GCLs in cold temperatures

Q: I am working on supporting a guide (independent) on what to consider when geosynthetic clay liners (GCLs) are installed in minus temperature regions (e.g., –4˚F [–20˚C]). There is not much published on this, especially independently. This is the only thing I found:

• Designation: D6102-20
• Standard Guide for Installation of Geosynthetic Clay Liners
• 5.3.8 The GCL should not be installed when it is frozen.

The question is, when does it get critical? Bentonite does not shrink if the moisture content is less than 12%–15%. I ran some tests with GCLs with a moisture content of 59˚F (15˚C) and allowed them to be for three days at –6˚F (–21˚C) and then unroll them—no problem. However, I never went higher. GRI-GCL3 mentions an acceptable value of 95˚F (35˚C), and I am pretty sure that rolls could not be handled on-site under these conditions.

A: Nice to hear from you and a great question. 

ASTM D6102 Standard Guide for Installation of Geosynthetic Clay Liners does state in section 5.3.8, “The GCL should not be installed when it is frozen.” However, in reality, we now see many projects that take exception to this requirement. For example, the temperature is below freezing for half the year in places like the Fort McMurray oil sands project in Alberta, Canada. We know that CETCO installed its CL GCL product there year-round from 2005 to 2008. One needs to use a bit of common sense. Store the GCL in a heated warehouse and bring it out when needed on days of opportunity.

A cold-weather GCL installation guide might contain the following:

• Only allowed above 14˚F (–10°C) under special provisions and approval of owner and regulatory agency
• Moisture content of GCL needs to be less than 15%
• Cannot be placed over frozen puddles (nature of subgrade will become very important—i.e., sand is okay, silty-clay is not)

There are many questions; however, we are pushing the envelope and filling a need for critical, time-sensitive projects.