Floor heave due to biochemical weathering of shale

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Pages151158; # of pages: 8
Subjectfloors; heave; biochemical corrosion; weathering; shale; soulevement; compose biochimique; action des intemperies; schiste
AbstractHeave of a basement floor in a three-storey building in Ottawa was recently investigated. The building is founded on black shale of Ordovician age known as the Billings formation. Examination in the heaved zone revealed that the shale had been altered physically and chemically to a depth of 0.7 to 1 m. Below this the unaltered shale was sound but contained numerous pyrite veins and also had a general pyritic sulfur content as high as 1.6%. The main alteration products that were responsible for the heave, jarosite and gypsum, were located between shale laminae and in fissures in the altered zone. Acidity measurements ranged from pH 2. 8 to 4.4, pointing to biochemical weathering by autotrophic bacteria belonging to the Thiobacillus-Ferrobacillus group. Heaving was arrested by creating conditions unfavourable for bacterial growth. This involved neutralizing the heaved area by flooding the shale with a basic solution and keeping the water table high artificially to reduce air entry and acid build-up.
Publication date
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedNo
NRC number13722
NPARC number20374750
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Record identifierbe9eddaa-8b6d-479f-aac7-9856276448c0
Record created2012-07-23
Record modified2016-05-09
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