PSI - Issue 81

Mykhailo Hud et al. / Procedia Structural Integrity 81 (2026) 205–209

206

To enhance the functional characteristics of construction materials, polymer materials with high thermal resistance Stukhliak et al. (2024) , as well as advanced physical-mechanical properties and wear resistance Stukhliak et al . (2024), are being increasingly employed. In the article by Kononchuk et al. (2022), the results of a numerical investigation of the stress – strain state of bent reinforced concrete elements before and after their strengthening with carbon-fiber composites under static loading conditions are examined. The authors performed a comparative analysis of the calculated data obtained using the finite element method with the available experimental results. They also conducted a prediction of the subsequent behavior of strengthened and unstrengthened reinforced concrete elements, which highlights the effectiveness of the finite element method for assessing the strength and deformation characteristics of structures in engineering practice. In their study, Wang et al. (2025) investigate the effectiveness of using fine aggregate in combination with various polymer modifiers — epoxy resin (ER), styrene – butadiene rubber (SBR), and vinyl acetate – ethylene copolymer emulsion (VAE). The influence of these components on the strength characteristics, permeability coefficient, abrasion resistance, and frost resistance of the modified concrete is analyzed. The experimental results demonstrated that the use of 5% VAE makes it possible to achieve a compressive strength of 34.6 MPa while maintaining permeability at the level of 2.75 mm/s. Modification of concrete with 2% ER provides the highest flexural strength — 4.2 MPa — at a permeability of 2.78 mm/s. The most significant improvement in durability indicators is observed when 4% epoxy resin is used: after 100 freeze – thaw cycles, the mass loss amounted to only 0.28%, and the reduction in strength was 6.17%. Compared with SBR and VAE, ER exhibits the most favorable combined effect on strength and frost resistance parameters, while simultaneously maintaining the required permeability of the material. The article presents a systematic investigation of the shear behavior of adhesive joints in timber – concrete composites (TCC). Brosch et al. (2025) compared three configurations of small-scale tests under short-term loading and found that the Vertical Slip Block (VSB) test yields the lowest variability in results and consistently leads to cohesive failure of the substrate. Using the VSB method, five types of epoxy formulations were evaluated, with the more ductile variants demonstrating up to 35% higher shear strength and shifting the failure mode to a more favorable one — from adhesive to cohesive failure. In the study by Xia et al., the potential for enhancing the mechanical properties of polycarbonate concrete (PC) was analyzed by optimizing its composition through the incorporation of recycled coarse aggregate, fly ash, and polypropylene fibers. The application of orthogonal experimental design made it possible to identify a mixture that provides a compressive strength exceeding 30 MPa while significantly reducing carbon emissions during production. Additional modification with waterborne epoxy resin improved the microstructure of the pore space and contributed to increased strength and overall performance of

permeable recycled concrete. 2. Methodology and materials

Three series of concrete mixtures were prepared for the experimental investigation. In the initial series, water was the sole constituent utilised, with a volume of 3 litres per 10 litres of the prepared concrete mixture (Fig. 1a). In the second series, the water volume was reduced to 2.0 litres, after which 0.5 litres of epoxy resin (ED20) was incorporated into the water-based concrete batch that had been mixed previously. In the third series, 1.5 litres of water and 1.5 litres of epoxy resin were utilised. The proportions of cement, sand, and coarse aggregate were determined in accordance with the requirements for achieving the design compressive strength of C25/30 concrete. For a more detailed analysis of concrete mix designs and test specimens, please refer to Table 1.

Table 1. The parameters for prescription of concrete mixtures in experimental series Serial number of test specimens Number of test specimens in the series Cement class Water – cement ratio

Aggregate grading

Avarage sizes of specimens, mm

Average strength value of specimens, MPa

Portland cement M500 (3.5 kg), sand (8 kg) and crushed stone (10 kg, fraction 5-20 mm)

Series 1

10

1:3

151 × 150 × 151

30.7

Portland cement M500

Series 2

10

1:2,5

152 × 151 × 151

17.4

Series 3

10

1:1,5

151 × 151 × 151

16.6