Engineering and Technology Journal

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 the
addition 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 temperatures
The 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 PPFRC
Specimens containing PPF ( 0.25 , 0.5 , and 0.75 %) the percentage of
reduction 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 ◌ْ