Assessing the Role of Kaolin in Cement-Based Concrete: Strength Development and Material Performance

Abstract

This study investigated the influence of kaolin as a partial cement replacement on the fresh and mechanical properties of concrete for road pavement applications. The Research was carried out through laboratory experiments using five kaolin replacement levels: 0%; 7,5%; 15%; 22,5%; and 30% by weight of cement. The evaluated parameters included XRF testing, slump, compressive strength, and flexural strength. The XRF results of cement and Kaolin show similarities in CaO and SiO₂ in the formation of cement clinker phases. The test results showed that incorporating kaolin affected the workability of the concrete mixture. The control mixture produced the highest slump value of 6 cm, while the mixture containing 30% kaolin showed the lowest slump value of 1 cm, indicating a considerable reduction in workability at higher replacement levels. A similar trend was observed in compressive strength, which decreased from 33 MPa in the control concrete to 27 MPa, 22 MPa, 19 MPa, and 14 MPa for the 7.5%, 15%, 22.5%, and 30% kaolin mixtures, respectively. This finding suggests that excessive kaolin replacement may reduce the binder system's ability to develop compressive strength effectively. In contrast, flexural strength remained relatively consistent, ranging from 5 to 6 MPa across all mixtures. This indicates that, although kaolin reduces compressive strength, its effect on flexural performance is less pronounced. Overall, kaolin replacement levels of 7.5% to 15% appear to be the most promising range for concrete pavement materials, as they still provide acceptable mechanical performance while offering the potential to reduce cement consumption.