Belite–ye’elimite–ferrite cements produced from London Clay

Abstract

London Clay (LC) is generated in significant quantities from major infrastructure development projects within and around London, UK. Excavated LC spoils are typically landfilled or used for landscaping purposes with minimal value. This study investigates the feasibility of producing belite–ye’elimite–ferrite (BYF) cements using LC in combination with kaolin or low-grade bauxite. Six cement clinkers with varying compositions were synthesised at 1300°C. The phase composition of the synthesised clinkers was quantified using X-ray diffraction analysis (XRD) coupled with Rietveld refinement. The hydration behaviour, phase assemblage evolution and mechanical performance of the cements were examined using isothermal calorimetry, XRD, thermogravimetric analysis and compressive strength testing, respectively, up to 90 days of curing. It is demonstrated that LC can be used either on its own or with kaolin or low-grade bauxite to produce BYF cements with a wide range of composition: 31 to 64 wt% belite, 9.3 to 27 wt% ye’elimite and 2.1 to 31 wt% ferrite. The use of LC as the sole alumina source resulted in low compressive strength at early stages. Nevertheless, the strength developed over time, reaching 27.8 MPa at 90 days (0.5 w/b). Possible approaches to develop LC further for producing viable BYF cements are discussed.