The quality control of the compressive strength of concrete is typically performed on standardized specimens at the age of 28 days. However, the pressure to fulfil construction deadlines and the need to reduce costs by reducing construction time has resulted in the removal of formwork at the earliest convenient time possible. Often, there is no precise knowledge of the in situ strength of the concrete, let alone durability parameters, and often the influence of the environment on curing and concrete maturity are not considered. A simple procedure is proposed for the prediction of the compressive strength of concrete based on electrical resistivity measurements. Prior to formwork removal, electrical resistivity can be assessed and based on an electrical resistivity vs. compressive strength correlation curve, and the strength of concrete can be estimated. This procedure ensures, for example, that the formwork is only removed when the concrete reaches a predefined compressive strength, dispensing with the calculation of concrete maturity. On the other hand, the whole surface of the concrete structure can be systematically tested so as to estimate 28-day compressive strengths and detect areas that could potentially not conform to the specified requirements. In this manner, a realistic overview of the in situ compressive strength of the whole structure can be obtained.
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