Search

A large number of harmful components are produced during asphalt pavement construction under high-temperature conditions, causing heavy environmental pollution. Adding emission reduction agents to asphalt as an effective emission reduction technology has been widely used in different nations. However, few studies have attempted to compare the used emission reduction agents and their performances, resulting in the difficulty of the selection of emission reduction agents to reduce volatile organic compounds effectively and purposely. The objective of this review paper is to systematically summarize and analyze the state-of-the-art studies on asphalt volatile organic compounds emission reduction. In this study, the components in asphalt volatile organic compounds were summarized and the restrictions on asphalt volatile organic compounds emission in different nations are reviewed and summarized firstly. Then, the commonly used emission reduction agents of asphalt volatile organic compounds were completely investigated and sorted. Afterward, the emission reduction effect and engineering performance were compared in detail. Finally, the emission reduction mechanisms of different emission reduction agents were illustrated. The main findings show that the asphalt volatile organic compounds contain nearly ten categories of main components. The emission reduction effect of inorganic porous materials is superior to others. The organic polymer materials and the appropriate amount of inorganic materials can improve asphalt's engineering performance. The emission reduction mechanisms of emission reduction agents were divided into crosslinking reaction, adsorption, and piezoelectric/thermoelectric effect according to the interaction between asphalt volatile organic compounds and emission reduction agents. [ABSTRACT FROM AUTHOR]

The manufacture of conventional hot mix asphalt (HMA) for paving has a substantial environmental footprint, and the production of clean asphalt mixture with good engineering performance is critically important. The introduction of cementitious filler is a promising approach to achieve outstanding mechanical properties for cold mix asphalt (CMA) as a clean paving material. This study aims to develop a novel CMA formulation through the combination of ordinary Portland cement (OPC) with two industrial by-products: fly ash (FA) and ground-granulated blast furnace slag (GGBS), which could make CMA even cleaner. To achieve this objective, the effects of ternary blended cementitious fillers on the early-age strength, engineering performance, and microstructural properties of CMA are characterized through comprehensive laboratory tests. The experimental results indicated that the indirect tensile strength of CMA-B containing 2% OPC, 1% FA, and 1% GGBS is approximately 20% higher than that of the mixture with 2% OPC (CMA-2% OPC). The residual Marshall stability ratio of CMA-B was increased to about 95% and its dynamic stability was approximately 10 times that of CMA-2% OPC. Employing blended cementitious fillers in CMA facilitates the formation of hydration products with excellent stiffness, reduces the air voids, and enhances interface bonding between aggregate and asphalt matrix, and thus suitable for applications in road pavements subjected to harsh service conditions in terms of moisture and temperature. • A novel CMA formulation incorporating ternary blended cementitious fillers was developed. • Optimized combination (2% OPC, 1% FA, and 1% GGBS) of CMA was identified. • Dynamic stability of the mixture with 2% OPC, 1% FA, and 1% GGBS was approximately 10 times that of CMA-2% OPC. • Combined OPC, FA, and GGBS reduced voids, improved the interface, and produced a dense microstructure. [ABSTRACT FROM AUTHOR]

As a response to the reduction of environmental pollution and energy consumption in the maintenance or building of a road pavement, this research aims to provide innovative asphalt mixture solutions when designing asphalt base layers containing solidified Jet Grouting Waste (JGW) particles. This involved adding (or not) solutions made up from Reclaimed Asphalt Pavement (RAP) obtained by milling old pavements. The first step focused on a JGW and RAP leaching test before going on to design two non-traditional mixtures: a) a hot asphalt mixture made by replacing 4% of the limestone filler by the total weight of the aggregates with JGW (HMAJ), mixing all of them at a high temperature (160 ÷ 180°C), and b) a cold asphalt mixture made by adding 3% JGW as a filler, 70% RAP (CMRAJ), and 27% limestone by the total weight of the aggregates at low temperatures (40 ÷ 50°C). These innovative mixtures were investigated from the point of view of engineering performance by ascertaining their physico-mechanical features and environmental impact through a Life Cycle Assessment (LCA) test. Further comparison with traditional ones was then carried out using a hot mix asphalt (HMA) and a cold mixture made up from RAP, substituting a portion of the limestone aggregates (CMRA). Such mixtures are subject to special tender specification requirements. Engineering performance assessment showed that, compared with HMA, when JGW is added to both hot and cold mixtures, the ITS is 11% higher for HMAJ and CMRAJ, and cumulative strain is reduced by 17% for HMAJ and 39% for CMRA, while the cold asphalt mixtures (CMRA and CMRAJ) showed greater stiffness levels (on average 50%) at all test temperatures (10, 25, and 40°C). LCA analysis provided significant results for the solutions being compared. Specifically, use of HMAJ as the base layer helped save 65 g/m3 of CO 2 compared with HMA, at the same time helping to reduce 29.7 kg of CO 2eq. /m3 global warming potential. On the other hand, the use of CMRA as the base layer, again compared with the HMA, helped save 45 g/m3 of phosphorous compound emissions in water. In terms of terrestrial ecotoxicity and human non-carcinogenic toxicity, the best performance was obtained using a CMRAJ mixture, whose indicators showed a 60% reduction compared with the HMA solution base layer. • Road asphalt mixtures using jet grouting waste and reclaimed asphalt pavement. • Waste chemical composition and leaching test analysis. • Designing base layers with hot and cold component-mixing procedures. • Assessing the life cycle of the designed road asphalt pavement stratigraphies. • Indirect tensile strength, water sensitivity, dynamic stiffness, and creep rate. [ABSTRACT FROM AUTHOR]

• Two types of new 3-ply composite cross-laminated timber panels were manufactured from bamboo mat-curtain panels and hem-fir lumber. • The engineering performance of bamboo-wood composite cross-laminated timber was investigated, and hem-fir glued-laminated timber and cross-laminated timber were used as controls. • A comparative study on the theoretical modulus of elasticity and experimental modulus of elasticity of bamboo-wood composite cross-laminated timber was presented. • The effect of layer thickness and layup on the modulus of elasticity of the 3-ply bamboo-wood composite cross-laminated timber was investigated. During the global industrialization process of manufacturing cross-laminated timber (CLT), attempts have been made to use local wood species. For areas rich in bamboo resources but relatively short in timber resources, the use of bamboo- and wood-based composites to manufacture composite CLT (CCLT) has great potential. In the present work, two new types of 3-ply CCLT panel structures constituting bamboo mat-curtain panel and hem-fir lumber were investigated. In the major and minor strength directions, flatwise bending and shear tests were conducted to investigate their failure modes, maximum bending moment, bending stiffness, modulus of elasticity (MOE), bending strength, interlaminar shear strength, and specific bending and shear performance. Moreover, 3-ply hem-fir glued-laminated timber and CLT were used as controls. The effective MOE of each panel structure was calculated according to shear analogy theory and modified gamma theory and then was compared to the measured MOE. Based on the shear analogy theory, the effect of the thickness of layers on the MOE of the panels was investigated. Results showed that unlike other types of CCLT, the new CCLT exhibited distinct plate-like orthogonal strength characteristics. Its theoretical MOE agreed well with the measured MOE as the accuracy changed with the panel structure. By changing the panel structure of the new CCLT, if the MOE of one strength direction was reduced, the MOE in the other strength direction could increase accordingly based on the layer characteristics. The results presented in this paper can provide a guidance for future design and optimization of bamboo-wood CCLT. [ABSTRACT FROM AUTHOR]

• Contribution and function of each unit were recognized along the "MBR+NF" process. • The "MBR+NF" process removed 83.2%-92.2% of DOM molecules in terms of richness. • Preferential removal of lignin/CRAM-likes with relatively high saturation. • Lignin/CRAM-likes, lipids and aliphatic/proteins played key roles in sCOD and DOC. • Bio-derived aliphatic/proteins were resistant and positively correlated with DON. Mature landfill leachate contains a substantial fraction of recalcitrant dissolved organic matters (DOM) that is a challenging for conventional wastewater treatment that is typically focused on the removal of biodegradable organic matter. "Biological treatment + membrane treatment" has been widely employed to treat complex leachate. However, the performance of each unit based on both conventional bulk indicators and molecular information has not been well understood. Therefore, the fate of DOM chemodiversity along the full-scale treatment process across ten sampling points over three different seasons were analyzed to determine the efficiency of every unit process with the assistance of ultra-performance liquid chromatography coupled with hybrid quadrupole Orbitrap mass spectrometry. Results showed that the process performance, visualized through the molecular signals, were relatively stable in the temporal dimension. The process removed 83.2%-92.2% of DOM molecules in terms of richness, where lignin/carboxyl-rich alicyclic compounds (CRAM)-likes with relatively high saturation was preferentially removed, while newly generated bio-derived N-containing compounds (N/C wa 0.15-0.17) became resistant. The relationship between conventional bulk physicochemical indicators and molecular indexes suggested that soluble chemical oxygen demand (sCOD) and dissolved organic carbon (DOC) were contributed by the refractory DOM with high weighted average double bond equivalents (DBE wa), which was distributed in the region of O/C 0.2-0.5 and H/C 1.2-1.8. This refractory DOM required ultrafiltration and nanofiltration for removal. DOM molecules were positively correlated with five-day biochemical oxygen demand (BOD 5) and revealed that approximately 96.9%-98.4% of the DOM could be removed or transformed in the primary anoxic zone. In addition, the bio-derived aliphatic/proteins, lipids and lignin/CRAM-likes (O/C > 0.2) with condensed aromatization were the sources of dissolved organic nitrogen (DON) and still remained in the final effluent. The present study suggests that the design and operation of the combination process with biological and membrane treatment could be specifically optimized based on the DOM molecular characteristics of the wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

• Porous asphalt concrete using limestone aggregate has been formulated with Marshall design method. • Engineering performance of PAC with limestone has been evaluated. • The impact of compaction numbers on voids volume, dynamic modulus and tensile strength of PAC is studied. • The master curves of dynamic modulus for PAC with limestone is analyzed. This study aims to explore the possibility of utilizing limestone in porous asphalt concrete (PAC), targeting to the lower layer of the double-layer porous asphalt pavement. Limestone aggregate, which features relatively lower strength and desirable adhesion with asphalt, is used to replace basalt aggregate in PAC due to the shortage and high price of basalt. Both PAC with limestone and PAC with basalt are formulated with Marshall design method. Engineering performance evaluation verified that in comparison with PAC using basalt, PAC using limestone has less optimum asphalt content, lower Marshall compaction numbers, inferior drainage capacity, superior low-temperature cracking resistance, comparable rutting resistance and moisture stability, while satisfy the specification requirements. Furthermore, Superpave compaction model is employed to simulate the site compaction process. The results demonstrated that Superpave compaction process is divided into initial and over densification stages, in which the voids reduction in PAC with limestone is accelerated compared to that in PAC with basalt. The dynamic modulus of PAC increases with loading frequency, decreases with test temperature, and remarkably increases with gyration numbers. The master curves of dynamic modulus for PAC are constructed, which are approximately consistent for both PACs at equivalent compaction numbers. The tensile strength of PAC is found to increase with gyration numbers and both PACs present comparable tensile strength at the given compaction numbers. It is recommended to compact PAC using limestone with 40 gyrations. Therefore, limestone PAC with appropriate design and compaction parameters is prospective as the lower layer of the double-layer porous asphalt pavement. [ABSTRACT FROM AUTHOR]

• Using recycled aggregates in emulsified asphalt mixtures is feasible. • Emulsified asphalt mixtures can have up to 100% recycled aggregate content. • A moisture susceptibility evaluation indicator is proposed for emulsified asphalt mixtures. The rapid increase of construction and demolition waste (CDW) brings huge pressure to environmental engineers. Meanwhile, pavement industry is suffering from the diminishing of available natural aggregate and the increasingly stringent environmental pressures. Application CDW into emulsified asphalt mixtures (EAM) as pavement materials could be a win-win solution for the above concerns. This study aims at evaluating the feasibility of replacing natural aggregate in EAM by recycled aggregates produced from CDW. To this end, the optimum moisture content and optimum emulsified asphalt content of EAM samples were determined. EAM samples containing different content of recycled aggregates were prepared in laboratory. The effect of cement and recycled aggregate content on the service performance, including moisture damage resistance performance, high- and low- temperature performance, of EAM samples were evaluated. Based on the experimental results, it was found that the recycled aggregate enhanced the high-temperature performance but deteriorated the low-temperature and moisture damage resistance performance of EAM. Adding cement improves the entire service performance of EAM. When combined with cement, CDW can be used as a substitute for natural aggregates of EAM. [ABSTRACT FROM AUTHOR]

• Cement can be replaced by sintered limestone ash (SLA) for soil stabilization. • Beneficial replacement ratio was ≤20 wt% of cementitious materials. • Beneficial ratio enhanced engineering performances of cemented soil. • SLA enhanced formation of calcium aluminate hydrate and AFm phases. • High CaCO 3 in SLA refined micro-porosity of cemented soil. The enormous cement demand for soil stabilization intensifies the carbon footprint on the environment, which can be relieved by replacing cement with supplementary cementitious materials (SCMs). However, such application of common SCMs is limited by the availability and the reactivity of the materials. To deal with this issue, sintered limestone ash (SLA), a novel waste from the steelmaking industry, was investigated for the feasibility of replacing cement for soil stabilization. The SLA was first characterized by means of a laser particle sizer, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), thermogravimetry (TG) and X-ray fluorescence (XRF), and was revealed to process a certain hydration reactivity. To prepare the stabilized soils, the mass fraction of cementitious materials (i.e., cement and SLA) was controlled to 10% of the total dry mass of the solids, and the SLA was then used to replace the cement in mass fractions of 0%, 5%, 10%, 15%, 20%, 50%, 80% and 100%. Subsequently, unconfined compression test revealed that the unconfined compressive strength (UCS) of the stabilized soils were benefitted from an SLA replacement ratio of ≤20%, while they decreased substantially thereafter. Following the UCS test, the compactability and hydraulic conductivity of representative soil samples were investigated, while XRD, SEM-EDS, TG and mercury intrusion porosimetry (MIP) were employed for the micro-scale characterization and mechanism analysis. With increasing SLA replacement ratios, the compactability and hydraulic conductivity value of the stabilized soils were improved. The beneficial effects were produced by the enhanced formation of calcium aluminate hydrate (CAH) and Al 2 O 3 –Fe 2 O 3 –mono (AFm) phases, as well as the filling effect of high content CaCO 3 of SLA, while the deteriorative effects were produced by the relatively low reactivity of SLA compared to that of cement. In addition, the SLA replacement promoted the formation of Fe-AFm, and the high CaCO 3 content hindered the carbonation process of AFm phases, enhancing their stability. [ABSTRACT FROM AUTHOR]

Crumb rubber modified asphalt mixture (CRMA) has gained rapid-growing interest as a sustainable paving material, because it allows value-added recycling of waste tire into durable and low-noise asphalt pavements. However, the poor workability of CRMA leads to higher construction temperature, which results in more energy consumption and hazardous emission. Surfactant, a typical warm mix asphalt additive, has been proven to be effective in alleviating the workability concern of CRMA without obviously deteriorating its mechanical properties. Nevertheless, performance of CRMA with surfactant may be influenced by the mixing sequence of different components (raw asphalt, crumb rubber, surfactant and aggregates), which unfortunately has not been well investigated yet. This study aims to address this issue by characterizing the engineering performance of warm CRMA prepared by six different mixing sequences. Properties including Marshall stability and flow value, workability, rheological property, rutting resistance, moisture sensitivity and fatigue resistance of prepared mixtures were measured and compared. Analytic hierarchy process (AHP) was employed to determine the optimal mixing sequence of warm CRMA considering the overall engineering performance. Test results showed that the effect of warm CRMA's mixing procedure on its engineering performance is noticeable. Earlier incorporation of surfactant additive had limited negative influence on mechanical properties of warm CRMA but allows for more energy saving during the production of rubberized asphalt binder. The AHP analysis results indicated that among the six mixing sequences, the optimal option is to make rubber absorb surfactant first, then incorporating the rubber-surfactant compound to raw asphalt and finally blending the modified binder to aggregates. Image 1076 • Mixing sequence of warm rubberized mixture had influence on its engineering performance. • Mixing procedure of warm mix crumb rubber modified asphalt can be optimized. • Early incorporation of surfactant additive has limited negative effect on service properties of rubberized asphalt mixture. [ABSTRACT FROM AUTHOR]

In this study, a high-gravity (HiGee) process incorporating CO 2 and NO x reduction from flue gas in a petrochemical plant coupled with petroleum coke fly ash (PCFA) treatment was established. The performance of HiGee was systematically evaluated from the engineering, environmental, economic, and energy aspects (a total of 15 key performance indicators) to establish the air pollution, energy efficiency, waste utilization nexus. The engineering performance was evaluated that lower energy consumption of 78 kWh/t-CO 2 can be achieved at a capture capacity of 600 kg CO 2 /t-PCFA. A net emission reduction of 327.3 kg-CO 2 /t-PCFA could be determined based on six environmental impact indicators. A cost-benefit analysis was conducted using operating cost, product sale, carbon credit, and savings in air pollution fees to present a better technological selection compared to existing carbon capture and storage plants. The waste heat recovery from the flue gas via the HiGee process could be measured via moisture condensation and attendant elimination of white smog emissions. Retrofitted heat recovery and energy intensity up to 131.8 kJ/t-PCFA and 0.21 kWh/t-PCFA were assessed. Finally, a comprehensive analysis of the HiGee process based on three daily load scenarios of CO 2 capture scale were conducted, suggesting an optimal operating condition of the HiGee for generating profitability. Image 1 • CO 2 daily capture of 600 kg and energy consumption of 80 kWh/t-CO 2 were evaluated. • Marginal cost of 31.4 USD/t-CO 2 and capture scale of 0.79 t-CO 2 /day were assessed. • Impacts of global warming potential, human health and ecosystem were quantified. • Comprehensive evaluation of HiG was identified using 15 KPI by 4E analysis. [ABSTRACT FROM AUTHOR]

• Commercial chemical agents enhanced early performance of slag cement binder. • Commercial water glass induced slag cement with reduced strengths. • Commercial sulfate remarkably improved setting times and strengths of slag cement. The current study aims at exploring existing problems of a supplementary cementitious material with slag cement mixture, and distinguishing benefits of using different commercial chemical agents to improve the performance of the binder. Experimental results showed that although slag replacement led to fresh pastes with improved workability and lowered hydration heat liberation, it generally caused impacts of delayed setting times and reduced early compressive strengths of the binder. The sulfate activator of N a 2 S O 4 was more suitable than the sodium silicate solution to enhance the performance of sulfate modified slag cement binder, e.g., to reduce its setting times and increase the early strengths. On the other hand, CaS O 4 · 2 H 2 O could be preferable to prolong heat liberation during hydration. At the very early age, the additions of CaS O 4 · 2 H 2 O and N a 2 S O 4 only changed hydration products of the sulfate modified pastes because of the precipitated secondary gypsum and hydrotalcite, respectively. [ABSTRACT FROM AUTHOR]

Engineering and design activities are crucial to construction projects which certainly require an effective tool to evaluate engineering performance among alternative projects. This paper presents a framework for engineering performance evaluation using Multiple Criteria Decision-Making (MCDM). It demonstrates the merits or drawbacks of the engineering performance measures among alternative projects. The appropriate actions are applied to manage and control a project. Fuzzy logic is applied to address the vagueness and imprecision of human subjectivity in the evaluating process. An illustrative application is provided through expert opinion to show the assessment of total and relative engineering performance. [ABSTRACT FROM AUTHOR]