Sulfate resistance testing of shotcrete - Sample preparation in the field and under laboratory conditions

When shotcrete is in contact with sulfate containing ground water, there is a risk of a drastically reduced service life. In this case, the use of sulfate-resisting cement is recommended. Since physical characteristics of the cement matrix of shotcrete differ from conventional concrete, sulfate-resisting cements do not always guarantee sufficient shotcrete durability. Thus, testing of the sulfate resistance in accelerated tests is necessary. Providing test samples from on-site (real) shotcrete is time consuming and demanding. In this study, the sulfate resistance and physical properties such as compressive strength and transport properties of samples produced in the laboratory without spraying are compared to the properties of field samples. A new compaction method is proposed, which is apt to allow high accelerator dosages. For different alkali-free set-accelerators and cement types, the laboratory-produced samples not only reveal similar sulfate resistance test results as on-site shotcrete, but also exhibit comparable porosity, transport properties and chemical phase assemblage. (C) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

Sulfate-resisting cement is recommended for shotcrete in contact with sulfate-containing groundwater, but it may not guarantee sufficient durability. Testing sulfate resistance in accelerated tests is necessary, and laboratory-produced samples showed similar properties to on-site shotcrete in terms of sulfate resistance, porosity, transport properties, and chemical phase assemblage.