Influence of Nano Composites on the Impact Resistance of Concrete at Elevated Temperatures

Abstract

The addition of nanomaterials to concrete efficiently fills the pores of the concrete, thereby improving its hardening characteristics. However, no research is available in the literature that investigated the influence of nano-cement (NC), nano-silica-fume (NS), nano-fly-ash (NF), and nano-metakaolin (NM), which are used as partial replacements for cement, on the impact strength (IS) of concrete at elevated temperatures. This issue is addressed herein. Nanomaterials were used in this study to replace 10%, 20%, and 30% of the cement in four different grades of concrete, starting from M20 to M50, at different temperatures. This nano-blended matrix was exposed to various temperatures ranging from 250 °C to 1000 °C, with an increment of 250 °C. In total, the results of 384 new tests were reported. In addition, morphological changes undergone by the concrete specimens were observed through a scanning electron microscope (SEM). The study revealed that the type of binder, proportion of binder, heating intensity, duration, and cooling type directly influenced the impact strength of concrete when subjected to elevated temperature. In comparison to NC, NF, NS, and NM, the mix with NC possessed superior performance when it was heated at 1000 °C. Prior to being subjected to elevated temperatures, the MK blended concrete mix performed well; however, when subjected to elevated temperatures, the MK blended concrete also experienced severe damage.