Effect of Elevated Temperature on Toughness of Concrete Structures

Study of concrete properties at high temperatures remained a focus of many researchers since years. In this research, the impact of heating on concrete specimens was studied while considering the toughness parameter, and then the outcomes were matched with the unheated concrete specimens. For this purpose, experimental data from previous studies was collected, analyzed and functions were proposed for various properties of concrete. The working was carried out on the after-peak portion of the stress-strain curves obtained from the compression testing of concrete specimens in a strain-controlled environment. The stress-strain curves were imported in AutoCAD and scaled as required. Several points were marked on the post-peak portion of each stress-strain curve and the values were imported in an excel spreadsheet. Furthermore, the post-peaks were analyzed by following a methodology and toughness parameter was computed for each available stress-strain curve. After that, the toughness parameter was normalized with respect to room temperature value. The trend of toughness parameter (AF) was analyzed by plotting normalized AF versus temperature and a function was proposed for its variation. Different types of concretes studied in this research include normal strength concrete, concrete with polypropylene fibers, steel fibers, PET, rubber, Meta kaolin etc. The impact of heating on other properties of concrete like compressive strength, elastic modulus and peak strain was also studied at high temperatures and different functions were proposed for these as well after analyzing the collected data. The post-peaks of the tentative stress-strain curves were matched with the ones gained from the models to understand the variation. Two additional post-peaks were also plotted including one using the minimum toughness parameter (AF) and the second using the maximum toughness parameter (AF) at a specific temperature. The trends were observed with respect to the maximum temperature attained as well as considering the concrete constituents.