Mechanical performance comparative analysis of concrete pipes reinforced with steel and polymeric fibers

Abstract

There is a huge need of sewerage systems in Brazil where more than 35 million inhabitants is not provided for any kind of established public service. In that sense, some research projects were developed focusing the use of steel fibers in concrete pipes what leads to the publication of the Brazilian standard NBR 8890, which permits the use of this kind of reinforcement. Although the concrete pipe durability should be increased when the regular reinforcement is replaced by steel fibers, the use of polypropylene macrofibers will provide much better conditions to aggressive environment resistance. Nowadays, this kind of fibers could be easily found in the Brazilian market. The main doubt remaining is the macrofibers mechanical performance due to their lower elastic modulus when compared to steel fibers. In that sense, this research project aims to evaluate the mechanical performance of concrete pipes with the reinforcement of steel and polypropylene fibers. This evaluation will be carried out through the determination of mix-design curves correlating the fiber content to the post-peak performance determinate by the crushing strength test of the concrete pipes. The fiber content necessary to fit the Brazilian standard requirements could be determinate by this process, and the values associated to each kind of fibers could be compared. Two types of macrofibers will be compared to the steel fiber used as reference. The concrete pipe inner diameter will be one meter because it is the maximum allowed by the Brazilian standard. The fiber reinforced concrete pipes will be produced and tested in the Fermix factory, which had compromised to the technical support in that sense. The other tests will be made at the labs of the University. In these tests will be include the fiber and row materials characterization. A test method for fiber content determination in hardened concrete will be also used.