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.

Pavement surface characteristics are important to both the safety of the pavement surface and the comfort of the drivers. As of yet, texture and friction measurements have not been incorporated into the design of pavement surfaces. Seven different wearing surface mixtures, placed at the Virginia Smart Road pavement facility, were studied over a one year time period for both friction and texture properties. A locked wheel skid trailer and a laser profilometer were used to assess the pavement surface characteristics. Laboratory testing of the pavement wearing surface mixtures was performed to determine volumetric and mixture specific characteristics. Testing included gyratory compaction, specific gravity, maximum theoretical specific gravity, ignition testing, and gradation analysis. These material properties were used to study the impact of material properties on pavement surface characteristics. The pavement surface characteristics were analyzed using regression analysis with some measured and calculated parameters relevant to the pavement wearing surface properties. Analysis variables included the skid number at 64 kilometers per hour measured using the ASTM E501 (smooth) and ASTM E524 (ribbed) tires, the mean profile depth, the slope of a linear SN-speed model, the skid number at zero speed from the Pennsylvania State University (1) model, and the International Friction Index parameters. Analysis determined that testing particulars such as the grade of the test did not significantly affect the measured skid number. However, there is a significant difference between the skid numbers measured using the two tires. Additionally, the relationship between speed and skid resistance is assessed differently between the two test tires. Regression analysis concluded that there is a relationship between surface characteristics and HMA design properties such as the VMA, VTM, Percent Passing #200 sieve, and Binder Type. The influence of these variables on each of the analysis parameters varied. / Master of Science

No description available.

Segregation, or non-uniformity, in Hot Mix Asphalt (HMA) induces accelerated pavement distress(es) that can reduce a pavement's service life up to 50%. Quality Assurance procedures should detect and quantify the presence of this problem in newly constructed pavements. Current practices are usually based on visual inspections that identify non-uniform surface texture areas. An automatic process that reduces subjectivity would improve the quality-assurance procedures of HMA pavements. Virginia has undertaken a focused research effort to improve the uniformity of hot-mix asphalt (HMA) pavements. A method using a dynamic (laser-based) surface macrotexture instrument showed great promise, but it revealed that it may actually miss significant segregated areas because they only measure very thin longitudinal lines. The main objective of this research is to develop a non-contact system for the detection of segregated HMA areas and for the identification of the locations of these areas along a road for HMA quality assurance purposes. The developed system uses relatively low cost components and innovative image processing and analysis software. It computes the gray level co-occurrence matrix (GLCM) of images of newly constructed pavements to find various parameters that are commonly used in visual texture analysis. Using principal component analysis to integrate multivariable data into a single classifier, Hotelling's T2 statistic, the system then creates a list of the location of possible nonuniformities that require closer inspection. Field evaluations of the system at the Virginia Smart Road proved that it is capable of discriminating between different pavement surfaces. Verification of the system was conducted through a series of field tests to evaluate the uniformity of newly constructed pavements. A total of 18 continuous road segments of recently paved roads were tested and analyzed with the system. Tables and plots to be used by inspection personnel in the field were developed. The results of these field tests confirmed the capability of the system to detect potential nonuniformities of recently completed pavements. The system proved its potential as a useful tool in the final inspection process. / Ph. D.

The Superpave mix design system is being adopted by most of the states in the Unites States. Since the Superpave system was developed on the basis of data mostly obtained from medium to high traffic volume roads, there is a need to develop criteria for mix design for Hot Mix Asphalt (HMA) mixes for low traffic volume roads. In this study funded by the six New England states, research was carried out to develop a proper mix design system for low volume roads from the standpoint of durability properties and then, once a good mix design system was available, check it to determine if it meets required strength properties. For low volume roads the performance is primarily affected by the environment and not by traffic, the approach in this study has been to determine the optimum value of a key volumetric property and an optimum number of design gyrations for producing compacted HMA mixes with adequate resistance against aging/high stiffness related durability problems. Six mixes were obtained in which only one can be characterized as a fine mix, and the remaining five were all relatively close to the maximum density line - three of them were with 9.5 mm Nominal Maximum Aggregate Size (NMAS), and the other two were with 12.5 mm NMAS. Based on the results from performance testing, film thickness of 11 microns in samples compacted to 7 percent voids was found to be desirable from considerations of stability and durability and a design VMA of 16 percent was determined to be optimum for producing durable and stable mixes for low volume roads. Results from testing of in-place mixes from good performing 10 to 12 year old low volume roads indicated a design gyration of 50 for obtaining a void content of 4 percent for mixes with gradations close to the maximum density line.

" The determination of strain is an important step when using a mechanistic-empirical structural design, such as the AASHTO 2002 Design Guide. This thesis investigated the use of accelerated pavement testing system on Hot Mix Asphalt pavements to determine actual transverse and longitudinal strains under loads of varying frequency at different temperatures. A Model Mobile Load Simulator (MMLS3) was used in this study. Laboratory compacted pavement slabs were instrumented with thermocouples for monitoring the pavement's temperature, and with strain gauges in transverse and longitudinal directions at the bottom surface to measure strain. The slabs were subjected to loading by the MMLS3, running at different speeds. The pavement slab and accelerated loading equipment were enclosed in an environmental chamber to control temperatures during testing. Strains were also determined from layered elastic analysis after determining modulus values by two different methods - Resilient modulus testing and Witczak’s dynamic modulus equation. Comparisons of pavement strains calculated through the use of layered elastic design software and actual strains obtained during loading were made. The test results have shown a significant difference between strain values obtained using an instrumented pavement slab and those obtained with the use of standard resilient modulus values or dynamic modulus values determined by using a typical layered elastic design model. To avoid the discrepancies, two approaches are proposed - The first is modeling strain with accelerated pavement testing and the second one is using a correction factor. "

The research presented in this thesis: (1) quantifies and qualifies the Surface Free Energy (SFE) of neat and Liquid Anti-Strip (LAS) modified asphalt binders (binder); and (2) identifies volumetric mix properties that inhibit or assist in the susceptibility of Hot Mix Asphalt (HMA) to moisture damage based on time dependent phenomenological mechanical responses. These two research elements provide insight into the physical, chemical, mechanical and volumetric mix properties that inhibit or facilitate moisture damage in HMA. Moisture damage is a mechanism that causes distress and failure in asphalt concrete (AC) pavements due to a loss of durability resulting from the presence of moisture, in the form of a vapour or liquid, originating internally or externally. This reduces the pavements performance by promoting distresses such as: longitudinal cracking, spalling, rutting, shoving, stripping and ravelling. When moisture originates or is introduced in the AC a weakening of adhesion and cohesion of the material occurs, due in part to: binder properties, aggregate properties, volumetric mix properties, environmental conditions, traffic volume and loads, pavement design and construction practices. The research performed was split in two parts. The first part consisted of conducting SFE measurements on two PG 58-34 binders with different sources. One binder was modified with a LAS agent at concentrations of 0.5%, 2.0% and 5.0% by mass of binder and the other binder was kept neat. The neat and LAS modified binders were subjected to short-term aging by oxidation and then tested with a goniometer to determine their SFE and wettability. The SFE measurements revealed that an LAS concentration of 0.5% maximizes: (1) the work of adhesion of an unaged and aged binder, and (2) the ability of the binder to repel water. Furthermore, the process of aging increases the hydrophobicity or tendency of the binder to repel water regardless of the LAS concentration. Hence, an LAS concentration of 0.5% minimizes the potential for moisture damage in HMA. The second part of the research consisted of investigating the potential for moisture damage of seven bituminous type B (Bit B) and eight bituminous type C (Bit C) mix specified by Manitoba Infrastructure and Transportation. Laboratory testing of the resilient modulus and creep compliance was conducted to determine the fundamental mechanical response of the material. The resilient modulus and creep compliance test program were conducted on samples before and after moisture conditioning. As a result of the testing program, it was observed that the susceptibility of AC to moisture damage based on volumetric mix properties can be dependent on the air voids ratio, aggregate gradation and binder content of the mix.

The research presented in this thesis: (1) quantifies and qualifies the Surface Free Energy (SFE) of neat and Liquid Anti-Strip (LAS) modified asphalt binders (binder); and (2) identifies volumetric mix properties that inhibit or assist in the susceptibility of Hot Mix Asphalt (HMA) to moisture damage based on time dependent phenomenological mechanical responses. These two research elements provide insight into the physical, chemical, mechanical and volumetric mix properties that inhibit or facilitate moisture damage in HMA. Moisture damage is a mechanism that causes distress and failure in asphalt concrete (AC) pavements due to a loss of durability resulting from the presence of moisture, in the form of a vapour or liquid, originating internally or externally. This reduces the pavements performance by promoting distresses such as: longitudinal cracking, spalling, rutting, shoving, stripping and ravelling. When moisture originates or is introduced in the AC a weakening of adhesion and cohesion of the material occurs, due in part to: binder properties, aggregate properties, volumetric mix properties, environmental conditions, traffic volume and loads, pavement design and construction practices. The research performed was split in two parts. The first part consisted of conducting SFE measurements on two PG 58-34 binders with different sources. One binder was modified with a LAS agent at concentrations of 0.5%, 2.0% and 5.0% by mass of binder and the other binder was kept neat. The neat and LAS modified binders were subjected to short-term aging by oxidation and then tested with a goniometer to determine their SFE and wettability. The SFE measurements revealed that an LAS concentration of 0.5% maximizes: (1) the work of adhesion of an unaged and aged binder, and (2) the ability of the binder to repel water. Furthermore, the process of aging increases the hydrophobicity or tendency of the binder to repel water regardless of the LAS concentration. Hence, an LAS concentration of 0.5% minimizes the potential for moisture damage in HMA. The second part of the research consisted of investigating the potential for moisture damage of seven bituminous type B (Bit B) and eight bituminous type C (Bit C) mix specified by Manitoba Infrastructure and Transportation. Laboratory testing of the resilient modulus and creep compliance was conducted to determine the fundamental mechanical response of the material. The resilient modulus and creep compliance test program were conducted on samples before and after moisture conditioning. As a result of the testing program, it was observed that the susceptibility of AC to moisture damage based on volumetric mix properties can be dependent on the air voids ratio, aggregate gradation and binder content of the mix.

Este trabalho teve como objetivo avaliar o módulo de resiliência de misturas asfálticas densas sob duas condições. A primeira foi o estudo dos efeitos do enrijecimento de misturas asfálticas densas em condições ambientais diferentes (cinco condições) que são: AAAL (ao ar e à luz), AASL (ao ar e sem luz), AVAL (baixa pressão atmosférica e à luz), AVSL (baixa pressão atmosférica e sem luz) e CLIMA (ao clima e intempéries), tendo sido utilizados para este experimento CAP 20, centro da faixa C do DNER como distribuição granulométrica e preparados segundo a AASHTO PP2. Neste estudo concluiu-se que não houve efeito significativo da exposição da luz artificial nas condições AL e SL, assim como não houve, também, efeito significativo na variação do módulo de resiliência nas condições de exposição ou não ao ar (AV e AA); nas demais condições houve melhora significativa nos resultados. Na segunda parte foram avaliados os efeitos de alguns fatores na susceptibilidade térmica de misturas asfálticas densas: tipo de agregado (basalto, gabro e granito), tipo de asfalto (CAP 20 e CAP 40), teor de asfalto (5%, 5,5% e 6%), presença de aditivo (com e sem cal) e temperaturas de ensaio (10ºC, 25ºC e 40ºC). Todos os corpos-de-prova foram preparados segundo procedimento da AASHTO PP2. Na segunda parte do experimento, concluiu-se que o CAP 40 produziu valores médios de Vv superiores aos do CAP 20, as misturas com teor de 5,5% apresentaram maior resistência à tração a 25°C, o módulo de resiliência e a relação MR/RT diminuem com o aumento do teor de CAP. / This work intended to evaluate the resilient modulus of dense-graded hot-mix asphalt under two conditions. The first condition comprehends a study of the hardening effects of densegraded hot mix asphalt submitted to five environmental conditions: AAAL (air and artificial light), AASL (air and no artificial light), AVAL (low atmospheric pressure and artificial light), AVSL (low atmospheric pressure and no artificial light) and CLIMA (exposition to intemperism). In this phase, it was used an AC-20 asphalt binder and DNER middle band \"C\" as aggregate\'s particles size distribution. Specimens were prepared according to AASHTO PP2. Based on the results of the first part of the experiment, it was concluded that there was no significant effect of the artificial light exposition on AL and SL conditions, as well as on the variation of resilient modulus under air conditions (AV and AA). The other conditions presented better performance results. The second part of the experiment aimed to evaluating the effect of some factors in the thermal susceptibility of dense-graded HMA, that are: aggregate type (basalt, gabbro, granite), asphalt type (AC-20 and AC-40), binder content (5,0%, 5,5% and 6,0%), presence of additive (with or without lime) and test temperature (10ºC, 25ºC and 40ºC). As in the first part of the experiment, all specimens were prepared according to AASHTO PP2. Results of the second part of the experiment led to the following conclusions: mixtures using AC-40 showed average air voids higher than mixtures using AC-20, mixtures with a binder content of 5,5% showed the highest values of tensile strength, at 25°C, the resilient modulus and the MR/RT ratio reduce when binder content increases.

Este trabalho teve como objetivo avaliar o módulo de resiliência de misturas asfálticas densas sob duas condições. A primeira foi o estudo dos efeitos do enrijecimento de misturas asfálticas densas em condições ambientais diferentes (cinco condições) que são: AAAL (ao ar e à luz), AASL (ao ar e sem luz), AVAL (baixa pressão atmosférica e à luz), AVSL (baixa pressão atmosférica e sem luz) e CLIMA (ao clima e intempéries), tendo sido utilizados para este experimento CAP 20, centro da faixa C do DNER como distribuição granulométrica e preparados segundo a AASHTO PP2. Neste estudo concluiu-se que não houve efeito significativo da exposição da luz artificial nas condições AL e SL, assim como não houve, também, efeito significativo na variação do módulo de resiliência nas condições de exposição ou não ao ar (AV e AA); nas demais condições houve melhora significativa nos resultados. Na segunda parte foram avaliados os efeitos de alguns fatores na susceptibilidade térmica de misturas asfálticas densas: tipo de agregado (basalto, gabro e granito), tipo de asfalto (CAP 20 e CAP 40), teor de asfalto (5%, 5,5% e 6%), presença de aditivo (com e sem cal) e temperaturas de ensaio (10ºC, 25ºC e 40ºC). Todos os corpos-de-prova foram preparados segundo procedimento da AASHTO PP2. Na segunda parte do experimento, concluiu-se que o CAP 40 produziu valores médios de Vv superiores aos do CAP 20, as misturas com teor de 5,5% apresentaram maior resistência à tração a 25°C, o módulo de resiliência e a relação MR/RT diminuem com o aumento do teor de CAP. / This work intended to evaluate the resilient modulus of dense-graded hot-mix asphalt under two conditions. The first condition comprehends a study of the hardening effects of densegraded hot mix asphalt submitted to five environmental conditions: AAAL (air and artificial light), AASL (air and no artificial light), AVAL (low atmospheric pressure and artificial light), AVSL (low atmospheric pressure and no artificial light) and CLIMA (exposition to intemperism). In this phase, it was used an AC-20 asphalt binder and DNER middle band \"C\" as aggregate\'s particles size distribution. Specimens were prepared according to AASHTO PP2. Based on the results of the first part of the experiment, it was concluded that there was no significant effect of the artificial light exposition on AL and SL conditions, as well as on the variation of resilient modulus under air conditions (AV and AA). The other conditions presented better performance results. The second part of the experiment aimed to evaluating the effect of some factors in the thermal susceptibility of dense-graded HMA, that are: aggregate type (basalt, gabbro, granite), asphalt type (AC-20 and AC-40), binder content (5,0%, 5,5% and 6,0%), presence of additive (with or without lime) and test temperature (10ºC, 25ºC and 40ºC). As in the first part of the experiment, all specimens were prepared according to AASHTO PP2. Results of the second part of the experiment led to the following conclusions: mixtures using AC-40 showed average air voids higher than mixtures using AC-20, mixtures with a binder content of 5,5% showed the highest values of tensile strength, at 25°C, the resilient modulus and the MR/RT ratio reduce when binder content increases.