Ultrasonic assessment of initial compressive strength gain of cement based materials

• New reliable US technique to determine early age compressive strength of different cement based materials
• Strong correlation between the development of frequency spectrum and early age compressive strength
• The technique enables recognition of clearly plastic and rather solid behavior of the material during setting.
• Extension of possible application of US P-waves to determine early age properties of cementitious materials

In this paper, a possibility of using frequency spectrum of ultrasonic P-waves to determine very early age compressive strength (fc) of cement based materials (CBMs) is analyzed. TG parameter, representing the ratio between maximum amplitudes of high and low frequency ranges that appear in the frequency spectrum of the transmitted signal, is used to observe the changes in the spectrum. Both fc and TG start to increase simultaneously and later develop according to similar trend. Thus, strong correlation between fc and TG is established, regardless of the CBM's composition. By comparing stress–strain curves and time derivatives of TG–t curves, the stage when the material is clearly plastic and stage when material exhibits solid behavior, can be distinguished. These results explain physical meaning of TG parameter in more detail and expand the range of practical applications of methods based on spectral analysis of transmitted P-waves.