Shotcrete usage in declines and developments has become pervasive as
operators strive to achieve production improvements. Issues of mix control,
fibreload, thickness control, temperature and curing conditions all play a part
in the quality control. Often to overcome some of the quality control issues
designers over specify the strength requirements in order to meet their
operational constraints. Adherence to the standard civil testing requirements of
28 days moist cured at 21ºC without properly calibrating these results to the
changing environment underground leads to contractual disputes. There are a
number of standard tests specified including cylinder tests, cored tests, beam
tests and round determinate panel (RDP) panel tests. The logistics of storing
these samples and then transporting them to concrete testing laboratories
without due regard to temperature changes with time can influence the results.
All the samples can be readily handled by personnel except the RDP panel. The
standard RDP panel is 800 mm diameter by 75 mm thick and requires an ITH machine
at the mine and a fork lift at the laboratory to move it around. This paper will
examine the possibility of a panel which provides scalable results to the
standard RDP panel but can be easily handled by personnel and/or tested on site
with suitable equipment. This allows for faster turn around and better quality
control for the sample prior to testing. This enhances the identification of
quality control issues at the mine and improves safety.
Dight, P M and McKenzie, R, 2011. Quality control aspects of
shotcrete in mining – the round determinate panel test, in Proceedings 11th AusIMM Underground Operators’
Conference , pp 187-190 (The Australasian
Institute of Mining and Metallurgy: Melbourne).