Designing low-clinker green cement with high bypass dust content: a resource-efficient approach using industrial wastes

Abstract

There are increasing efforts in research and industrial scale to develop sustainable solutions that get rid of Cement bypass dust (CBD) in safe way or/and incorporate it as a supplementary cementitious material (SCM) in building materials. However, its pozzolanic reactivity, which is the ability to react with calcium hydroxide and form cementitious compounds, is very low and variable. Therefore, this study introduces a novel and eco-efficient approach to valorizing high levels of CBD—up to 34.8%—as a supplementary cementitious material (SCM) in the production of hydraulic green cement with a reduced clinker content (37.8–38.7%). Unlike conventional research which typically focuses on low CBD replacement rates or single SCM additions, as the prior studies report that CBD content exceeding 10% often leads to significant strength reduction, this study explores the synergistic effect in an optimized ternary blend combining CBD with two other industrial wastes: de-aluminated kaolinite (DAK) and calcined clay (Cclay), with the objective of addressing CBD’s limitations and improving pozzolanic reactivity. A comprehensive experimental program was established, resulting in the production and testing of eight cementitious mixtures. The results demonstrated that an optimized mixes containing 17.1%−34.8% CBD and 17.4%−34.2% calcined clay and ∼ 5.75% Industrial waste in normal fineness ranges (∼3.6% SR 45u and ∼ 3894 Blaine) achieved a compressive strength of 36.2 MPa at 28 days and 38.2 MPa at 90 days, while maintaining setting times within acceptable limits (initial setting up to 245 min and final setting up to 360 min). This research offers novel insights into the design of low-clinker, high-performance green cement utilizing various waste streams, considerably advancing the circular economy and sustainable construction practices.