Investigation of the mechanical properties of Ultra High Performance Concrete with steel and polypropylene fibers considering the initial age and accelerated aging.

• Grant number: 25/01437-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2025
• End date: May 31, 2026
• Field of knowledge: Engineering - Civil Engineering - Structural Engineering
• Principal Investigator: Lisiane Pereira Prado
• Grantee: Leticia Raquel Alves Batista
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil
• Associated research grant: 23/04403-4 - Numerical and experimental investigation of the interface of high strength concrete and ultra-high-performance concrete, AP.R

Abstract

Ultra-high-performance fiber-reinforced concrete (Ultra High-Performance Concrete - UHPC) has emerged as a material of choice for structures subjected to high mechanical stresses due to its remarkable properties of compressive strength, tensile strength, modulus of elasticity, and ductility. These characteristics are directly influenced by the type of fiber added to the mixture, which transfers internal stresses in the cement matrix during the cracking process. Depending on the desired behavior of the material, different types of fibers, such as steel and polypropylene, can be used in the composition of UHPC. Careful selection of these fibers is essential to optimize the performance and durability of structures built with UHPC. This study aims to investigate the mechanical properties of ultra-high-performance concrete reinforced with fibers considering the combination of two types of fibers, steel and polypropylene microfibers, evaluated at 28 and 365 days of age. Ideal proportions of mixtures between steel and polypropylene microfibers will be studied to optimize the mechanical properties of concrete. The research will evaluate parameters such as compressive strength, flexural tensile strength, diametrical compression tensile strength, and modulus of elasticity at 28 days and after 365 days of curing. In addition, the effect of accelerated aging on the mechanical properties of UHPC will be investigated. This process will be analyzed using two methods: immersion in hot water and alternating immersion and drying cycles. The project seeks to contribute to a deeper understanding of the behavior of fibers in UHPC, aiming to obtain a more resistant and economically viable concrete over time. (AU)