Nominal Particle Research Articles

Inference of Verb Meaning Using Morphosyntactic Clues in Preschool Children with Delayed Language Development

Objectives: The purpose of this study is to determine whether preschool children with delayed language development use morphosyntactic clues such as particles or arguments when understanding the meaning of new verbs. Methods: The participants were 16 children aged 4 to 5 years with delayed language development and 16 children whose chronological age was matched. We analyze the characteristic of the two groups understanding the meaning of sentences containing new actions through particles tasks and argument tasks. Results: First, as a result of comparing the differences between the two groups in the particles conditions (nominative, objective), there was no significant difference in the correct response scores between the two groups in the nominative particle condition. Second, there was a significant difference in the correct response scores between the two groups in the objective particle condition. Lastly, there was no significant difference in the response ratio according to the group and argument condition. Regardless of the number of arguments, all children chose more relational action scenes than independent action scenes. Conclusion: In the particles task, children with language delay showed similar performance to typical children in the nominative case condition, but showed difficulty in the objective case condition. Children with language delay were able to infer verb meaning using particle cues, just like typical children. However, this ability was limited in the objective particle condition. In the argument task, there was no significant difference between the two groups, indicating that inferring verb meaning was not affected by the number of nouns.

Development and Road Performance Verification of Aggregate Gradation for Large Stone Asphalt Mixture.

The pavement base and subbase are the main load-bearing structures of asphalt pavement, and their materials need to have sufficient bearing capacity. Therefore, in the development of LSAM-50 mixtures with higher bearing capacity, after significant research and engineering practice, conventional particle size asphalt mixtures have formed their own excellent mineral gradation and have been incorporated into relevant specifications, while LSAM-50 mixtures, including mineral gradation, have not been involved in related research and engineering applications. According to the strength composition mechanism of asphalt mixtures, under the same circumstances of asphalt, due to the large nominal maximum particle size of LSAM-50 and the small amount of asphalt used, the strength of mineral grading is more important than that of asphalt, which is one of the key issues to be solved in the research of LSAM-50 mixtures. This study aims to enhance the road performance of asphalt mixtures with a maximum nominal particle size of 50 mm (LSAM-50). The variation of void ratios in coarse aggregate skeletons was investigated when aggregates of 37.5-53 mm (designated as D1), 19-37.5 mm (designated as D2), and 9.5-19 mm (designated as D3) were mixed in different proportions. Meanwhile, the effects of fine aggregate gradation on the strength of asphalt mortar and the influence of the ratio of coarse to fine aggregates on the mechanical strength of LSAM-50 were examined. A densely graded structure with strong interlocking for LSAM-50 was proposed, and its road performance was verified. The results indicate that when the ratio of D1, D2, and D3 is 5:2:3, the void ratio of the mixed coarse aggregate is minimized. When the decrement factor i is 0.75, the compressive strength and splitting strength of asphalt mortar reach their maxima. Compared with the densely graded asphalt-stabilized aggregate mixture (ATB-30) with a maximum nominal particle size of 37.5 mm, the dynamic stability of LSAM-50 with the proposed gradation is increased by 400%, the low-temperature bending strain by 3%, the SCB bending strength by 47%, and the residual SCB strength by 90%.

Long-term skid resistance evolution and influence mechanism of asphalt pavement based on self-developed wear equipment

Skid resistance decay is the critical functional distress of asphalt pavement, directly restricting its safety and service life. In order to grasp the characteristics and mechanism of long-term skid resistance evolution, this study developed a laboratory wheel-accelerated wear equipment (WAWE) and its testing methodology for asphalt pavement and coarse aggregate. Five coarse aggregates and five gradations combinations were selected to investigate the evolution. The accuracy of the evolution model and the loading conversion relationship were analyzed based on the Research Institute of Highway (RIOH) Track. Finally, the pavement anti-skid texture tester (PATT) was used to investigate the evolution characteristics of coarse aggregate microtexture. Results showed that the Asymptotic evolution model could characterize the skid resistance under the influence of coarse aggregate and gradation. RIOH Track verified the model's accuracy and showed that a single WAWE wear was equivalent to 265 loading times on actual pavement. The long-term skid resistance could be improved by increasing the nominal maximum particle size and the gradation fractal dimension indexes D and Df. The microtexture roughness of the coarse aggregate decreased after wear, then stabilized and fluctuated, which showed "regeneration" characteristics. The study can guide asphalt mixture design and maintenance timing decisions based on long-term skid resistance.

Image-driven prediction system: Automatic extraction of aggregate gradation of pavement core samples integrating deep learning and interactive image processing framework

Aggregate gradation plays a crucial role in determining the asphalt pavement performance, necessitating assessment post-construction. Additionally, efficient gradation measurement is vital for the design and construction of reclaimed pavement. This study proposes a methodology for predicting gradation based on imagery. Initially, a scanning device is devised to capture unfolded side surface images of pavement core samples. Subsequently, an interactive software named PyImageJ is developed for image post-processing and acquiring aggregate feature information. A morphological model is then introduced to determine the mass ratios among various grading levels of coarse aggregates with nominal particle sizes greater than 2.36 mm. Finally, sequence prediction models are established to forecast the mass ratios among different grading levels of fine aggregates with nominal particle sizes smaller than 2.36 mm. Simple conversion of the mass ratios can yield the gradation. Experimental results indicate that the Long Short-Term Memory (LSTM) network offers more accurate predictions for the mass ratios of fine aggregates in stone mastic asphalt (SMA-13), with an R-squared value of 0.8985. Conversely, one-dimensional convolutional neural networks (1D CNN) are better suited for predicting the fine aggregate mass ratios in asphalt concrete (AC-20 and AC-25), with R-squared values of 0.9010 and 0.8824, respectively. Visualization results demonstrate that the predicted complete gradation closely aligns with the actual values (R-squared > 0.99), opening a new avenue for evaluating pavement quality.

The variation of particle concentration with height of wind-blown coral sand

Wind-blown coral sand movement is common in the marine coral sand island environment but received much less research attention compared to desert and coastal sands. We used the particle image velocimetry technique with wind tunnel experiments to determine the decay trends of the particle number density, nominal particle area density, and actual particle area density with height for wind-blown coral sands from the South China Sea. Then, a new morphology factor FM that consists of volume V, density ρs, drag coefficient CD, and projected area A of sand particles, was defined to evaluate the influences of particle characteristics on wind-blown sand movement and the results were compared with those of quartz sands from an inland desert. We found that the average FM of coral sands is more comparable to that of coarse quartz sands than smaller size groups. Coral sands tend to move nearer the surface during aeolian processes compared to smaller quartz ones due to their larger FM. The decay rate of particle number density of coral sands with height is similar to that of coarse (0.8–1 mm) quartz sands, but significantly larger than that of smaller quartz ones. The decay rate of the actual particle area density of coral sands with height is larger than that of their nominal particle area density, so that significant deviations may exist if a fixed particle size and spherical shape are assumed to study wind-blown particle movement. The present work contributes to understand the effect of particle characteristics on the wind-blown sand movement from a physical mechanism perspective for both desert quartz sands and marine coral sands.

Temperature Distribution in Asphalt Concrete Layers: Impact of Thickness and Cement-Treated Bases with Different Aggregate Sizes and Crumb Rubber

The temperature estimation within asphalt concrete (AC) overlaid on cement-stabilized bases (CSB) is necessary for pavement analysis and design. However, the impact of different CSB gradations and rubberized CSB on AC temperature has not been thoroughly investigated. This study aims to clarify this effect by examining two types of CSB with nominal particle aggregate sizes of 25 mm and 31.5 mm, as well as the substitution of 5%, 10%, and 20% graded aggregates with rubber aggregates (RA) in CSB Dmax 25 using Ansys-based numerical simulations. The modelling also investigated 11 scenarios with different AC thicknesses (hAC) ranging from 6 to 26 cm. The results indicated that CSB Dmax 31.5 reduced the daily maximum temperature fluctuation at the bottom of the AC (∆TbottomAC) by approximately 8% compared to CSB Dmax 25. The inclusion of 5% RA in CSB Dmax 25 decreased ∆TbottomAC by up to 20%. Additionally, the rubberized CSB increased the maximum temperature gradient between the top and bottom of the AC (ΔTmaxAC) by 9.5% with 5% RA and a 6 cm AC thickness; however, this increase was insignificant when hAC exceeded 12 cm. This study also proposed the use of artificial neural network (ANN) models to predict the AC’s temperature distribution based on depth, the time of day, surface paving temperatures, and hAC. The proposed ANN model demonstrated high accuracy (R2 = 0.996 and MSE = 0.000685),which was confirmed by the numerical simulations, with an acceptable RMSE ranging from 0.28 °C to 0.67 °C.

Research on the Skidding Resistance and Attenuation Characteristics of Asphalt Pavement Based on Image Recognition-Analysis Strategy

To accurately evaluate the skidding resistance of asphalt pavements, a texture imaging device was developed to realize the standardized acquisition of pavement images. Based on the gray-level co-occurrence matrix and multifractal theory of texture structure, the influence of segregation degree and gradation type on the texture properties of asphalt pavement was studied. Meanwhile, a comprehensive evaluation index of skidding resistance was proposed for asphalt pavement. Furthermore, the attenuation characteristics of the anti-skidding performance for asphalt mixture were explored, and the corresponding attenuation model of asphalt pavement was established. The results show that the segregation degree and gradation type significantly affected the texture parameters and anti-skidding performance of asphalt mixture. Specially, with an increase in the segregation degree of coarse aggregate, the parameters of energy, entropy, and multifractal spectrum width gradually increased, whereas the inertial moment gradually decreased. The variation range of the multifractal spectrum difference initially increased and subsequently decreased. For the texture parameters such as energy, entropy, inertial moment, and multifractal spectrum width Δα, the values of the asphalt mixture with larger nominal maximum particle were higher than those of the mixture with smaller nominal maximum particle, whereas the multifractal spectrum difference value showed the opposite law. In addition, the texture parameters of energy, entropy, and multifractal spectrum width exhibited good linear correlation with the texture depth (TD) of asphalt mixtures with various segregation levels and gradation types. The index based on the texture parameters of energy, entropy, and multifractal spectrum width effectively evaluated the skidding resistance of asphalt pavements, which showed the same trend as the TD with the increase of the abrasion number. The achievement provides an effective solution for the evaluation of skidding resistance and attenuation characteristics of asphalt mixtures.

On the second law of thermodynamics: A global flow spontaneously induced by a locally nonchaotic energy barrier

It is well known that, inherently, certain small-scale nonchaotic particle movements are not governed by thermodynamics. Usually, such phenomena are studied by kinetic theory and their energy properties are considered “trivial”. In current research, we show that, beyond the boundaries of the second law of thermodynamics where Boltzmann’s H-theorem does not apply, there may also be large-sized systems of nontrivial energy properties: when the system is isolated, entropy can decrease; from a single thermal reservoir, the system can absorb heat and produce useful work without any other effect. The key concept is local nonchaoticity, demonstrated by using a narrow energy barrier. The barrier width is much less than the nominal particle mean free path, so that inside the barrier, the particle-particle collisions are sparse and the particle trajectories tend to be locally nonchaotic. Across the barrier, the steady-state particle flux ratio is intrinsically in a non-Boltzmann form. With a step-ramp structure, the nonequilibrium effect spreads to the entire system, and a global flow is generated spontaneously from the random thermal motion. The deviation from thermodynamic equilibrium is steady and significant, and compatible with the basic principle of maximum entropy. These theoretical and numerical analyses may shed light on the fundamentals of thermodynamics and statistical mechanics.

Study of the Cold Curing Characteristics of Isocyanate-Modified Asphalt.

Isocyanate esters are widely recognized for their superior curing capabilities. Leveraging this attribute, the current research formulated a modified cold-mixed asphalt blend using 4,4'-methylene diphenyl diisocyanate (MDI). Tests and analyses of the MDI-modified asphalt with varying inclusion percentages of MDI revealed that a mixture containing 15% rock asphalt and 15% MDI-modified asphalt exhibited a more balanced, comprehensive performance. We also conducted an examination of the role and properties of MDI in asphalt modification using molecular dynamics simulations. The cold-curing properties of MDI-modified asphalt as compared to petroleum asphalt were evaluated based on its density, free volume analysis, cohesive energy density, and glass transition temperature. Implementing the LB-13 gradation-a cold-mixed asphalt gradation with a nominal particle size of 13.2 mm recommended by Chinese specifications-we prepared MDI-modified cold-mixed asphalt and carried out analyses of its mechanical characteristics, high-temperature performance, and water damage resistance. The results demonstrated that MDI-modified asphalt showcases excellent ductility, flexibility, and aging resistance, surpassing the performance of petroleum asphalt. The stability, high-temperature rutting, and water damage resistance of the MDI-modified cold-mixed asphalt exceeded the requirements for hot-mixed asphalt. This research provides theoretical and experimental support for isocyanate ester applications in asphalt engineering, presenting significant value for practical engineering applications.

Experimental Study on Two-Phase (Solid-Liquid) Flows of Ground Wheat Straw in Inclined Pipes

Highlights Knife milled wheat straw-water slurry flow through inclined pipes at various inclinations is experimentally studied. Slurry concentration and pipe inclination affect the onset velocity of drag reduction and the percentage of drag reduction. The critical mass concentration of maximum drag reduction is a vital function of velocity and is independent of the pipe angle. Downhill wheat straw slurry flows exhibit the most significant reduction in drag and the smallest onset velocities. Wheat straw slurry flows moving uphill exhibit nonmonotonic variations in onset velocity and drag reduction. Abstract. Long-distance pipeline hydro-transport of lignocellulosic biomass for industrial-scale biofuel production at levels comparable to conventional oil refineries presents an economically and logistically viable alternative to fossil fuels. There is very limited understanding on the behavior of the transportation of agricultural biomass slurries in an inclined pipeline. This research is focused on a laboratory-scale investigation of 6.4 mm nominal particle length (d50 = 4.85 mm) knife-milled wheat straw-water suspensions' uphill and downhill flows for a range of pipe inclination and saturated mass concentrations. The range of pipe inclination and saturated mass concentration was -7° to +21° and 5%-30%, respectively. The inclined test section was 29 m long with a 50 mm inside diameter of a closed pipeline loop. The accuracy of the measurements was verified by calibrating the inclined pipe section with fine sand (d50 = 0.103 mm)-aqueous slurries and comparing the results with established correlations. Most wheat straw-aqueous suspensions in the inclined flows showed the characteristics of the plug flow and the transition flow regions together for saturated mass concentration, Cm = 5%-30% and the entire flow range (0.5-4.7 m s-1), with a clear dependence of both the onset velocity of drag reduction (vOD) and drag reduction (%DR) on the pipe inclination as well as the slurry concentration and the critical concentration of maximum drag reduction (Cm)cr on a specific range of suspension velocity. Because of the accelerating effect of gravity, downhill slurry flows had the lowest vOD and the highest %DR at every Cm and pipe inclination with a maximum drag reduction of 25.53% at vm = 4.5 m s-1 and Cm = 25%. Uphill flows demonstrated some nonmonotonic changes in vOD and %DR, which need more experimental data for us to reach a firm conclusion. The research outcomes could help design and operate a long-distance integrated pipeline network for biomass transportation to produce biofuels on a large scale. Keywords: Biomass transport, Drag reduction, Flow regions, Frictional pressure drop, Pipe inclination, Wheat straw slurry.

Laboratory investigation for the bridge deck pavement performance of conventional asphalt mixtures based on fuzzy comprehensive evaluation method

The performance of asphalt mixtures greatly influences the long-term performance of bridge deck pavements. It is essential to optimise the asphalt mixtures with the best overall performance according to different regional conditions for use in engineering practice. This study proposes a comprehensive assessment method based on the Analytical Hierarchy Process (AHP) and Fuzzy Comprehensive Evaluation (FCE) to evaluate the serviceability of asphalt mixtures from different perspectives. It is used to optimise the best asphalt mixtures. The results show that the skeleton-dense structure asphalt mixture has better engineering applicability than the suspension-dense structure asphalt mixture, and the comprehensive performance of the asphalt mixture decreases with the increase of the nominal maximum particle size. The FCE determines that the total performance of the seven types of asphalt mixtures in the order of their superiority and inferiority are SMA-13 >asphalt mastic sand (AMS)>SMA-10 >AC-25 >AC-13 >AC-16 >AC-20. The study combines qualitative and quantitative factors, which makes the selection of engineering materials more scientific and rigorous and improves the rationality of material suitability evaluation.

Investigation on the high-temperature stability and fatigue behavior of cold mixed epoxy asphalt mixture with different gradations

Cold mixed epoxy asphalt mixture (CMEAM) is widely applied on steel deck bridge pavements due to its excellent high temperature and fatigue resistance. However, previous studies investigated above two properties through destructive test or without considering water-damage factor, respectively, which is far away from real servicing condition. To distinguish above two properties of EA-05 and EA-10 (mixture with nominal maximum particle size of 4.75 mm and 9.5 mm), uniaxial static creep tests, dynamic modulus test and four-point bending beam fatigue test were applied in this paper. At the same time, to comprehensively acquire elastic, viscous-elastic and plastic performance of CMEAM, four kinds of constitutive models were also put forward. Results showed that seven-element viscous-elastic-plastic creep model has the highest correlation coefficients which proves there exists plastic deformation in CMEAM. Meanwhile, EA-10 is likely to present viscous-elastic deformation while EA-05 is more likely to show plastic deformation. Dynamic modulus among different gradation type mixture at 40 °C is not so apparent. But with the increase of frequency and testing temperature, this difference would be clear. The middle gradation of EA-10 has the most excellent high temperature stability under dynamic load. In terms of the resistance to fatigue damage of control or freeze-thaw treated samples, EA-05-U(the upper limit of EA-05 gradation type) always takes the first place and has the lowest sensitivity to the change of stress level and water damage.

Experiment Investigation and Influence Evaluation of Permeability Ability Attenuation for Porous Asphalt Concrete under Repeated Clogging Conditions

One of the problems that limit the development of porous asphalt concrete (PAC) is that the pores become clogged, which leads to severe deterioration in its permeability performance. This paper focuses on PAC’s permeability characteristics under repeated cycles of clogging. First, sand (S), clay (C), and sand and clay mixtures (S + C) were used as clogging materials for repeated clogging tests. Then, the permeability coefficients in the initial state and after clogging were measured with an improved permeability device. Based upon porosity, maximum nominal particle size, and clogging materials, the paper analyzed the permeability regulation of PAC under repeated clogging conditions. In addition, we compared the restoration effects of vacuum cleaning, high-pressure cleaning, and surface cleaning with cleaning tests and proposed a response surface methodology prediction model. Finally, the particle size distribution of sensitive particles that cause different porosities in PAC clogging was explored. The results showed that the initial permeability coefficient and the permeability coefficient with PAC’s repeated clogging increased with the increase in the nominal maximum particle size and porosity. PAC clogged by sand has the greatest rate of reduction in the coefficient of permeability. In addition, we suggested that in PAC pavement maintenance work, water is first sprinkled to wet the road, then high-pressure cleaning used, and finally vacuum cleaning. The prediction model is reliable and the cleaning method has the most significant effect on the permeability coefficient. Further, the particle size distribution that caused PAC-13 and PAC-10 clogging ranged from 0.15 to 2.36 mm and 0.075 to 2.36 mm, respectively.

Experimental investigation of heating augmentation by particle kinetic energy conversion in dust-laden supersonic flows

The presence of particles in supersonic flows can cause significant increases in stagnation point heat fluxes (Dunbar et al. in AIAA J 13:908–912, 1975). This effect is commonly named ‘particle-induced heat flux augmentation’ or just ‘heating augmentation.’ Heating augmentation can be described as the sum of the conversion of kinetic energy of the particles into thermal energy, characterized by the energy conversion efficiency, also called accommodation coefficient, and the increase of convective heat flux (Polezhaev et al. in High Temp 30:1147–1153, 1992; Vasilevskii and Osiptsov in Experimental and numerical study of heat transfer on a blunt body in dusty hypersonic flow 33rd thermophysics conference, American Institute of Aeronautics and Astronautics, 1999). Although the accommodation coefficient is fundamental for heating augmentation characterization, there is only a small number of experimental datasets for it. This work focusses on the experimental determination of the accommodation coefficient in flow regimes at Mach number 2.1, Reynolds number, based on the probe nose diameter, from approx. 6e5 to 1.8e6, and nominal particle sizes of approx. 20 µm. The decrease of particle velocity and kinetic energy flux in the shock layer is measured with highly resolved shadowgraphy for individual particles. The particle kinetic energy flux is decreased by 29% on average by particle deceleration in the shock layer. Negligible kinetic energy fluxes of rebounded particles were measured. The accommodation coefficient is approx. 0.36 for Al2O3 and SiO2 particles, while it is approx. 0.09 for MgO particles. Hence, it is significantly smaller than the widely used value of 0.7, based on the study of (Fleener and Watson in Convective heating in dust-laden hypersonic flows 8th thermophysics conference, 1973), but in good agreement with values given in (Hove and Shih in Reentry vehicle stagnation region heat transfer in particle environments 15th aerospace sciences meeting, 1977) and (Molleson and Stasenko in High Temp 55:87–94, 2017. https://doi.org/10.1134/S0018151X1701014X ). No difference between erosive and elastic particle reflection mode was detected on the conversion efficiency. The data from a simplification of the modeling approach of the conversion efficiency for elastic particle reflection by Molleson and Stasenko (2017) are in poor agreement with experimental data.

Microscopic mechanical properties and fabric anisotropic evolution law of open graded gravel permeable base under dynamic loading

Under traffic dynamic load, the microscopic mechanical properties and the fabric anisotropic evolution of open graded gravel permeable base directly determine the ability of open graded gravel permeable base to resist external loads and maintain stability in service. Firstly, this article constructed a discrete element numerical model for open graded gravel permeable base, and verified the accuracy of the model through experiments. Then, the effects of gradation, nominal maximum particle size, friction coefficient between aggregate particles, and effective elastic modulus of aggregate on the microscopic mechanical properties, migration behavior, and the fabric anisotropic evolution of open graded gravel aggregate particles were studied in sequence. The research results indicate that the proposed image moving target tracking algorithm based on the three branches twin network can achieve precise tracking and measurement of particle microscopic migration behavior. The method proposed in this study for constructing a three-dimensional surface model of gravel particles based on the principle of multi view averaging and the scale invariant feature transformation algorithm can achieve rapid numerical reconstruction of the three-dimensional morphology of gravel particles at a low cost. The internal aggregate particles of intermediate grade gravel are more likely to form a stable network force chain topology structure that can effectively resist external loads. As the maximum nominal particle size increases, the topological structure of the contact force of gravel particles becomes sparse, and the proportion of strong contact force increases. Increasing the friction coefficient of the contact interface between aggregate particles can to some extent hinder the migration behavior of aggregate particles inside the graded gravel. As the effective elastic modulus of the aggregate increases, the internal network strong contact force chain topology of open graded gravel gradually forms. Under external loads, the migration speed and displacement of the aggregate particles inside open graded gravel decrease, and the degree of internal normal contact force and branch vector anisotropy also decrease.

Aggregation in experimental studies with microparticles: Experimental settings change particle size distribution during exposure

The ubiquitous occurrence of microplastics is raising broad concerns and motivating effect studies. In these studies, however, particle behaviour in the water and aggregation are rarely considered leading to contradictory results reported by different studies. Using an environmentally relevant experimental setup with Daphnia magna as a test organism, we investigated how experimental conditions affect particle aggregation and the aggregate heterogeneity in terms of the particle size distribution. The experimental factors considered were (1) exposure duration (48 h vs 120 h), (2) the total mass of suspended solids (0–10 mg/l) composed of natural mineral particles (kaolin) and microplastics, (3) the proportion of the microplastics in the particle suspension (0–10% by mass), (4) dissolved organic matter (DOM; 0 vs 20 mg agarose/l), and (5) presence of the test organism (0 and 5 daphnids/vial).We found that particle aggregation occurs within the first 48 h of incubation in all treatments, no substantial change in the aggregate heterogeneity is observed afterwards. The median aggregate size was ∼2-fold higher than the nominal average particle size of clay and microplastics in the stock suspensions used to prepare the experimental mixtures. The strongest positive driver of the aggregate size and heterogeneity was DOM, followed by the presence of daphnids and the concentration of the suspended solids in the system. Also, microplastics were found to facilitate aggregation, albeit they were the weakest contributor. Moreover, besides directly increasing the aggregation, DOM relaxed the effects of the total solids and daphnids on the aggregate size. Thus, the particle size distribution was established early during the exposure and shaped by all experimental factors and their interactions. These findings improve our understanding of the processes occurring in the exposure systems when conducting effect studies with microplastics and other particulates and demonstrate the necessity to access the particle size distribution to characterise the exposure. Aslo, relevant experimental designs with microplastics must include relevant natural particulates and DOM to ensure environmentally realistic particle behaviour and adequate particle-biota interactions.

Clogging characteristics and recovery effects of porous asphalt concrete with different gradations

ABSTRACT Permeable pavement is easy to be blocked, which significantly affects the functions of drainage and skid resistance. Relevant researches lack void clogging and cleaning for PAC with different air voids and nominal maximum particle sizes. This paper designed seven kinds of PAC specimens to study PAC's clogging characteristics and cleaning methods. Specifically, the permeability coefficient decay of PAC caused by clogging was tested. Then, a novel test called fluorescence tracing method was proposed to evaluate the clogging depth and area. Afterward, high-pressure washing, vacuum cleaning, and the combination of high-pressure washing and vacuum cleaning (H&V) were used to study void recovery characteristics. Results showed that the critical clogging particle size of PAC-13 with 16% air voids and PAC-10 with 20% air voids were 0.15-0.3 mm; the critical clogging particle size of PAC-13 with 18% air voids was 0.3-0.6 mm; the critical clogging particle size of PAC-13 and PAC-16 with air voids of 20%, 22%, 24% were 0.6-1.18 mm. Furthermore, the clogging depths of PAC-13 didn't exceed 28 mm, and the proportions of the clogging area didn’t exceed 37%. The average recovery rates of vacuum cleaning and H&V were more than 70%, obviously better than that of high-pressure washing.

Experimental Study on the Dynamic Modulus of an Asphalt Roadbed Grouting Mixture under the Influence of Complex and Multiple Factors

After long-term service, the ground will experience settlement and the stability of the roadbed will be lost. In order to effectively reinforce the roadbed, an asphalt roadbed grouting mixture has been applied to the filling of the roadbed. The rotary compaction method was used to prepare different gradation types of lime composite-modified oil sludge pyrolysis residue asphalt, mixtures Sup13, Sup19, and Sup25. This article takes the dynamic modulus of an asphalt roadbed grouting mixture as the mechanical index, and the uniaxial compression dynamic modulus test is carried out on three kinds of rotary compaction asphalt mixtures, Sup13, Sup19, and Sup25. The dynamic modulus master curves of different gradation composite-modified oil sludge pyrolysis residue asphalt mixtures are fitted to study the dynamic modulus of asphalt mixtures under different nominal maximum particle sizes, loading frequencies, and temperatures. The results show that (1) The dynamic modulus of different gradation composite-modified oil sludge pyrolysis residue asphalt mixtures increases with the decrease in temperature and the increase in frequency; (2) when other conditions are the same, the compound-modified asphalt mixture’s dynamic modulus decreases significantly under low-frequency and high-temperature conditions; (3) in the range of 4.4–37.8 °C and medium loading frequency, the dynamic modulus of the compound-modified asphalt mixture is more affected by temperature and loading frequency; (4) in the low-temperature and high-frequency range, the compound-modified asphalt mixture with a larger nominal maximum particle size has a higher dynamic modulus, and the asphalt mixture with better stability of skeleton structure has a higher dynamic modulus. The research results of this article will provide scientific guidance for the study of the mechanical properties of asphalt roadbed grouting mixtures.

Compaction method development and materials performance evaluation of large size cement-treated macadam materials

Existing research mainly focuses on cement-treated macadam materials with a maximum nominal particle size (MNPS) of ≤ 37.5 mm, and there is little research on large size cement-treated macadam (LSCM) with an MNPS of ≥ 53 mm. In this paper, a self-developed vertical vibration testing equipment (VVTE) was used to compact an LSCM with an MNPS of 53 mm (hereafter, LSCM-50). Then, an appropriate specimen size for compacting LSCM-50 was determined. Moreover, a self-developed vertical vibration compaction method (VVCM) for laboratory-based compaction of LSCM-50 was proposed and its reliability was verified. Subsequently, the indoor mechanical properties and durability of the VVCM-fabricated LSCM-50 were studied. The results show that when the working frequency of VVTE = 32 Hz, upper system weight of VVTE = 122 kg, lower system weight of VVTE = 180 kg, nominal amplitude of VVTE = 1.2 mm, and static eccentric moment of VVTE = 0.215 kg·m, the compaction effect of LSCM-50 is the best. The correlation between the laboratory-VVCM-fabricated LSCM-50 samples and the on-site-drilled LSCM-50 cores is more than 90%. The mechanical properties of the LSCM-50 samples increase nearly linearly with the increase in the cement content but increase nonlinearly with the increase in the curing period. Additionally, the strength deterioration coefficient of the LSCM-50 samples does not decrease when the freeze–thaw cycles exceed seven, and the mass loss percentage of the LSCM-50 samples does not increase after being soured for 25 min. This paper provides a new method for compacting the LSCM and an evaluation of its mechanical properties and durability.

Characterization of Lubrication Layer of Fresh Concrete Acquired Using the Modified Pipe Flow Apparatus

A thin layer of micromortar called a lubrication layer (LL) forms around the inner periphery of the pipe during the pumping of fresh concrete. This LL aids in the movement of concrete under pressure. The composition of the LL is of prime importance in understanding the flow behavior of concrete under the action of shear and the prediction of pressure for pumping applications. In the present study, an attempt was made to determine the LL composition of the concrete mixtures using fly ash, ground granulated blast-furnace slag, and limestone calcined clay as supplementary cementitious materials with a water to binder (w/b) ratio ranging from 0.3 to 0.5 supplemented with a superplasticizer. In this regard, the LL was extracted by modifying the existing pipe flow apparatus. The collected LL was characterized for its composition, which includes w/b, binder to sand ratio (b/s), and particle-size distribution. The results indicated that the nominal maximum particle size of LL was around 600 μm. The average binder to sand ratio of LL obtained was 3.0. The w/b of LL was found to be higher than that of the bulk concrete. The characterization of LL carried out in the current work generated a database regarding the potential composition of LL, which would aid in the rheological studies for fundamental understanding and the pressure prediction of concrete.