Mechanical Properties and Microstructure Characteristics of Self-compacting Concrete with Different Admixtures Exposed to Elevated Temperatures

Self-compacting concrete (SCC) is a high-performance concrete widely used as a building material. The present investigation examines the effects of age and cooling type (air-cooled and water-cooled) of SCC after being exposed to elevated temperatures and compares them to those of normal conventional concrete (NCC). Two types of concrete; i.e., NCC and SCC, were developed and studied for early-age and residual strengths. SCC was developed with three different types of admixtures; namely, fly ash (FA), silica fume (SF) and metakaolin (MK) as binder materials, by replacing the cement. The mechanical characteristics of FA- and SF-blended SCC before heating show similar results, whereas MK-based SCC possesses greater strength than other mixes. In the case of specimens exposed to high temperature of 1000℃, MK-blended SCC produced the lowest residual strength compared to FA- and SF-based mixes. Further microstructural investigation was conducted to examine the internal structure of the specimens exposed to various heating temperatures. From the results, it is concluded that the higher the strength gain upon aging, the greater the strength loss upon temperature rise. KEYWORDS: Self-compacting concrete, Fly ash, Silica fume, Metakaolin, Residual strength, Microstructure.