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An alite-calcium sulfoaluminate (ACSA) clinker containing approximately 50% alite and 10% ye'elimite was synthesised at 1300°C using a laboratory furnace and 1% calcium fluoride (CaF2) as a mineraliser, ground and blended with 5% anhydrite. The hydration mechanism of the resulting ACSA cement was investigated experimentally using quantitative X-ray diffraction and thermogravimetry, as well as by thermodynamic modelling. During the first hours, mainly alite reacts. Ye'elimite starts to dissolve significantly after 2 d, as it is predominately present as inclusions within the alite matrix and thus reacts only after sufficient alite has dissolved to expose the ye'elimite domains within the clinker particles. The main hydration products are calcium–silicate–hydrates (C–S–H), ettringite, monosulfate and portlandite. Mortars prepared using the ACSA cement rapidly develop compressive and flexural strength at early ages corresponding to the fast hydration reactions. It was estimated that the manufacture of this ACSA clinker releases about 11–12% less carbon dioxide than the production of Portland cement clinker.

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In this study limestone powders with different particle sizes of 5, 10 and 20 μm were used to replace a part of Portland cement in different replacement levels to produce Portland-limestone cement pastes. The percentages of limestone replacement are 0, 5, 7.5, 10, 12.5, 15 and 20% by weight. The effect of fineness and the amount of limestone powders on compressive strength and setting time are investigated. It has been established that limestone replacement causes reduce the compressive strength due to the dilution effect, but it can reduce energy consumption and CO2 emission in cement manufacturing. The fineness of limestone powder used has influence on the observed compressive strength values. From the standard consistency results, it seems that limestone has no effect on water requirement compared to Portland cement. Moreover, the increase in level of fine particles would require much water. Both initial and final setting times were decreased with an increase in the amount of limestone. Furthermore, at the same level replacement, the cement pastes using 5 μm of limestone show lower setting time than those using 10 and 20 μm, respectively.

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