PSI - Issue 81

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

207

A)

B)

C) Fig. 1. Concrete specimens based on epoxy resins (a) Series 1. With no epoxy resin content. (b) Series 2. With 2.0 L of epoxy resin and 0.5 L of water. (c) Series 3. With 1,5 L of epoxy resin and 1.5 L of water Following the preparation stage, the mixtures were placed into moulds and left to cure for a period of 14 days, during which they were periodically and uniformly moistened. Subsequent to the demoulding process, a series of control measurements were conducted on the specimens' geometric dimensions. The mean dimensions of all cubes were approximately 151 × 150 × 151 mm. Thereafter, the specimens were subjected to a subsequent 14-day curing period at an average temperature of 18 °C and a relative humidity of 75%, with regular and consistent moistening procedures applied to ensure uniform conditions for all samples. At the age of 28 days, the specimens were weighed. The mean mass of the samples with the highest epoxy resin content was 7.8 kg (Series 3), for Series 2 it was 8.20 kg, and for the samples without epoxy resin it was 8.8 kg (Series 1). Water absorption testing was conducted under atmospheric pressure in accordance with the standard procedure for determining changes in specimen mass after saturation. Prior to the commencement of the experiment, the concrete specimens were subjected to a process of pre-drying, with the objective of achieving a constant mass. This procedure was implemented to eliminate the potential influence of residual moisture on the subsequent outcomes of the experiment. Subsequent to the drying stage, the specimens were immersed in water at a temperature of +20 °C, where they remained for a period of two days. Subsequent to the completion of the saturation period, the specimens were extracted from the water, their surfaces being gently dried with a soft cloth. Thereafter, a control weighing procedure was conducted. 3. Research results All fabricated specimens were subjected to compressive strength testing in order to assess the influence of epoxy resin content on the mechanical properties of the modified concrete. The highest compressive strength values were obtained for the control series, which did not contain epoxy resin. The average 28-day compressive strength was 30.7 MPa, consistent with the design strength for C25/30 concrete. Conversely, the lowest strength characteristics were recorded in the series with the maximum epoxy resin content: the mean compressive strength reached only 16.6 MPa. This result indicates a significant weakening of the cementitious matrix and a disruption of bonding between the mineral constituents when a substantial portion of water is replaced by a polymer component. Intermediate values were observed for the series with a moderate amount of resin, where the average compressive strength was 17.4 MPa, further demonstrating the adverse effect of excessive polymer binder on the formation of the concrete structure.