Optimizing decarbonation and sustainability of concrete pavement: A case study

A number of spectral analysis of surface wave tests were performed on asphaltic and cement concrete pavements by dropping freely a 6.5 kg spherical mass, having a radius of 5.82 cm, from a height (h) of 0.5–1.5 m. The maximum wavelength (λmax), up to which the shear wave velocity profile can be detected with the usage of surface wave measurements, increases continuously with an increase in h. As compared to the asphaltic pavement, the values of λmax and λmin become greater for the chosen cement concrete pavement, where λmin refers to the minimum wavelength. With h = 0.5 m, a good assessment of the top layers of both the present chosen asphaltic and the cement concrete pavements, including soil subgrade, can be made. For a given h, as compared to the selected asphaltic pavement, the first receiver in case of the chosen cement concrete pavement needs to be placed at a greater distance from the source. Inverse analysis has also been performed to characterise the shear wave velocity profile of different layers of the pavements.

In the last 10 years it has been seen a significant increase the application of Portland Cement Concrete (PCC) pavements on the national highway network. The leading technology among cement concrete pavements are the dowelled and anchored ones. The distinctive feature of this solution is the division of the homogeneous pavement into a series of slabs by means of contraction and construction joints. Their purpose is to prevent the formation of random shrinkage cracks. The incorporation of dowels and anchors, on the other hand, improves the road load-bearing capacity determined by a measure of the cooperation of the slabs and also ensures that the slabs move freely due to thermal loading. The correct operation of dowels depends on their embedment, the material from which they are made, or geometric parameters such as length, diameter or cross-sectional shape. In this paper, a literature review is carried out to determine the influence of the dowel bar parameters on the behaviour of cement concrete pavements

ABSTRACTAs a result of repeated rehabilitation efforts over the past few decades, often asphalt pavements have become deep-strength pavements. Consequently, top-down cracking has become a primary distress type. In particular, the top-down cracking performance of warm mix asphalt (WMA) pavements, i.e. how does it compare with similar hot mix asphalt (HMA) pavements is largely unclear mainly due to the lack of field performance data. This paper presents an effort of monitoring the top-down cracking performance of 28 pavement projects including WMA pavements and their corresponding HMA control pavements with service lives ranging between 4 and 10 years. These pavements cover different climate zones, WMA technologies, service years, pavement structures and traffic volume levels. Two rounds of distress surveys were conducted at a two-year interval, and the material (asphalt binder and mixture) properties of the pavements were determined using field cores. The top-down cracking performance of the HMA and WMA pavements was compared based on the first and second round distress surveys. It was found that the HMA and WMA pavement in general exhibited comparable performance. The significant determinants (material properties) for top-down cracking were determined, which were vertical failure deformation of mixes measured at 20 °C from indirect tension test.

The construction of conventional hot mix asphalt (HMA) pavements results in a number of economic and environmental issues, such as the cost of new overlays and associated impacts on natural resources. Although the cold recycling with an emulsified asphalt-recycling agent holds certain benefits over the HMA, its implementation on different road types, ranging from farm-to-market roads to expressways, is yet contentious due to the need for sophisticated equipment and trained workforce. The present research developed a methodology to evaluate all the three dimensions of sustainability, including economic (construction cost), environmental (natural resource depletion), and social (need for advanced equipment and skilled labor) of various scenarios of RAP and conventional asphalt pavements. The present study evaluated an equivalent thickness of the Cold In-place Recycling (CIR) pavement, which behaves similar to HMA pavement under the influence of different traffic loads. Fifty CIR and HMA scenarios for different traffic volumes and pavement layers thicknesses were developed. Finally, the sustainability of all the scenarios was evaluated for traffic designation in Saudi Arabia using fuzzy-based multicriteria analysis. Ranking of scenarios found CIR as a more sustainable overlay option for the feeders, collectors, main urban streets, expressways, and heavily trafficked highways in industrial areas where ESALs (Equivalent Single Axle Loads) range between 2,000,000 and >31,000,000. Considering the limited availability of advanced equipment and skilled labor for CIR pavements, HMA was found be a more sustainable option for farm-to-market roads with the “very light” traffic class. The methodology will help the pavement managers in decision making regarding the selection of sustainable pavement technologies for different road types in Saudi Arabia and the rest of the world.

Objective:To assess the feasibility of integrating environmental sustainability into clinical guidelines for operating rooms (ORs) and provide evidence-based recommendations.Background:Surgical practices contribute significantly to health care’s environmental impact. Incorporating sustainability into evidence-based clinical guidelines can support environmentally responsible decision-making. However, guidance on integrating environmental considerations into clinical recommendations remains limited.Methods:A systematic review was conducted on the environmental impact of ORs, focusing on 5 key topics: (1) surgical techniques, (2) disposables versus reusables, (3) cover materials, (4) anaesthesia, and (5) OR ventilation. The search was conducted in December 2022 in PubMed (through NCBI), Embase (through OVID), Web of Science (through Webofscience), Cochrane (through Cochrane Library), and Emcare (through OVID). The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach was used to assess the quality of evidence and formulate recommendations.Results:A total of 42 studies were included, of which 28 employed life cycle assessment (LCA) methods. Grading of Recommendations, Assessment, Development, and Evaluation assessments indicated “very low” to “low” quality of evidence. Key contributors to the OR environmental impact included energy-intensive and resource-intensive surgical technologies, reliance on disposables, anaesthetic gas emissions, and energy consumption for OR ventilation.Conclusions:Despite “very low” to “low” levels of evidence, environmental outcomes consistently point in the same direction. Studies using LCA methods are instrumental in identifying environmental hotspots for targeted mitigation. Integrating LCA findings into clinical guidelines can support sustainability efforts in surgery, helping guideline panels develop evidence-based recommendations that promote environmentally responsible practices.

Purpose In the USA, several studies have been conducted to analyze the energy consumption and atmospheric emissions of Warm-mix Asphalt (WMA) pavements. However, the direct and indirect environmental, economic, and social impacts, termed as Triple-Bottom-Line (TBL), were not addressed sufficiently. Hence, the aim of this study is to develop TBLoriented sustainability assessment model to evaluate the environmental and socio-economic impacts of pavements constructed with different types of WMA mixtures and compare them to a conventional Hot-mix Asphalt (HMA). The types of WMA technologies investigated in this research include Asphamin® WMA, Evotherm™ WMA, and Sasobit® WMA. Methods Toachievethisgoal,supplyandusetablespublished by the U.S. Bureau of Economic Analysis were merged with 16 macro-level sustainability metrics. A hybrid TBL-LCA model was built to evaluate the life-cycle sustainability performance of using WMA technologies in construction of asphalt pavements. The impacts on the sustainability were calculated in terms of socio-economic (import, income, gross operating surplus, government tax, work-related injuries, and employment) and environmental (water withdrawal, energy use, carbon footprint, hazardous waste generation, toxic releases into air, and land use). A stochastic compromise programming model was then developed for finding the optimal allocation of different pavement types for the U.S. highways. Results and discussion WMAsdid not perform betterinterms of environmental impacts compared to HMA. Asphamin® WMA was found to have the highest environmental and socio-economic impacts compared to other pavement types. Material extractions and processing phase had the highest contribution to all environmental impact indicators that shows the importance of cleaner production strategies for pavement materials. Based on stochastic compromised programming results, in a balanced weighting situation, Sasobit® WMA had the highest percentage of allocation (61 %); while only socio-economic aspects matter, Asphamin® WMA had the largest share (57 %) among the asphalt pavements. The optimization results also supported the significance of an increased WMA use in the U.S. highways. Conclusions This research complemented previous LCA studies by evaluating pavements not only from environmental emissions and energy consumption standpoint, but also from socio-economicperspectives.Multi-objectiveoptimizationresults also provided important insights for decision makers whenfinding the optimum allocationof pavement alternatives based on different environmental and socio-economic priorities. Consequently, this study aimed to increase awareness of the inherent benefits of economic input–output analysis and multi-criteria decision making through application to emerging sustainable pavement practices.

PURPOSES: This research is to evaluate the mechanical performance of different types of Hot Mix Asphalt (HMA) pavement cells prepared for MN/Road field testing section through an extensive experimental analysis of air voids and simple statistical evaluation tools (i.e. hypothesis test). METHODS: An extensive experimental work was performed to measure air voids in 82 asphalt mixture cores (238 samples in total) obtained from nine different types of road cell located in MN/Road testing field. In order to numerically and quantitatively address the differences in air voids among the different test Cells built in MN/Road, a simple statistical test method (i.e. t-test) with 5% significance was used. RESULTS: Similar trends in air voids content were found among the mixtures including conventional HMA, Reclaimed Asphalt Pavement (RAP) and Warm Mix Asphalt (WMA) combined with taconite aggregate this provides support to the use of RAP and WMA technology in the constructions of asphalt pavement. However, in case of acid modified HMA mixtures, significant differences in air void content were observed between on the wheel path and between wheel path location, which implies negative performances in rutting and thermal cracking resistances. Conclusions : It can be concluded that use of RAP and WMA technology in the construction of conventional asphalt pavement and the use of PPA (Poly Phosphoric Acid) in combinations with SBS (Styrene Butadiene Styrene) in asphalt binder production provide satisfactory performance and, therefore, are highly recommended.

Quantifying the environmental burdens of the hot mix asphalt (HMA) pavements and the production of warm mix asphalt (WMA)

This article is dedicated to the development of a joint filler for cracks in asphalt concrete pavement, as well as for expansion joints in cement concrete pavement. The article presents the choice of unified units and units of the joint filler unit being developed for cracks in asphalt concrete pavement and for expansion joints in cement concrete pavement. Some methods for calculating the main parameters of the created joint filler are presented. In addition, a suitable prototype of a joint filler, cracks in the asphalt concrete pavement and expansion joints in the cement concrete pavement were selected from several types.

Surface rehabilitation of Portland cement concrete (PCC) pavements using single or double surface dressings with soft bitumen, conventional or modified emulsions

Interface bonding between hot-mix asphalt (HMA) overlays and portland cement concrete (PCC) pavements can be one of the most significant factors affecting overlay service life. In this study, a direct shear test device was built and used to investigate the characteristics of the HMA–PCC interface and to determine the interface shear strength. Several parameters affecting the interface performance were included in this study, such as HMA type, tack coat type, tack coat application rate, PCC surface texture, and temperature. The test results showed that the use of SS-1hP emulsion resulted in a greater interface bonding strength than the use of RC-70 cutback. Surface mix SM-9.5 was found to have a better interface strength than binder mix IM-19.0. Among the four residual application rates considered in this study, 0.05 gal/yd2 was found to be the optimum rate, independent of test parameters. The direction of tining in the PCC surface was found to have no effect on interface shear strength at 20°C. At the optimum tack coat application rate, the PCC smooth surface showed a higher interface shear strength than tined surfaces. When tests were performed at the intermediate temperature range, as the temperature increased, the interface bonding strength decreased.

The Strategic Highway Research Program (SHRP) identified rutting as a major cause of distress for Hot Mix Asphalt (HMA) pavements. The resulting Superior Performing Asphalt Pavements (Superpave(TM)) mix design system specifically addressed the aggregate and asphalt binder properties that contribute to permanent deformation. However, the Superpave(TM) system does not currently include a laboratory proof-test to quickly assess the rutting susceptibility of HMA. In the early 1980's, the Georgia Department of Transportation funded research to develop and refine a laboratory wheel-tracking device. Based on the results of this research, Pavement Technology, Inc. (PTI) developed the Asphalt Pavement Analyzer (APA). Various laboratory studies have been conducted since the development of the APA to assess the suitability of this device as a proof-test for HMA. In 1998, the Tennessee Department of Transportation (TDOT) initiated a study with the University of Tennessee to further evaluate the merits of the APA. In this study, over 30 mixes from various locations across the state of Tennessee were tested in the APA. The results of this study indicate that the APA is sensitive to critical material properties that have been documented to contribute to rutting of HMA on the roadway.

The electric power industry is one of the major industries in terms of carbon dioxide (CO2) emissions, and it is necessary to explore low-carbon green power generation models. In recent years, more research has focused on the difference in carbon emissions in fossil energy versus renewable energy but ignored the impact of energy on human well-being. The life cycle assessment (LCA) method is a better method for assessing the impact of the low-carbon model on human well-being. In this paper, the carbon footprints of coal power plants and photovoltaic power (PV) plants generating 1 Kilowatt hour (kWh) of electricity are compared to analyze the degree of carbon emissions at different stages of the two models, and the environmental impact potential of the two models is analyzed using the LCA method. The differences between the two models in terms of human well-being were analyzed through questionnaires and quantified using the hierarchical analysis method. The impact of the different models on human well-being was compared using LCA method. The results of the study were as follows: the total CO2 emissions from coal-fired power generation at the 1 kWh standard were 973.38 g, while the total CO2 emissions from PV power generation were 91.95 g, and the carbon emission intensity of coal-fired power plants was higher than that of PV power plants. The global warming potential and eutrophication potential of coal-fired power plants were higher than those of PV power plants, and the rest of the indicators were lower than those of PV power plants. The composite human well-being index of PV power plants was 0.613 higher than that of coal-fired power plants at 0.561. The per capita income–global warming potential of PV power plants was higher than that of coal-fired power plants, indicating that PV power plants were a low carbon-emission and high well-being model. In conclusion, the PV power plant model is a low-carbon and high human well-being industrial model that is worthy of application in the Qilian Mountains region. The low-carbon industrial model proposed in this study can have a positive effect on regional ecological environmental protection and human well-being enhancement.

An evaluation of the performance of hot mix asphalt containing calcium carbide residue as a filler

The article contains general characteristics of Lithuanian motor roads and possibilities of their development. 63.72% of Lithuanian motor roads of national importance (according to their length) have asphalt pavement. It is shown that modernization of national motor roads mainly includes paving of gravel roads. It is pointed out that the main indices characterizing the condition and service life of asphalt pavement and its construction are: hot mix asphalt (HMA) concrete resistance to binding tension, tensile elasticity modulus and fatigue resistance. The values of these indices highly depend on the componential composition and structure of HMA concrete as well as on the degree of its compaction. The suitability of HMA concrete for road pavement construction is well characterized by its physical mechanical indices according to Marshall: stability S, flow F, volume of air voids Va etc. These indices also are highly dependent on the composition and structure of HMA concrete. Investigations carried out in the Lithuanian motor roads and in laboratory helped to determine asphalt concrete dependencies between the componential composition of HMA concrete and values of its physical and mechanical properties according to Marshall. Conclusions and recommendations are included.