Vikasonic - Measuring the Early Setting and Hardening with Ultrasonic Waves

The early setting is usual measured with the penetrometers or the Vicat apparatus. This kind of measurement has some disadvantages. In the early sixties some researchers suggested to use the ultrasonic transition time as method for measuring the setting of mortars or fresh concrete. In recent years the ultrasonic method was developed and used in the Vikasonic.

Measurement Principle

The fresh mortar is setting between two ultrasonic transducers, which are supplied with 0.25s or less pulses per second at a frequency of 54 kHz. The mortar changes, according to the setting, the ultrasonic transition time. From the beginning of first contact of the growing binder-stone, the ultrasonic sound speed increases. If there is a complete crystalline structure the change of the sound speed will be slower. Until further aggregation of the cement stone the ultrasonic sound speed increases again.

Measurement Setup

Each measurement cell is supplied with a pair of ultrasonic transducers. The Vikasonic continuously measures the ultrasonic transition time and the signal damping. The data sets are recorded digitally to a common USB stick. Also the sound speed and the elastic modulus is calculated and recorded. Additionally, the temperature inside the specimen is measured with a type K thermocouple.

The Vikasonic is an autonomous instrument and thus, during the tests no PC is required. The data may be directly imported into an Excel worksheet.

Application Example

There are some tests to compare the Vicat and the ultrasonic method.