Polypropylene fiber reinforced concrete in railway crossties

Concrete crossties;Polypropylene macro fibers;Fiber reinforced concrete;Self-consolidating concrete

Master, Abhishek ; Lange ; David A.

关键词: Concrete crossties;    Polypropylene macro fibers;    Fiber reinforced concrete;    Self-consolidating concrete;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/99407/MASTER-THESIS-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Cracking of concrete crossties is a performance problem that reduces service life and increases maintenance costs. While strong in compression, plain concrete is relatively weak and brittle under tensile stresses. Inclusion of synthetic polypropylene macro fibers in concrete is known to improve crack resistance and is a feasible solution for prolonging the life of crossties. The present study investigated the performance of synthetic polypropylene macro fiber reinforced concrete and their application in railway crossties.The study involved a thorough review of the properties and testing of synthetic polypropylene fiber reinforced concrete (FRC). A standard test method for obtaining average residual strength of FRC was used to evaluate the performance of various concrete mixtures reinforced with synthetic polypropylene macro fibers. It was found out that the concrete with higher fiber proportions showed significantly higher residual load carrying capacity (post-cracking response). Moreover, the concrete mixtures had acceptable workability and showed only slight loss in compressive strength due to inclusion of fibers.Self-consolidating concrete (SCC) is an emerging class of concrete which flows and consolidates on its own without vibration. Fiber reinforcement can be used in SCC to enhance the mechanical properties of concrete. The present study investigated the rheological and mechanical properties of SCC reinforced with different proportions of fibers. Fresh property tests included slump flow test and rheological tests using a concrete rheometer. The study underscored the potential for fibers to be accommodated by adjusting the mixture proportions of concrete. It was shown that inclusion of fibers in SCC is feasible for the purpose of manufacturing structural elements like railway crossties.The present study also considered the current state of prestressed concrete crosstie design and the impact of FRC on mechanical performance of concrete crossties. The applicability of FRC in railway crossties was investigated by developing and testing prototype crossties. A comparative study was performed between a conventional crosstie and a fiber reinforced crosstie through tests at rail seat and center of crosstie. It was found out that the synthetic polypropylene fibers provided sustained capacity for deformation in the concrete crossties along with an improved crack resistance.Lastly, this study developed a tensile stress-strain model for FRC behavior. Four point bending test results of FRC beams were used to determine tensile behavior of FRC using an inverse analysis approach and a back calculator tool. Preliminary tensile stress-strain models were established which can be used to define constitutive properties for concrete when using finite element analysis (FEA) to analyze experimental results. FEA has not been performed as a part of this thesis work, but will be pursued in subsequent research activities at the University of Illinois.