No abstract

Fatigue is the main design criterion for cold recycled cement-treated mixtures (CRCTMs). However, the literature shows that the fatigue behavior of such mixtures is still not well known. For example, the effect of increasing reclaimed asphalt pavement (RAP) contents is yet a topic of discussion. This experimental and modeling study helps fill knowledge gaps on CRCTM fatigue behavior using long-term curing fatigue tests and three design methods currently being used in different countries. The objectives of this study were: (1) to characterize the mechanical and fatigue behavior of mixtures of RAP, aggregates and cement; (2) to evaluate the fatigue life of pavements with base and subbase layers of such mixtures using the novel Brazilian design method (MeDiNa); and (3) to compare the results with those obtained using the South African Pavement Engineering Manual (SAPEM) transfer functions and the American Association of State Highway and Transportation Officials AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software. The mixtures were tested in the laboratory using flexural static and cyclic tests, and the required parameters to use the methods were obtained. Experimental results and modeling demonstrated a superior fatigue behavior of recycled layers with higher RAP contents. On the other side, layers with lower RAP contents abruptly lost stiffness in short periods, making thicker structures necessary. Therefore, using high RAP contents is not only a sustainable practice, but also a technical benefit. The equivalent single axle loads obtained using the SAPEM were higher than those obtained using MeDiNa, while the PMED ones were higher than both previous methods. Despite the inherent differences, this suggests that MeDiNa is more conservative. It also highlights the importance of calibration based on long-term pavement performance data.

Road pavements are spread over large areas and convey various possibilities for energy sources such as high thermal gradients due to their materials and colors, wind corridors, large flat areas for solar harvesting, and heavy loading from traffic. The latest advances in road energy generation have been discretely implemented and have mainly focused on photovoltaic surface applications; other studies have explored the use of piezoelectric transducers with high stresses for better energy-production performance but limited life span. This study explores the stresses on pavement surfaces from traffic loading shockwaves that yield to the natural frequency vibration a piezoelectric harvester using a cantilever array. The passing vehicles triggered 16 piezoelectric sensors divided into four embedded steel profiles. The peak electrical power obtained in the experiment was 55.6 µW with a single transducer using a tip mass of 16 g. The proposed harvester demonstrated potential for applications in micro-generation of energy with limited infrastructure modification and high endurance under traffic loading over time. Its generation capacity is around 50 mWh a month with 16 piezoelectric cantilevers installed (for a commercial traffic volume of 1500 vehicles a day), enough to power a 200 m flashing LED raised marker strip to guide drivers for lane alignment during night shifts.

Há um limitado número de bases de dados climáticos históricos para estações brasileiras disponíveis para a modelagem do comportamento mecânico de pavimentos flexíveis; nenhum que contemple todos os parâmetros necessários para o uso com modelos de previsão de desempenho destes materiais. O objetivo deste trabalho foi o de compilar um banco de dados climáticos para uso com o método de dimensionamento da AASHTO – um dos mais completos pacotes de dimensionamento mecanísticos para pavimentos flexíveis da atualidade. O método necessita longas séries históricas com parâmetros específicos para a projeção do clima ao longo da vida de serviço dos pavimentos dimensionados. Para tanto, foi feita a criação de um arquivo HCD (hourly climatic data) para as cidades de Porto Alegre, Brasília, Fortaleza, Rio de Janeiro e São Paulo, possibilitando a utilização do software da AASHTO – Pavement ME Design. O arquivo HCD foi montado com dados disponibilizados pelo INMET. Após a compilação dos dados, foram determinados os parâmetros adicionais necessários (e.g. incidência de luz nos pavimentos). Os resultados das análises mostram que os resultados para Porto Alegre foram coerentes e com significativas diferenças para as estações norte-americanas que podem ser usadas na falta de dados locais (Miami e Savannah). Após as análises de consistência foi realizada uma análise de sensibilidade com variação de ±5% da temperatura média, para avaliação do desempenho dos pavimentos frente a variação de temperatura. Os resultados demonstraram que um aumento de 5% na temperatura média é capaz de aumentar em até 12% o afundamento de trilha de rodas nas cidades testadas.