Flexural Strength and Drying Shrinkage Cracking of Concrete Mixed with Hwang-toh

Recently, public interest in eco-friendly structure has been increasing and many Hwang-toh researches are being actively performed. Hwang-toh is one of traditional environment friendly construction materials used as a construction and plastering material. Also, Ondol, traditional Korean under floor heating system, used in Korean style house uses Hwang-toh as its main construction material for duct and floor system due to its favorable heat absorbing capacity. Hwang- toh has many advantages as construction material due to its high heat storage capacity, auto- purification, antibiotic ability, and infrared ray emission characteristic. But, currently it is not been developed and used in modern construction due of its low strength and dry shrinkage cracking prone characteristics. According to the recent researches and study results, Hwang-toh can be used as a natural pozzolanic material such as fly-ash or pozzolan. The possibility of using Hwang-toh as a construction material became favorable after the research findings showed that its chemical and mineralogical proportions are like Metakaolin and Kaolinite. In this study, drying shrinkage and structural flexure behavior experiments of slag and Hwang-toh added concrete are carried out. The variables in this study were the replacement ratios of Hwang-toh and slag. The test results showed that drying shrinkage of concrete mixed with Hwang-toh has relatively higher drying shrinkage than OPC concrete, but has similar RC flexural strength.