The next-generation of pavement maintenance and rehabilitation (M&R) decision-making needs to weigh multiple strategic goals to achieve sustainable development through the pavement maintenance ...management system (PMMS). Motivated by good versatility in solving highly complex conflict problems, the application of multi-objective optimization (MOO) for pavement M&R has recently become a hot-spot issue. This review aims to provide the state-of-the-art development and application of MOO methods for the PMMS decision-making module and the associated MOO model, decision-making tools, and optimization techniques. The strategic decision-making goals, decision processes, sources and characterization methods of uncertainty, intelligent algorithm followed across the globe were reviewed. Further, the latest development of multi-objective decision-aid tools (MODAT) for PMMS was discussed while emphasizing the importance of establishing joint MOO optimization model of multiple facilities and multiple M&R techniques for PMMS to achieve intelligent decision-making. The existing deficiencies and future direction of research have been discussed.
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•Reviewed multi-objective optimization studies on pavement maintenance management.•Classified MOO models in pavement maintenance management system.•Discussed utilization of various heuristic techniques for PMMS decision making.•Proposed the design concept of a new generation of MOO decision-aid tools for PMMS.•Recommended joint multi-objective optimizations for future studies.
At present, there are no specific indicators and requirements for the low-temperature crack resistance of emulsified asphalt cold recycled mixture (CRME) in the Chinese road mixture specifications. ...In order to expand the application of this technology in the asphalt surface layer in cold areas, this paper studied the influence of 10 influencing factors on the low-temperature anti-cracking performance of CRME through the semicircular bending test (SCB) with fracture energy as the evaluation index. The research results show that the fracture energy index of the SCB test can be used to evaluate the low temperature crack resistance of CRME. After 10 kinds of influencing factors were analyzed, it was found that the biggest factor affecting the low-temperature cracking resistance of the mixture was the recycling agent, which had an effect on the fracture energy index of over 60%. Followed by cement, fiber and compaction work, the degree of influence exceeded 30%. Finally, combined with engineering application experience, some specific measures to improve the low-temperature anti-cracking performance of CRME were proposed.
The inconsistences of the higher-order shear resultant expressed in terms of displacement(s) and the complete boundary value problems of structures modeled by the nonlocal strain gradient theory have ...not been well addressed. This paper develops a size-dependent Timoshenko beam model that considers both the nonlocal effect and strain gradient effect. The variationally consistent boundary conditions corresponding to the equations of motion of Timoshenko beams are reformulated with the aid of the weighted residual method. The complete boundary value problems of nonlocal strain gradient Timoshenko beams undergoing buckling are solved in closed forms. All the possible higher-order boundary conditions induced by the strain gradient are selectively suggested based on the fact that the buckling loads increase with the increasing aspect ratios of beams from the conventional mechanics point of view. Then, motivated by the expression for beams with simply-supported (SS) boundary conditions, some semiempirical formulae are obtained by curve fitting procedures.
Porous concrete (PC) is considered a promising paving material due to its eco-friendly and multi-functional characteristics. Compressive strength and coefficient of permeability are two key ...performance parameters of PC, but limited research has been conducted so far on their mutual relationship. In this paper, PC with three target porosities (15%, 20% and 25%) were prepared and 10 water–cement ratios between 0.2 and 0.4 were designed for each target porosity. After the samples were cured, the porosity and permeability coefficients were tested, followed by the compressive strength test. The porosity, permeability coefficient, and compressive strength characteristics of PC and their interrelationships were analyzed based on the test results. Moreover, a mathematical model is developed to characterize the relationship between compressive strength and permeability coefficient by analyzing empirical results and theoretical derivations. The results show that the effective porosity approaches the target porosity when the water–binder ratio (
w
/
b
) is in the range of 0.26–0.34. The strength and permeability of the PC can be both maintained at a high level when the effective porosity is in the range of 18–21%. Specifically, the PC may lose its water permeability by sealing the bottom with a
w
/
b
of 0.4 or more. Moreover, a new empirical model for the compressive strength and permeability coefficient of PC is established based on Griffith’s fracture theory. The model proposed presents a better agreement with the experimental data and could provide a better prediction of the compressive strength of PC by selecting the appropriate parameters. This research enriches the performance prediction model of PC and provides a basis and reference for PC material design and objective optimization.
Permeable pavement (PP) can be used to decrease urban surface runoff. However, few studies have been conducted to explore the runoff reduction effect of various structures of PP in the carriageway. ...In this study, several structures of PP used in the carriageway of sponge cities in China were investigated and divided into three types: surface drainage, base course storage and drainage, and fully permeable. Then, the runoff models were developed by Storm Water Management Model to simulate the effect of the three types under various rainfall recurrence periods. Results show that rainfall recurrence period, structure and thickness of the permeable layer were identified as the most influential factors in PP runoff reduction. The surface drainage can reduce total runoff depth and coefficient by more than 14%, and also delay runoff start time and duration by more than 40 minutes. Surface runoff in the base course storage and drainage can only be generated when recurrence period is 50 years. The fully permeable does not generate any runoff under all recurrence periods. Based on simulation results, a series of runoff coefficient values for PP were recommended to help the design and implementation of PP in mitigating urban waterlogging problems.
Permeable pavements (PPs) are used to address water quality impacts from urban roads. However, the effectiveness of different structure combinations in removing runoff pollutants throughout the ...permeable system remains unclear. In this study, 26 PP structures were tested to investigate their pollutant removal efficiency by the self-developed laboratory apparatus to provide a quantitative understanding of these combinations. The results showed PP was the most effective in removing total suspended solids (TSS) and lead (Pb) among all pollutants studied, with maximum removal rates of 91% and 96%, respectively. PP also can remove ammonia (NH
4
+
-N), nitrogen (TN), phosphorous (TP), and chemical oxygen demand (COD) to some extent; the removal rate was 1 ~ 36%. Furthermore, the pollutant removal efficiency was not dependent on a simple stacked combination of structures or materials. The combined surface structure of permeable asphalt mixture (PAM) and permeable cement concrete (PCC) was more effective in removing runoff pollutants than a single surface structure of the same thickness, and the optimal surface layer thickness (8 cm) and base course thickness (26 cm) of PCC were recommended respectively. Based on experiment findings, the relationships between TSS removal rates and the other six pollutants were established, and independent target pollutants removal rates (75%, 80%, 85%) based on TSS were selected for proposing a series of PP structures and thicknesses. The insights generated from this study will help in the design and implementation of PP for runoff pollution abatement.
Aiming at the maladies of high labor intensity, the low efficiency of ice and snow removal, and environmental pollution in traditional ice-deicing and snow-melting methods, we successfully developed ...a material that can effectively reduce the adhesive force between ice and snow with the pavement, aimed at the characteristics of the road ice de-icing and snow melting. According to the evaluation index and method of de-icing performance, we determined the ratio of the three components of the film-forming component, the adhesive component, the modified ice suppression component, and the preparation technology. It has no perfect evaluation index and method for the viscosity-reducing and ice-defending materials at present, this paper further evaluates the performance of the viscosity-reducing and ice-defending materials from the aspects of ice-deicing performance, durability, and environmental performance. The results show that the viscosity-reducing and ice-defending material has good permeability and water resistance. The material still has good ice-deicing performance after seven rounds of cycle tests at the same time, indicating that it has a good slow-release performance. It is verified that the viscosity-reducing and ice-defending materials have good durability using the low-temperature accelerated test. Finally, from the analysis and evaluation of the environmental protection performance of the viscosity-reducing and ice-defending materials, the materials have no effect on the growth of plants and their average corrosion rate is much lower than the average corrosion rate of the snow melting test piece, which means that the viscosity-reducing and ice-defending materials have good environmental performance.
As a common preventive maintenance technique for asphalt pavement, micro-surface (MS) has the advantages of waterproofing and crack sealing. However, issues such as the fact that the conventional MS ...generates large noise and the evaluation of the indexes of tire-road noise are relatively less studied. The traditional surface texture index cannot reveal the range and distribution of pavement surface texture, thus hindering research of low-noise MS. To study the mechanism of tire-road noise generated by MS, and propose the tire-road noise and surface texture indicators for MS. In this study, the mechanism of five low-noise MS was systematically analyzed and compared through surface texture and noise tests. Then, a three-dimensional digital texture model (3D-DTM) of MS surface texture was constructed using a series of digital image processing techniques, including grayscale identification, binary conversion, and noise reduction. The results show that optimizing the gradation, adding sound-absorbing materials, and improving the workability of construction can improve the noise reduction performance of MS, it is worth mentioning that the MS prepared with sound-absorbing materials and low-noise gradation has the greatest noise reduction effect, with a maximum reduction of 6.3 dB(A). In addition, it was also found that the 3D-DTM can well reflect the surface texture characteristics of MS. The probability of convex peak distribution (PCD) and the proportion of convex peak area (PCA) with peak heights greater than 0.25 mm (
K
h ≥ 0.25
), which are extracted from the 3D-DTM, can well reflect the surface texture, tire-road noise, respectively. The results show that the 3D-DTM is a promising tool to optimize the design of low-noise MS.
Pervious concrete (PC) has been widely used in recent years. With increasing attention on PC, it promotes further understanding of its mechanism responsible for the resulted performance. The ...objective of this study is to propose a 3D discrete element method (DEM) model to simulate the uniaxial compression process and analyze the meso mechanical properties of PC. The user-defined ellipsoid composed of pebble discrete elements was used to simulate aggregate. In the DEM, the mechanical behaviors of materials were simulated with contact constitutive models of discrete elements. The linear contact model and parallel-bond model were employed to simulate the strength properties between two adjacent aggregates, and between cement paste and aggregate. The parallel-bond parameters were calibrated based on the stress-strain curve obtained from the laboratory test. The reliability of the method was verified by comparing the virtual results with the laboratory tests of PC with 6 groups of different aggregate sizes. It was proved that the DEM model established can be used to simulate the rising section of the stress-strain curve of PC accurately. The maximum absolute error of uniaxial compressive strength is 0.67 MPa, and the relative error is within 5%. By analyzing the number of contact points, the contribution rate of different sizes of aggregates to the contact force and the distribution of the force chain, it can be concluded that the coarse aggregate plays a major role in resisting compression load in PC, while fine aggregate mainly increases the number of contact points to achieve force transmission.
The energy consumption and greenhouse gas emission of asphalt pavement have become a very serious global problem. The high-temperature stability and durability of polyurethane (PU) are very good. It ...is studied as an alternative binder for asphalt recently. However, the strength-forming mechanism and the mixture structure of the PU mixture are different from the asphalt mixture. This work explored the design and performance evaluation of the PU mixture. The PU content of mixtures was determined by the creep slope (K), tensile strength ratios (TSR), immersion Cantabro loss (ICL), and the volume of air voids (VV) to ensure better water stability. The high- and low-temperature stability, water stability, dynamic mechanical property, and sustainability of the PU mixture were evaluated and compared with those of the stone matrix asphalt mixture (SMA). The test results showed that the dynamic stability and bending strain of the PU mixture were about 7.5 and 2.3 times of SMA. The adhesion level of PU and the basalt aggregate was one level greater than the limestone, and basalt aggregates were proposed to use in the PU mixture to improve water stability. Although the initial TSR and ICL of PU mixture were lower, the long-term values were higher; the PUM had better long-term water damage resistance. The dynamic modulus and phase angles (φ) of the PU mixture were much higher. The energy consumption and CO2 emission of the PU mixture were lower than those of SMA. Therefore, the cold-mixed PU mixture is a sustainable material with excellent performance and can be used as a substitute for asphalt mixture.
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