Sustainable concrete for rigid pavement construction using de-hydroxylated Kaolinitic clay: Mechanical and microstructural properties

Abstract

Abstract The huge amount incurred in the construction of rigid pavement necessitates the use of cheaper alternative materials. This experimental research assessed the rheology, strength and microstructure of de-hydroxylated Kaolinitic clay in self-compacting concrete for pavement construction using a special brand of Portland limestone cement (Technical Cement). The huge demand for the use of supplementary cementitious material in concrete technology and the variation in the physical and chemical composition of these materials require the need for the design of their use in concrete work. The Kaolinitic clay was de-hydroxylated at 750 °C. This was used as a partial replacement for cement at 0%, 5%, 10%, 15%, 20% and 25%. Six (6) concrete samples were developed varying the cement brand. Both strength and workability properties of the developed self-compacting concrete were assessed. Slump flow, L-box test and V-funnel test were carried out alongside the compressive, split tensile and flexural strength test. Response surface analysis was carried out to know the relationship between the mechanical properties of the concrete. Additionally, the microstructure of the concrete at maturity was also assessed. The result of the research revealed that at 15% addition of metakaolin the slump flow, passing ability and filling ability did not satisfy the EFNARC standard for self-compacting concrete. From the numerical optimization of the flexural strength, the maximum predicted flexural strength of 4.86 MPa was obtained. The response surface also revealed that at lower values of metakaolin, the compressive strength increased as the age of the concrete increased from 3 to 150 days. The age with the optimum concrete strength formation was 110 days with the metakaolin addition of 52.73 kg based on the optimization analysis. In a bid to encourage the use of sustainable supplementary materials in rigid pavement construction, the choice of de-hydroxylated Kaolinitic clay is a viable option.