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In order to save costs for the potential construction of roller compacted concrete (RCC) dams in Tibet, China, local tuff is ground and used as a substitute for fly ash powder to prepare RCC. Through compressive strength test, X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), and scanning electron microscope (SEM) analysis, the hydration and compressive strength development of cement-tuff powder composite system were studied. The results showed that tuff powder reduced early hydration rate and cumulative hydration heat release, which could replace fly ash as a mineral admixture. Thermal curing could increase the pozzolanic activity of tuff powder, while the alkaline phases in tuff powder could promote the early hydration of composite system to improve the early compressive strength. A specific surface area of 590 m2/kg was sufficiently high, and further grinding had little effect on the compressive strength growth though would increase the costs. Unlabelled Image • Tuff powder as pozzolanic activity can replace fly ash as mineral admixture. • Thermal curing can stimulate the pozzolanic activity of tuff powder. • Tuff powder of 590 m2/kg is sufficiently fine for concrete preparation. [ABSTRACT FROM AUTHOR]