UndergroundQ We will be shotcreting the inside of a tunnel entrance. The plan is to apply 3 ft (0.9 m) of shotcrete on the walls and ceiling to support a large section of limestone rock 22 ft (6.7 m) high, 30 ft (9.1 m) wide, and 20 ft (6.1 m) deep above the tunnel at the entrance that has moved and is wedged and supported with an existing steel structure. We would like to test the shotcrete and are wondering what type and quantity of tests you recommend and which testing labs are in our area that would be able to conduct the testing?
The article “Shotcrete Testing—Who, Why, When, and How” in ASA’s Summer 2011 issue of Shotcrete magazine should help answer most of your questions on testing of shotcrete. ACI 506R, “Guide to Shotcrete,” and ACI 506.2, “Specification for Shotcrete,” also have helpful information on shotcrete testing. Most competent testing labs should be able to test the compressive strength of cores extracted from shotcrete panels or sections, as they are very similar to concrete cylinder tests. If conducting more advanced testing, you may want to consider selecting a lab experienced with shotcrete.
