Fatigue and fracture mechanical properties of selected concrete for subtle precast structural elements

K. Kotrasová,E. Kormaníková,Vlastimil Bílek,Petr Miarka,Stanislav Seitl,S. Kmeť

doi:10.1051/matecconf/202031000033

Abstract

Precast concrete elements used as a civil structure are usually made of a cement-based matrix and natural aggregates (such as sand, gravel, crushed stone, etc.). These structures are usually exposed not only to a static load but also to a cyclic load if they load the bearing part of a bridge (traffic etc.). The knowledge of fatigue and fracture mechanical characteristics is important in designing and modelling new structures. This paper introduces and compares fracture mechanical properties obtained from static and fatigue tests for three kinds of concrete. The focus was set on the bulk density, flexural and compressive cube strength, fracture toughness and fatigue properties (S−N − Wöhler curve). All of these tests are important for a practical application in the design of precast concrete structures. The experimental results were statistically analysed and they showed that the fatigue and mechanical fracture properties improved with improved mechanical parameters of concrete.

Highlights

Concrete made these days is not environmentally friendly because of the amount of cement used in mixture composition, which results in high CO2 production [1]
Produced precast elements are light frames and beams for small span bridges. These subtle structural elements have to be designed with higher attention to durability, fatigue behaviour and fracture behaviour. Both Activated Concrete (AAC) and High Performance Concrete (HPC) are compared to concrete C50/60, which is commonly used in production of concrete precast and pre-fabricated structural elements
A comparison of the experimentally obtained fatigue results for HPC and C50/60 are shown in Fig. 3, where the bending stress amplitude [MPa] applied during the fatigue experiments is plotted against the logarithm of the number of cycles to failure or at 2 106 cycles [N], a limited number of cycles, for run-outs i.e. for unbroken specimens

Summary

Introduction

Concrete made these days is not environmentally friendly because of the amount of cement used in mixture composition, which results in high CO2 production [1]. Less use of concrete means reduction of used materials, which eventually results in less CO2 consumed per structure Both AAC and HPC should reduce the amount of Portland cement used in the mixture composition, which is the main reason why concrete produces a high amount of CO2 in its production. Produced precast elements are light frames and beams for small span bridges These subtle structural elements have to be designed with higher attention to durability, fatigue behaviour and fracture behaviour. Both AAC and HPC are compared to concrete C50/60, which is commonly used in production of concrete precast and pre-fabricated structural elements (e.g. double T-shaped beam elements for roofing). The investigated and compared properties were the bulk density, the flexural strength, compressive strength, the fracture toughness and the fatigue properties presented by the Wöhler curve were tested during the research programme

Materials and their static properties

Comparison of concrete investigated properties

Experimental data processing procedure

Results and discussion

Conclusions