Compressive strength and environmental impact of sustainable blended cement with high-dosage Limestone and Calcined Clay (LC2)

Abstract

Replacing half of the clinker by a blend of limestone powder and low-grade calcined clay (in 1:2 weight ratios) has been recently proposed as a new version of economical and green cement named Limestone-Calcined Clay (LC2) cement, also known as LC3. The LC2 blend emits much less carbon dioxide than traditional Portland clinker and has a sufficiently high cementing efficiency factor for maintaining compressive strength under high replacement levels. In this study, the feasibility of blending more than 50% of LC2 in cement was explored in order to achieve greener blended cement. Five LC2 replacement levels were studied, including 25%, 50%, 60%, 70% and 80% by weight of cement. Compressive strength of BS EN 196-1 standard mortar mixes at 3–360 days was evaluated, and the fresh property, hydration heat as well as environmental impact of the blended cement were investigated. The results showed that the blended cements with 50%, 60% and 70% LC2 achieved the compressive strength of 53.6 MPa, 43.9 MPa and 33.4 MPa at 28 days, respectively; thus they fulfill the 28-day strength requirements for 52.5N, 42.5N and 32.5N cements, respectively. The blended cements with 50–60% LC2 had a lower material cost index than Portland cement and blended cement with fly ash. In addition, blended cements with 50–60% LC2 showed lower embodied energy/carbon emission indices at the early age but higher at the later age as compared to blended cements with fly ash. In the context of the substantial contribution of Portland cement manufacture towards the climate crisis, these findings can help the efforts to reduce the carbon footprint in the construction industry.