High temperature resistance of normal strength and autoclaved high strength mortars incorporated polypropylene and steel fibers

The effects of high temperatures up to 900 °C on normal strength, water cured and autoclave cured high strength mortars were investigated within the scope of this study. Mechanical properties such as, compressive strength, flexural strength, modulus of elasticity, and weight loss of the specimens were determined. The effect of polypropylene (PP) and steel fibers incorporation on high temperature behavior of high strength mortars were also investigated. Microstructure investigations were also carried out by SEM analyses. Test results indicated that compressive strength of all mixtures increased with increasing temperature up to 300 °C. However, above 300 °C all specimens showed explosive disintegration except normal strength mortars, and high strength mortars with PP fibers. It seems that, PP fiber inclusion is effective in preventing the explosive spalling behavior of high strength mortars. On the other hand, steel fibers did not improve high temperature resistance. To prevent spalling, minimum PP dosage for autoclave and water cured high strength mortars has been determined as 0.2% and 0.1%, respectively.