Calcined kaolin as cement replacing material and its use in high strength concrete

• Published in: Construction & building materials 2015-04, Vol.81, p.313-323
• Main Authors: Shafiq, Nasir, Nuruddin, Muhd. Fadhil, Khan, Sadaqat Ullah, Ayub, Tehmina
• Format: Article
• Language: English
• Subjects: Analysis; Clay; Concrete; High strength concrete; Kaolin; Mechanical properties; Metakaolin; Mineral admixtures; Pozzolan
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2015.02.050

•Highly reactive metakaolin was produced by calcination of Malaysian kaolin.•Optimum condition for the calcination is 800°C (1472°F) and 3h duration.•15% is optimum content of produced metakaolin based on compressive strength.•Higher mechanical properties of metakaolin concrete better than silica fume.•The cost of metakaolin is about 33% lesser than commercially available silica fume. This experimental investigation has been carried out to examine the effects of temperature and duration on Malaysian kaolin to form highly reactive metakaolin. Metakaolin has been produced through the calcination process at temperatures 600–800°C (1112–1472°F) for the duration from 1 to 5h. X-ray diffraction and loss on ignition are the usual process to identify the optimum temperature and duration of calcination required. In this study, to confirm the reactivity of metakaolin, compressive strength, splitting tensile and flexural strength of concrete at the age of 7, 28, 56 and 90days have been investigated using locally produced metakaolin as cement replacing material. It was found that locally produced metakaolin enhance the mechanical properties of concrete and compressive strength is about 5% higher than silica fume concrete at the age of 28days. This study divulges that calcination at 800°C (1472°F) for 3h is the most suitable condition to convert kaolin into highly reactive metakaolin.