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The primary objective of this research project was to evaluate geotextiles placed under or within a hot mix asphalt (HMA) overlay to reduce the severity or delay the appearance of reflection cracks. Researchers evaluated six geosynthetics, representing fabrics, grids, and composites in the laboratory using the TTI Overlay Tester. The overlay tester accommodates a 3x6x20-in. HMA beam and evaluates the relative ability of different beams (with and without a geosynthetic) to resist thermal cracking. Geosynthetics consistently increased number of cycles to failure in laboratory tests. Researchers then used fracture mechanics to evaluate the laboratory results and develop a new evaluation methodology termed the "reinforcing factor."
This volume contains the proceedings of the 12th International Conference on Geosynthetics (12 ICG), held in Roma, Italy, 17-21 September 2023. About 750 Authors - Academics, Researchers, Students, Practitioners, Contractors and Manufacturers – contributed to the peer-reviewed papers of this volume, which includes the Giroud lecture, the Bathurst lecture, the Rowe lecture, four keynote lectures and 296 technical papers. The content of these proceedings illustrates the sustainable use of geosynthetics in a variety of innovative as well as consolidated applications. After the sustainability implications in the correct use of geosynthetics, the ability to overcome the natural events effects, often related to the climate change, and to adequately afford the human activities (as the increase of pollution) forced to refer to a new keyword: Resiliency. The 12 ICG intends to become the base for the next step, hence the conference theme is 'Geosynthetics, Leading the Way to a Resilient Planet'. The conference topics, through general and parallel sessions, invited presentations and keynote lectures, address the most recent developments in geosynthetic engineering, and stimulate fruitful technical and scientific interaction among academicians, professionals, manufacturers, students. The 12 ICG proceedings contain a wealth of information that could be useful for researchers, practitioners and all those working in the broad, innovative and dynamic field of geosynthetics.
In the recent past, new materials, laboratory and in-situ testing methods and construction techniques have been introduced. In addition, modern computational techniques such as the finite element method enable the utilization of sophisticated constitutive models for realistic model-based predictions of the response of pavements. The 7th RILEM International Conference on Cracking of Pavements provided an international forum for the exchange of ideas, information and knowledge amongst experts involved in computational analysis, material production, experimental characterization, design and construction of pavements. All submitted contributions were subjected to an exhaustive refereed peer review procedure by the Scientific Committee, the Editors and a large group of international experts in the topic. On the basis of their recommendations, 129 contributions which best suited the goals and the objectives of the Conference were chosen for presentation and inclusion in the Proceedings. The strong message that emanates from the accepted contributions is that, by accounting for the idiosyncrasies of the response of pavement engineering materials, modern sophisticated constitutive models in combination with new experimental material characterization and construction techniques provide a powerful arsenal for understanding and designing against the mechanisms and the processes causing cracking and pavement response deterioration. As such they enable the adoption of truly "mechanistic" design methodologies. The papers represent the following topics: Laboratory evaluation of asphalt concrete cracking potential; Pavement cracking detection; Field investigation of pavement cracking; Pavement cracking modeling response, crack analysis and damage prediction; Performance of concrete pavements and white toppings; Fatigue cracking and damage characterization of asphalt concrete; Evaluation of the effectiveness of asphalt concrete modification; Crack growth parameters and mechanisms; Evaluation, quantification and modeling of asphalt healing properties; Reinforcement and interlayer systems for crack mitigation; Thermal and low temperature cracking of pavements; and Cracking propensity of WMA and recycled asphalts.
Hot mix asphalt (HMA) is used as the primary overlying material of concrete pavements during rehabilitation because of its inexpensive nature when compared to most Portland cement concrete (PCC) rehabilitation/reconstruction alternatives. However, due to the majority of the PCC pavements being in average to poor condition, many HMA overlays are exposed to extreme movements (both vertical and horizontal). The combination of associated load and environmentally induced movements creates complex stresses and strains in the vicinity of expansion joints and cracks in the PCC, thus dramatically reducing the life of the HMA overlay, typically in the form of reflective cracking. Reflective cracking is a fatigue cracking distress, which is initiated at the bottom of the HMA overlay and propagates to the surface. When the crack reaches the HMA overlay surface, not only does it affect the ride quality and overall integrity of the pavement surface, but it also creates a path for which water can migrate down into and below the PCC layer. This can ultimately reduce the overall structural support of the composite (HMA and PCC) pavement and result in a complete pavement failure. Medium to high severity reflective cracking results in poor surface conditions that could lead to poor driving conditions and higher accident rates. Therefore, this research is timely in that it not only addresses the structural integrity of the pavement system, but also the safety of the driving public, which is one of the main objectives of the administration at state agencies. To better understand the mechanisms associated with the development of reflective cracking, an extensive literature review was conducted. Analysis of the literature review indicated significant gaps in the current state of the practice in using bituminous overlays on PCC pavements. To fill in these gaps, a survey was developed, distributed to the state transportation agencies of all fifty states, and compiled to better define the scope of the research. The survey clearly identified that a major gap in the current state of the practice is linking the field conditions (climate, deflections, traffic levels) to appropriate laboratory testing protocols. Therefore, field test sections were selected with appropriate field forensic testing and traffic collection. During construction of the bituminous overlays, loose mix was collected and brought back to the laboratory for material characterization testing that would simulate the loading conditions associated with the respective test section. The research conducted during the development of this thesis has led to a rational approach in the prediction of reflective cracking potential in HMA overlays placed on PCC pavements. This methodology utilizes field forensic information that would normally be collected during the evaluation of the PCC/composite pavement prior to rehabilitation and laboratory fatigue and stiffness characterization of the HMA mixture(s), to predict the potential for reflective cracking in the bituminous overlay mixture(s). The extensive laboratory testing and field calibration/verification information utilized in the research has also led to "decision tree" methodology that would allow state agencies to properly select asphalt mixtures for overlaying PCC pavements.
This volume contains contributions by eminent researchers in the field of geotechnical engineering. The chapters of this book are based on the keynote and theme lectures delivered at the Indian Geotechnical Conference 2018, and discuss the recent issues and challenges, while providing perspective on the possible solutions and future directions. A strong emphasis is placed on proving connections between academic research and field practice, with many examples and case studies. Topics covered in this volume include contemporary infrastructural challenges, underground space utilization, sustainable construction, dealing with problematic soils and situations and geo-environmental issues including landfills. This book will be of interest to researchers, practitioners and students alike.
This book presents the detailed results of five task groups of the RILEM technical committee TC 237-SIB on Testing and Characterization of Sustainable Innovative Bituminous Materials and Systems. It concentrates on specific new topics in asphalt binder and mixture testing, dealing with new developments in asphalt testing, in particular also in view of new innovative bituminous materials, such as hot and cold recycled mixtures, grid reinforced pavements and recycled Reclaimed Asphalt Pavements (RAP), where test methods developed for traditional asphalt concrete are not a priori applicable. The main objective is providing a basis for pre-standardization by comparing different test methods and showing ways for fundamental improvements. Thus, the book also points the way for a further advanced chemo-physical understanding of materials and their role in pavement systems relying on fundamental material properties and suitable models for describing and predicting the intrinsic mechanisms that determine the material behavior.
Reflective cracking due to shrinkage and brittleness in asphalt pavements can seriously degrade an asphalt overlay before it is near its design life. Geosynthetics have been used to impede the reflection of existing transverse cracking to the new overlay. The geosynthetics are intended to minimize the tension transferred to the overlay from the existing pavement. The Oregon Department of Transportation (ODOT) installed a test section consisting of 120 transverse cracks treated with five different geosynthetic types, 22 transverse cracks treated with crack filling only and a control section of 20 untreated transverse cracks. The test and control sections were constructed over an open-graded asphalt concrete pavement. The overlay was also an open-graded mix. The 140 transverse crack section is located on US Highway 97 between Milepoint 213.58 and Milepoint 217.64.