Exploratory machine learning analysis of research trends in photocatalytic cementitious materials

We investigated research trends in photocatalytic cementitious materials over the past decade by analyzing 130 peer-reviewed papers (systematically selected from an initial corpus of approximately 1400 publications) using computational approaches, including topic modeling, citation network analysis and temporal trend evaluation. Our methodology achieved satisfactory validation metrics, with a coherence score of 0.68, a perplexity of 142.3 and a cross-validation accuracy of 0.71 (±0.03), as confirmed by an expert review. The research field has evolved through four distinct phases: foundational studies (2014–2016), performance enhancement (2017–2019), early applications (2020–2022) and practical implementation (2023–2024). Topic analysis revealed eight major research themes with environmental cleanup dominating the current work (55.4 % of publications), followed by self-cleaning applications (34.6 %) and antimicrobial functions (20.0 %). The frequency analysis identified TiO₂ (85 occurrences), performance (81 occurrences) and photocatalysis (76 occurrences) as the most prominent terms. Notable technological progress includes enhanced NO_x removal efficiency, improving from 15 % to 25 % in early studies to a peak performance of 70 % by 2024. Visible-light activation has advanced significantly, with graphene-TiO₂ nanocomposites achieving efficiencies of 60–75 %. Long-term field studies have demonstrated encouraging durability, with 75–85 % of the initial performance maintained after seven years. Economic viability has also improved, with manufacturing costs decreasing from a 300 % to a 150 % premium over conventional cement production. The Technology Readiness Level (TRL) assessment indicates that the scientific foundations have reached TRL 4–5, while commercial implementation remains at TRL 2–3, identifying a substantial development gap that requires focused attention on standardization and operational optimization. We found the intensification of international collaboration particularly interesting, which increased from approximately 29 % during 2014–2017 to nearly 47 % in recent years, reflecting the growing interdisciplinary integration among the domains of materials science, environmental engineering, and construction.