ABSTRACT
It i s well known that the strength of the concrete in an actual structure i s less than that obtained from standard cured control specimens (1). Concrete in a structure differs from that in a control specimen in terms of method of placing and i t s effects, compaction effort, temperature di f f e r e n t i a l s , curing, rate of drying, moisture/relative humidity gradients, etc. - almost a l l factors that effect significantly the overall and long term strength, s t a b i l i t y and safety of the structure. From an engineering point of view, strength i s very much an essential parameter in design, and i s also a reasonably relia b l e indirect indicator of durability, such as resistance to carbonation. The most important aim of in-place testing i s thus often to establish a reliable estimate of the strength of the concrete in the structure, particularly at early ages. Prediction of the early age strength of concrete during construction has also special relevance and significance in the current climate of growing concern and awareness of possible causes of concrete deterioration in service. In-place testing can therefore help to assess and enhance the quality of construction.
