Performance of high strength concretes at elevated temperatures

In this study, the effect of temperature on compressive strength, spalling and mass loss of High Strength Concretes (HSCs) by fc′>65 MPa is discussed. Average compressive strength of the HSCs was from 65 to 93 MPa, which was optimized by Taguchi’s method as a powerful tool for optimizing the performance characteristic of a product/process. This paper presents results of an experimental program on the effects of elevated temperature exposure on the mechanical properties and potential for explosive spalling of HSCs. Effects of four parameters; water to cement ratio (w/c), sand ratio, silica fume ratio and amount of silica fume (sf) addition are considered in tests. Mechanical properties of HSCs were measured by heating 150×300 mm cylinders at 20∘ C/min to temperatures of up to 800∘ C. The tests include sixteen mixtures; twelve contain sf and four are without sf that are selected by Taguchi’s method. The paper presents results of measurement that indicate the effect of sf, cement, fine aggregate, coarse aggregate and water on residual strength, spalling and mass loss of the HSCs. The presence of silica fume had no statistically significant effect on the relative compressive strength while it had an overall statistically significant effect on increasing spalling. The type of aggregate had a significant influence on the thermal properties of HSCs at elevated temperatures. In most cases, by increasing sand ratio, residual compressive strength increased while this trend is inversed for coarse aggregate.