Asphalt Concrete Mixtures Research Articles

Mechanical and economical feasibility of LDPE Waste-modified asphalt mixtures: pathway to sustainable road construction

This research study evaluates the impact of low-density polyethylene (LDPE) modified asphalt binder on the mechanical performance and economical feasibility of asphalt concrete (AC) mixtures. LDPE-modified mixtures were compared with conventional mixes prepared with various binders commonly used in India, i.e., VG 30, VG 40, Polymer-Modified Binder (PMB), and Crumb Rubber Modified Binder (CRMB). LDPE-modified mixtures exhibit superior mechanical performance, increasing the stiffness of AC mixtures by 171% and 125% at 25 °C and 35 °C, respectively, compared to VG 30 base binder. Additionally, the indirect tensile strength (ITS) improved by 51% over VG 30. LDPE-modified mixtures also showed improved resistance to permanent deformation, with RTIndex values up to 133.46% higher than VG 30, and higher fatigue resistance, as indicated by increased CTIndex values compared to VG 30 and CRMB. However, the CTIndex values for LDPE-modified mixtures were 26.32% and 56% lower than those for VG 40 and PMB, respectively. Pavement analysis using 3D-Move showed lesser deflections at pavement layer interfaces, resulting in higher rutting and fatigue life for LDPE-modified pavements. Furthermore, LDPE-modified pavements showed up to 57% higher fatigue life (Nf) and up to 42.33% higher rutting life (Nr) than other pavements. The economic analysis showed that the cost of LDPE-modified pavements is comparable to VG 40 and around 10% more economical than pavements containing PMB. Using LDPE also offers environmental benefits by repurposing up to 750 kg for every kilometer of single-lane pavement section having 50mm thick surface course. Overall, LDPE-modified asphalt mixtures present a sustainable and high-performance solution for asphalt pavement construction.

Effect of Waste Plastic Polyethylene Terephthalate on Properties of Asphalt Concrete Mixtures

Effect of Waste Plastic Polyethylene Terephthalate on Properties of Asphalt Concrete Mixtures

Evaluation of the Mechanical Behavior of Asphaltic Mixtures Utilizing Waste of the Processing of Iron Ore

Mineral extraction is an important operation for the economy of different countries and generates millions of tons of mining waste. In this context, and in association with the high demand for paving aggregates and the lack of raw materials for this purpose, the feasibility of using iron ore processing waste has emerged as a promising alternative. This study evaluates the physical and mechanical behavior of asphalt mixtures incorporating waste from the company Samarco S.A., collected in Mariana-MG, to replace the fine aggregate in asphalt concrete mixtures, with a view to applications in the bearing layer of local traffic roads. Two mixtures, M2 and M3, containing 20% and 17% waste, respectively, were formulated and analyzed, compared to a reference mixture, M1. Evaluations were carried out using the Marshall method parameters, mechanical tests of resilience modulus, and fatigue life under controlled tension, as well as mechanistic analysis. Brazilian mechanistic–empirical design software (MeDiNa—v 1.5.0) contributed to this analysis. This analysis revealed that, for a traffic level of N = 5 × 106 (average traffic) on a local road, pavements containing the M1 and M3 mixtures had the same layer thicknesses (6.9 cm), as well as the same fatigue class, equal to 1. The pavement with the M2 mixture had the thickest asphalt layer (8.2 cm) and a lower fatigue class equal to 0. But if compared in terms of the percentage of cracked area over 10 years, it still offers ideal performance conditions compared to the M1 and M3 mixes. Thus, it can be considered feasible to replace fine aggregate with iron ore waste in asphalt concrete for use on local roads in the region without altering the bearing capacity of the pavement.

Evaluation of asphalt mixtures modified with low-density polyethylene and high-density polyethylene using experimental results and machine learning models

The widespread use of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) plastics has resulted in a large amount of waste plastic that requires appropriate disposal or reuse. One potential solution is to use them in the modification of asphalt concrete (AC) mixtures for more sustainable highways. To study this possibility, permanent deformation and dynamic modulus (DM) of the LDPE and HDPE modified AC mixtures was investigated by conducting flow number (FN), flow time (FT) and DM tests on Superpave gyratory compacted specimens. Machine learning models; multi-layer perceptron (MLP), radial basis function neural network (RBFNN), generalized regression neural network (GRNN) and support vector machine (SVM) were used to predict the DM on the basis of frequency and temperature parameters. The model’s performance was gauged by analyzing the root mean square error, mean relative error, and coefficient of determination. The study findings revealed that the LDPE and HDPE modified AC mixtures provide 2.07 times and 1.27 times better resistance to permanent deformation, respectively, than their counterpart. It was also found that the LDPE and HDPE modified AC mixtures have 2.1 times and 1.4 times higher DM values, respectively, than the Control AC mixtures. Among the machine learning models, MLP (R2 = 0.98) showed best accuracy in predicting DM and thus is recommended to be used in similar studies due to its robustness. Additionally, the feature importance analysis revealed that frequency has the highest impact on DM predictions, followed by temperature and the inclusion of the LDPE.

Pengaruh Penambahan Zat Aditif Anti Striping (WETFIX-BE) Pada Kinerja Campuran Aspal Beton (AC-WC)

The asphalt concrete layer is the top layer of road pavement construction which is in direct contact with vehicle wheel loads and the influence of weather. One type of asphalt concrete layer is Asphalt Concrete – Wearing Course (AC–WC). Asphalt functions as an aggregate adhesive. In asphalt concrete mixtures it is very important to maintain its characteristics. During the maintenance period, the mixture will easily experience striping or peeling of the asphalt from the aggregate. To maintain and improve the properties of asphalt, one way is to use an anti-striping additive, this additive is Wetfix-Be, which is a compound that contains chemicals. Anti-peeling materials are only used if the residual Marshall stability value (IRS-Index of Retained Stability) or the Indirect Tensile Strength Ratio (ITSR) value of the asphalt mixture before adding the anti-peeling agent is less than required. If an anti-flaking agent must be used then before the anti-flaking agent is added to the mixture, the residual marshall stability (after 24 hour immersion, 60 °C) must be at least 75%.

Development of a flow diagram for the production of asphalt concrete mixture using polyethylene waste, contaminated with oil products

Large quantities of low-pressure polyethylene containers used for transportation and storage of oil products (motor oils) entail higher environmental risks produced by their utilization or disposal. An urgent scientific task is to search for new ways for utilization of such containers, to involve them in production of new target products without thorough cleaning of waste from contaminants and residues of motor oils. The present study involved crushed containers used for storage and transportation of motor oil in order to explore the possibility of including polyethylene in the production of asphalt concrete mixture. A sample, containing 17.5% of low-pressure polyethylene (contaminated with motor oil by 8% of asphalt mass), and a control sample of asphalt concrete mixture free of polyethylene, were made in order to investigate the change of properties, occurring in the low-pressure polyethylene asphalt concrete. Results. The study assessed main physical and mechanical properties of asphalt concrete samples containing low-pressure polyethylene and motor oil. According to the assessment, a number of properties exceed the values stated in GOST 9128-2013. In addition, the study results included development of technological regulations for producing asphalt concrete mixture with polyethylene as well as the flow diagram for obtaining asphalt concrete mixture. Using polyethylene waste contaminated with motor oil in the production cycle of asphalt concrete mixtures will reduce the consumption of raw materials for asphalt concrete production and the negative impact on the environment.

Performance assessment of sustainable asphalt concrete using steel slag, with an artificial neural network prediction of asphalt concrete behavior

This research evaluated the possibility of using Moroccan steelworks slag as a substitute for natural aggregates in asphalt mixtures, using chemical and mechanical analyses to demonstrate its compatibility with this application. Two granular mixtures, M1 and M2, were developed, incorporating respectively 15% and 25% natural sand (0/1.25) with slag aggregates to obtain granular mixtures complying with local standards. These mixtures were then tested with three different asphalt contents (4.7%, 5.2%, and 5.7%). Mechanical tests, including a gyratory compactor, Marshall stability, and Duriez strength, were carried out. In particular, the M1:5.2 and M2:5.2 mixtures met compaction criteria and showed remarkable Marshall Stability values, reaching 23.49 kN and 21.81 kN respectively. In comparison, the control mixtures only achieved a maximum stability of 11 kN. Thermal properties were also assessed, showing that the maximum thermal conductivity was achieved at an asphalt content of 5.2%. The slag-based mixtures, M1 and M2, showed higher thermal conductivity than the control mix M0, with maximum values of 0.74W/mK for M1 and 0.86W/mK for M2, compared with 0.56W/mK for M0. The overall results show that the M1 and M2 mixtures had improved thermal and mechanical properties compared with the M0 control mix. Artificial neural network (ANN) modelling was carried out using Marshall Test data. It showed excellent performance in predicting the stability and flow properties of asphalt mixtures. These results suggest that incorporating steelmaking slag into asphalt concrete mixtures was an effective strategy for simultaneously improving their thermal and mechanical properties.

Gradation optimization of AC-20 asphalt mixture based on the fuzzy analytic hierarchy process and comprehensive evaluation method

The aggregate gradation of asphalt mixture is one of the most important factors affecting the service life of asphalt pavement. In order to study the gradation of asphalt mixture with the best comprehensive performance, this study puts forward a new method of mineral aggregate gradation optimization based on the fuzzy analytic hierarchy process and comprehensive evaluation method, aiming at the multi-level and multi-index evaluation of the road performance of asphalt mixture. First, the orthogonal test design method is applied to design nine target gradations with coarse aggregate (>4.75 mm) and fine aggregate (<4.75 mm) of AC-20 (asphalt concrete) mixture serving as two factors and the upper, middle, and lower positions of the gradation curve as three levels, and then the road performance test research is carried out. Second, a comprehensive model for evaluation of road performance of mineral aggregate gradation is established. A fuzzy complementary judgment matrix is constructed, and the index weights of each level and the hierarchical total ranking weight are calculated. Then, the membership function is introduced into the comprehensive evaluation model for the road performance of mineral aggregate gradation, and the membership values of each index of asphalt mixture road performance are obtained. Finally, the fuzzy comprehensive evaluation method is used to find out the comprehensive evaluation value of the road performance of the nine graded asphalt mixtures, and the mineral aggregate gradation is optimized. The research results show that the 1# gradation of the asphalt mixture has the highest comprehensive road performance evaluation value, and the combination of the fuzzy hierarchical analysis process and comprehensive evaluation method can more objectively and comprehensively evaluate the comprehensive road performance of the asphalt mixture and provide a useful reference for the optimal selection of asphalt mixture mineral gradation.

Development of the technology of restoration of the tail part of the body of the cutter of the road cutter

Purpose. The purpose of this work is to study the patterns of wear and develop a technology for restoring the tail part of the cutter body of the road cutter. They conducted an analysis of the wear of the cutters and found that most of them are suitable for use, since the shape of the carbide tip has not changed much and can still be used for grinding asphalt-concrete mixture. Methodology/approach. The method of restoration of the caudal part of the body of the incisors was developed and proposed. The recovery route is as follows: 1. Cleaning the incisor. 2. Heating the tail part of the cutter with a propane-oxygen flame. 3. Plastic deformation of the cutter body in the die. 4. Air cooling. 5. Control measurement of size changes. The recommended heat treatment temperature for plastic deformation depends on the concentration of carbon and alloying elements of the steel, and lies in the temperature range from 800 to 1280°С, the heating time is 1.33 min. Before distribution, the body of the cutter was heated using a propane-oxygen flame. Deposition was carried out in a closed die with the help of a special Poisson. A cutter head was placed in the matrix, on which a guide with a punch was installed. The developed technology of restoration of the tail part of the incisor by handing. Findings. According to the proposed technology, the tail part of the cutter body is distributed from 0.04 mm to 0.73 mm per side. Research limitations/implications. In this way, the cutters of the road cutters are restored to almost the dimensions of a new part, which enables repeated use.

Utilization of Buton Granular Asphalt (BGA) as Asphalt and Filler Content Substitution Material – in Asphalt Concrete Mixture- Wearing Course

Roads are one of the infrastructure that is urgently needed in improving the accessibility of an area and has a crucial role as a connecting infrastructure that facilitates the transportation of people and goods. This road must be able to handle the volume of traffic according to the plan, so planning must ensure smooth transportation. Asbuton can be used as a binding material on road pavements. However, the use of buton asphalt as a road construction material in Indonesia has not had a significant impact on infrastructure development carried out by the government. The purpose of this study is to analyze the characteristics of Marshall’s test value using Buton Granural Asphalt as a substitute for filler and Fine Aggregate in the mixture of Asphalt Concrete – Wearing Course (AC – WC). The type of data used is primary data obtained from laboratory test results and secondary data obtained from SNI Bina Marga 2018 rev.2. The results showed that with the addition of 19% BGA (Buton Granular Asphalt) as a filler and fine aggregate material, the stability of the mixture could be increased up to 2369,8 kg with the addition of BGA, when compared to aggregate without BGA, the stability value was higher. Based on the test of the characteristics of the 0% BGA mixture marshall obtained a density value of 2,304 t/m³, stability of 1240,6 kg, fatigue of 3.4 mm, Marshall Quotient (MQ) of 366,0 kg/mm, VMA of 16,3%, VFB of 76.2%, VIM of 3.9%. Marshall testing on a mixture of 19% BGA obtained a density value of 2325,0 t/m³, Stability of 2369,8 kg, Fatigue of 3.4 mm, Marshall Quotient(MQ) of 697,1 kg/mm, VMA of 15,4%, VFB of 80,0%, VIM of 3.1%. All test parameters meet the standards set out in the 2018 General Bina Marga specification for revision 2 road and bridge construction work, so that AC-WC asphalt concrete with 0% and 19% BGA substitution can be used.

Economic and environmental assessment of the Korea urban railway and its greenhouse gas mitigation potential

Railways can simultaneously transport large quantities of freight and passengers, making them energy-efficient and economical modes of transportation. Changing the materials that constitute a significant portion of rail track systems can help mitigate climate change. Gravel and concrete trackbed methods are commonly employed in railway construction. This study proposes the utilization of the asphalt concrete trackbed method, which is currently being researched and developed in South Korea, in addition to traditional gravel and cement concrete methods, and presents its economic feasibility and environmental benefits. The asphalt concrete trackbed method, which has already been implemented in regions such as China, Australia, and Europe, can also be applied in other areas. This study analyzed the carbon emissions and economic feasibility in the construction, usage, and disposal stages of cement concrete and asphalt concrete trackbeds. Previous research on carbon emissions analysis has faced challenges in applying geographical and climatic, as well as energy sources, to individual cases in the context of construction in Korea. Using the Korean Life Cycle Inventory database, this study indicated that asphalt concrete exhibits approximately 2.65-times lower carbon emissions than cement concrete. In Korea, railway construction involves 1,998 tons of asphalt concrete mixture, 1,820 cubic meters of cement concrete, and 59 tons of rebar per kilometer. Furthermore, the asphalt concrete trackbed method shows potential cost savings of approximately 29,000 EUR when converted to the 2021 EAU value. Thus, asphalt concrete trackbeds not only provide environmental benefits, they are also economically viable. However, further research is required to establish precise standards for on-site construction. This study is expected to provide foundational data for promoting the widespread adoption of asphalt concrete trackbeds in areas that produce asphalt concrete.

Low-Temperature Mixed Mode (I/II) Fracture Characterization of Polymerized Sulfur Modified AC Mixtures

In this study, asphalt concrete (AC) mixtures were modified with polymerized sulfur, using PG58-22 bitumen, and crushed siliceous aggregate. Modifications involved replacing the base binder with 20%, 30%, and 50% polymerized sulfur, compared to a control mix with no replacement. The mixtures were subjected to Single Edge Notched-Beam (SE(B)) fracture tests under mixed mode (I/II) conditions with notch offset value of 48 mm, with temperatures ranging from 0 °C to -20 °C. These tests, focusing on the mixtures' response to mixed mode loading, provided load-displacement curves, enabling the determination of fracture energy. Results indicated an increase in fracture energy for 20% and 30% sulfur-modified mixtures. However, a trend towards increased embrittlement was also observed, as fractures occurred at lower displacements. Significantly, higher sulfur content correlated with similar or decreased mixed-mode (I/II) fracture energy, suggesting an improved resistance to low-temperature cracking for lower replacement percentages.

Mechanical behaviour of bridge expansion joint interfaces filled with novel polyurethane-modified asphalt

The use of Asphalt Plug Joints (APJs) in bridge construction has rapidly expanded due to their distinct advantages in driving comfort, shock absorption, noise reduction, and maintenance ease. However, prolonged exposure to vehicular loads and environmental factors renders this expansion joint susceptible to interface effects and stress concentration, leading to damage, particularly at the interface layers between the expansion joint pavement and the expansion joint-cross joint plate contact areas. To address issues such as stress concentration, this study proposes a polyurethane-modified asphalt concrete mixture as the joint filling material. Pull-out and inclined shear tests are used to identify a bonding agent with superior adhesive properties. Additionally, a finite element model of pull-out specimens containing bilinear cohesive elements is established to simulate the cohesive damage process of the interface layers. Through parameter design analysis, the study examines the influence of individual parameter variations on interface damage behavior, obtaining comprehensive simulated analysis data on interface crack resistance performance. Based on interface test data, a bilinear cohesive force model and a viscoelastic material model of the asphalt concrete mixture are employed to establish a scaled-down model of the improved geometry design of the new APJ. This model simulates the interface mechanical characteristics of APJs under temperature effects and vehicle loads. The results demonstrate that the bilinear cohesive force model effectively simulates the nonlinear behavior of interface bonding slip. Furthermore, the use of SZ interface bonding agents and improvements in cross joint plate form can effectively mitigate issues such as uneven settlement and low-temperature cracking.

Innovative use of nanomaterials for improving performance of asphalt binder and asphaltic concrete: a state-of-the-art review

ABSTRACT Rising costs of constructing and maintaining asphaltic concrete pavements present a challenge requiring an alternative solution. Nanomaterials can be cost-effectively integrated with asphalt binder to provide beneficial effects for asphaltic concrete mixture. This paper investigated seven different types of nanomaterials, namely nanoclay, carbon nanotube, nanosilica, nano-titanium dioxide, nano-zinc oxide, graphene oxide, and carbon nanofiber by examining their production methods, benefits, applications, and limitations based on the data available in published literature. Challenges and limitations discussed include economic, production, and blending problems, some of which are due to the lack of research on the topic. This study provides a framework from which the pavement engineering community can conduct experimental research on nanomaterials for applications in asphaltic concrete pavements. The review of previous studies reveals that new asphalt binders and asphaltic concrete mixtures incorporating nanomaterials can be developed for improved performance of flexible pavements. It is expected that further research can be devoted to overcoming the current challenges faced by aging transportation infrastructure through use of nanomaterials in asphalt binder and asphaltic concrete. Above all, research gaps in the present state of knowledge have been identified and certain recommendations are given for future investigations.

Study on Low Temperature Cracking Resistance of Carbon Fiber Geogrid Reinforced Asphalt Pavement Surface Combined Body.

Currently, there are limitations in the research on the use of carbon fiber geogrids to prevent low-temperature cracking in asphalt pavements. This study aims to comparatively investigate the effects of carbon fiber-based geogrid type and dense-graded asphalt concrete mixture (AC) surface combined body (SCB) type on the low-temperature cracking resistance of reinforced asphalt pavement through low-temperature bending damage tests. Two geogrid types were prepared: a carbon fiber geogrid (CCF) and a glass/carbon fiber composite qualified geogrid (GCF). Two SCB types were studied: AC-13/AC-20 and AC-20/AC-25. The results show that the improvement in the flexural tensile strength of CCF is similar to that for GCF. Moreover, under reinforced conditions, the improvement in the low-temperature cracking resistance of AC-20/AC-25 is better than that for AC-13/AC-20 by 16.26-24.57%. Based on the analysis, the reasonable ratio range of the aperture sizes to the major particle sizes in the dense gradation can achieve a more effective interlocking effect. This can improve the low-temperature cracking resistance of carbon fiber-based geogrid-reinforced samples. Then, increasing the bending absorption energy is a key way of improving the low-temperature cracking resistance of carbon fiber-based geogrid reinforcements. Eventually, the fracture type of carbon fiber-based geogrid-reinforced samples is a mixed plastic-brittle fracture. These results can provide a reference for the road failure analysis of geogrid-reinforced asphalt pavement.

Experimental Investigation of Water Vapor Concentration on Fracture Properties of Asphalt Concrete.

The effect of moisture on the fracture resistance of asphalt concrete is a significant concern in pavement engineering. To investigate the effect of the water vapor concentration on the fracture properties of asphalt concrete, this study first designed a humidity conditioning program at the relative humidity (RH) levels of 2%, 50%, 80%, and 100% for the three types of asphalt concrete mixtures (AC-13C, AC-20C, and AC-25C).The finite element model was developed to simulate the water vapor diffusion and determine the duration of the conditioning period. The semi-circular bending (SCB) test was then performed at varying temperatures of 5 °C, 15 °C, and 25 °C to evaluate the fracture energy and tensile strength of the humidity-conditioned specimens. The test results showed that the increasing temperature and the RH levels resulted in a lower peak load but greater displacement of the mixtures. Both the fracture energy and tensile strength tended to diminish with the rising temperature. It was also found that moisture had a significant effect on the tensile strength and fracture energy of asphalt concrete. Specifically, as the RH level increased from 2% to 100% (i.e., the water vapor concentration rose from 0.35 g/m3 to 17.27 g/m3), the tensile strength of the three types of mixtures was reduced by 34.84% on average, which revealed that the water vapor led to the loss of adhesion and cohesion within the mixture. The genetic expression programming (GEP) model was developed to quantify the effect of water vapor concentrations and temperature on the fracture indices.

Определение параметров реологической модели по данным лабораторных исследований

Different types of models are used to study the stress-strain behavior of asphalt concrete mixture during compaction. For modeling it is necessary to know the values of model parameters in the whole range of changes in the characteristics of the compacted material. The aim of the paper is to develop a methodology for determining model parameters based on the results of laboratory creep-recovery testing of asphalt-concrete mixture. In the paper, a model reflecting elastic, visco-elastic and visco-fluid properties of the compacted material is adopted. A differential equation representing the law of behavior of the asphalt-concrete mixture layer under load is obtained. The stages of creep-recovery testing are analytically described, namely: rapid loading with a constant load and deformation under this load; load removal and recovery. Initial conditions for the mentioned stages are determined. Taking into account the initial conditions, analytical expressions of the laws of deformation of the model under the action of a constant load and in the process of recovery are obtained. The methodology of laboratory experiments on creep-recovery is described, according to the results of which the required values of the model parameters with minimum absolute error are obtained. The developed methodology allows to determine the parameters of the model describing the stress-strain behavior of asphalt-concrete mixture of different density and temperature. Consequently, it is possible to simulate the behavior of the asphalt concrete mixture layer at the preliminary, main and final stages of compaction in order to determine the effective operating modes of compaction equipment.

Fatigue performance analysis of fine aggregate matrix using a newly designed experimental strategy and viscoelastic continuum damage theory

Fine aggregate matrix (FAM), as the matrix phase in asphalt concrete (AC), significantly affects the fatigue behavior of AC. To accurately assess the mechanical properties of FAM, a newly designed experimental strategy for FAM testing was developed, and the viscoelastic continuum damage theory (VECD) theory was applied to analyze FAM’s fatigue cracking characteristics. In this study, a dumbbell-shaped geometry for dynamic shear rheometer testing was designed and verified through the FE-aided method. Subsequently, three AC mixtures’ FAM specimens with this special geometry were fabricated for the frequency sweep and linear amplitude sweep tests. Results showed that the specially designed specimens effectively capture the viscoelastic and fatigue properties of FAM with high replicability. Analyses based on the VECD theory indicated that FAM of porous asphalt (FAM(PA13)), featuring a higher asphalt content, exhibits a significant reduction in pseudo stiffness with increasing damage at the initial stage, but the reduction rate diminishes as damage progresses when compared to the other two FAMs. It was speculated that the higher aggregate content in FAM of dense-graded AC mixture (FAM(AC20) induces stress concentrations in the asphalt mastic near the protrusion areas of aggregates, thereby rendering the sample more susceptible to damage. The proposed methods will be readily extended to characterize other mechanical properties of FAM.

STABILIZING ADDITIVE FOR CRUSHED STONE-MASTIC ASPHALT CONCRETE BASED ON A LOW-GRADE PRODUCT AND WASTE FROM THE PRODUCTION OF CHRYSOTILE ASBESTOS

The results of a study of adsorption activity for bitumen and the physical and mechanical characteristics of the additive for crushed stone-mastic asphalt concrete (SMA), made on the basis of low-grade chrysotile and dusty waste from the enrichment of chrysotile-asbestos production, are presented. Structuring of the surface of layered magnesium silicates 3MgO 2SiO2 2H2O by treatment with dilute solutions of mineral acids is proposed, in which magnesium dissolution occurs only from the surface layers of magnesium silicate. At the same time, due to the structural features of the tubular structure - multilayering, the initially fibrous structure of magnesium hydrosilicate is preserved, and a layer enriched with silicon is formed on the surface of the fibers. As a result, the surface acquires a more amorphous state, which causes an increase in adsorption activity for bitumen. Based on the results of establishing the physical and mechanical characteristics of an additive made from low-grade chrysotile and powdered waste chrysotile-asbestos in the prepared crushed stone-mastic asphalt concrete mixture (ShchMAS-20), it is shown that the selected composition meets all the requirements of GOST 31015-2002 “Asphalt concrete mixtures and crushed stone asphalt concrete - mastic. Technical conditions".

Advancing Sustainability and Performance with Crushed Bottom Ash as Filler in Polymer-Modified Asphalt Concrete Mixtures.

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.