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Field Performance of Asphalt Mixture Modified with Reactive Isocyanate Based Modifier
(Canadian Science Publishing, 2024-09-04) Tran, Nam; Moraes, Raquel; Taylor, Adam; Timm, David
The reactive isocyanate-based modifier chemically reacts with asphalt components, overcoming the issues of increased viscosity and phase separation encountered with conventional modified binders. It can be used to modify binders to meet the highest performance grades currently specified by state highway agencies. This project aimed to demonstrate the constructability of an asphalt mixture modified with the reactive isocyanate-based modifier in the field and compare its performance with that of a control mixture. The project involved milling an approximately 5.0-cm (2-in) thick surface layer of two 30.5-m (100-foot) sections with similar foundation support. One section was resurfaced with a reactive isocyanate-modified mixture and the other with a conventional SBS-modified mix. The mixtures have shown no significant difference in field performance and laboratory performance test results. This study has provided insights into the field applicability of reactive isocyanate-based modifiers in asphalt mixtures, facilitating the ongoing efforts to develop durable road surfaces.
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Diaphragm wall lateral movement in deep excavations in Bangkok clays: impacts and influencing factors
(Canadian Science Publishing, 2024-05-29) Boonyarak, Thayanan; Aung, A. Y.; Kamchoom, Viroon; Aye, Zaw Zaw
Deep excavation in Bangkok clay layers involving diaphragm walls can cause ground movement, potentially affecting nearby structures. Understanding the magnitude and profile of this movement is crucial for assessing its impact on adjacent buildings. This study examines factors influencing the lateral displacement of rigid diaphragm walls in Bangkok's deep excavations, including construction methods, excavation duration, depth ratios, soft clay depth, and system stiffness. The research data were collected from 230 dataset of lateral movement in diaphragm walls with a thickness ranging from 0.60m to 1.50m. These walls had toe depths between 14m and 65m, across various excavation depths (He) from 6m to 35m. Maximum lateral wall displacements ranged from 0.10%He to 0.27%He for the top-down method, and from 0.20%He to 0.50%He for the bottom-up method. If the system stiffness is sufficient, variations in wall thickness and construction method have minimal impact on wall deflection. However, with the bottom-up method and 1.0m thick walls, long excavation times can lead to displacements up to 0.60%He. This is mainly due to consolidation and creep in the clay beneath the area where the base slab construction is delayed.
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Seabird inputs drive changes in Cladocera assemblages in freshwater ponds
(Canadian Science Publishing, 2024-07-13) Kane, Zoe Adria; Duda, Matthew P.; Simmatis, Brigitte; Smol, John P
Seabirds are biovectors that transport large concentrations of nutrients from their marine feeding areas to terrestrial breeding grounds. Here, we used subfossil cladoceran assemblages to assess if, and how, changes in the world’s largest colony of Leach’s Storm Petrels affected the structure of Cladocera assemblages over the past ~1700 years. Using sediment cores from four ponds impacted by Leach’s Storm-Petrel colonies on Baccalieu Island (NL, Canada), we observed a consistent transition in cladoceran assemblages from benthic/littoral to pelagic taxa in association with high seabird presence. This shift aligns with previously published limnological changes that tracked the growth of the colony. Compared to trends in sedimentary chlorophyll-a, pelagic cladoceran taxa lagged behind algal shifts driven by seabird activity. The main drivers of cladoceran assemblage shifts were likely alterations to the physical habitat structure and food availability driven by seabird inputs. Furthermore, deposition of calcium from seabirds may have also contributed to changing the composition of cladoceran communities. Our study provides information on food web shifts associated with seabird-driven eutrophication, which can be compared to future paleoecological studies.
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Challenges and Strategies for Advancing Property Registration Efforts in Senegal
(2024-12) Nyirakamana, Colette; Barras, Camille; Marie-Reine, Mukazayire
Revenue generated from property taxes has the potential to strengthen local governments’ financial capacity. However, local government often struggle to fully realize this potential. This poor performance is largely due to the inability to regularly identify and register all properties, as is the case in Senegal. To address this challenge, the Senegalese government has supported three nationwide property identification and registration programs. This policy brief describes these programs and outlines their current achievements and challenges. It provides recommendations to inform Senegal’s tax administration strategies to improve the ongoing efforts and promote their sustainability. -- Les revenus générés par l’impôt foncier ont le potentiel d’améliorer la capacité financière des gouvernements locaux. Toutefois, ces derniers peinent à en exploiter pleinement le potentiel. Cette faible performance est en grande partie attribuée à leur incapacité à identifier et enregistrer régulièrement toutes les propriétés, comme c’est le cas au Sénégal. Afin de remédier à ce défi, le gouvernement sénégalais a appuyé trois programmes d’identification et d’enregistrement des propriétés à l’échelle nationale. Ce bulletin politique décrit ces programmes, présente leurs réalisations actuelles ainsi que les défis rencontrés. Il présente ensuite des recommandations pour guider les stratégies de l’administration fiscale du Sénégal, afin d’améliorer les efforts en cours et d’en assurer la pérennité.
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Inter-Institutional Collaboration in Property Tax Administration in Senegal: Challenges and Perspectives
(2024-12) Barras, Camille; Nyirakamana, Colette; Mukazayire, Marie-Reine
Effective property tax mobilization depends on a combination of many factors. One crucial but relatively understudied aspect of property tax performance is inter-institutional collaboration. In many francophone African countries like Senegal, property tax administration is primarily controlled by the central government, while the revenue generated accrue to local governments. Furthermore, close collaboration is required between government institutions, particularly those in charge of the cadastre, taxation, and collection. This policy brief presents the ways in which the different actors in charge of property taxation collaborate in Senegal and examines how these inter-institutional dynamics affect performance. It also proposes recommendations for improving collaboration structures and practices. --- Une mobilisation efficace de l’impôt foncier repose sur une combinaison de nombreux facteurs. Un aspect crucial, mais relativement peu étudié de la performance de l’impôt foncier, est la collaboration interinstitutionnelle. Dans de nombreux pays africains francophones comme le Sénégal, l’administration de l’impôt foncier est largement contrôlée par le gouvernement central, tandis que les recettes générées sont transférées aux gouvernements locaux. De plus, une collaboration étroite est nécessaire entre les institutions publiques, en particulier celles en charge du cadastre, de l’imposition et du recouvrement. Ce bulletin politique présente les modalités de collaboration entre les différents acteurs responsables de l’impôt foncier au Sénégal et examine comment ces dynamiques interinstitutionnelles influencent la performance. Il propose également des recommandations pour améliorer les structures et les pratiques de collaboration.