Mechanical properties of set concrete at early ages. Test methods

Our knowledge of the properties of concrete till the end of exponential strenght-development is not satisfactory. Within the RILEM COMMITTEE 42-CEA-concrete at early ages a collection of different test methods was made as a basis of former testing. After a short description an analysis shows the advantages of the different methods. Whereas there are no problems with compressive strength for tensile strength there exists a lot of different test methods. With the ring test stresses are calculated with the assumption of elasticity. Beams and columns are discussed. Ultrasonic pulse velocity seems to be better for characterisation of young concrete than the modulus of elasticity whose definition is not uniform. For strain-measurement inductive gauges allow great accuracy in short time, wire-strain-gauges are better to eliminate influences of time and temperature.