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Civil engineers' lack of humanities values might result in mismatches between the former and latter. One major hiccup and potential remedy to this situation lie in the civil engineering curriculum. This study aims to explore liberal arts in the civil engineering curriculum through a systematic literature review. This study is among the few recent undertakings that have relived the importance of liberal arts in the civil engineering curriculum to produce well-rounded civil engineers. Both technical and human skills are required to confront the dynamic and ever-changing society inherent in the growth of civil engineering students as future engineers. Keywords: civil engineering; curriculum; liberal arts; systematic literature review eISSN: 2398-4287 © 2022. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open access article under the CC BYNC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians/Africans/Arabians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. DOI: https://doi.org/10.21834/ebpj.v7i19.3261

The exploratory research assessed the Covid-19 impacts on Construction Industry 4.0 implementation during the first year of pandemic restrictions. The research used a case study approach with industry professionals as the unit of analysis geographically located in the southeast United States. Data was collected through a survey of industry professionals, capturing their views of individual and company competencies before and during the pandemic. The survey indicates the perceptions about the application of Industry 4.0 in construction have changed during Covid-19, from March of 2020 to March of 2021, and views on expected future utilization. The industry professionals were asked to describe their opinions of Industry 4.0 abilities and how they changed during the pandemic. That data was then assessed through qualitative and quantitative analysis and supported the research aim. BIM, Big Data, and Analytics were shown to be where most professionals felt company reliance increased during the pandemic. The analysis also indicates that most participants expect a future increase in their company’s support on Industry 4.0. The response to Covid-19 has changed the perceptions and implementation of these methods within construction.

Cooling a building can be approached with several different methods, but determining which method to pursue can be a matter of operator preference. This study examines four equipment systems of building cooling (Variable Refrigerant Flow, Rooftop Units, Hydronic Chiller, and Split Systems) and their capacities, abilities, and inabilities. These systems are then compared against one another for efficiency and operating cost in a one-year timeframe. Yearly operating cost, energy usage, and system operating time were analyzed from each unit’s performance and then compared against one another. The efficiencies, energy usage, and cost are compared to find the most efficient and cost-effective system for various owner needs and applications. Depending on the performance of the individual systems, it may be more suited to a specific application. Variable Refrigerant Flow was the most efficient due to its method of heat rejection and higher efficiency components. The chiller was also an efficient option, with the heat rejection through water being an efficient method. Rooftop units and split systems were less efficient but lowered initial capital cost. Overall, capital cost and operating expense priority determine the best method for an individual application.

This paper focuses on the life cycle assessment (LCA) of different types of biochar modified bioasphalt (BMBA) by considering greenhouse gas (GHG) emission and environmental pollution factors. Bioc...

The objective of this paper is to evaluate differences and similarities of construction programs across various countries in order to encourage international cooperation of construction training and study abroad programs. The information illustrated in this paper was collected through a survey that was administered to construction programs from 11 different countries. The survey was divided into the following four categories: Program Structure, Curriculum, Industry Involvement and General Program. The study identified challenges and opportunities for students in construction programs to study abroad, with specific reference to financial funding at institutions, funding support from industry, lack of understanding around international articulation platforms, wide variation across internship requirements, and the importance of industry recognized certifications. The study demonstrated that 64% of the surveyed programs receive industry support and that all the surveyed programs are engaged and familiar with articulation agreements. In addition, besides programs in Australia and Portugal, internships are a requirement in all other countries surveyed. Also, among all surveyed countries, only Malaysia and South Africa require students to obtain industry certificates during the course of the program.

Based on the novel coronavirus, COVID-19, businesses throughout the US were affected by closures, by status as essential or nonessential businesses, and by other new and unforeseen regulations which were implemented with little notice. In order to understand how these changes affected construction contractors, a short survey was created. The survey was initially distributed in May 2020, so responses are based on initial reactions to the pandemic. The survey questions included both yes/no and long-answer response types. Additionally, virtual focus group discussions occurred through a university industry advisory board and the local AGC chapter. The multiple data sources provided an opportunity of the triangulation of the data to produce a more robust view of the issue. From the survey long-answer questions and the focus group discussions, a thematic analysis was performed. Many themes were found in all three sources demonstrating the most common responses in regards to safety and operations.

The purpose of this research is to analyze the perception of sustainability-related issues among construction students. The perceived importance of sustainable construction is analyzed based on students’ source of knowledge, university education, and future aspirations toward sustainability goals. This study involved conducting surveys from construction management students to determine their perception of the following eight options: environmental sustainability, societal sustainability, economic sustainability, energy sustainability, water sustainability, material choice sustainability, zero-emission sustainability, and lean zero-waste sustainability. The survey aimed to explore construction students’ perception of sustainable design and construction, and what role education plays in this perception. To support these aims, survey evaluation includes both quantitative and qualitative data analysis. Students are best equipped to explain their understanding of the listed options, based on their individual experiences. The results show that most students think water sustainability, environmental sustainability, and energy sustainability are “extremely important”. In addition to providing insight into students’ perception of the relative importance of these sustainability approaches, analysis of the survey responses offers key findings on the source of students’ sustainability knowledge, the degree to which students have made decisions about their career paths, and the potential relationship between knowledge gained and students’ perception of the impact of sustainable design and construction options. Analysis of these perceptions is a crucial tool for educators in improving students’ understanding of sustainability goals.

Online education has seen rapid growth through teaching and learning in university degrees. Higher education faculty have identified challenges while transitioning from face-to-face to online because of time management issues and the different instruction modalities. This study analyzes how construction faculty feel about the delivery of online instruction. A survey was developed to determine construction faculty expertise in delivering online content and their level of expertise after the changes due to the pandemic. The survey was conducted during the pandemic (May/August 2020). We asked faculty to reflect on the pre-pandemic vs pandemic perception course delivery method. The relevant survey questions focused on teaching experience, different delivery types, online teaching experience, course management resources, and proficiency of online teaching. While most responding faculty indicated traditional lecture was typically used for content delivery, the remaining faculty indicated “project-based learning, experimental laboratory course, or computer lab studio," as the content delivery method. From the faculty responses, there are challenges in delivering online construction courses having components of project-based learning, experimental laboratory course, and computer lab studio. The survey responses identified specific concerns about online courses from construction faculty members. Online delivery is difficult for teaching hands-on or experimental lab types of construction courses. Some construction faculty also identified concerns about academic integrity in the online delivery of construction courses.

The swelling behavior of clay minerals is widely known for its importance in soil and environmental sciences and its detrimental effects in engineering fields. Although more than 70 percent of all clays are of mixed-layer types, the vast majority of the previous experiments and simulations are focused on pure clays, which cause the swelling mechanism of the widespread mixed-layer clay (MLC) and its role in soils are little understood, especially the most common illite-montmorillonite (I-M) mixed-layer clay (MLC). This paper reports on a molecular dynamics (MD) study of the differences in swelling behavior between I-M MLCs containing K+ and Na+ and Na-montmorillonite (MMT). It captures the evolution of quantitative properties such as basal spacing d, interaction energy, and many hydrogen bonds in the clay interlayer, increasing hydration for the first time through the scripts. It is found that MLCs have smaller swellings than Na-MMT due to the asymmetric interlayer charges and mixed counterions in the I-M interlayer. However, in terms of the interaction energy for the in-depth reason of swelling, it is found that the clay-clay interaction energy and the clay-ion interaction energy drop, while the clay-water interaction energy increases with increasing hydration. In addition, the attractive interaction of clay-bound water seriously promotes swelling, and it is mainly composed of Coulomb interaction and Van der Waals interaction. The higher the K+ concentration, the more noticeable these phenomena are. Besides, it is also reported that the number and distribution mechanism of hydrogen bonds in MLCs are very different from that of pure clay. This work provides insight into the molecular mechanism for initial swelling and clay-bound water interaction in widespread MLCs. This will help to decipher its specific role in soils and minimize clay swelling.

In order to understand the energy consumption and environmental pollution level of Shanxi highway construction, the life cycle environmental and energy impact assessment of asphalt mixture and cement concrete were conducted. One representative cement concrete pavement and two asphalt mixtures highways were selected for quantitative evaluation and LCA analysis. The total energy consumption values of Taichang highway are 20 % higher than that of the Dayun highway. The global warming potential indicators of Taichang (asphalt mixture), Dayun (asphalt mixture), and Deda (cement concrete) are 181 kg eq.CO2, 285 kg eq.CO2, and 330 kg eq.CO2, respectively during the materials production stage. The results indicated that the environmental effects of global warming had the biggest impact on the life cycle of the asphalt mixtures and the respective highways. Based on the study results, environmental pollution was highest on the Taichang highway whilst the Deda highway had the highest values of freshwater toxicity. Furthermore, energy consumption during the construction stage and environmental impacts at the end-of-life stage were found to be alarmingly high. Thus, reducing the energy consumption during the material preparation and highway construction stages as well as controlling the environmental pollutants and emissions during service are key to conserving energy, preserving the surrounding environment, and optimizing the life cycle of Shanxi highways.

In recent years, lignin has been receiving more coverage as an asphalt modifier because of its wide variety of sources, low price, renewability, and potential to improve the performance of asphalt pavement. This research aims to develop lignin-modified asphalt by adding soda lignin powder in different proportions to overcome some drawbacks of traditional modified asphalt. A series of tests, including empirical, viscosity, rutting, fatigue, cracking, storage stability, and chemical tests, were performed to determine the influence of soda lignin on asphalt binder. Test results revealed that the addition of lignin helps to reduce the temperature sensitivity of the asphalt by increasing its hardness and decreasing its ductility. At the same time, the incorporation of soda lignin powder also increased the viscosity of base asphalt with the increase in lignin content. Furthermore, rheological performance test results revealed that the addition of soda lignin significantly enhanced the rutting resistance and fatigue performance for all the dosages incorporated. And also, a slight reduction in low-temperature cracking performance was observed. In addition, the storage stability test result depicted that the dispersion of lignin powder in asphalt was comparatively uniform and stable, indicating excellent thermal storage stability for all the lignin amounts incorporated. Moreover, chemical test results suggest that the soda lignin and bitumen can be mixed physically without new chemicals.

Adoption of renewable energy sources such as biomass has been increasing worldwide. In this study, fast pyrolysis as an acceptable and viable method to get renewable bio-oil and biochar is used. Different temperatures and N2 flow velocities were used in the fast pyrolysis process to evaluate the pyrolysis yield of biochar and bio-oil. The waste wood and pig manure were utilized to prepare biochar and bio-oil. X-ray fluorescence, X-ray diffraction, high-pressure liquid chromatograph, Micro confocal laser Raman spectrometer, Fourier transform infrared spectrometer, and dynamic shear rheometer were used to measure the chemical compositions, structure, and pyrolysis yield of biochar and bio-oil. The obtained results indicate that pyrolysis temperature increases the purity of inorganic oxide in biochar and N2 flow velocity promotes the yield of carbon in biochar. The increase of N2 flow velocity would increase the acid property of bio-oil and damage the products yield of bio-oil. It was also observed that biochar could remarkably alter the fundamental performances of petroleum asphalt including penetration, softening point, ductility, viscosity, and complex modulus. The most important is that the upgraded bio-oil can be used to replace partly or fully the petroleum asphalt which is a promising biomass application.

Presence of moisture can weaken the asphalt-aggregate bond and result in aggregate stripping and moisture damage in asphalt mixture. This study investigates how the moisture affects the asphalt-aggregate bond and simulates moisture distribution of nano-scale in asphalt-aggregate interface. Effects of aggregate type (basalt, dolomite and limestone minerals), humidity and hydraulic pressure on moisture diffusion in asphalt-aggregate interface are studied. Diffusion coefficient (D), radial distribution function (RDF), contact angle (CA), free volume (FV) are calculated through molecular dynamic simulations. Polarizability of moisture in the asphalt-aggregate interface was measured using density function theory (DFT). Nano-scale moisture migration model in the asphalt-aggregate interface is built for the first time. The results show that D depends more on the hydraulic pressure than humidity and aggregate type which represents the significance of hydraulic pressure on the moisture diffusion. In addition, the aggregate type has significant effects on RDF, CA and FV. DFT results indicate that polarizability of moisture changes for different types of aggregate and hydraulic pressure values. In the asphalt-water-aggregate interface, the asphalt competitively interacts with moisture and ions from minerals through intermolecular forces.

The purpose of this study was to determine the relationship between the coefficient of permeability, porosity, and voids in total mixture (VTM) of fine-graded hot-mix asphalt (HMA). Two fin...

Volatile organic compounds (VOCs) emission not only cause the environmental pollution, but also severely threaten human health as they are known to be toxic and carcinogenic. This study investigates the effects of biochar on removing the VOCs emission from asphalt. The biochar was obtained from the pyrolyzed productions of pig manure, waste wood and straw biomasses. Molecular model for the adsorption of the VOCs was developed and used to measure the adsorption energy and heat. The VOCs removal model was built and used to determine the VOCs removal mechanism in the asphalt. The results showed that biochar could remove alkanes, polycyclic aromatic hydrocarbons (PAHs) and sulphide compounds because of its intrinsic carbon negativity and porosity. Furthermore, source of the biochar was an influential factor on the adsorption of the VOCs compounds. Based on the results, waste wood-based biochar had the best adsorption performance which could be related to the amorphous carbon, graphite and its porous structure. Also, it shows that biochar has the great potential to be used as VOCs inhibitors.

To understand the prospects of rubber-modified and polymer-modified asphaltic materials, pavement engineers must have a proper knowledge of the physical mechanisms of polymer materials in asphalt binder so that asphalt materials reflect the various rheological properties and pavement distresses along the wide range of testing conditions. Accordingly, the study reported here is aimed to present a mechanistic investigation on characteristics of rubber-modified and polymer-modified asphalt binders based on the evaluation of various rheological properties and primary modes of failure (i.e. low-temperature cracking, rutting and fatigue cracking in this study). In this experimental work, crumb rubber (hereinafter referred to as rubber), styrene–butadiene styrene (SBS), and ethylene–vinyl acetate (EVA), were introduced individually to the asphalt binder at different rates to prepare the blends. The physical and mechanical characteristics of the modified asphalt binders were discussed in the light of rotational viscosity (before and after aging), linear and nonlinear rheological measurements, rutting susceptibility, fatigue cracking, and relaxation modulus. Susceptibility to low-temperature cracking also was analyzed for all possible aging states. The results revealed that the viscosity of modified asphalt binders (using rubber, SBS, and EVA) is highly dependent on the aging state and the additive type and the content. The modified binders are able to allow good stress relaxation and better resistance to low-temperature cracking (even after short- and long-term aging), rutting, and fatigue cracking. Interestingly, the low-temperature cracking performance of the SBS-modified asphalt binder had improved much more after long-term aging compared to the unmodified binder and rubber/EVA modified binders. EVA-modified binder can sustain higher strains than rubber-modified binder (RMB), while comparing both small and large shear strain measurements. Storage and viscous moduli were determined to identify the rheological properties along the range of linear and nonlinear domains, and polymer-modified binders (PMBs) showed higher moduli in linear and nonlinear rheological conditions compared to the unmodified binder. Likely, higher cross-linking generated by polymer is the main contributory cause of such result. EVA polymer is a good choice to mitigate rutting, whereas SBS is more helpful to control fatigue cracking of the binders.

Although often overlooked, infrastructure has a significant role in modern society. It is necessary means of transportation for goods and services needed to support commerce. It is this need and the need for continued economic development that causes the continuous infrastructure construction and its’ associated greenhouse gas emissions. Infrastructure construction requires energy to process raw materials, transport, mix and final construction. Greenhouse gas emissions from pavement sections have previously been identified for pavement preservation techniques. This research further evaluates greenhouse gas emissions for typical pavement sections from Indiana and Oklahoma to determine the carbon footprint based on linear foot of pavement. The comparison of CO2e of two typical roadway sections finds the difference in carbon footprint since variation in their minimum roadway. The carbon footprint of typical utility pipe with HDPE produces minimum CO2e and steel produces maximum CO2e. Soil base remediation options produce minimum CO2e and stabilized aggregate base produces maximum CO2e. Carbon offsets are determined by choosing vegetative options, soil remediation methods and appropriate pavement. This study is limited to a few pavement sections with a small variety of typical anticipated carbon offsets that would be seen in roadway construction. The index presented allows users to simply quantify benefits of the carbon offsets.

Bio-asphalt replaced petroleum-asphalt for paving asphalt pavements, which is a technology with a wide range of application prospect. This work is aimed at improving the performance of aged bio-oil modified asphalt (bio-asphalt) for use in road pavement construction. Biochar and bio-oil are renewable resources and use in this research that are pyrolyzed from waste wood. The effects of different aging conditions on biochar-modified bio-asphalt and ordinary bio-asphalt were investigated in terms of their chemical functional groups, molecular formulas, radius distribution functions, rheological parameters, and phase separation. The aging conditions considered in this research are short-term aging, ultraviolet (UV) aging, pressure aging vessel (PAV), and low-temperature hardening. Biochar plays a significant role in the UV aging process. This study found that, with an increase in biochar modification, the alkyl group numbers increased and the sulfoxide and carbonyl numbers decreased during the aging process of bio-asphalt. It also shows that the inclusion of biochar improved the aging resistance of the bio-asphalt, but that biochar modification did not affect the bio-asphalt’s low-temperature hardening performance. Four asphalt components were studied: saturates, asphaltenes, resins, and aromatics (SARA). The effects of biochar on saturates and aromatics were significant, and the biochar was able to adsorb these components. This study also found that, with an increase in UV aging and PAV, the phase separation grows.

The paper at hand focuses on modeling the stress response of different mastics and asphalt binders exposed to small and large shear strains using Bergstrom-Boyce (BB) constitutive model as well as Finite Element (FE) approach. In this paper, a set of experiments based on Large Amplitude Oscillatory Shear (LAOS) test were designed and conducted to capture the state of strain dependence of bituminous mastics and binders over a broad spectrum of strain domain (0.5%, 10%, 20%, 30%, and 40%) pertaining linear and nonlinear regimes of such materials. Using the experimental data, the BB constitutive model was utilized to describe the attained behavior at two temperatures (30 °C and 40 °C) and varied strain amplitudes. The material properties derived from the BB model were further implemented into a Finite Element Model (FEM) using the ABAQUS platform to simulate the stress response of bituminous materials for a wide range of strain amplitudes. It has been shown that the bituminous mastics and binders have strong nonlinearity at high strain amplitudes, depicted graphically based on the progressive distortion from the elliptical form of Lissajous-Bowditch (LB) plot. Based on the observed goodness of fitting, the BB model well-described the experimental results for linear and nonlinear behaviors. Using the optimized parameters, it was confirmed that the BB model is well suited to build a numerical model that could reproduce stress responses derived from the LAOS results for a wide range of strain levels. The advantage of the methodology presented herein allows adaptable model constants of the BB model depending on the imposed level of strain and temperature and hence, the FEM can describe both linear and nonlinear behaviors of bituminous mastics and binders. From this paper, researchers can take advantage of capturing the stress response of binders and mastics under small and large strain amplitudes to stimulate the research on better representation of the complex behavior of asphalt mixes based on the role of mastic and asphalt binder.

Quantitative analysis was conducted in this study using a three-dimensional field microscope, scanning electron microscope, energy dispersive spectroscopy, and molecular simulation to investigate the surface and interface adhesive properties of three fine aggregate asphalt mixtures (FAM): basalt, steel slag, and andesite. The roughness of the aggregate and the contact angle of the asphalt on the aggregate surfaces also were analyzed quantitatively. Molecular dynamics simulations were carried out to evaluate the adhesive properties, molecular diffusion, and interfacial failure mechanisms of the basalt-, steel slag-, and andesite-based FAM. The average roughness values of the basalt, steel slag, and andesite were found to be 138.2 µm, 244.0 µm, and 185.2 µm, respectively. The stripping percentages of the basalt, steel slag, and andesite were 11.3%, 3.3%, and 10.8%, respectively. The diffusion coefficients of the resins (3.32 × 10−9 m2/s) and asphaltenes (3.05 × 10−9 m2/s) were higher than the diffusion coefficient of the oils (2.98 × 10−9 m2/s). The results indicate that the surface roughness and adhesive capacity of the aggregate used in this study can be ranked in decreasing order as steel slag, andesite, and basalt. The asphaltenes and resins contributed to the asphalt’s increased adhesion to the aggregate particles. Both adhesive and cohesive failure were found for the basalt-, steel slag-, and andesite-based FAM, but the steel slag FAM exhibited more cohesive failure, whereas the basalt and andesite FAM exhibited more adhesive failure.

The incomplete mixing of fuel and the drag induced in the engine are the main problems encountered in scramjets. Proper mixing of fuel can be achieved if the fuel is injected from the inlet of the engine. The fluid domain of Busemann Inlet at Mach 7 with boundary layer fuel injection using slot injectors along the wall was simulated with hydrogen fuel. Static pressure ratio at throat and inlet, along with Mach number at the throat were the design parameters of the Busemann inlet. Hydrogen fuel injection at two different equivalence ratios (0.3 and 0.7) was simulated successively at a temperature of 100 K and Mach 2.5. The state of mixing was studied for three different injection angles (30°, 45°, and 60°) for different equivalence ratios. The injection angles do not have a substantial effect on the hydrogen fuel mixing with the mainstream flow for equivalence ratio 0.3 Whereas, the dispersion of fuel increases as the increase in injection angles for equivalence ratio 0.7. But the total pressure recovery is maintained to the design value for equivalence ratio 0.3 rather than 0.7. Similarly, 45° fuel injection maintains a higher total pressure recovery than in other injection angles of 30° and 60°. Injection technique other than slot injection can be used to study further the effect of fuel mixing in Busemann Inlet.

Flow-induced crystallization (FIC) in polymers is an important problem that occurs on a very rapid time scale. This study aims to evaluate the flow-induced crystallization of bio-asphalt modified with different contents of biochar under various aging conditions. Small angle X-ray scattering and molecular dynamic simulations were performed to impose extensional deformation and the nucleation process. The rheological properties were measured using the dynamic shear rheometer (DSR) and the morphology of biochar modified bio-asphalt (BMBA) was measured using an optical microscope. The relative scattering intensity during crystallization appeared to peak at four strain rates: 13.2 s−1, 19.6 s−1, 25.4 s−1, and 27.3 s−1. The results showed that the addition of biochar could improve the flow-induced crystallization and enhance the high-temperature properties of bio-asphalt. Moreover, crystallization status of BMBA is lamellar crystals. Ultraviolet and pressure aging vessel aging could remarkably affect the crystallization status of BMBA and promote the formation of crystals.

Background: The ocular surface is separated by a thin layer of tear film from outdoor air pollutants making individuals exposed to outdoor air pollution prone to various ocular surface disorders. The aim of this study was to determine the magnitude of ocular surface disorders symptoms among traffic police officers of Kathmandu, Nepal. Methods: Two hundred traffic police officers working at different traffic police office branches of Kathmandu, Nepal were invited to the police headquarters for eye and vision examination. Among them, 91 individuals (95% males) completed the ocular surface disease index (OSDI) questionnaire and underwent Schirmer’s I tear test. Results: Symptoms of ocular surface disorders were reported by over 80% of the individuals. Approximately two-fifths of the individuals (38%) reported severe symptoms. Only 17% of the individuals’ tear secretion was found to be below normal using the Schirmer’s tear test. No significant association was observed between the OSDI score and Schirmer’s tear test scores (r = 0.008, p = 0.94). A weak but significant relationship was observed between the OSDI score and job duration (r=0.21,p = 0.04). Individual exposed to outdoor air pollution for more than 10 years had higher odds of reporting ocular surface complaints as compared to those who were exposed for less than 10 years (OR = 3.94, p = 0.02). Conclusion: Ocular surface disorder symptoms are common among traffic police officers of Kathmandu, Nepal. The duration of exposure appears to significantly contribute to the increased symptoms in this exposed population.

The purpose of this study was to analyze the cost effectiveness of building new-construction single-family homes through the Leadership in Energy and Environmental Design (LEED) program in six counties of Kentucky. The estimated added LEED construction cost was calculated as well as its respective payback period based on the expected utility savings of LEED certification. A mortgage cost comparison was also performed comparing traditional code built to non-LEED single-family homes. Using descriptive statistical analysis on the simple payback period, mortgage costs were compared internally and by county. This study found that The LEED Certified and Silver level had payback periods less than 30 years, and the total 30 year net difference between non-LEED and LEED certified ranged from $-1,193.20 to $1,667.64.

A three-dimensional finite element model (3D FEM) is built using ABAQUS to analyze the dynamic response of a concrete pavement structure with an asphalt isolating layer under moving loads. The 3D model is prepared and validated in the state of no asphalt isolating layer. Stress and deflection at the critical load position are calculated by changing thickness, modulus of isolating layer and the combination between the isolating layer and concrete slab. Analysis result shows that the stress and deflection of the concrete slab increase with the increase of thickness. The stress and deflection of the concrete slab decrease with the increase of combination between the isolating layer and concrete slab. The influence of changing the isolating layer modulus to the stress and deflection of the concrete slab is not significant. From the results, asphalt isolating layer design is suggested in concrete pavement.

Settlement and non-uniform deformation of frozen soil subgrade introduce fatal cracks on semi-rigid base asphalt pavements. This research aims to use reinforced wire mesh to reduce serious cracks on semi-rigid asphalt pavements in frozen regions. Three impact factors, diameter and interval as well as two types of wire mesh have been analysed by loading tests. Results have shown that after setting the reinforced wire mesh: (a) failure load and displacement of the cement-stabilised crushed gravel samples have been improved; (b) diameter and interval of the wire mesh have interactive impacts on reinforced sample load capacity; (c) the reinforced wire mesh can limit cracks by redistributing stress in the specimen; and (d) the multiple linear regression model well reflects the variation of loading properties; the results make sense from the statistics view as well. Results also represent that the strengthened wire mesh can help spread out the applied load, and increase the overall loading capacity of cement-st...

Engineering and technological applications of renewable energy installations, such as photovoltaic (solar) energy, are making important contributions toward the development of environmentally friendly products and processes for a more sustainable future. This article presents the design, assembly, and operation of a solar powered floating fountain system for analysis of aeration in stagnant water. The goal was to increase the level of dissolved oxygen in a body of water by harnessing solar energy for submerged aeration. The system is composed of six solar panels, a kit of batteries, a linear current booster, pressurized water tank, two pumps, an air compressor, and a float. The design factors for dissolved oxygen (DO) measurements were determined from depth of water, time of the day, location of fountain, and status of fountain (on or off). A Split Plot design was used to investigate the performance of the fountain, based on the changes in levels of DO in the pond. Statistical analysis showed a 120% gain in DO concentration during a 20-day period with significant destratification of the pond. This applied research will be of interest to engineers and technologists in various areas, including environmental development, green construction, and aquatic and energy conservation.

Warm mix asphalt (WMA) is good technique to reduce temperature of 20–30 °C. It has developed for more than a decade, but it is still challenging to determine the mixing and compaction temperatures of asphalt mixture. The objective of this study is to use a “equi-torque temperature” method that determin the mixing and compaction temperatures conveniently and accurately. The workability of WMA was measured by a prototype workability device. A criterion torque range was proposed by measuring the workability of mixtures with virgin bitumen. Three different warm-mix additives (including Aspha-Min®, Sasobit®, and Evotherm DAT®) were studied by identical SBS modified asphalt mixture to assess the reasonableness of the mixing and compaction temperatures determined according to the torque range. The results indicated that the criterion torque range was reasonable and the production temperatures of WMA mixtures determined in this study were approximately consistent with other references. The final performance tests also indicated that the “equi-torque temperature” methodology was feasible and effective.

A phase change material (PCM) has a significant capacity to store thermal energy. Because of the complex and tough environment of a highway such as traffic load, drainage, and ultraviolet light, the recent studies on PCM cannot be directly applied to highway construction. The composite shape-stabilized phase change material (CPCM) was prepared by using a membrane layer to encapsulate the PCM to ensure stability. Preparation of the CPCM in highway construction discussed in this research includes: (a) CPCM material properties, (b) proper proportioning for preparing the CPCM by Scanning Electronic Microscope (SEM), Differential Scanning Calorimetric (DSC) and the orthogonal test. CPCM was developed using Teradecane, silica, Ethyl Cellulose (EC) and a dispersant. Performance of the CPCM due to the influence of EC and a dispersant also studied to determine exact proportions used in the CPCM. The optimized ratio of Teradecane, silica, EC and dispersant is 1:1:0.1:0.1. Phase change enthalpy of the PCM was calculated to be 178 J/g and the phase change temperature was determined to be 5.8 °C.

In order to improve the dielectric and overall properties of cyanate ester (CE) resin, octa(aminopropyl)silsesquioxane (POSS-NH2) was used to modify CE. A series of POSS-NH2/CE hybrids containing different contents of polyhedral oligomeric silsesquioxane (POSS) were elaborated by melt casting and then curing. The curing kinetics and reaction mechanisms of the resin systems were studied using Fourier-transform infrared (FT-IR). Dielectric properties, thermal stability, and hot/wet resistance of the hybrids have been investigated. FT-IR results show that both temperature and POSS content may influence the curing reaction of CE. POSS-NH2 mainly displays the catalytic effect at higher temperature (220°C). Dielectric results indicate that NC1 containing 1 wt% of POSS displays not only the lowest dielectric constant but also the lowest dielectric loss. The increase in POSS content leads to significant increase in glass transition temperature ( Tg) at lower POSS content (≤5 wt%). However, further increase in POSS content (>5 wt%) does not lead to great increase in Tg. Besides, all the POSS-NH2/CE hybrids show lower water absorption than that of CE.

The objective of this study is to investigate the sensitivity of aggregate size within sand mastic by modeling the microstructure of an asphalt mixture. The sensitivity of the maximum aggregate size on the sand mastic phase is investigated through discrete-element simulations. A three-dimensional (3D) discrete-element model of asphalt mixture was prepared from X-ray computed tomography (X-ray CT) images. In the discrete-element model, an asphalt mixture is divided into aggregate, sand mastic, and air void phases. In this study, the sand mastic is defined as fines and fine aggregates mixed with asphalt binder. Three different nominal maximum aggregate sizes (NMASs) of sand mastic, namely, 1.18 mm, 0.6 mm, and 0.3 mm, were used in the 3D model to investigate the best gradation of sand mastic. The dynamic moduli of three different NMASs of sand mastic were measured for use in the 3D discrete-element modeling simulation. Laboratory-measured dynamic moduli of asphalt mixtures were compared with prediction results. The sand mastics with NMASs of 1.18 mm and 0.6 mm could be used to predict the asphalt mixture modulus across a range of temperatures and loading frequencies with good accuracy. The sand mastic with a NMAS of 0.3 mm overpredicted at high and low temperatures. The overprediction resulted from the difficulty of proper visualization of the smaller aggregate size in the model.

In this study, an idealised asphalt mixture was modelled with the discrete element method for both two-dimensional (2D) and three-dimensional (3D) cases. The air voids were randomly generated and counted within the models to reach a specific air void level (e.g. 6%). The 2D models were used to compute the strain and stress responses when the specimens were subjected to a compressive load. Then, the moduli of the specimens were computed from the stress–strain curves. The 3D idealised model was generated using a number of layered 2D models. The air void distribution patterns were also studied with 2D and 3D randomly generated models at specific air void levels. The results showed that the modulus deviation increases when the air void level increases. In addition, the modulus deviations of the 3D models were found to be much lower than those of the 2D models. When comparing the modulus predictions from the 2D models with those from the 3D models, the research proved that the 3D models yielded higher moduli t...