engleski

Ultrasonic characterization of cement materials

Potential of NDT ultrasonic method for investigation and in-situ monitoring of properties of cement material during hydration has been studied. Two different compositions of calcium aluminate cement (CAC) mortars prepared at water to cement ratio of 0.44 were analysed at 20 C. One sample had quartz sand (fractrion: 0, 63-1, 25 mm) to cement ratio 3:1, and the other had standard quartz sand (fraction: 0, 063-1, 6 mm) to cement ratio of 2:1 with the lithium carboate added as a setting accelerator. Samples of cement material are characterized in two ways: firstly using ultrasonic non-destructive testing, with immersive through-transmission pulse mode technique, and secondly by compressive strength measurement. The characterization is based in the former case on the values of parameters of transmited ultrasonic impulse fit and in the latter case on the value of compressive strength. The linearity between the measured compressive strength and the maximum velocity of the particles of the material is found. These results makes it possible direct real-time reliable and precise, non-destructive determination of the degree by which the hydration is finished. Furthermore, the relation between ultrasonic impulse group velocity and the material porosity is established, which enables one to infer about the fractal structure of the material.

cement materials; characterisation; ultrasound; compressive strength; fractals

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