F/F) and laboratory-compacted plant mixed (F/L), laboratory mixed and compacted per field design (L/L), and laboratory designed, mixed, and compacted (D/L) specimens. The applied load was chosen to induce a strain ranging between 150 and 500 microstrains. Two sizes of laboratory compacted specimens (100-mm in diameter and 62.5-mm-thick and 150-mm in diameter and 76.5-mm-thick) were tested to investigate the effect of specimen size on the resilient modulus. At 5°C, the measured resilient moduli for both specimen sizes were similar. However, the specimen size has an effect on the measured resilient modulus at 25 and 40°C, with larger specimens having lower resilient modulus. At 5°C, HMA behaves as an elastic material; correcting for the specimen size using Roque and Buttlar's correction factors is applicable. However, at higher temperatures, HMA behavior becomes relatively more viscous. Hence, erroneous resilient modulus values could result when elastic analysis is used. In addition, due to difference in relative thickness between the 100- and 150-mm diameter specimens, the viscous flow at high temperature may be different. In general, both specimen sizes showed the same variation in measurements. Resilient modulus results obtained from F/L specimens were consistently higher than those obtained from F/F specimens. This could be due to the difference in the volumetric properties of both mixes; where F/F specimens had greater air voids content than F/L specimens. A compaction shift factor of 1.45 to 1.50 between the F/F and F/L specimens was introduced. The load was found to have no effect on resilient modulus under the conditions investigated. However, the resilient modulus was affected by the load pulse duration. The testing was performed at a 0.1s and 0.03s load pulses. The resilient modulus increased with the decrease of the load pulse duration at temperatures of 25°C and 40°C, while it increased at 5°C. This could be due to the difference in specimen conditioning performed at the two different load pulses. Finally, a model to predict HMA resilient modulus from HMA volumetric properties was developed. The model was tested for its fitting as well as predicting capabilities. The average variability between the measured and predicted resilient moduli was comparable to the average variability within the measured resilient moduli. / Master of Science

Creep compliance of Hot Mix Asphalt (HMA) is an important property to characterize the material's viscoelatic behavior. It is used to predict HMA thermal cracking at low temperature and permanent deformation at high temperatures. There are several experimental methods to measure the creep compliance. Two of these methods were used in this thesis; uniaxial compressive and indirect tension (IDT) creep compliance. The tests were conducted at five temperatures (-15, 5, 20, 30, and 40°C) with a static loading for 1000-sec to characterize two typical HMA mixes used in Virginia, a base and a surface mix. Creep compliance master curves (CCMC) were developed by shifting the curves to a reference temperature using time-temperature superposition. Three mathematical functions, Prony series, power and sigmoidal, were fitted to the experimental data using regression analysis. Uniaxial CCMC were also predicted based on dynamic modulus measurements using method for interconversion of vicoelastic properties recommended in the literature. Finally, the susceptibility of the mixes to thermal cracking was evaluated based on the creep compliance measurements at low temperature. The regression analysis showed that the three mathematical models considered are appropriate to model the CCMC over a wide ranger of reduced times. The sigmoidal model provided the best fit over the entire range of reduced times investigated. This model also produced the best results when used in the interconversion procedures. However, there were noticeable differences between the CCMC predicted using interconversion and the experimental measurements, probably due to nonlinearity in the material behavior. The m-values for the base mix were higher using the creep results measured with both configurations. / Master of Science

Asphalt’s fatigue and modulus characteristics play an important role in pavement design. Ultimately they govern the required thickness of asphalt to structurally support heavy vehicles. The thickness of the asphalt layer is a major contributor to the cost of construction. In New Zealand, the design of structural asphalt layers has been a problem for some time and gives rise to two areas of concern. First, the present fatigue failure criterion, the Shell fatigue transfer function, which has been adopted from overseas, not only underestimates the fatigue life of the country’s asphalts, but does not accurately characterise the fatigue behaviour of our local asphalt mixes. Consequently, asphalt thicknesses are overdesigned. Second, asphalt’s fatigue behaviour is influenced by numerous factors and therefore can be difficult to characterise. The primary objective of this thesis is to develop fatigue and modulus models, by carrying out fatigue and modulus tests, to characterise the behaviour of two typical New Zealand structural asphalts. Both resilient and stiffness moduli tests were performed at a range of temperatures and loading rates developing moduli master curves, which predict the asphalt’s modulus for any pavement temperature and vehicle speed. A general full factorial experiment was carried out utilising the four-point flexural beam fatigue test. Tests were carried out at different strain levels, temperatures, and loading rates. An analysis of variance showed that the impacts of strain amplitude, temperature, binder type, the interaction of strain amplitude and temperature, and the interaction of strain amplitude and binder type have a significant effect on fatigue behaviour. The developed models, which account for temperature effects give the pavement engineer the ability to undergo a more accurate assessment of fatigue damage than at present for different climatic temperatures demonstrated by using an incremental damage analysis approach. The research shows that with such characterisation for the given pavement’s design life, thinner and less expensive roads can be constructed in New Zealand.

No Estado do Pará, convencionalmente são empregados rocha britada ou seixo rolado natural como agregados nas misturas asfálticas. Nas proximidades da região metropolitana de Belém, não há disponibilidade destes materiais, obrigando o transporte destes agregados de boa qualidade de pedreiras e jazidas distantes mais de 170 Km, aumentando consideravelmente os custos de pavimentação. Com o objetivo de redução de custos, buscou-se o estudo de um outro agregado natural nãoconvencional, a laterita, abundante nas proximidades de Belém. Três tipos de ligantes asfálticos foram utilizados nas misturas asfálticas pesquisadas: um asfalto convencional CAP de penetração 50-60 proveniente da refinaria da LUBNOR, no Ceará; um asfalto da refinaria da REMAN da Amazônia modificado por asfaltita; e um asfalto-borracha da região sudeste. Uma quarta alternativa da mistura asfáltica foi considerada, empregando conjuntamente laterita e seixo rolado como agregados. Foi realizada uma análise comparativa das misturas asfálticas baseada em ensaios laboratoriais tais como: dosagem Marshall, danos por umidade induzida, deformação permanente em simulador de tráfego, resistência à tração por compressão diametral, módulo de resiliência e fadiga. Um processo inovador foi concebido para separação e lavagem das lateritas. Os resíduos desta seleção de agregados foram testados de modo a viabilizar seu emprego como material de base ou sub-base. Foi realizada também uma breve análise mecanicista de estruturas de pavimentos com o auxílio do programa ELSYM 5. Concluiu-se que as misturas asfálticas com laterita lavada podem ser usadas em revestimentos de pavimento de vias públicas e de rodovias de baixo volume tráfego obtendo-se os melhores resultados para as misturas de lateritaasfalto com o ligante modificado por asfaltita. / Crushed igenous rocks and washed quartzite gravels are conventional aggregates for asphalt mixes in the State of Pará, northern Brazil. However, these materials are not available in many parts of the state, specially near the city of Belem, the state capital. The current practice is to import these high quality aggregates from the few quarries located in remote sites, leading to a considerable increase in construction costs. To cut down costs, it is necessary to look for alternative sources of natural aggregates. This study attempts to present an alternative solution for asphalt mixtures using a non-conventional natural aggregate: laterites, which are widely available in the metropolitan area. Three types of asphalt binders were used: a conventional one – AC penetration of 50-60, an asphalt cement modified by gilsonite, and an asphalt rubber. A fourth type of asphalt mix was considered, using washed quartzite gravels in addition to the laterite. A comparative analysis was conducted using parameters obtained from laboratory tests like Marshall design, stripping test, wheel tracking test, indirect tensile strength, resilient modulus, and fatigue life. An innovative process was developed to clean the laterite by water washing. Residuals from the process were tested regarding its possible use as a material for pavement base or subbase. Finally, a mechanistic analysis was performed, using ELSYM 5 software. Results indicate a good performance to the hot-mixes and the one with gilsonite modified binder presented the best performance.

There are many factors which contribute to fatigue failure in HMA. While studies have been made with respect to binder aging, little has been done to investigate the effect of aging on the fatigue failure of asphalt mixtures. The lack of an effective and efficient method of testing field samples has contributed to this deficiency. This study focused on the development of a method for preparing and testing field samples in direct tension. This methodology was then be employed in combination with the VEC and RDT* tests to investigate several factors that affect fatigue in HMA. Particular emphasis was placed on the role of aging in the fatigue process. A method of testing field samples in direct tension was successfully developed. Results from the VEC and RDT* tests performed on several field samples collected from across the state of Texas were analyzed. US 277 field sample results were compared to laboratory mixed and compacted (LMLC) sample results as well as results obtained from extracted binder testing. Findings show that oxidative aging has an impact on the stiffness and performance of HMA. Chip seal surface treatments can extend the life of the pavement, but their affects are found primarily at the surface. Two additional field sites were tested, analyzed, and compared to LMLC results. These comparisons verified the effects of aging and show that a relationship between LMLC samples and field samples can be developed. Modulus values for one month of artificial aging of LMLC samples is equivalent to 10.5 months of aging in the field. Finally, 21 Texas sites used for the study were analyzed and a multivariate linear regression was performed to determine the factors that play the most significant role in the aging process. A linear regression model was constructed to determine the number of loads to failure from fatigue cracking due, primarily, to aging.

Today, a large quantity of waste is generated from the replacement of residential and commercial roofs. Many of the roofs being upgraded with previously constructed from asphalt shingles. Recycled Asphalt Shingles (RAS) contain nearly 30% of asphalt cement by mass, which can be a useful additive to asphalt pavements. In addition, shingles can offer significant potential savings through recycling and recovery as a construction material in flexible pavement. Currently, one and a half million tons of roofing shingle waste is generated each year in Canada related to the replacement of residential and commercial roofs and 90% of this valuable material is sent to landfills. If engineered properly, the addition of RAS into Hot Mix Asphalt (HMA) can provide significant benefits. The University of Waterloo’s Centre for Pavement and Transportation Technology (CPATT) is committed to working with public and private sector partners to develop sustainable technologies for the pavement industry. Using RAS in HMA can lead to economical, environmental and social benefits. Examples of which are reduced waste going to landfills and a reduction in the quantity of virgin material required. This research has involved the Ontario Centres of Excellence (OCE) and Miller Paving Limited. It was conducted to evaluate the performance of HMA containing RAS in both field and laboratory tests. A varying percentage of RAS was added to six common Ontario surface and binder layer of asphalt mixes. The intent was to determine if RAS could be added to improve performance and provide longer term cost savings. Laboratory testing was performed to evaluate the mix behavior. The elastic properties, fatigue life and resistance to thermal cracking were all evaluated at the CPATT laboratory. The characteristics of the mixes were evaluated by carrying out Dynamic Modulus, Resilient Modulus, Flexural Fatigue and Thermal Stress Restrained Specimen Test (TSRST) tests following American Association of State Highway and Transportation Officials (AASHTO) and American Society for Testing and Materials (ASTM) standards. Field test sections were constructed from HMA containing RAS to monitor the pavement behavior under natural environmental and traffic loading conditions. Evaluation of the field sites was performed using a Portable Falling Weight Deflectometer (PFWD) and carrying out distress surveys following the Ministry of Transportation Ontario (MTO) guidelines. The results to date show the sections performing very well with minimal to no distress developing. The results of the laboratory testing and field performance evaluations have shown encouraging results for the future use of RAS in HMA. If RAS can properly be engineered into HMA it can be a useful additive in both the surface and binder layers of the flexible pavement structure. Ultimately, the use of RAS in HMA can provide both an environmentally friendly and cost effective solution to the Ontario paving industry.

Warm mix asphalt (WMA) technology has now been successfully used in Ontario for a few years. This shift in usage relates to extensions in construction season, reduced emissions, larger compaction windows, and potential fuel savings. This research between Miller Paving Ltd. and the Centre for Pavement and Transportation Technology attempts to better quantify the difference in hot mix asphalt (HMA) and WMA. The object of this study was three-fold. The first part of the research was to examine the strength characteristics of HMA and WMA as a function of storage time. The purpose of this evaluation was to quantify indirect tensile strength (ITS) and moisture susceptibility of HMA and WMA over time. The second objective involved evaluating the performance characteristics of HMA and WMA. Resilient modulus and dynamic modulus testing were completed on plant-produced HMA and WMA material, which was used to determine long-term performance properties of both mixes. The third and final objective of this study was an economic analysis performed to determine the difference in cost for construction and maintenance for the HMA and WMA pavements. This was completed to determine if the cost of the warm mix technology used in the production of the WMA was offset by fuel savings at the plant. The findings of the research included: • HMA and WMA had statistically equivalent air voids over a four-week storage period. • Dry and wet ITS results for the WMA increased over a four-week storage period while the HMA specimens did not show this same increase. • WMA material had slightly better workability than the HMA material although the values were statistically equivalent. • WMA mix had higher resilient modulus values than the HMA mix. • Dynamic modulus testing showed that at high temperatures, WMA showed to be slightly more susceptible to rutting than the HMA mix, and at lower temperatures, the HMA showed to be slightly more susceptible to fatigue cracking than the WMA mix. • The MEPDG showed that both the HMA and WMA pavements were deemed to be structurally adequate. • An economic analysis of the HMA and WMA pavements compared a life cycle cost analysis over a 20-year design life which included all costs associated with construction, maintenance, and rehabilitation of both the HMA and WMA and showed that the HMA was slightly more cost effective than the WMA. • A field trial was performed by Miller Paving Limited on Highway 62 in Madoc, Ontario showed that the WMA material was more effective at maintaining the temperature of the asphalt mixture during long hauling distances. • Overall the WMA exhibited the same performance properties as the HMA.

The underlying purpose of any pavement is to provide a safe, smooth and reliable surface for the intended users. In the case of hot mix asphalt (HMA) pavements, this includes producing a surface that is resistant to the principal HMA distress types: permanent deformation (or rutting) and fatigue damage (or cracking). To protect better against these distress types, there have recently been changes in HMA mixture design practice. These changes have had the positive effect of producing more damage resistant mixtures but have also had the effect of producing mixtures that require more compaction effort to obtain required densities. It is important to understand what properties of an HMA mixture contribute to their compactability. This study presents analysis of the correlation between HMA mixture properties and laboratory compaction parameters for the purpose of predicting compactability. Mixture property data were measured for a variety of mixtures; these mixtures were compacted in the laboratory and compaction parameters were collected. A statistical analysis was implemented to correlate the mixture data to the compaction data for the purpose of predicting compactability. The resulting model performs well at predicting compactability for mixtures that are similar to the ones used to make the model, and it reveals some mixture properties that influence compaction. The analysis showed that the binder content in an HMA mixture and the slope of the aggregate gradation curve are important in determining the compactability of a mixture.