Development of Thermal Remote Sensing NDT Method for Early Age Strength Estimation of Concrete

Abstract

Infrastructural development is the major key factor for overall growth in India. Construction industry lacks continuous monitoring and evaluation for structural parameters which can reduce structural failures. Monitoring the concrete at early ages during construction can be done by various non-destructive techniques (NDT) methods. Concrete maturity method (CMM) is one among the NDT methods, specially employed for estimating the early age strength by analysing heat produced in concrete. Temperature emitted through hydration process of concrete is considered as a key parameter in evaluating maturity of concrete. CMM in conjunction with thermal Remote sensing imaging sensor is a motivating alternative for thermocouples to estimate strength in early stages of concreting. Three different concrete mix designs, i.e. M20, M40 and M60, are chosen for evaluating the study. A controlled curing environment is established for specimens in a thermocol box for conducting the study which does not get affected to external climatic conditions. According to the specified imaging time intervals of 30, 60, 120 and 180 min, around 2500 thermal images of concrete specimens are obtained by thermal camera and processed for surface temperature variations. By examining the developed time–temperature graphs, it is observed that there is a gradual downfall of temperature during the initial setting time of concrete. Maturity indices of concrete are generated by time–temperature graphs of specimens. Calibration curve is derived by the observed temperatures at specific time interval and simultaneously compressive strengths of concrete at the same time. The hybridisation of thermography, photogrammetric and computer vision techniques like image analysis serves in interpreting the early age strength gain of concrete.