The bond strength by pull-off and direct tensile strength of concrete damaged by elevated temperatures

I Rozsypalova,P Danek,O Karel

doi:10.1088/1757-899x/385/1/012047

Abstract

This paper presents the results of an experimental study of selected characteristics of concrete following its exposure to high temperatures. The monitored parameter was the influence of high temperatures on the bond strength and tensile strength of concrete. The bond strength was tested by a pull-off test, the tensile strength was determined as the direct tensile strength. Experimental concrete panels of 2300 × 1300 × 150 mm were exposed to high temperatures (corresponding to the temperatures in a normal fire) using a fire test furnace at the AdMaS Science Centre of the Faculty of Civil Engineering, Brno University of Technology. The direct tensile strength test was performed on cylinders (diameter of 100 mm and length of 100 mm) made from core samples taken from the panel. The pull-off test was performed on the surface exposed to high temperatures. The results of the experiment show a significant influence of high temperatures on the examined characteristics, and both characteristics were found to significantly decrease with a growing thermal load.

Highlights

At present, concrete ranks among the most commonly used building materials
The results of experimental work are summarized in the form of average values and standard deviations in Figure 4 for bond strength determined by a pull-off and in Figure 5 for direct tensile strength of concrete
The characteristics declined the most significantly for temperature 1000 °C, the bond strength drops to 28.2 % and the direct tensile strength decreased to 17.1 % compared to the unloaded concrete

Summary

Introduction

Concrete ranks among the most commonly used building materials. The most important mechanical property of concrete, according to the current practice, is the compressive strength, according to which the concrete is classified into individual strength classes. Another important and no less significant role is played by the tensile characteristics of concrete, because they have a major influence on the occurrence and development of cracks in concrete structures [1,2]. It is necessary to take into account material degradation caused by extraordinary influences which include a load in the form of fire. Elevated temperatures cause damage of the concrete internal structure [1]

Methods

Results

Conclusion