Performance Of Mixtures Research Articles

The Production of Porous Asphalt Mixtures with Damping Noise Reduction and Self-Healing Properties through the Addition of Rubber Granules and Steel Wool Fibers.

Conventional asphalt roads are noisy. Currently, there are two main types of mainstream noise-reducing pavements: pore acoustic absorption and damping noise reduction. However, a single noise reduction method has limited noise reduction capability, and porous noise-reducing pavements have a shorter service life. Therefore, this paper aimed to improve the noise-damping performance of porous asphalt mixture by adding rubber granules and extending its service life using electromagnetic induction heating self-healing technology. Porosity and permeability coefficient test, Cantabro test, immersion Marshall stability test, freeze-thaw splitting test, a low-temperature three-point bending experiment, and Hamburg wheel-tracking test were conducted to investigate the pavement performance and water permeability coefficients of the mixtures. A tire drop test and the standing-wave tube method were conducted to explore their noise reduction performance. Induction heating installation was carried out to study the heating rate and healing performance. The results indicated that the road performance of the porous asphalt mixture tends to reduce with an increasing dosage of rubber granules. The road performance is not up to the required standard when the dosage of rubber granules reaches 3%. The mixture's performance of damping and noise tends to increase with the increase of rubber granule dosage. Asphalt mixtures with different rubber granule dosages have different noise absorption properties, and the mixture with 2% rubber granules has the best overall performance (a vibration attenuation coefficient of 7.752 and an average absorption factor of 0.457). The optimum healing temperature of the porous asphalt mixture containing rubber granules and steel wool fibers is 120 °C and the healing rate is 74.8% at a 2% rubber granule dosage. This paper provides valuable insights for improving the noise reduction performance and service life of porous asphalt pavements while meeting road performance standards.

Enhancement of porous asphalt mixtures modified with various fibers and ethylene–vinyl acetate polymer

Porous asphalt mixture is conventional hot mix asphalt (HMA) with substantially decreased fines, which produces an open-graded mixture that enables the water to flow through an interconnected void space. Porous asphalt is a permeable system that has a lot of benefits. However, because of its open structure, the durability of this mixture decreases, and both its stability and resilient modulus are much lower compared to the dense conventional asphalt mixtures. Also, the high void percentage may lead to an increase in the draindown proportion. Fibers (cellulose or mineral) and polymer-modified binders are recommended for porous asphalt mixtures, especially in hot and moderate climates. The objective of this study is to improve the porous asphalt mixture's performance by using ethylene–vinyl acetate (EVA) polymer-modified bitumen. Two types of fibers (cellulose fibers and glass wool fibers) were used, separately to determine the control mixture. Four different proportions of EVA polymer were added to the bitumen (1%, 2%, 3%, and 4%) and Scanning Electron Microscopy (SEM) was used for better investigating of the bitumen microstructure, then The Marshall mix design was used to determine the optimum EVA content (OEC) for the porous asphalt mixture. Several performance tests were conducted to investigate the characteristics of the porous asphalt mixture, such as the infiltration rate, binder draindown, the wheel track and the cantabro abrasion tests. The findings of the study conclude that the addition of EVA polymer to the porous asphalt mixtures enhances the performance as it increases stability by 20.8% and the infiltration rate by 20.6%. It decreases binder draindown proportion by 33.3%, cantabro abrasion loss by 25.1% and the rut depth at 5,000 cycles and 10,000 cycles by 29.8% and 19.7%, respectively.

Investigating the Influence of Mineral Fillers at Australian Asphalt Mixtures

Abstract It is commonly known that mineral fillers significantly affect the asphalt mixture's performance. Superior flexible pavement performance can be ensured by gaining a deeper understanding of the function of filler. This research investigates the influence of three different fillers: granite dust, cement, and hydrated lime, at Australian asphalt mixtures. The testing program includes Marshall testing, moisture damage resistance, indirect tensile strength (ITS), and indirect tensile stiffness modulus (ITSM) tests of asphalt mixtures. Analysis of variance (ANOVA) was used to statistically assess the results obtained, besides damage analysis. The results indicate that using natural granite dust yields the highest resistance to moisture, while cement produces the highest stability, ITS, and ITSM. Unexpectedly, using hydrated lime filler decreases the stability/stiffness and moisture resistance of asphalt mixtures. ANOVA tests indicate that the type of filler affects ITS, TSR, and ITSM results (i.e., the p-value <0.05). The damage analysis shows that the design life of the asphalt mixture made with cement filler is higher than that of mixtures made with natural granite dust and hydrated lime fillers respectively. The findings indicate the important role of nontraditional fillers at the performance of Australian asphalt mixtures.

Polyurethane modified asphalt mixture incorporating waste glass with a wide particle size range: Preparation and performance evaluation

Increasing the utilisation rate of waste glass in asphalt mixtures, especially that with a wide range of particle sizes, is of great importance to resource recycling, while it may bring drawbacks to the engineering performance of asphalt mixtures. Incorporating polyurethane (PU) as a modifier can enhance asphalt mixture's performance, but there is limited research considering the usage of waste glass as aggregates. In this study, PU modified asphalt mixtures were prepared, incorporating waste glass particles ranging in size from 2.36 mm to 9.5 mm as a portion of the aggregates. Optimal preparation methods and mix designs for the PU-modified asphalt binder were determined through a series of tests designed based on Orthogonal method. The performances of the PU-modified asphalt binders were then evaluated to guide the selection of the optimal preparation method and mix design. PU-modified waste glass asphalt mixtures were then prepared and their engineering performances were assessed at various glass-to-aggregate ratios. The results show that scheme PU-1 with a shearing temperature of 140°C, a shearing time of 10 min, a PU content of 10% and a compatibiliser content of 2% is suggested for preparing the PU-modified asphalt binder, which shows the best performances due to superior chemical modification and compatibility. Higher glass content decreases the high/low-temperature performance, but it can be improved by adding silane coupling agent or hydrated lime, with the latter showing better results. The incorporation of glass particles has little impact on anti-sliding performance, and asphalt mixtures maintain excellent anti-sliding properties up to a 20% replacement rate. Overall, the performance of the asphalt with waste glass up to 15% can meet the specification requirements. This novel approach offers a potential solution to enhance the incorporation of waste materials in asphalt construction, contributing to sustainable and environmentally-friendly road construction.

Performance improvement of waste oyster-shell powder–cement binary system via carbonation curing

The dumping of significant amounts of industrial waste oyster shells causes marine pollution and economic loss. Grinding and processing waste oyster shells into oyster shell powder (OSP) to substitute a portion of cement can potentially reduce marine pollution and greenhouse gas emissions. Herein, 0, 15, and 30% OSP were added to cement and cured by employing different methods with and without CO2. The dilution effect of the OSP reduced the heat of hydration. The compressive strength and electrical resistivity of all the mixtures increased after carbonation curing compared to the seal cured specimens. The CO2 absorption contents and rate of carbonation increased with an increase in the OSP content. During carbonation curing, OSP contributes to the carbonation of the cement material, forming large amounts of carbonation products (calcite, aragonite, and vaterite). The precipitation of carbonation products acts as a pore filler, significantly increasing the mixture's performance more than seal curing. Therefore, OSP has significant potential as a replacement material for cement via carbonation curing, and its promising CO2 capture and storage capacities provide a viable solution for greenhouse gas reduction.

Rheological and physicochemical characteristics of asphalt mastics incorporating lime kiln dust and dolomite powder as sustainable fillers

The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance. However, despite numerous studies, in-depth knowledge of filler-bitumen reciprocity at a microscale level is yet to be ascertained. The goal of this research is to gain a better understanding of the filler-bitumen microscale interaction in terms of the synergy and coaction between the physicochemical and rheological performance of mastics due to filler inclusions. The rheological properties of two sustainable mastics, dolomite powder (DP) and lime kiln dust (LKD), together with a neat PEN 60/70 binder, were analysed based on a temperature sweep at elevated temperature conditions. Meanwhile, frequency sweep and multiple stress creep recovery (MSCR) tests were also conducted at pavement serviceability temperature using the dynamic shear rheometer (DSR). Physicochemical tests using a scanning electron microscope (SEM) and energy dispersive X-rays (EDX) were conducted to analyse the impact of parameters such as particle shape, grain size, texture, and chemical compositions. The DSR test results showcased how the incorporation of fillers in asphalt binder considerably improved the performance of the binder in terms of rutting and fatigue. Likewise, its strain and non-recoverable compliance parameters were substantially reduced at higher filler and binder concentrations. Physical filler attributes of low rigden voids (R.V), high fineness modulus (FM), and high specific surface area (SSA) led to greater interfacial stiffness and elasticity in LKD mastics compared to DP mastics at different loading frequencies and temperature levels. The SEM/EDX results also indicated that the elemental calcium and carbon composition of each filler component, together with its grain morphology, strongly influenced its rheological performance.

Influence of crumb rubber incorporating different warm mix asphalt additives on the mechanical performance of the WMA mixture

The compacting and mixing processes involving hot mix asphalt during asphalt production can lead to air pollution as a result of a high volatile organic compound. An alternative solution that can reduce greenhouse gas emissions is by using warm-mix asphalt (WMA). A proper application of additives to the WMA can improve the asphalt mixture's strength, durability, and workability. In this study, a 60/70 grade asphalt binder was added with 5% of crumb rubber (CR) and three different WMA additives at the recommended dosages, namely Sasobit, Cecabase, and Rediset. The wet method was used to blend the additives with virgin asphalt binders. The mixing and compacting temperatures were set at 135°C and 125°C, respectively, to mix the asphalt mixture. Mechanical performance tests were performed to evaluate the impact of WAM additives with CR on asphalt mixture. Based on the results, all the modified asphalt mixtures showed a better mechanical performance than the virgin asphalt mixture in terms of indirect tensile strength, moisture resistance, permanent deformation, and stiffness. Among all the WMA additives, Sasobit with CR showed the most significant impact on the asphalt mixture's performance.

Influence of rejuvenator preheating temperature and recycled mixture’s curing time on performance of hot recycled mixtures

The recycled hot mix asphalt mixture performance is improved by a rejuvenator with good diffusion ability. This paper investigates the rejuvenator-aged asphalt diffusion and its influencing factors, including the rejuvenator's preheating temperature and curing process of recycled mixtures. A molecular dynamic simulation of the diffusion process between rejuvenator and aged asphalt is performed. Its results are then validated by a gel permeation chromatography test. Laboratory tests are also employed to evaluate these two factors' influence on the recycled mixture's performance on a macroscale. Simulated and experimental results strongly indicate that a proper combination of rejuvenator preheating and recycled mixture curing improves the rejuvenator diffusion ability and the recycled mixture performance. Following this, the 110℃ preheating temperature of rejuvenator and the 3-hour curing time after completing the mixing process of the hot plant-mix asphalt mixture are recommended based on the above results.

A new approach to laboratory roller compaction method and its influence on surface texture and permanent deformation of asphalt mixtures

ABSTRACT Pavement structures must guarantee safety, trafficability and comfort to highways users during its service life. The quality of these parameters is related to distresses that may occur as surface distortions, that might be caused by mechanical behaviour problems and to surface texture, which also affect highway safety. The surface texture is evaluated by parameters such as microtexture and macrotexture, related to aggregate rugosity and mixture characteristics, respectively. Both mechanical behaviour and surface texture can be affected by the compaction method of the mixture, as it affects the internal structure and the internal friction between aggregate particles, resulting in alterations in the permanent deformation resistance and surface aspects of the mixture. Hence, this paper proposed a new laboratory compaction method, using roller compaction with vibration, considering three aggregate gradations. This study evaluated the effect of the laboratory compaction method in the permanent deformation resistance and the surface texture of samples, comparing to field mixtures. The proposed compaction method presented efficiency for dense-graded mixture. The mixture's performance regarding mechanical behaviour and surface texture according to the compaction method variation was also dependent on the aggregate gradation. Mixtures with a discontinuity on the gradation presented a negative impact due to the vibration process.

Evaluation of fracture behavior of modified Warm Mix Asphalt (WMA) under modes I and II at low and intermediate temperatures

Cracking is considered to be one of the most important distress of the Warm Mix Asphalt (WMA) mixture, which can occur in different climatic conditions due to a lack of proper bonds between aggregate and bitumen. Since the WMA mixture consists of coarse aggregates in different parts of the asphalt layer, cracks can develop and grow at an angular position. Therefore, this study investigates the fracture behavior of WMA mixtures under vertical (Pure mode II) and angular (Pure mode I) cracking states using a semi-circular bend (SCB) sample at −18 °C and +25 °C using the fracture mechanics method. To improve the WMA mixture's performance, additives of Calcium Lignosulfonate (CL) and waste Polyester (PE) fibers, which were economically justifiable, were used separately and simultaneously in different percentages. According to numerical-experimental results, the proposed samples in both pure mode I (angular crack) and pure mode II (vertical crack) were able to model the WMA's fracture behavior and therefore can be used as suitable specimens for studying the pure mode crack deformation of WMA at intermediate and low temperatures. The results also showed that the coarse aggregate distribution in the ligament section of the specimen had a significant contribution in improving the WMA mixture's fracture performance. As a result, fracture energy (GF), fracture toughness (KI and KII), The Flexibility Index (FI), Cracking Resistance Index (CRI), and the Toughness Index (TI) depended on the type of additive used in the WMA mixture. Finally, 0.25PE-6CL, 0.25PE, and 6CL mixtures had the best results in terms of fracture mechanics.

The TEAGE ageing method for asphalt mixtures

Exposure to the environmental conditions, particularly ultraviolet (UV) radiation, temperature, and precipitation, causes progressive and irreversible ageing of the in-service asphalt mixtures. Due to the ageing effect, the initial mechanical performance of the asphalt mixture degrades over time. Thus, the evaluation of the asphalt mixture's performance under aged conditions is essential to predict service performance better and avoid durability issues.This article presents a recently developed method for the accelerated ageing of compacted asphalt mixtures specimens in the laboratory called TEcnico accelerated AGEing (TEAGE). The TEAGE intends to simulate ageing due to the exposure to environmental conditions, allowing a relation with the field conditions (location) and exposure period (age). Four asphalt mixtures were selected and tested for stiffness and fatigue resistance under unaged and aged conditions by TEAGE.The obtained results highlighted the TEAGE potential to implement an accurate field ageing simulation. The aged mixtures presented a more stiff and brittle behaviour, revealed by an increase in stiffness modulus, a decrease in phase angle, and the reduction of the fatigue resistance.

Characterization of Low Temperature Crack Resistance of Crumb Rubber Modified Asphalt Mixtures Using Semi-Circular Bending Tests

AbstractThe objective of this study was to assess the low temperature anti-cracking performance of crumb rubber modified asphalt mixtures by performing the semi-circular bending tests. The flexural tensile strength, fracture energy density, and fracture resistance were used to evaluate the rubber modified asphalt mixture's performance based on fracture mechanics J-integral concept. The semi-circular bending (SCB) tests were conducted to study the effect of crumb rubber dosage, crumb rubber size, and testing temperature on the low temperature anti-cracking performance of rubber modified asphalt mixtures. Two gradations (a dense gradation mixture and a gap-gradation mixture) were selected, and five rubber application dosages (15, 18, 20, 22, and 25 %, all by the weight of base binder) were studied in the paper. The tests were performed at temperatures of 0, −10, and −20°C. The testing results indicated that the flexural tensile strength and fracture energy density increased initially, reached to a peak point and then decreased with the increase of rubber dosage. Flexural tensile strength and fracture energy density reached its maximum value at the 20 % rubber dosage among the five rubber application dosages. The flexural tensile strength, fracture energy density, and the J-integral fracture toughness of the gap-graded rubber asphalt mixture specimens were higher than those of the dense gradation. The smaller sized particle rubber modified mixture provided a better low temperature anti-cracking performance as compared to those with bigger particle sizes. Through the comprehensive consideration of laboratory test results and field results, it was recommended that the J-integral fracture toughness should be no less than 2.8 KJ/m2 for new asphalt rubber pavement in Shannxi province.

Experimental Study of Hot Recycled Asphalt Mixtures with High Percentages of Reclaimed Asphalt Pavement and Different Recycling Agents

Hot recycled mixture has been widely used as binder course on highways in the Jiangsu Province, China. The objectives of this study were to evaluate recycled mixture's performance with different Reclaimed Asphalt Pavement (RAP) contents and recycling agents (RA). At first, optimum RA contents were determined according to asphalt blending charts based on penetration index. Secondly, the performance of recycled mixtures and control virgin asphalt mixture was evaluated based on retained stability, Tensile Strength Ratio (TSR), dynamic stability (DS), failure strain, and fatigue life. Thirdly, statistical significance on the basis of analysis of variance was evaluated as a function of RAP contents and RA type. The results indicated that adding RA could improve moisture stability, low temperature cracking resistance, while decreasing high temperature stability and strength performance of recycled mixture. Recycled asphalt mixture Sup-20 with RA has similar performance compared to virgin asphalt mixture Sup-20. The former has better moisture stability and high temperature stability than that of the latter, with a slight reduction in low temperature cracking and fatigue resistance. With a fixed RA-2, TSR, and failure strain of recycled mixes decreases, and DS first slightly decreases and then increases, while fatigue life first increases and then decreases with increasing RAP contents. The results indicated that the interface status and blending level between recycled asphalt and aggregate is variable due to the mixing process and material compositions, which results in the varied performance results of recycled mixes due to the different test temperatures, loading modes, and testing periods, etc. Furthermore, the results of analysis of variance are consistent with the experimental test results.

Numerical–Experimental Approach to Characterize Fracture Properties of Asphalt Mixtures at Low Temperatures

Fracture damage mechanisms are some of the most significant causes of structural failure in asphalt mixtures. Ye t much research is still needed to understand properly the fracture process in such complex materials. The study reported in this paper investigated several experimental testing protocols available in the literature to characterize fracture properties of asphalt mixtures. Two bending tests (i.e., semicircular bending, single-edge notched beam) and one tension test (disk-shaped compact tension) were performed. An integrated approach that combined experimental tests and numerical simulations was applied to characterize fracture properties of a fine aggregate mixture. The experimental tests were simulated with a computational model on the basis of the finite element method, which was incorporated with material viscoelasticity and cohesive zone fracture. Two cohesive zone fracture parameters (i.e., cohesive strength, fracture energy) were determined through a calibration process until a good match between experimental and numerical results was observed. To illustrate the efficiency of the integrated numerical–experimental approach, fracture properties also were determined through a traditional methodology that used globally averaged material displacements far from the actual fracture process zone. The results indicated that different fracture properties at low temperatures might be obtained from simulations of a single test, regardless of the sample geometry or loading configuration. Through further testing and analysis, it is expected that the modeling approach employed in this work can provide meaningful insights into the effects of constituents on an overall mixture's performance, with significant savings in experimental cost and time.

Solubility, light output and energy resolution studies of molybdenum-loaded liquid scintillators

The search for neutrinoless double-beta decay is an important part of the global neutrino physics program. One double-beta decay isotope currently under investigation is 100Mo. In this article, we discuss the results of a feasibility study investigating the use of molybdenum-loaded liquid scintillator. A large, molybdenum-loaded liquid scintillator detector is one potential design for a low-background, internal-source 0 ν β β search with 100Mo. The program outlined in this article included the selection of a solute containing molybdenum, a scintillating solvent and the evaluation of the mixture's performance as a radiation detector.

Self-consolidating concrete in congested sections: Mixture characteristics and assessment of performance

Eight planar 6-in.-thick x 6-ft-deep x 6-ft-wide (150 mm x 1.8 m x 1.8 m) wall sections and eight 13-ft-long (4.0 m) bulb-tee (BT-72) beam sections, all with highly congested reinforcement, were fabricated in two precast concrete plants using self-consolidating concrete (SCC). The compressive strengths of cores, taken at different locations on each of the walls and beams, were compared to determine whether properties varied with location. Also, the specimens were cut vertically at different locations to assess segregation of the SCC throughout the depth and length of the elements. Analysis included the use of digital image analysis. While conventional SCC testing by slump flow, U-flow, and L-box methods suggested that most of the mixtures were of good quality, this research showed that such test methods were not sufficient for predicting a mixture's performance in congested sections. Only construction of mock-up sections showed the true self-consolidating performance in congested sections.

Composition shift in liquid-recirculation refrigerating systems: an experimental investigation for the pure fluid R134a and the mixture R32/134a

The ability of zeotropic mixtures with a remarkable temperature glide to operate in liquid-recirculation systems is investigated and the results of an experimental comparison between the performances of the pure fluid R134a and the zeotropic mixture R32/134a (25/75% by mass) are presented. R134a performs slightly better in the liquid-recirculation mode than in the traditional dry-expansion mode; on the other hand, liquid-recirculation configuration has a detrimental effect on the zeotropic mixture's performance. The reason for this detrimental effect is the mixture component separation which occurs at the liquid/vapor separator. The effect of this separation is investigated using gas chromatograph analysis.

Polymer Modification of Paving Asphalt Binders

Abstract • Polymer modification of asphalt binders has become a more accepted method for addressing pavement distresses. The heavier vehicle loads, higher traffic volumes and increased tire pressures have forced user agencies to explore polymer modification for asphalt pavement applications. • The compatibility between the asphalt and polymer depends on many factors. The most significant of these, based on microscopy, are the asphalt crude source, polymer microstructure and the thermal/mechanical history of the polymer-modified asphalt binder. • Classical methods and methods derived specifically for measuring the effect of polymers in the asphalt have poor correlation to mixture performance. The tests also seem to be specific to the different polymers tested. The test conditions make it difficult to extract basic information about the binder's mechanical properties. • Considerable work has been done on the rheology of asphalt and polymer-modified asphalt binders over a wide range of temperatures and rates of loading. Time-temperature superposition has been used to describe the effect of rate of loading on the complex shear modulus (G*) of both polymer modified and unmodified asphalt binders. The addition of polymers has been found to dramatically change the properties at high temperatures or low rates of loading. This has been correlated with varying degrees of success to permanent deformation in the asphalt mixture. • The bending beam rheometer and the direct tension test are ideally suited for measuring the low temperature properties of polymer-modified asphalt binders. Good correlation was found with bending beam results and the fracture temperature of the mixture using the TSRST method. Failure strains, measured for polymer-modified asphalt binders with the direct tension test, were up to ten times greater than that observed for unmodified binders. Polymer-modifiers generally decreased the fracture temperature of the mixture by 6–10°C. • Polymer modifiers for asphalt binders which contain a large percentage of butadiene (50% or greater), exhibit improved low temperature properties. This was observed as a decreased Tg for a polybutadiene modified asphalt measured using dynamic mechanical analysis. Also direct tension results for SB (50% butadiene) -modified asphalt binders showed a marked increase in low temperature failure strains. • The performance-based specifications (SHRP) show good correlation with mixture performance. The best correlations were observed between the binder's Theological properties and the load-associated fatigue and low-temperature thermal cracking resistance. For permanent deformation, it was observed that the aggregate plays a significant role in the resulting rutting. Further testing and field studies are required to validate these laboratory measurements. • Asphalt-rubber mixtures have been shown to have useful properties with respect to distresses observed in asphalt concrete pavements. Most notably a large increase in viscosity and improved low-temperature cracking resistance have been measured. Only a limited body of test results exists and further testing is required to fully understand the contribution of asphalt-rubber to the mixture's performance.

Weed Control in Rainfed Cotton in Northern Ghana

Abstract In field experiments conducted at the Nyankpala Agricultural Station, Ghana, during 1976–77, soil moisture conditions appeared to be the deciding factor in determining the frequency of handweeding needed to obtain maximum seed cotton yields. In 1976, when planting was early and the late, heavy rains in October prolonged weed growth, two handweedings at 4 and 8 weeks after seeding (w.a.s.) gave comparable yields to continuous weeding and significantly better yields than an alachlor + fluometuron herbicide mixture. Supplementary weeding did not enhance the mixture's performance. In 1977, planting was relatively late and in the peak of the rainy season and so late weed growth was reduced. A single handweeding at 4 w.a.s. gave as good a yield as repeated handweeding treatments under these conditions. The alachlor + fluometuron mixture also gave adequate weed control and again supplementary weeding did not improve it significantly. In herbicide evaluation experiments, the safety and performance of pen...