In this study, the phase composition and mechanical performance of Portland cement modified with ceramic brick waste were comprehensively investigated. X-ray diffraction (XRD) analysis confirmed the presence of main clinker phases such as C₃S (alite), C₂S (belite), C₃A (celite), and C₄AF (brownmillerite) in the base clinker, with no detectable free CaO, indicating complete mineral formation and thermal stability. Experimental cement samples were prepared by partially replacing clinker with 15–20% ceramic brick waste and adding 5% gypsum, while a standard composition (95% clinker + 5% gypsum) was used as a control. The compressive strength of 4×4×16 cm prism specimens was evaluated after 2, 7, and 28 days of curing, in accordance with GOST 310.1–310.4 standards. Results showed that while the strength of the modified cement was slightly lower at early ages, it reached comparable levels to the control at 7 and 28 days. All compositions exceeded 36 MPa at 28 days, meeting the strength class 32.5H requirements as per GOST 31108–2020. Statistical analysis using the Student’s t-test (t = 32.4) revealed a significant increase in compressive strength in samples containing the brick waste additive, confirming its high pozzolanic or hydraulic activity within the cement composition.