Hydration Properties and Physical Characteristics of Belite Cements

Belite cements (BCs) have been suggested as innovative environmentally-friendly materials, inasmuch as they can allow a reduction of CO2-emissions up to about 30% with respect to normal portland cements (NPCs); furthermore, the manufacturing process of BC, compared to that of NPC, is characterized by reduced limestone requirement, lower synthesis temperatures and, consequently, reduced specific fuel consumption. The peculiar composition of BC can be also exploited for achieving valuable technical properties (e.g. better durability against sulfate and carbonation attacks as well as low heat of hydration). This paper examines the influence of temperature (20°C and 40°C) on the hydration behaviour and the technical properties of a pilot-scale industrial BC (w/c=0.50) up to 180 days. A NPC class 52.5 R was employed as a reference term. It was found that, compared with NPC, BCs showed lower mechanical properties at early ages (2 days), whilst, at longer curing periods, the compressive strength values were always greater at both 20°C and 40°C. However, stability tests displayed that BCs shrinked less than NPC in air, while they exhibited approximately the same expansion values when submerged in water. BC pastes showed the best hydration behaviour for curing periods longer than 28 days.