Employing nondestructive testing technologies throughout concrete’s life cycle

Embedded IoT sensors

Embedded sensors are designed and engineered to provide highly accurate results. They are attached directly to the rebar within the concrete slab or formwork and allow for continuous monitoring of concrete temperature and strength. Newer versions of these sensors connect directly to smartphones and tablets, allowing contractors and engineers to see the data in real time. The ability to embed sensors within the formwork and obtain strength results on the jobsite eliminates the need to transport samples to a laboratory for testing and thus reduces the margin for error.

These real-time sensors provide data on concrete maturity, a function of temperature history in field-cured concrete described in ASTM C1074, Standard Practice for Estimating Concrete Strength by the Maturity Method, and Netherlands Standardization Institute (NEN) 5970, Determination of Strength of Fresh Concrete with the Method of Weighted Maturity. The use of sensors is the only NDT method currently accepted by building codes and standards for formwork removal, post-tensioning, saw-cutting, and similar tasks. It is accepted by the Canadian Standards Association’s (CSA’s) codes and standards, CSA A23.1, Concrete Materials and Methods of Concrete Construction, and CSA A23.2, Test Methods and Standard Practices for Concrete, which are used in the construction of all concrete structures across Canada.

Wired maturity sensors and thermocouples have allowed contractors and engineers to obtain accurate predictive data on the state of their concrete. In turn, this allows them to make informed decisions relating to project scheduling and operations. New, wireless mobile-based technologies provide even more advantages to workers, as they have been developed to eliminate the hassle of wires on the jobsite and the need to connect to cumbersome data loggers, making data collection and analysis less time consuming. Utilizing such wire-free sensors further reduces the cost and time requirements for concrete quality control by allowing contractors and engineers to view concrete maturity data in real time and proceed to the next steps in a project as soon as the concrete has reached the required strength. This eliminates the need to wait on break test results, which can take up to 24 hours to receive.

Demand for NDT for the condition evaluation and maintenance of aging structures has been increasing over the last several years, especially in North America, where many concrete buildings are nearing the end of their life cycles. Many engineers are increasingly choosing NDT methods over traditional testing methods, as they are proving to be more powerful, reliable, and effective. In-situ tests (such as pullout, rebound, penetration, and dynamic tests) aim to detect the condition of reinforced structures, assess their various properties, and rank their condition.