On water freezing in slag-blended cementitious materials at early ages

Abstract

Concretes casted in cold climate can be threatened by frost action from the initial stages of maturing. Hence, to secure their long-term functionality, it is essential to be acquainted with the material's early response to sub-zero temperatures. Addressing this challenge, the article concerned the resistance of young slag-blended cementitious materials against the early frost attack. An extensive experimental analysis covering both macro- and microscales was designed for this purpose. At first, development of the pore size distribution and ice content profile of the 100 % Portland cement and slag-blended pastes were evaluated from the early ages until maturing via mercury intrusion porosimetry and differential scanning calorimetry. It was reported that the distinction between gel pore and capillary pore is created after 3rd day for OPC and after 21st day for slag-blended paste. Next, the destructive impacts of a single freezing-thawing cycle on the mechanical properties of the young Portland cement and slag-blended mortars were measured. Subsequently, the strength development of the Portland cement and slag-blended concretes that experienced the frost exposure were evaluated and compared with each other. It was observed that the early freezing strengthen (up to 15 %) the OPC based concrete and weaken (up to 13 %) the slag-blended concrete. Additionally, the analysis was proposed to simulate the winter conditions at the building sites. The strength development of the Portland cement and slag-blended concretes that were cured at low temperatures and experienced an early freezing episode were assessed. The decrease of curing temperature caused the reduction of compressive strength of OPC-based concrete around 25 % and slag-blended concrete around 50 %. As a result, micro- and macrostructural requirements were proposed to secure the proper resistance of the slag-blended cementitious materials against the possible early frost damage.