Valorisation of Limestone in Sustainable Cements

This study investigates the development of two sustainable cements, CEM II/B-LL and CEM VI, in accordance with the UNI EN 197-1 and 197-5 standards. CEM II/B-LL was produced by replacing Portland cement with limestone (LS) at varying dosages (0%, 15%, 25%, and 35% by mass), and CEM VI was made by substituting blast furnace slag with limestone at different levels (0%, 10%, 20%, 30%, and 40% by mass). The results show that both binders are classified as structural cements. LS substitution increases the setting time of CEM II/B-LL but does not significantly affect the setting time of CEM VI. When cured at low temperatures (10 °C), CEM VI mortars retain their mechanical properties even at high LS levels, making them particularly suitable for cold climates. Mortar properties such as total porosity and capillary water absorption increase with LS content, with CEM VI exhibiting lower sensitivity to LS additions. Free shrinkage in CEM II/B-LL mortars decreases with LS content, whereas in CEM VI mortars, it initially increases with up to 20% LS and then decreases at higher LS levels (30–40%). Restrained shrinkage is also lower in CEM VI than in CEM II/B-LL. The Global Warming Potential (GWP) of CEM II/B-LL decreases significantly with increased LS content, whereas in CEM VI, it remains almost constant up to a 40% substitution. However, CEM VI demonstrates a 50% lower environmental impact compared to CEM II/B-LL, underscoring its superior sustainability.