The Research On High Temperature Damage And Temperature Field Simulation Of High Performance Concrete

High performance concrete is widely used and plays an important role in all areas of civil engineering for its higher strength, high durability, outstanding working capability and volume stability. However, due to more compact internal structure and lower permeability of high performance concrete, there is a great possibility for high performance concrete to burst, spall when the structure is subjected to a fire, which leads to direct exposure of internal steel reinforcement to high temperature, instant loss of bearing capacity, causing the collapse of buildings, loss of life and property and difficulties in rescue work. Therefore, to explore the high temperature(fire) effect on the performance of high performance concrete, to reveal the deterioration law of the performance and to seek for reasonable prevention measures have become the focus of the research on the high performance concrete.Funded by the National Natural Science Foundation(51478290), this paper makes a basic exploration about mechanical properties and thermal performance of the material before and after high temperature, taking high performance concrete with strength grade of C60 as the research object which is a local material and making a preliminary research on the slab temperature field and the thermal strain of high performance concrete by using high-temperature thermocouple and vibrating wire strain meter. Also, the numerical simulation of high performance concrete slab temperature field is carried out with the help of ABAQUS simulation software. The main contents are listed as follows:I. Tests on high performance concrete performance: The basic performance test included axial compressive strength, elastic modulus, splitting tensile strength and thermal conductivity before and after high temperature. The experimental results show that after high temperature, the properties of high performance concrete decreases with increasing of the temperature and degradation of elastic modulus is faster than the splitting tensile strength and axial compressive strength. The experiment establishes a relation among the axis compressive strength, elastic modulus, split tensile strength and coefficient of thermal conductivity with temperature changes.II. Tests on high performance concrete thermal expansion: High temperature horizontal expansion instrument was used to explore the concrete internal different components under the action of high temperature expansion characteristics. Results show that expansion rate of each material is not identical--- coarse aggregate expansion rate is greater than that of cement mortar, while concrete expansion rate is between the rates of coarse aggregate and mortar.III. Tests on high performance concrete slab thermal strain: With the help of vibrating wire strain gauge, the concrete slab heating process in different depth of thermal strain was explored. Results show that in the concrete slab heating process, temperature rises faster when the material is placed near fire, thermal strain is higher during the same period of time; This paper also analyzes the effect of temperature on the value of strain, the conclusion of which is that the higher temperature is, the larger the strain values are, and the author establishes the relation between concrete and strain temperature, making a theoretic and numerical comparison between concrete thermal strain and rate of expansion which are related to each other.IV. Research on high performance concrete slab temperature field: Used the temperature measured by high-temperature thermocouple measuring plate placed inside the concrete slab during the process of heating to analyze the temperature field inside the concrete slabs; and with the help of ABAQUS stimulated the temperature field, compared and analyzed the test results. Results show that in the heating process, there is a temperature gradient related to the thickness of concrete slab. The results of computer simulation generally are consistent with the temperature trend in the test, but the simulation values are higher than the experimental values because of the neglect of the water content of concrete during the stimulation.