STRESS-STRAIN BEHAVIOR OF NORMAL AND HIGH-STRENGTH STEEL-FIBER CONCRETE POST BURNING

Abstract

This paper presents the results of experimental testing on steel fibrous concrete cylinder specimens after being burned for a certain period of time. The purpose of this research is to explore and develop an analytical expression on the stress-strain behavior of steel-fiber concrete by considering various variables. Precisely, the variables reviewed are the compressive strength of concrete which is defined as concrete with normal-strength, medium-strength and high-strength; the volume of fiber fraction in the concrete, namely 0%, 1% and 2%; and burning time for 1 hour, 2 hours and 3 hours. All cylindrical specimens measuring 100 x 200 mm were tested against uniaxial loads. The experimental results showed that all the fiber-free specimens had experienced a decrease in strength with increasing firing time. Normal-strength concrete specimens lose strength by 30-35% after burning for 1 hour or 2 hours, and the strength degradation increases to 60% at 3 hours after burning. Medium-strength concrete specimens lost 10% strength afterbeing burned for 1hour, then lost 30% and 60% strength after 2 hours and3 hours of  burning, respectively. High-strength concrete specimens lose 10% strength if burned for 1 hour, then the strength is lost 20% and 55% after burning 2 hours and 3 hours, respectively. Another result is a trend of increasing peak strain of concrete with increasing burning time. In this paper, an analytical expression of stress-strain post-burning steel-fibrous concrete is developed. The comparison results show that the analytical expression is able to predict the experimental results of normal and high-strength steel-fiber concrete with various variations in the volume of the steel fiber fraction effectively.