Low carbon and high efficiency limestone-calcined clay as supplementary cementitious materials (SCMs): Multi-indicator comparison with conventional SCMs

Abstract

The increasing shortage of conventional supplementary cementitious materials, including fly ash (FA) and ground granulated blast furnace slag (GGBS), further obliterates the sustainability potential of Portland cement. Fortunately, recent studies have proved that limestone-calcined clay (LC2) is a feasible substitute. In this study, LC2 was used as SCM to study the properties of blended cement, and compared with FA and GGBS, the relevant mechanisms leading to the unique properties of LC2 were also explained. The evaluation indexes related to energy consumption and carbon emission were proposed. Results show that, contrary to the positive effects of FA and GGBS, LC2 has a negative effect on normal consistency and workability. LC2 slightly shorten the setting time at normal consistency, but at large content, the setting time was significantly prolonged due to the increase of consistency. LC2 diminished drying shrinkage and is superior to FA and GGBS. LC2 has higher cementing efficiency than FA and GGBS, and it is more obvious at early age. The environmental impact analysis also showed that LC2 reduced the relative energy consumption and carbon emission of cement, and reduces by about half at the substitution rate of 45 ∼ 60%.