Natalia de Souza Correia

Geosynthetics are commonly used in pavement systems to mitigate reflective cracking; however, their potential contribution to improving the structural capacity of asphalt overlays has not been fully quantified. This study evaluates the structural benefits of geosynthetic paving interlayers using full-scale instrumented pavement models tested in an Accelerated Pavement Testing (APT) facility. Asphalt strain gauges were used to monitor tensile strains under repeated wheel loading. By quantifying stable response parameters such as tensile strain reduction, rutting rate reduction, and modulus Improvement Ratio (MIR), this work provides the experimental and analytical foundation required for the development of simplified design modification approaches. The geogrid-reinforced section exhibited reductions of approximately 38% in cumulative plastic displacement, 38% in rut depth, and over 50% in tensile strain at the bottom of the distressed asphalt layer compared with the unreinforced section. These reductions indicate an apparent increase in the modulus of the asphalt layer, quantified through a MIR of 2.85. The experimentally derived MIR, which is product specific, temperature and interface condition dependent, was incorporated into an empirical pavement design framework based on the AASHTO 1993 methodology, allowing the structural benefits to be translated into design parameters such as increased structural number (SN) or reduced asphalt thickness. A design example indicated that the reinforced system could result in a 32% reduction in asphalt thickness for a design traffic of 30 million standard axles. Findings highlight the potential of geosynthetic paving interlayers not only for reflective cracking mitigation but also as a structural reinforcement mechanism capable of improving pavement performance and enabling more efficient pavement designs.

This study aimed to assess the impact of different paving geosynthetics on crack propagation and the mitigation of reflective cracking in asphalt mixtures based on four-point bending tests combined with Digital Image Correlation (DIC). The study evaluated pre-notched beam configurations of double-layered asphalt slabs, both with and without paving geosynthetics. DIC analysis was used to measure strain patterns in the central area of the specimens during crack propagation. Results clearly showed that paving geosynthetics significantly delayed crack propagation, as reinforced beams endured more cycles than the control beam. Geosynthetic-reinforced asphalt samples achieved tensile strains reduction factors ranging from 0.07 to 0.36, indicating their superior effectiveness in mitigating strain concentrations and maintaining the neutral axis position for longer periods. Findings highlight the critical role of interface shear bond and reinforcement characteristics in prolonging pavement service life.

O uso crescente de intercamadas geossintéticas, como geogrelhas, geocompostos e mantas de pavimentação em obras de reabilitação asfáltica, implica um aumento dos projetos de fresagem de camadas asfálticas contendo esses materiais. A experiência com a fresagem de pavimentos convencionais é ampla, mas ainda é limitada quando se trata de camadas com intercamadas poliméricas ou de fibra de vidro. Este estudo buscou avaliar o desempenho mecânico de misturas asfálticas recicladas com Pavimento Asfáltico Reciclado contendo fragmentos de geossintéticos (G-RAP). Para isso, um trecho experimental foi construído no Aeroporto Internacional de Salvador (Brasil), incluindo cinco seções de teste reforçadas com geossintéticos que foram fresadas após a construção. Os resultados de campo indicaram que todas as intercamadas eram fresáveis, embora com eficiências de fresagem variáveis e subprodutos com diferentes características físicas. Observou-se uma redução média de 18% na eficiência de fresagem nas camadas reforçadas em comparação às não reforçadas. Os resultados indicam que não há diferenças significativas entre os fresados de G-RAP e o RAP de controle, além da presença de fragmentos de geossintéticos, destacando a viabilidade de reutilizar G-RAP em aplicações semelhantes ao RAP convencional. A análise das misturas asfálticas com 20% de G-RAP demonstrou que a presença de fragmentos geossintéticos manteve a distribuição granulométrica do RAP de controle e não comprometeu o módulo de resiliência. Além disso, o G-RAP mostrou-se benéfico para propriedades mecânicas como estabilidade Marshall, fluxo e resistência à tração indireta, validando sua viabilidade para uso em misturas recicladas de pavimentação.

The main objective of this study is to evaluate the influence of geosynthetic reinforcement on the fatigue performance of asphalt overlays using double-layered specimens extracted from experimental sections. Notched beam fatigue tests were conducted, together with Digital Image Correlation (DIC) technique to assess the initiation and propagation of cracks, along with strains mobilized at the geosynthetic interface. The geosynthetic-reinforced specimen demonstrated notable improvement compared to the unreinforced counterpart in reducing vertical deformations with an increase in fatigue life by a factor of 7. DIC analysis demonstrated that geosynthetic reinforcement absorbed the tensile stresses from the crack tip and reduced the tensile strains, contributing to minimize the propagation of reflective cracks into the asphalt overlay. Overall, research findings contribute to understanding the factors that enhance fatigue life through the incorporation of geosynthetic reinforcements in asphalt overlays.

The incorporation of geosynthetic reinforcements during the rehabilitation of flexible pavements has significantly increased due to the ability of geosynthetic reinforcements to minimize reflective cracks. However, the performance of the geosynthetic-reinforced asphalt depends on the interface bond strength between the geosynthetic and the adjacent asphalt layers. Tack coat is generally used to maintain adequate bonding between the geosynthetic-reinforced asphalt layers. This study focusses on evaluating the influence of interface bond strength on the fracture resistance of geosynthetic-reinforced asphalt utilizing a new testing approach. The fracture resistance of geosynthetic-reinforced asphalt specimens was evaluated via cross-shear testing device, while interface bond strength was evaluated using interface shear strength testing. A Performance Grade (PG) 64-22 binder was applied as a tack coat at the geosynthetic-asphalt interface at four different rates that are relative to the asphalt retention capacity of the geosynthetic reinforcement. A fiberglass geocomposite was used as geosynthetic reinforcement in this study. The results indicate a correlation between interface shear strength tests and cross-shear tests, suggesting that the optimum tack coat rate is 125% of the asphalt retention capacity of the geosynthetic reinforcement to improve the fracture resistance as well as the interface bond strength of geosynthetic-reinforced asphalt layers.

Due to the increasing use of geosynthetic pavement interlayers, such as geogrids, paving geocomposites, and paving mats in asphalt rehabilitation works, asphalt milling projects involving milling the geosynthetic layers will significantly increase in the upcoming years. Thus, it is essential to understand how the milling process of conventional asphalt layers differ from milling paving interlayers. An experimental field section was constructed at the Salvador International Airport (Brazil) with different geosynthetic sections. Results showed that all geosynthetic pavement interlayers were “millable”, but with certain differences in the milling efficiency, as well as in the physical characteristics of the RAPs.

Numerous studies have analysed the influence of subgrade on the hydration process of GCLs and have shown that initial soil moisture content, particle sizes and soil mineralogy significantly affect the GCL hydration process. However, recent works have revealed that GCLs structure and bentonite characteristics are also a major variable in this process, affecting the water retention curve (WRC), hydration levels and long-term performance of the GCLs. This study examines the impact of bentonite particle size on the hydration process of a GCL when in contact with lateritic subgrades. The hydration process of three different GCLs was analyzed under isothermal conditions in a closed system. The results indicated an influence of bentonite particle sizes on the GCL hydration processes. GCL with granular bentonite showed difficulty in hydration from lateritic subsoils compared to GCLs with powdered bentonites.

The factors influencing bonding between geosynthetics, and asphalt layers have been extensively investigated through monotonic interface shear tests. However, little is known about how the geosynthetic pavement interlayers behaves under cyclic shear loading. Dynamic shear testing is recognized as more appropriate to understand the performance of pavements under traffic loads. This paper presents the characterization of bond stiffness and shear fatigue life using dynamic interface shear tests on three different geosynthetic-reinforced asphalt interlayers, including a geogrid and two reinforcement geocomposites. Double-layered samples of 150 mm diameter were compacted in the laboratory using Marshall adapted method. The dynamic interlayer shear behavior was evaluated using cyclic Leutner device at a frequency of 5 Hz. The bitumen coating content and thickness of the fabric backing showed to most influence the shear fatigue life of geosynthetic interlayers. This research shows that distinct shear fatigue behaviors were obtained for the different types of geosynthetics.

This study investigates the swelling potential of blends of a Brazilian sodium-activated calcium bentonite with linear structure polymers and a cross-linked structure polymer in contact with aggressive mining solutions (sodium hydroxide, calcium chloride, simulated bauxite liquor, copper tailing and gold tailing leachates). Results showed that the polymer addition contributed to the swelling of the bentonite under aggressive solutions. The effectiveness of the polymers varied with the permeant liquid and concentration. Sodium Polyacrylate and Carboxymethyl Cellulose proved the most effectiveness in bentonite swelling capacity. Research presents valuable insights into the chemical compatibility of bentonitepolymer blends when exposed to aggressive liquids.