Residual strength and degradation of cement mortar containing polypropylene fibers at elevated temperature

The elevated temperatures caused by fire affect the physical and chemical properties of the mortar and thus, influence its mechanical properties. This study presents the results of an experimental investigation on the mechanical properties and microstructure of cement based mortar composites contained polypropylene (PP) at high temperatures. The mortar was prepared and cured as per the relevant international standards. Upon curing, tested specimens were exposed to 250, 450, 600 and 900 °C for 2 h. The influence of the high temperatures on the physical and chemical changes of the blended cement mortar was also analyzed by Scanning Electron Microscopy. Mortar specimens exposed to different high temperatures were tested for compressive and flexural strengths, and compared with control specimens (i.e. unheated). Results revealed that even low fiber dosage of PP fibers with mortars was helpful in completely preventing explosive spalling due to significant increase of permeability. Mechanical results and microstructural analysis of mortar specimens showed that both compressive and tensile strengths were initially increased at 250C°, followed by considerable reduction at higher temperatures.