Concrete strength gain monitoring with non-destructive methods for potential adoption in quality assurance

Abstract

During concrete production, simple and quick testing methods are desired for assessing concrete properties. Non-destructive testing methods, NDT, are particularly valuable in the Quality Assurance and Quality Control (QA/QC) process since do not interfere with production of concrete and reduce testing time and cost. Concrete hardening, and thus strength gain, is one of the most important parameters in concrete production since it can immediately identify potential issues in concrete proportioning, curing conditions, and use of questionable ingredients that affect strength and stiffness. NDTs can provide early warnings in meeting strength requirements at early ages as well as long term strength. NDTs are also valuable in providing strength gain predictions so that follow-up construction can continue once the minimum critical strength is achieved. This research was developed based on the recommendations of a recent national study undertaken by the authors for Federal Highway Administration in developing an NDT based QA process for highway materials. Thus, it was the objective of this research to identify and assess alternative NDT methods that can be used in monitoring and/or estimating strength gain in concrete, and thus for potential adoption an NDT based QA plan. These NDTs should be fast, accurate, reliable and simple to run. The NDT methods explored in this study included: infrared thermography, ultrasonic pulse velocity, and fundamental resonance frequency. The results from such testing methods were coupled with maturity modeling for monitoring and predicting concrete strength at early ages. The results provided good relationships with the maturity index. Even though the relationships of these NDT outputs with the maturity index were based on limited set of experimental data, it is expected that their accuracy will improve with complementary testing on additional concrete mixtures. The methodology of this study is applicable elsewhere where similar materials and construction methods are used.