Analytical Tools for Strength Prediction of Thermally Deteriorated HPC

Abstract

Analytical tools for strength prediction of thermally deteriorated HPC” is an experimental study on development of analytical tools for strength prediction of High Performance Concrete (HPC) exposed to elevated temperatures. The prime objective is to study the behaviour of HPC at different exposure durations and temperatures. The work also focuses on the residual strength assessment of concrete exposed to elevated temperature by non-destructive testing. Exhaustive review of literature has been done to understand the state of the art, to identify the points needing further research and then to design the experimental investigation. First phase of the study deals with properties of four types of HPC mixes that include unblended and blended mixes, with partial replacement of cement by Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS), at exposure temperature range of 100°C-800°C and exposure duration of 1, 2 and 3 hours. Colour change and crack patterns have been observed. Porosity and density determination, Ultrasonic Pulse Velocity (UPV) measurements to assess the quality of concrete, have been made. Residual compressive and splitting tensile strengths have been determined by destructive testing. Second phase explores the potential of drilling resistance test on thermally deteriorated concrete as an NDT tool. Drilling time for a designated depth of drilling and sound measurement while drilling have been recorded. Determination of residual compressive strength of plain and reinforced concrete, exposed to elevated temperature has been carried out in the third phase of experiments by core recovery tests to understand the behavioural differences. From the above investigation very interesting conclusions have been drawn that highlight the superiority of blended concrete’s fire endurance properties. The potential use of drilling time and sound levels as an NDT tool, nomographs that can be used as valid decision making tools in failure forensics and also elaborate the care and caution necessary in conducting and interpretation of core test results of fire damaged structural elements.