Experimental Study On Durability Of High-strength Concrete Containing Hybridization Of Steel And Polypropylene Fibers And Analysis Of Durability Evaluation Method

In this paper, polypropylene fiber and steel fiber as research object. General mechanical properties and durability of single doped fibers of concrete and hybrid fibers of concrete were researched.Polypropylene fibers and steel fibers were used at three different fiber volume fractions of 0.25%, 0.50%, 0.75% mixed into C60 concrete. Three mixtures with the combination of polypropylene and steel fibers at the volume ratio of 1:1, 1:2, 2:1 were used at three different fiber volume fractions of 0.25%, 0.50%, 0.75% by volume of concrete as well. The compressive strength, splitting tensile strength, flexual strength, and freeze-thaw resistance, penetration resistance, and anti-sulfate corrosion which were about durability of concrete were examined after maintenance for 28 days.(1) Results of the experimental study indicate that the use of fibers in any form and volume fraction resulted in a decrease in the compressive strength, the hybrid fiber reinforced concrete(HFRC) attained a large reduce in the compressive strength than fiber reinforced concrete(FRC) under the same fiber volume fraction; The results also indicate that introducing fibers to concrete resulted in a big increase in splitting tensile strength, and the hybrid fiber specimens attained a bigger increase than single doped fiber specimens under big fiber volume fractions The best performance was the specimen of polypropylene and steel fibers at the volume ratio of 1:2 and the content was 0.75%; Finally, the results show that introducing fibers to concrete resulted in a significantly increase in flexural strength. Hybrid fiber specimens attained a bigger increase than single doped fiber specimens at the same content, the best performance was the specimen of polypropylene and steel fibers at the volume ratio of 2:1 and the content was 0.5%.(2) The results show that introducing fibers to concrete resulted in a significantly increase in freeze-thaw resistance. The best performance of strength loss and mass loss after 50 freeze-thaw cycles was the specimen of polypropylene and steel fibers at the volume ratio of 1:1 and the content was 0.5%.(3) The experimental study indicate that the use of fibers with polypropylene fibers and hybrid fibers resulted in an increase in the anti-sulfate corrosion, but the use of steel fibers resulted in a decrease in the anti-sulfate corrosion. The hybrid fiber reinforced concrete performed better in anti-sulfate corrosion than single doped fiber concrete. The best performance of anti-sulfate corrosion after concrete soaked in solution of sodium of 7days was the specimen of polypropylene and steel fibers at the volume ratio of 2:1 and the content was 0.25%. The best performance of anti-sulfate corrosion after concrete soaked in solution of sodium of 14 days was the specimen of polypropylene and steel fibers at the volume ratio of 1:2 and the content was 0.75%.(4) Results of the experimental study indicate that the use of fibers in any form and volume fraction resulted in a decrease in the permeability resistance. Single doped polypropylene fibers significantly affected the permeability resistance but single doped steel fibers had a little impact on permeability resistance of concrete. Hybrid fiber specimens attained a smaller decreased range than single doped polypropylene fiber specimens but a bigger decreased range than single doped steel fiber specimens under the same fiber volume fraction. The minimal decreased range was the specimen of single doped steel fiber with the content of 0.75%, and the maximal decreased range was the specimen of single doped polypropylene fiber with the content of 0.25%.(5) Based on the existing evaluation system. Fitting function between the relationship of 50 freeze-thaw cycle strength loss and corrosion resistant coefficient of compressive strength of 14 d resistance to sulfate corrosion with impermeability of concrete by test results to establish specific function formulas to evaluate the durability of steel-polypropylene fiber concrete with the perspective of impermeability.