The Metakaolin Waste Effect on the Physical and Mechanical Properties of High-Performance Concrete

This paper discusses the structure and properties of high-performance concrete (HPC) analysed by scanning electron microscopy, X-ray diffraction analysis, exothermic temperature, density, bending, and compressive strength. A certain amount of cement (5%, 10%, 20%) was replaced in the concrete mixes with metakaolin waste generated in the expanded glass manufacturing. This metakaolin waste consists of a high amount of SiO₂ + Al₂O₃ – 92.2% and has significant pozzolanic activity according to the Chapelle test – 1148mg/g. The results presented in the paper show that metakaolin waste is an active additive that accelerates the setting of HPC and makes its structure denser. HPC with up to 10% of cement CEM I 52,5 R substituted with metakaolin has approximately 28 day flexural and compressive strengths similar to control samples – 15 MPa and 135 MPa, respectively. The article also presents test results showing that metakaolin waste reduces the maximum temperature of the exothermic reaction in concrete and does not cause the formation of new compounds. Standard concrete minerals: portlandite, calcite, quartz, and alite were identified.