Bentonite question

Bentonite swells when exposed to moisture. When it dries, does it shrink?

What’s going on with bentonite Kenton?

Back in my younger days, we built containment walls around Waste Management abandoned landfills and installed collection pipes for the leachate in front of the slurry wall. The juice from the landfills was collected in manholes and sent to an incinerator, because of the toxicity.

The bentonite was mixed with water and clay with bulldozers and made into a slurry, we pumped it back into the ground in front of the track-hoe which was digging the trench with an extended arm built to dig 55 feet deep, which was considered resistance or hard-pan. The trench would stay with vertical walls without collapsing as long as the slurry was continually pumped, because it is heavier than the original soil excavated. The bentonite and clay acted as a dam and will not let anything pass through it.

But Bentonite by itself when moistened and dried, will shrink back to its original form…basically a very soft mineral.

I took an HVAC class in Denver and the instructor stated strongly that it didn’t shrink when it dried. Everyone talks about how it swells when wet, but it was the first time I ever heard anyone mention one way or the other about whether or not it shrinks when it dries. Seems like there ought to be a yes or no answer to this one.

I don’t have a clue what bentonite and HVAC systems have in common.

Raw bentonite shrinks, there are numerous applications in which it can be mixed with other substances, that might prevent it from shrinking, but I don’t know any.