Flexural strength of silica fume, fly ash, and metakaolin of hardened cement paste after exposure to elevated temperatures

The mechanical properties of concrete based mainly on flexural and compressive bearing capacity. Generally, researchers have an interest in the evaluation of compression property through the importance of the flexural performance of the material in the constructions, namely the significance of each mechanical property based upon the position of the structural element. The present experimentally work is directed toward improving the flexural strengths performance of ordinary hardened cement paste (HCP) at ambient and after elevated temperatures exposure. The used parameters were different pozzolanic materials with different replacements ratios to cement mass and different levels of temperature. Results proved the significant contribution of pozzolanic material to enhance the flexural properties of HCP after being exposed to elevated temperatures. The low content of CaO, the high grinding fineness, and the physical morphology of the used pozzolanic materials, made their adoption effective to HCP after exposure to elevated temperatures. Using 3%, 12%, and 15% of silica fume (SF), metakaolin (MK), and fly ash (FA), respectively, showed the highest heat endurance among the other replacements. However, the optimum replacement of MK has shown a better heat endurance than the optimum replacements of SF and FA. On the other hand, the spalling has occurred at high replacements of SF. Finally, the results are supported by means of thermo-gravimetric, SEM, and computed tomography investigations.