Behavior of Plain and High Performance Polypropylene Fiber Concrete Subjected to Elevated Temperatures

Abstract

The aim of this work is to determine the residual compressive strength and splitting tensile strength after exposure to an elevated temperature (between100 to 500 C ◌ْ ) of plain and polypropylene fiber reinforced concrete (PPFRC) in comparison with specimens exposed to ordinary temperature 25C ◌ْ . High – performance concrete mixes were produced by using high rang reducing agent superplasticizer (SP) and 10% high reactivity metakaoline (HRM) as a partial replacement by weight of cement (350)Kg/m3 . A single concrete mix with HRM,SP and four PPF contents of (0.25, o.5, o.75 and 1%) by volume were adopted. The workability of the concrete was kept constant ( slump 100 ± 5mm ).Each group of specimens ( plain and PPFRC ) was heated to a specified temperature and kept at the temperature for one hour before being gradually cooled to room temperature and then they were tested .The results show at ordinary temperatures 25 C ◌ْ, the addition of fiber volume fraction (VF%) of (0.25%) increases the compressive ( 20.6% ) comparable to HPC without fiber . While the addition of ( 0.5 , 0.75 and 1% ) of polymer fibers , the compressive strength decreased (12.6 , 19 and 33%) respectively comparable to HPC without fiber . On the other hand the addition of (VF%) of (0.25) increased splitting tensile strength ( 15%) comparable to HPC without fiber . while theaddition of fiber volume fraction (VF%) of (0.5 ) increased splitting tensile strength by a percentage which is lower than that in specimens with VF% of 0.25 , the increase in splitting tensile strength was ( 6%) comparable to HPC without fiber at ordinary temperaturesThe results also shows that , when (1% ) fibers was used , the splitting tensile strength decreased ( 10.8%) in comparable to HPC without fiber At elevated temperature the results show an appreciable decrease in compressive strength and splitting tensile strength after exposure to temperature higher than 300 C ◌ْ of both plain and PPFRCSpecimens containing PPF ( 0.25 , 0.5 , and 0.75 %) the percentage ofreduction in splitting tensile strength is lower than that in HPC specimens ( without fibers ) after exposure to a temperature ( 500 ,300 and 100 C ◌ْ ) comparable to normal temperature 25C ◌ْ .While specimen containing PPF ( 1% ) the percentage of reduction in splitting tensile strength was higher than specimen without PPF after exposure to a similar temperature .On the other hand , specimens containing PPF ( 0.25 , 0.5 , 0.75 and 1 %) the percentage of reduction in compressive strength is higher than that in HPC specimens ( without fibers ) after exposure to a temperature (500 ,300 and 100 C ◌ْ). comparable to normal temperature 25C ◌ْ