To reduce CO₂ emissions from the cement industry, expanded use of supplementary cementitious materials has attracted attention. Blast furnace slag has been widely used as a supplementary cementitious material, but its supply is expected to decrease in the future. In this study, a limestone–blast furnace slag blended cement was produced by replacing 10% of the binder of blast furnace slag cement type B (BB) with limestone powder (LSP), and the concrete properties were evaluated by laboratory tests and a one-year exposure test. The ternary blended cement exhibited compressive strength and durability equivalent to those of BB, and no deterioration was observed in the exposure tests conducted in cold regions. Furthermore, it was estimated that the concrete made with the ternary blended cement, which had performance equivalent to BB, would yield an up to 11.1% reduction in CO₂ emissions compared with concrete made with BB.

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 The fluidity and passing ability of limestone-blast furnace slag cement, which contains both limestone and blast furnace slag as supplementary cementitious materials, were investigated through a series of experimental evaluations. Based on the surplus water film theory, it was inferred that the addition of limestone could increase the packing density of powder particles within the cement paste. This increase in packing density leads to an enhanced flowability of the paste, which is attributed to the influence of the thickness of the surplus water film surrounding the particles. To assess the passing ability, box filling tests and J-ring flow tests were conducted using both normal-strength and high-strength concrete mixtures. The results demonstrated that the addition of limestone significantly improved the passing performance, particularly when the clinker factor was low, indicating their potential to enhance workability in practical applications. Furthermore, a comparative analysis with the rheological parameters of mortar revealed that the relationship between plastic viscosity and passing velocity (V_pass) may vary depending on the strength level of the concrete. These findings suggest that the strength-dependent rheological behavior should be considered when designing mixtures for optimal placement performance.

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 The use of industrial by-products in cement has been promoted in the cement industry as part of efforts toward a carbon-neutral society. However, the production of industrial by-products such as blast furnace slag and fly ash is expected to decrease in the future. This study investigates the shrinkage cracking properties of concrete using natural zeolite as a supplementary cementitious material alternative to industrial by-products. The results showed that the drying shrinkage and restrained shrinkage of concrete using natural zeolite were slightly larger than those of concrete without natural zeolite in the early ages (up to 50 days), but became comparable at 364 days. Furthermore, as the natural zeolite content increased, cracking occurred at earlier ages, and the stress to strength ratio at cracking also decreased. Additionally, analytical identification of the creep coefficient revealed that the creep coefficient of concrete containing 15% natural zeolite was 0.7 times that of concrete without natural zeolite.

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 This research aims to clarify the effect of the physical characteristics of fly ash on the flowability of mortar. Fourteen types of fly ash were prepared, originating from different thermal power plants and subjected to various classification conditions, to produce fly ash cements. The flowability of mortars containing those cements was then evaluated. In addition, the physical characteristics of each fly ash were analyzed, and their correlations with mortar flowability were assessed. The results indicated that the finer the fly ash particles contained, the better the mortar flowability. In particular, particles smaller than approximately 20-40μm were found to have a significantly positive effect on the improvement of mortar flowability. To further elucidate the mechanism of the flowability improvement, the packing density of fly ash cement and related parameters were examined.
　It was found that mortars containing a higher proportion of particles smaller than 20μm required a smaller amount of cement paste to achieve the same level of mortar flowability.
　This phenomenon was attributed to the morphological characteristics of fine fly ash particles that could reduce internal friction within the mortar. These findings suggest that optimizing both the particle size distribution and the morphology of fly ash is a key factor in improving the flowability of mortar containing fly ash.

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