Barrier Technologies for Environmental Management Summary of a Workshop (1997) / Chapter Skim
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Self-Hardening Slurries and Stable Grouts from Cement-Bentonite to IMPERMIX
Self-Hardening Slurries and Stable Grouts from Cement-Bentonite to IMPERMIX
Pages 142-149
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From page 142... ...
Slac cement's long setting time is taken advantage ot In some applications like slurry trenching in difficult ground, or shortened when strength buildup is necessary, as in sludge solidification. Given the low viscosity and low-solids content of these suspensions, a very penetrating environmental grout for sealing contaminated fractured rock can be found in IMPERMIX~ Whereas cement-bentonite slurries have found limited applications in environmental remediation, due to excessive permeability, the permeability threshold of self-hardening slurries has been lowered with IMPERMIX'~' by one and two orders of magnitude and occasionally more.
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From page 143... ...
Slag cement: finely ground blast furnace slag cement is a hydraulic binder manufactured from a residue of modern steel making; molten slag is blown into a cold-water spray, with the slag cooling into glassy pellets; once finely ground In a cement mill, an industrial pozzolanic material is obtained. Cement-bentonite (CBJ: a generic mixture of Portland cement and bentonite, with a solids content of generally less than 35 percent, mixed into a stable grout and used for alluvium and fractured rock grouting as well as a self-hardening slurry for cutoff wall construction.
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From page 144... ...
LIMITATIONS OF CEMENT-BENTONITE For better understanding, economy, and quality assurance, design engineers generally prefer trenched cutoff walls to grout curtains. When designing water reservoir embankments or contemplating the repair of a leaky earth dam, a conductivity (K)
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From page 145... ...
QUALITY CONTROL/QUALITY ASSURANCE This writer has always been adverse to the use of soil bentonite barriers for permanent enclosures. A coarse technology and a crude construction method cannot provide the level of quality control (QC)
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From page 146... ...
When, 10 years ago, this writer constructed his first soil attapulg~te slurry trench at a chemical facility on the Gulf of Mexico, actually using seawater to prepare the slurry, a good clay mate for the slag cement was recognized. A clay that viscosities mechanically instead of swelling and doesn't blink at the sight of electrolytes appeared to be a good candidate indeed.
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From page 147... ...
and methods using low gradients through a large diameter and thin sample in an oversized biaxial permeameter cell (Haug, 19801. A new test for very lowpe~meability materials should be developed to establish threshold gradients below which the matenal can be considered truly impermeable.
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From page 148... ...
This attitude does not seem to factor in the constructability versus end-product quality elements that are essential to achieving one's objectives and has led to risky situations (not to mention law suits) that would not be tolerated in a permanent enclosure project.
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From page 149... ...
1984. Slurry trenches for containing hazardous wastes.
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