Issue 50

P. Qiu, Frattura ed Integrità Strutturale, 50 (2019) 300-309; DOI: 10.3221/IGF-ESIS.50.25 300 Experimental research on fracture behavior of concrete after high temperature Peng Qiu College of Architecture and Civil Engineering, Jiangsu City Vocational College Nantong Campus, Nantong, 226006, China qiupengrt@163.com A BSTRACT . High-strength concrete has been widely used in various complex buildings. The fracture and mechanical properties of high-strength concrete after fire have great research value. Based on the double K fracture model, the fracture properties of C70 strength grade concrete after being processed by high temperature of 25 °C ~ 800 °C were studied by three-point bending beam test. The change rules of fracture toughness KIC and fracture energy under different temperatures after being processed by high temperature were analyzed. The results showed that the initial crack toughness and instability toughness of C70 concrete decreased with the increase of temperature; the fracture energy first decreased rapidly and then decreased slowly with the development of temperature. K EYWORDS . High temperature; Concrete; Fracture toughness; Fracture energy. Citation: Qiu, P., Experimental research on fracture behavior of concrete after high temperature, Frattura ed Integrità Strutturale, 50 (2019) 300-309. Received: 08.04.2019 Accepted: 21.08.2019 Published: 01.10.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION n today’s construction industry, concrete as the most important engineering material has been widely used; high-rise buildings, bridges, channels will use a lot of concrete materials and there will be some small cracks in the use process of concrete. These cracks may be formed in the process of concrete forming, or may be formed by the external environment (high temperature, man-made) [1-3]. Cracks will expand in a very strong pressure state, leading to gradual increase of crack width and length and decrease of bearing capacity, which will ultimately cause the breakage of structure, and crack is one of the main factors leading to the decrease of bearing capacity of concrete structures [4,5]. Therefore, many researchers have concerned about the problem of concrete cracks and tried to find out why cracks generate, how cracks expand and how to prevent cracks [6]. However, the fracture mechanism of concrete is very complex as the uneven distribution of coarse aggregate and fine aggregate results in internal multi-level system. Fracture mechanics is a discipline that studies the law of crack generation and propagation in materials or structures by using elasticity and plasticity mechanics, starting from the point that macro cracks exist in materials or components. Its task is to obtain the fracture parameters of component materials and study the fracture problems of components under different external environments (high temperature, freeze thawing, external load, etc.). I