PSI - Issue 81

Oleh Bordiuzhenko et al. / Procedia Structural Integrity 81 (2026) 78–83

82

were obtained when the specimens were stored in a desiccator at a relative humidity close to 100%. Such conditions prevented moisture evaporation from the specimens. Slightly worse results were shown by curing in water. It can be assumed that both excess water in the material and its deficiency are detrimental to the structure formation processes, suggesting a mixed mechanism of structure formation in pressed composites contact-crystallization and hydration.

10 12 14 16

air-dry above water in water

0 2 4 6 8

`

Compressive strength, MPa

B1

B2

B3

B4

Concrete fines samples

Fig. 4. Influence of curing conditions on the strength of pressed composites.

Analyzing the above data, a certain dependence of the strength of pressed materials on the content of alite and calcium hydroxide in concrete can be observed (Table 2). It can be assumed that a rapid assessment of concrete waste for its potential suitability in producing pressed materials and products can be carried out by determining the content of these compounds, in particular through the pH of the aqueous extract. However, such a hypothesis requires confirmation through further research, which the studies should address. 4. Conclusions The results show that pressing the dispersed fraction of concrete waste produces specimens with strength and bulk density comparable to those of common wall materials, such as ceramics. The kinetics of strength development over time for pressed composites made from different types of concrete waste were established, and the influence of curing conditions was also investigated. The effect of the composition of the original concrete, from which the concrete waste is derived, on the strength characteristics of the pressed composites was analyzed. Acknowledgements This research was carried out within the framework of the project “S3RU – Safe, Sustainable, and Swift Reconstruction of Ukraine”, implemented by the National University of Water and Environmental Engineering as part of an international consortium led by The University of Sheffield, United Kingdom. The project is supported through the Innovate Ukraine Green Innovation Challenge Fund established under the UK – Ukraine Energy Partnership Memorandum and delivered within the Ukraine Resilience and Energy Security (URES) Programme, financed by the Foreign, Commonwealth & Development Office (FCDO), United Kingdom. The authors gratefully acknowledge this support. References Cantero, B., Bravo, M., de Brito, J., del Bosque, I.F.S., Medina, C., 2022. The influence of fly ash on the mechanical performance of cementitious materials produced with recycled cement. Applied Sciences 12(4), 2257. Davidovits, J., 2017. Geopolymers: Ceramic-like inorganic polymers. Journal of Ceramic Science and Technology 8(3), 335 – 350. Duchesne, J., 2021. Alternative supplementary cementitious materials for sustainable concrete structures: A review on characterization and properties. Waste and Biomass Valorization 12, 1219 – 1236. Dvorkin, L., Bordiuzhenko, O., Makarenko, R., 2024. Contact hardening binders using rock crushing waste. Journal of Chemical Technology and Metallurgy 59(4), 925 – 934. Dvorkin, L., Zhitkovsky, V., Bordiuzhenko, O., Ribakov, Y., 2023. High Performance Concrete Optimal Composition Design. CRC Press. Kaptan, K., Cunha, S., Aguiar, J., 2024. A review of the utilization of recycled powder from concrete waste as a cement partial replacement in cement-based materials: Fundamental properties and activation methods. Applied Sciences 14(21), 9775. Kwon, E., Ahn, J., Cho, B., Park, D., 2015. A study on development of recycled cement made from waste cementitious powder. Construction and Building Materials 83, 174 – 180.