Non-Destructive Assessment of Residual Strength of Thermally Damaged Concrete Made with Different Aggregate Types

The paper presents the results obtained for four concretes made with four different aggregate types: basalt, granite, dolomite and riverbed gravel. In this study, the cement paste and mortar compositions and their volumes remained the same for all the four concretes that allow clear comparisons and conclusions of aggregate type effect. Moreover, the aggregate particle size distribution is chosen to be quasi identical for all concretes so that this factor does not affect the concrete behaviour. The residual material properties (after heating and cooling down) are determined with the use of destructive and non-destructive testing methods for each concrete type being not thermally damaged and after thermal exposure at temperature of 200 °C. 400 °C, 600 °C, 800 °C and 1000 °C. Residual mechanical properties are compared with diagnostic parameters obtained with NDT methods. The aim of this study is to provide and compare the regression curves between selected non-destructive diagnostic parameters and the residual values of mechanical properties. The NDT methods used in this experiment are: surface hardness and Ultrasonic Pulse Velocity. (paper)