Search Results (19)

Asphalt concrete pavements in many regions suffer from premature deterioration caused by low-temperature cracking and rutting resistance under heavy traffic loads and high summer temperatures. While polymer-modified bitumen is widely used to improve pavement performance, the high cost of commercial polymers restricts its extensive application. This study evaluates the potential of polymer waste as an alternative modifier for asphalt binders to enhance mechanical performance while reducing economic and environmental costs. Experimental results demonstrate that an optimal plastic waste content of 1.0–1.5% significantly improves rutting resistance and increases binder rigidity. The incorporation of 1.5% low-density polyethylene (LDPE) and high-density polyethylene (HDPE) enhances deformation resistance, elastic modulus, and temperature stability. LDPE exhibits better compatibility with bitumen and dissolves more readily, contributing to improved binder homogeneity, whereas HDPE provides higher stiffness and thermal stability. The combined use of polymer waste with styrene–butadiene–styrene (SBS) produces a pronounced synergistic effect, leading to improvements in physical and mechanical properties exceeding 25% compared to Kazakhstan regulatory standards. Increasing polymer waste content further enhances the rigidity of both the binder and asphalt concrete, thereby improving rutting resistance and plastic deformation at elevated temperatures. The proposed approach offers a cost-effective and sustainable solution for road construction, promoting plastic waste recycling, reducing reliance on virgin polymers, and improving pavement durability, particularly under the climatic and traffic conditions of Kazakhstan. Full article

The need for potentially more sustainable road rehabilitation solutions has driven the use of reclaimed asphalt pavement (RAP) in bituminous mixtures. However, high-RAP content remains a technical challenge due to binder ageing, which increases mixture stiffness and adversely affects its mechanical performance. The aim of this research is to evaluate three strategies for correcting aged binder in asphalt concrete (AC) 16 surf S mixtures containing 50% RAP: rejuvenator, regenerator, and softer virgin bitumen. To this end, four asphalt mixtures were evaluated through tests on air void content, water sensitivity, resistance to permanent deformation, and stiffness modulus, in accordance with European standards. The results show that the reference mixture without binder correction exhibits excessive stiffness, whereas the mixture incorporating a rejuvenator showed the most favorable combination of the mechanical indicators evaluated, combining a significant reduction in stiffness modulus with high water resistance and adequate rutting resistance. The mixture with regenerator showed an intermediate response, while the exclusive use of a softer bitumen did not achieve satisfactory overall performance. The results confirm that the use of high-RAP contents in AC 16 surf S mixtures can be feasible, provided that an appropriate strategy for rheological correction of the aged binder is applied. Full article

The main goal of this study is to evaluate the feasibility of designing high-performance MASAI mixtures produced at ambient temperature. For this purpose, the impacts of certain variables, such as the type and amount of asphalt emulsion and the use or non-use of RAP, on its performance are evaluated. Subsequently, its stiffness modulus, tensile strength, permanent deformation, and resistance to thermal cracking were evaluated and compared against a conventional dense-graded asphalt concrete (AC 16) and an open-graded (BBTM11B) hot-mix asphalt used for wearing courses. The results showed that these materials could represent more sustainable and good solutions for the rehabilitation of some types of pavements. Full article

The aging of asphalt mixture is one of the primary factors influencing the durability and performance of pavements. This study analyzed the influence of short-term (STOA) and long-term (LTOA) aging on hot mix asphalt (HMA) with the incorporation of recycled concrete aggregates (RCAs). The effect of aging on these types of mixtures has not been previously evaluated. HMAs were produced with 0%, 12%, and 21% RCAs (by mass), referred to as HMA Control, HMA RCA12, and HMA RCA21. These replacement percentages correspond to particles ranging between 19 and 12.5 mm (12%) and 19 and 9.5 mm (21%). The Marshall test was employed to determine the optimal asphalt content, followed by indirect tensile strength, resilient modulus, and permanent deformation resistance tests on samples subjected to STOA and LTOA. Overall, the results demonstrate that the incorporation of RCAs could improve the durability of asphalt mixtures by reducing their susceptibility to aging. Specifically, HMA RCA12 exhibited the best balance between stiffness, deformability, and resistance to aging, suggesting a favorable technical potential for its application in sustainable pavements, although additional testing is required to validate its long-term performance. Despite this, high RCA contents may reduce resistance to rutting and moisture damage. The results suggest that the optimal performance is achieved by balancing binder content and aggregate absorption to minimize susceptibility to aging. Full article

Microwave heating is a method with a uniform heating effect and environmental friendliness in in-place hot recycling, but the microwave absorption capacity of traditional asphalt mixtures is still insufficient. As an excellent microwave-absorbing material, magnetite powder has the characteristics of high temperature resistance, corrosion resistance, and good thermodynamic stability. This study selects it as the microwave-absorbing material, prepares AC (Asphalt Concrete) type and SMA (Stone Mastic Asphalt) type microwave asphalt mixtures by adjusting its content, and investigates its influence on the microwave-heating characteristics and pavement performance of the mixtures. Simulations of the microwave-heating process of AC-type mixtures using COMSOL software (COMSOL Multiphysics 6.2) show that magnetite powder achieves optimal performance in terms of heating effect and economic efficiency when its content is 0.5%. Subsequently, laboratory tests are conducted to study the wave absorption and temperature rise performance of AC and SMA microwave asphalt mixtures; combined with economic factors, the optimal contents of magnetite powder for the two types of mixtures are determined to be 0.5% and 1%, respectively, and at the same time, these results are explained based on multiple physical theories. Furthermore, pavement performance is investigated through laboratory tests, including high-temperature rutting tests, low-temperature bending tests, immersed Marshall tests, and freeze–thaw cycle durability tests, and the results indicate that the high-temperature performance, low-temperature performance, and water stability of the microwave asphalt mixtures all meet the specification requirements for pavement performance. Subsequently, after 15 freeze–thaw cycles, the splitting tensile strength retention rate and stiffness modulus of the two types of mixtures show minimal differences from those of ordinary mixtures, and there is no durability degradation caused by the incorporation of magnetite powder. Finally, outdoor environment verification is carried out, and the results show that under complex conditions such as environmental factors, the wave absorption and temperature rise rates of AC and SMA mixtures at optimal contents are 52.2% and 14.6% higher than those of ordinary AC and SMA asphalt mixtures, respectively. In addition, these microwave asphalt mixtures have the advantages of both sustainability and reduced carbon emissions. By combining simulation methods and experimental verification, this study finally prepared two types of microwave asphalt mixtures with excellent performance, not only improving the microwave absorption and heating performance of asphalt mixtures, but also reducing environmental pollution and energy consumption, which conforms to the development of green transportation. Full article

Amid the growing demand for sustainable pavement solutions and the need to incorporate recycled materials into construction practices, this study explored the viability of using crushed thermal power plant bottom ash as a filler in polymer-modified asphalt concrete mixtures. Conventional lime filler was replaced with bottom ash at varying levels (0%, 25%, 50%, and 75%), and the resulting mixtures were evaluated using several performance tests. The optimal replacement level was determined to be 25%, based on the results of the indirect tensile strength (ITS) test. Comparisons between the control mixture and the 25% bottom ash-modified mixture were conducted using the dynamic modulus test, Cantabro test, Hamburg wheel tracking (HWT) test, and tensile strength ratio (TSR) test. The findings indicate that the 25% bottom ash-modified mixture demonstrated improved performance across multiple parameters. The HWT test showed enhanced rut durability, with a recorded depth of 7.56 mm compared to 8.9 mm for the control mixture. The Cantabro test results revealed lower weight loss percentages for the modified mixture, indicating better abrasion resistance. The dynamic modulus test indicated higher resilience and stiffness in both high- and low-frequency stages. The TSR test highlighted improved moisture resistance, with higher TSR values after 10 wet-drying cycles. These improvements are attributed to the fine particle size and beneficial chemical composition of bottom ash, which enhance the asphalt mixture’s density, binder-aggregate adhesion, and overall durability. The results suggest that incorporating 25% crushed bottom ash as a filler in polymer-modified asphalt concrete mixtures is a viable and sustainable approach to improving pavement performance and longevity. Full article

Nanomaterials enhance the performance of both asphalt binders and asphalt mixtures. They also improve asphalt durability, which reduces resource consumption and environmental impact in the long term associated with the production and transportation of asphalt materials. Thus, this paper studies the effectiveness of Nano Calcium Carbonate (Nano CaCO₃) and Nano Hydrated Lime (NHL) as modifiers and examines their impact on ranges from 0% to 10% through comprehensive laboratory tests. Softening point, penetration, storage stability, viscosity, and mass loss due to short-term aging using the Rolling Thin Film Oven Test (RTFO) were performed on asphalt binders. Results indicated a significant improvement in binder stiffness, particularly at 4% Nano CaCO₃ and 6% NHL content by weight. Dynamic Shear Rheometer (DSR) tests further revealed substantial improvements in rutting resistance, with NHL exhibiting superior high-temperature stability and a notable increase in the rutting factor. Marshall stability tests on asphalt concrete (AC) mixtures showed a 22.3% increase in stability with 6% NHL by weight, surpassing the 20.2% improvement observed with Nano CaCO₃ and indicating enhanced load-bearing capacity. The resilient modulus of the mixtures consistently increased with the addition of NHL, suggesting improved durability in rutting. Moisture susceptibility tests revealed that NHL significantly enhances moisture resistance, exceeding the 80% TSR benchmark at just 2% content by weight and reaching an impressive 94.6% at 10% content by weight. In contrast, Nano CaCO₃ demonstrated a more gradual improvement, achieving an 88.2% TSR at 10% content. Furthermore, permanent deformation analysis indicated a 68.64% improvement in rutting resistance with 10% NHL content by weight, exceeding Nano CaCO₃’s improvement rate. Optimal fatigue resistance was achieved at 4% for Nano CaCO₃ and 6% for NHL by weight, with respective CT index improvements of 30% and 35.4%, showing NHL’s consistent benefits across various nanomaterial contents. Overall, the study suggests that both Nano CaCO₃ and NHL positively impact asphalt performance, with NHL offering more pronounced benefits across a range of properties. These findings provide valuable insights for pavement engineers and underscore NHL’s potential as an effective additive in asphalt mixture design. Real-world applications and validations are essential for a comprehensive understanding of these nanomaterials in practical pavement engineering scenarios. Full article

This paper studies the decay law of low-temperature crack resistance performance of rubber powder basalt fiber composite-modified porous asphalt concrete (CM-PAC) under medium- and high-temperature water erosion. Firstly, the prepared Marshall specimens were subjected to water erosion treatment at different temperatures of 20 °C, 40 °C, and 60 °C for 0–15 days. Then, the processed specimens were subjected to low-temperature splitting tests, and acoustic emission data during the splitting test process were collected using an acoustic emission device. It can be seen that the low-temperature splitting strength and low-temperature splitting stiffness modulus of CM-PAC gradually decrease with the increase in water erosion time. The maximum reduction rates of the two compared to the control group reached 72.63% and 91.60%, respectively. The low-temperature splitting failure strain gradually increases. Under the same erosion time, the higher the temperature of water, the more significant the amplitude of changes in the above parameters. In addition, it is shown that as the water erosion time increases, the first stage of loading on the specimen gradually shortens, and the second and third stages gradually advance. As the water temperature increases and the water erosion time prolongs, the acoustic emission energy released by the CM-PAC specimen during the splitting process slightly decreases. The application of acoustic emission technology in the splitting process can clarify the changes in the failure pattern of CM-PAC specimens during the entire loading stage, which can better reveal the impact of medium- to high-temperature water on the performance degradation of CM-PAC. Full article

The main purpose of this paper is to present the development of a new predictive model intended for the calculation of stiffness modulus |E*| determined by a four-point bending beam test (4PBB or 4PB-PR). The model developed, called model A, was based on the Witczak model, which was developed for the dynamic-modulus (DM) method. Most of the asphalt mixtures used to develop the model were high-modulus asphalt concrete (HMAC). The most commonly used methods for determining the stiffness modulus |E*| of asphalt mixtures were also discussed. The paper presents the results of the study for 10 asphalt mixtures but 8 of them were used to develop the predictive model. In addition, the results of complex shear modulus G* tests on neat and modified bituminous binders carried out in a dynamic shear rheometer (DSR), necessary for the development of a predictive model, are presented. The tests carried out in the dynamic shear rheometer had significant measurement uncertainties. The results of the volumetric parameters of the asphalt mixtures are also reported. The developed model A has maximum absolute errors e = 1930 MPa (p = 95%) and maximum relative errors re = 50% (p = 95%). The distribution of the absolute errors of the model, after discarding outliers, has a normal distribution as in the development of other models of this type, which was confirmed by appropriate statistical tests. On the basis of the tests and calculations carried out, it was concluded that, in order to increase the precision of the predictive models, it is advisable to reduce the measurement uncertainty of the bitumen complex shear modulus G*. For the developed model A, the limiting values of the stiffness modulus |E*| are also shown, within which the determined stiffness modulus should fall. Full article

The present paper investigates the viscoelastic stress-strain responses of laboratory and plant produced warm mix asphalt mixtures containing basalt fiber dispersed reinforcement. The investigated processes and mixture components were evaluated for their efficacy in producing highly performing asphalt mixtures with decreased mixing and compaction temperatures. Surface course asphalt concrete (AC-S 11 mm) and high modulus asphalt concrete (HMAC 22 mm) conventionally and using a warm mix asphalt technique with foamed bitumen and a bio-derived fluxing additive. The warm mixtures included lowered production temperature (by 10 °C) and lowered compaction temperatures (by 15 °C and 30 °C). The complex stiffness moduli of the mixtures were assessed under cyclic loading tests at combinations of four temperatures and five loading frequencies. It was found that the warm produced mixtures were characterized by lower dynamic moduli than the reference mixtures in the whole spectrum of loading conditions, however, the mixtures compacted at the 30 °C lower temperature performed better than the mixtures compacted at 15 °C lower temperature, specifically when highest testing temperatures are considered. The differences in the performance of plant and laboratory produced mixtures were ascertained to be nonsignificant. It was concluded that the differences in stiffness of hot mix and warm mixtures can be attributed to the inherent properties of foamed bitumen mixtures and that these differences should shrink in time. Full article

The utilization of recycled materials is an important issue in the context of environmental protection. The large amounts of recycled material recovered from the demolition of asphalt road structures indicate the need to find new ways of utilizing them. In the case of road renovation projects, large amounts of recycled materials are, in most cases, recovered in the form of reclaimed asphalt pavement (RAP), reclaimed concrete (RC) and recycled aggregate (RA). To focus on the effects of the use of recovered materials (RAP, RC and RA), the same composition was used for all of the analyzed mixtures in terms of foamed bitumen (FB) and Portland cement (CEM) content. The scope of laboratory tests included the specification of the following parameters: the amount of air void content Vm, the determination of axial compression strength at +25 °C, indirect tensile strength (ITS) at +25 °C, water resistance, TSR, water and frost resistance, WR_W+M stiffness modulus (IT-CY) at 13 °C, dynamic dynamicmodulus. The plan of the experiment assumed addition recycled material in quantities between 20% and 80% in increments of 20%. The obtained results indicate that both the type and quantity of recycled material significantly affect the properties of the cold-recycled mixture with foamed bitumen. Using reclaimed asphalt pavement and recycled cement concrete guarantees high levels of stiffness in the recycled mixture. Howeverin the case of recycled aggregate, the authors did not observe any visible changes in the dynamicdynamic modulus, irrespective of the loading conditions. It was also indicated that it is necessary to reduce the quantity of reclaimed asphalt pavement in the composition of the FB-RCM mix to maintain the required air void content. Full article

This paper presents a study about a Machine Learning approach for modeling the stiffness of different high-modulus asphalt concretes (HMAC) prepared in the laboratory with harder paving grades or polymer-modified bitumen which were designed with or without reclaimed asphalt (RA) content. Notably, the mixtures considered in this study are not part of purposeful experimentation in support of modeling, but practical solutions developed in actual mix design processes. Since Machine Learning models require a careful definition of the network hyperparameters, a Bayesian optimization process was used to identify the neural topology, as well as the transfer function, optimal for the type of modeling needed. By employing different performance metrics, it was possible to compare the optimal models obtained by diversifying the type of inputs. Using variables related to the mix composition, namely bitumen content, air voids, maximum and average bulk density, along with a categorical variable that distinguishes the bitumen type and RAP percentages, successful predictions of the Stiffness have been obtained, with a determination coefficient (R²) value equal to 0.9909. Nevertheless, the use of additional input, namely the Marshall stability or quotient, allows the Stiffness prediction to be further improved, with R² values equal to 0.9938 or 0.9922, respectively. However, the cost and time involved in the Marshall test may not justify such a slight prediction improvement. Full article

The transportation sector is considered one of the driving forces behind the increased release of greenhouse gases (GHGs), with road transport being this sector’s main emissions contributor. In turn, efforts should be devoted to reducing emitted GHGs from this sector, and many such opportunities lie in the road transport life cycle. This paper investigated fourteen emission reduction scenarios based on the green initiatives issued by the Abu Dhabi Government. The explored measures are either related to road works and road municipal services or to traffic movement. The proposed measures were evaluated with reference to a baseline study previously reported by the authors for three different road projects in Abu Dhabi city. Findings reveal that normalized GHG emission reduction could be significantly reduced by (i) replacing 30% of internal combustion engine passenger cars with battery electric vehicles where the power demand is covered almost equally from nuclear and liquified natural gas (LNG) sources, (ii) reducing the number of passenger cars by 10%, and (iii) having one-fifth of passenger cars powered by LNG. A lesser significant reduction could be achieved by replacing conventional lamps with light-emitting diode (LED) lamps or by having one-fourth of lighting powered by solar energy. Even lesser reduction could be achieved by (i) replacing a portion of Portland cement with ground granulated blast furnace slag in concrete structures, (ii) fully utilizing treated sewage effluent for roadside-plant irrigation, (iii) reducing desalinated water used for roadside-plant irrigation by 20%, and (iv) increasing the number of higher efficiency passenger cars by 10%. Replacing hot-mix asphalt with warm-mix asphalt and using asphalt with a high stiffness modulus in the base layer results in low emission reduction. The use of 15% recycled asphalt or the use of 50% recycled aggregate in road construction has the least impact on emission reduction. When all explored scenarios were combined, an overall normalized GHG emissions reduction of 9–17% during the road project life cycle could be achieved. Full article

Hot-mix asphalts exposed to hot weather and high traffic volumes can display rutting distress. A material that can be used to increase the stiffness of asphalt binders is gilsonite. On the other hand, from an environmental point of view, the virgin natural aggregates of asphalt mixtures can be replaced with recycled concrete aggregates. For these reasons, this study modified the asphalt binder with gilsonite by wet-process to improve rutting resistance, and replaced (by mass and volume) part of the coarse fraction of the aggregate with recycled concrete aggregate in two hot-mix asphalts with different gradations. Unlike other studies, a larger experimental phase was used here. Marshall, indirect tensile strength, resilient modulus, permanent deformation, fatigue resistance, and Cantabro tests were performed. An ANOVA test was carried out. If the replacement of the virgin aggregate by recycled concrete aggregates was made by volume, both materials (gilsonite and recycled concrete aggregate) could be used in hot-mix asphalts for thick-asphalt layers in high temperature climates and any level of traffic. The use of both materials in hot-mix asphalts is not recommended for thin-asphalt layers in low temperatures climates. It is not advisable to replace the aggregates by mass. Full article

Half-warm mix asphalt (HWMA) mixtures can be produced at temperatures ranging from 100 °C to 130 °C, depending on the production methods used. The lowest mixing temperature can be achieved by using water-foamed bitumen. The mixture should be characterized by a long service life, defined by the resistance to permanent deformation and high stiffness modulus at temperatures above zero. It is therefore important to ensure the adequately high quality of the bitumen binder. Bitumen 50/70 was provided with appropriate quality foaming characteristics (expansion ratio, ER, half-life, t1/2) by adding a surface-active agent (SAA) at 0.6 wt % before foaming. Then asphalt concrete (AC) 8 S was designed and produced with the recommended water-foamed binder. Hydrated lime, an additive substantially affecting asphalt concrete mechanical parameters, was used at 0, 15, 30, and 45 wt % as a partial replacement for the limestone filler. The influence of the amount of hydrated lime on the content of voids, indirect tensile stiffness modulus at −10 °C, 0 °C, +10 °C, +20 °C, and +30 °C, and the resistance to permanent deformation was investigated. Statistical analysis of the test results showed the quantity of 30% to be the optimum hydrated lime content. The AC 8 S resistance to permanent deformation was determined at the optimum hydrated lime content. The comprehensive evaluation revealed a synergistic effect between bitumen 50/70, modified before foaming with 0.6 wt % SAA and 30 wt % hydrated lime as the limestone filler replacement, and the half warm mixture AC 8 S, in terms of the standard requirements and durability of the HWMA concrete in pavement applications. Full article