Shotcrete early strength calibration studies

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Shotcrete Early Strength Calibration Studies

Multicrete Systems Inc. are specialists in project solutions for the mining and tunnelling industries. Based in Canada, the company operates globally and provides leading-edge technical assistance through expertise with concrete materials and equipment, including construction programs using shotcrete. The development of new shotcrete products – aggregate materials and mix specifications, accelerator additives—and the selection of the most suitable product for a particular solution are areas of expertise which have built Multicrete’s reputation. A mining project raised the opportunity to use a new shotcrete mix for NATM/SEM tunnel design, but had an additional logistical challenge of assessing the early strength with a faster turnaround. Quick evaluation of the strength enables time, and hence cost, efficiencies, but is also safety-critical in determining when the workforce may re-enter the mine. The existing Field Early Strength Shotcrete Testing (FESST) and End-Beam Tester processes involve partial beam compression testing, which was labour-intensive and time consuming, and the equipment was cumbersome to transport, although accurate up to 4 MPa (FESST) and 35 MPa (End Beam). Thus, there was the requirement to speed up this component of the process whilst maintaining accuracy of readings and confidence that the new mix was delivering the desired performance improvements. Multicrete embarked on a thorough, controlled, calibration program at their Flin Flon facility to evaluate how a digital Mecmesin shotcrete penetrometer could help accomplish these objectives.

Shotcrete Early Strength Calibration Studies