AP22786668 «Scientific foundations for obtaining sustainable asphalt concrete with improved physical and mechanical characteristics based on waste from metallurgical and silicon production»

Blast furnace slag and microsilica are by-products of metallurgical production, used in the manufacture of construction materials and asphalt concrete. However, their use in asphalt concrete mixtures is currently carried out in a chaotic manner, without prior selective crushing of blast furnace slag to isolate the strongest grains, and without accounting for the influence of these components on the frost resistance of pavement. This leads to low durability of roads built with waste materials and highlights the relevance of an interdisciplinary project (at the intersection of ecology, construction, and metallurgy) aimed at developing the scientific foundations for producing durable asphalt concrete from industrial by-products, taking into account construction conditions.

The idea of the project is to improve the frost resistance and deformation–strength characteristics of asphalt concrete made from industrial waste through the synergistic effect of the combined use of selectively crushed blast furnace slag aggregate and microsilica in an optimal ratio.

1) Kunaev Vyacheslav Alexandrovich – PhD, Associate Professor, Director of the Department of Science and Innovation, Associate Professor of the Department of Technological Machines and Transport, Project Leader.

Scopus ID: 57200448577.

ResearcherID: AAR-2188-2020.

https://orcid.org/0000-0001-8283-7186 .

2) Akhmetova Gulzhaynat Esenzholovna – PhD, Associate Professor, Associate Professor of the Department of Metallurgy and Materials Science, Project Executor.

Scopus ID: 57195377183.

ResearcherID: AAX-4242-2021.

https://orcid.org/0000-0002-2081-0612

3) Batyrbek Alibek Yesimbekuly – Doctoral student, Lecturer of the Department “Energy”, Project Executor.

Scopus ID: 59213269200.

ResearcherID: NMK-8223-2025.

https://orcid.org/0000-0002-3369-6804.

4) Tavshanov Ilgar Suleymanovich – Master, Lecturer of the Department «Technological Machines and Transport», Project Executor.

Scopus ID: 58203718700.

ResearcherID: JNR-8253-2023.

https://orcid.org/0000-0002-9427-9748 .

5) Charny Dmitry Yurievich – Bachelor, Junior Researcher, Project Executor.

Scopus ID: 59914525300.

ResearcherID: NMO-0625-2025.

6) Kydyrbaeva Saltanat Zhaysanbekovna – Master, Senior Lecturer at the Department of Technological Machines and Transport, Project Executor.

Scopus ID: 57614186200.

ResearcherID: GME-7697-2022.

7) Zhaslan Rymgul Kuatkyzy – PhD, Senior Lecturer at the Department of Chemical Technology and Ecology, Project Executor (from 2025).

Scopus ID: 57200215253.

ResearcherID: HGB-6310-2022.

https://orcid.org/0000-0002-1809-8961

8) Romanov Danil Yurievich – Master’s student, Project Executor (until 2025).

For 2024 year: Multitude of factors that determine the quality indicators of asphalt concrete based on industrial waste will be established. A comprehensive optimality criterion and the main limitations for designing the composition of asphalt concrete from industrial waste will be proposed and justified. A laboratory assessment of the effect of selective crushing parameters on the change in volumetric expansion and abrasion resistance of the asphalt concrete coarse aggregate from blast furnace slag will be performed, and a mathematical model describing the correlation of these parameters will be obtained. The experimental samples of the enriched coarse aggregate for asphalt concrete from blast furnace slag will be obtained. The experimental samples of asphalt concrete with coarse aggregate of natural crushed stone and the enriched blast furnace slag will be obtained.

Participation and publication of 2 papers in the proceedings of the international conference will be ensured. 1 paper will be published in the journal recommended by Committee for Quality Assurance in the Field of Science and Higher Education of the Ministry of Science and Higher Education of the Republic of Kazakhstan.

For 2025 year: The results of determining the density, average density of the mineral part, water saturation and swelling of the asphalt concrete experimental samples will be obtained. Comparative deformation and strength characteristics of asphalt concrete with aggregate from natural crushed stone, regular and enriched aggregates from blast furnace slag will be empirically determined. Prototypes of asphalt concrete using enriched coarse aggregate from blast furnace slag and microsilica as a mineral additive will be designed and manufactured. The results of testing the prototypes of asphalt concrete with a variable content of blast furnace slag and microsilica for frost resistance, water resistance, swelling, strength and shear resistance will be obtained. A quantitative analysis of the prototypes microstructure will be carried out and patterns of distribution of the aggregate grains and voids in the structure of asphalt concrete prototypes will be established.

Participation and publication of 2 papers in the proceedings of the international conference will be ensured. 1 article (or review) will be published in a peer-reviewed scientific journal on the scientific direction of the project, indexed in the Science Citation Index Expanded of the Web of Science database and (or) having a CiteScore percentile in the Scopus database of at least 50 (fifty). 2 papers will be published in the journal recommended by Committee for Quality Assurance in the Field of Science and Higher Education of the Ministry of Science and Higher Education of the Republic of Kazakhstan.

For 2026 year: The morphology of the structure and the topography of the fracture of samples of the usual and proposed composition of asphalt concrete will be studied, which will allow to assess the effect of the mixture composition on the formation of cracks in the material structure and adhesion in the “bitumen + aggregate” system. Mathematical dependences that correlate values of structure-forming factors, physical and deformation-strength properties of asphalt concrete based on enriched slag aggregate and microsilica will be empirically established. The results of the assessment of the aggressive media impact on the characteristics of asphalt concrete containing enriched slag aggregate and microsilica will be obtained. The optimal composition and prototypes of asphalt concrete based on waste from metallurgical and silicon production with increased physical-mechanical characteristics will be obtained. The synergistic effect of the integrated use of microsilica and enriched slag aggregate in asphalt concrete will be evaluated and a mathematical model to assess the effect of microsilica and enriched slag aggregate content on the physical and mechanical characteristics of asphalt concrete will be constructed. An algorithm for selecting the composition of asphalt concrete based on man-made waste, depending on the required physical and mechanical characteristics will be developed.

Participation and publication of 2 papers in the proceedings of the international conference will be ensured.

1 article (or review) will be published in a peer-reviewed scientific journal on the scientific direction of the project, indexed in the Science Citation Index Expanded of the Web of Science database and (or) having a CiteScore percentile in the Scopus database of at least 50 (fifty). 2 papers will be published in the journal recommended by Committee for Quality Assurance in the Field of Science and Higher Education of the Ministry of Science and Higher Education of the Republic of Kazakhstan. 1 patent for a utility model will be obtained.

1 monograph and 1 textbook for students containing research results will be published.

1) Multitude of factors has been identified that determine the quality indicators of asphalt concrete based on industrial waste, which makes it possible to select and describe, using set theory, those factors that need to be taken into account and optimized in a particular design option of an asphalt concrete mixture, for example, when including a certain type of industrial waste in its composition. Based on the results of critical analysis, the following subsets (groups of factors) were distinguished: factors characterizing the mineral aggregate of asphalt concrete; factors characterizing the binder; factors characterizing the mineral filler; factors characterizing the proportional ratios of the asphalt concrete mixture components; factors determining the chemical resistance of asphalt concrete pavement to aggressive solutions; factors influencing the segregation of asphalt concrete mixtures; factors determining the heat resistance of asphalt concrete pavement; factors affecting the adhesion of bitumen to mineral aggregate grains; factors characterizing the technological process of asphalt concrete mixture preparation; factors characterizing the technological process of asphalt concrete transportation and laying; and weather–climatic factors.

2) A comprehensive optimality criterion and the main constraints for designing asphalt concrete compositions from industrial waste have been proposed and substantiated.

A possible comprehensive optimality criterion (COC) for the design of asphalt concrete compositions with industrial waste can be represented in the form of an objective function that incorporates several key indicators reflecting the quality, cost-effectiveness, and environmental sustainability of the mixture. This criterion takes into account:

– Key quality indicators of asphalt concrete: rutting resistance (MPa), splitting tensile strength (MPa), water absorption (%), frost resistance (loss of compressive strength in MPa after a specified number of freeze–thaw cycles).

– Environmental indicators: content of metallurgical waste (%) and silicon production waste (%) in the asphalt concrete mixture, radiation level of the wastes used in asphalt concrete production (Bq/kg), and the carbon footprint generated during asphalt concrete production (according to life-cycle analysis of asphalt concrete).

– Economic indicators: material cost (KZT), energy consumption during asphalt concrete production (KZT), and service life of the pavement before major repair (years).

To calculate the COC of the asphalt concrete composition, preliminary normalization (for example, by the min–max method) of the listed indicators is performed on a scale from 0 to 100. This allows for the comparison and integration of values expressed in different units into a unified assessment system. Each indicator is assigned weighting coefficients, which are determined depending on the priorities of the road construction project.

The proposed objective function may also be subject to additional constraints, including other quality indicators of asphalt concrete, such as water resistance, swelling, density, and the particle-size distribution of the aggregate, among others.

3) A laboratory evaluation was carried out to assess the influence of selective crushing parameters on the change in volumetric expansion (according to ASTM D4792-00) and abrasion resistance of coarse asphalt concrete aggregate from blast furnace slag in a shelf drum (according to GOST 8269.0-97). In addition, a mathematical model was developed to describe the correlation relationship between these parameters.

The experiment demonstrated a direct correlation between the duration of selective crushing and the abrasion resistance of blast furnace slag aggregate for asphalt concrete. The obtained results confirmed the hypothesis that stronger and denser slag aggregate particles are less susceptible to abrasion than weaker and less dense ones. At the same time, the relationship between the duration of selective crushing and the change in volumetric expansion of blast furnace slag aggregate was found to be negligible, which is explained by the overall sufficiently stable structure of the material against swelling (regardless of porosity and grain size fraction).

4) Experimental samples of enriched coarse aggregate (20–40 mm fraction) for asphalt concrete were obtained from blast furnace slag. The enrichment was carried out by selective crushing of slag aggregate with varying strength in a ball mill, using a grinding medium consisting of steel balls and cylpebs in equal mass ratio. As a result of selective crushing, the more brittle slag aggregate particles were completely or partially destroyed, while the stronger ones retained their integrity. To separate the destroyed particles from the intact ones, a laboratory sieve with 20 mm mesh openings was used.

5) Experimental samples of asphalt concrete were obtained using coarse aggregate from natural crushed stone and enriched aggregate from blast furnace slag. Petroleum road bitumen grade BND 90/130 was used as the binder. Mixing of asphalt concrete components was carried out in a laboratory mixer LS-AB-10. The asphalt concrete samples were molded in single molds (according to GOST 30491-2012) using a press. The prepared samples were designated for subsequent testing of density, water saturation, swelling, strength, rutting resistance (Marshall method), water resistance, and frost resistance.

6) Based on the results of the research obtained in 2024, one article was published in a journal recommended by the Committee for Quality Assurance in the Field of Science and Higher Education of the Republic of Kazakhstan, and two articles were published in the proceedings of international conferences.

7) Experimental results were obtained for the determination of density, average density of the mineral part, water saturation, and swelling of the asphalt concrete samples. The highest density was recorded for the samples with natural crushed stone – 2.35 g/cm³, which ensures the formation of a strong and low-porosity mineral framework. The use of ordinary slag aggregate led to a decrease in this indicator to 2.30 g/cm³, while the use of slag aggregate enriched by selective crushing partially compensated for the losses, increasing the density to 2.31 g/cm³. A similar trend was observed for the average density of the mineral part: the natural aggregate showed the maximum value of 2.23 g/cm³, while the values for the unenriched and enriched slag aggregates were 2.19 and 2.20 g/cm³, respectively.

In terms of water saturation, the best result was also demonstrated by the mixture with natural aggregate — 1.97%. When ordinary slag was used, this value increased to 2.96%, while the use of enriched slag reduced it to 2.81%, though it still remained higher than that of the mixture with natural aggregate. When assessing swelling, it was found that the samples with natural and enriched slag aggregates did not exhibit a tendency to this effect, whereas the use of unenriched slag aggregate resulted in swelling of 0.51%, which may be associated with the features of its porous microstructure.

8) The results of the conducted tests showed that the use of different types of aggregates significantly affects the deformation and strength characteristics of asphalt concrete. The highest rutting resistance was recorded for the mixture with natural aggregate (26.6 kN), while the use of ordinary slag aggregate reduced this value to 21.0 kN. The introduction of enriched slag aggregate increased rutting resistance to 26.03 kN, which is 23.95% higher than that of the mixture with unenriched slag and almost equivalent to the performance of the mixture with natural aggregate.

Analysis of flow values revealed that the mixture with natural aggregate exhibited the highest flow — 5.01 mm, exceeding the upper limit of the recommended range and indicating a tendency toward rut formation. At the same time, mixtures with ordinary and enriched slag aggregates showed values of 3.86 and 3.78 mm, respectively, which fall within the acceptable range. Among them, enriched slag aggregate provided the optimal balance between plasticity and strength of asphalt concrete.

In compressive strength tests, the mixture with natural aggregate again demonstrated the highest value — 7.23 MPa. Asphalt concrete with enriched slag aggregate achieved 6.74 MPa, only 7.27% lower than the mixture with natural aggregate, while the mixture with ordinary slag aggregate reached 6.64 MPa, 8.88% lower compared to the natural aggregate mixture.

When evaluating water resistance, the highest coefficient (0.88) was also observed for the mixture with natural aggregate. The mixture with enriched slag aggregate showed 0.85, which is 2.41% higher than the value for the mixture with ordinary slag aggregate (0.83).

The most contrasting results were obtained in frost resistance tests. Strength loss after 25 freeze–thaw cycles amounted to only 5.21% for asphalt concrete with natural aggregate. For asphalt concrete with enriched slag aggregate, this value was 11.3%, almost twice as high, but still lower than that of the ordinary slag aggregate mixture, where the loss reached 13.11%.

Thus, the experiments confirmed that the application of selective crushing technology significantly improves the performance of asphalt concrete based on blast furnace slag, bringing it closer to the properties of natural aggregate, especially in terms of rutting resistance, strength, and water resistance, although in terms of frost resistance the material still falls short of natural aggregate.

9) Asphalt concrete mix designs were developed and experimental samples were produced using enriched blast furnace slag as coarse aggregate and microsilica as a mineral additive. Three asphalt concrete mixtures were prepared, in which pre-enriched slag aggregate (19–25 mm) and ordinary slag aggregate (4.75–19 mm) were used as coarse aggregates, slag sand (0.075–4.75 mm) was used as fine aggregate, and microsilica served as the mineral additive. The microsilica was introduced directly into the bituminous binder before mixing with the coarse and fine aggregates. The main variable parameter was the percentage content of microsilica relative to the mass of bitumen (0, 3%, 6%). Mixing was carried out in a laboratory asphalt concrete mixer LS-AB-10.

Articles in international peer-reviewed scientific journals indexed in Scopus and/or Web of Science:

1) Kunaev V., Akhmetova G., Zhautikov B., Batyrbek A., Tavshanov I., Charnyi D., Kydyrbayeva S., Kamarova S., Fathi M.S., Suleyev B. Enhancing physical-mechanical properties of coarse slag aggregate via selective crushing for asphalt concrete // Results in Engineering. – 2025. – 26. – 105368. URL: https://doi.org/10.1016/j.rineng.2025.105368 (Web of Science: ESCI: Q1; Scopus: Q1, 86th percentile in the General Engineering category).

Articles in journals recommended by the Committee for Quality Assurance in the Field of Science and Higher Education of the Republic of Kazakhstan:

1) Kunaev V., Akhmetova G., Batyrbek A., Tavshanov I., Fathi M. Critical analysis of external and internal structure-forming factors affecting the quality indicators of asphalt concrete based on the industrial wastes // Труды университета. – 2024. – 3(96). – P. 239-246. (ISSN 1609-1825), http://tu.kstu.kz/publication/publication/download/898  .

2) Кунаев В.А., Батырбек Ә.Е., Романов В.И., Фатхи М.Ш., Чарный Д.Ю. Повышение эксплуатационной надежности транспортной инфраструктуры за счет обогащения и снижения истираемости заполнителя асфальтобетона // Труды университета. – 2025. – № 2(99). – С. 189-195. (ISSN 1609-1825), https://doi.org/10.52209/1609-1825_2025_2_189

Articles in the proceedings of international conferences:

1) Кунаев В.А. Батырбек Ә.Е., Тавшанов И.С., Романов Д.Ю. Установление множества факторов, определяющих показатели качества асфальтобетона на основе техногенных отходов // Синтез науки и общества в решении глобальных проблем: сборник статей Международной научно-практической конференции. – Уфа: Аэтерна, 2024. – С. 11-17. (ISBN 978-5-00249-045-5), https://aeterna-ufa.ru/sbornik/NK-604.pdf .

2) Кунаев В.А., Кыдырбаева С.Ж., Романов Д.Ю., Чарный Д.Ю. Новый взгляд на использование доменного шлака в качестве заполнителя дорожного асфальтобетона // Актуальные и перспективные научные исследования: сборник статей III Международной научно-практической конференции. – Пенза: МЦНС «Наука и Просвещение». – 2024. – C. 39-42. (ISBN 978-5-00236-495-4), https://naukaip.ru/wp-content/uploads/2024/08/MK-2110.pdf?utm_medium=email&utm_source=NotiSend .