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Factors Affecting the Dissolution of Gypsum-bonded Roof Bolts.

Authors
Gerdemann-SJ; Hansen-JS
Source
MISSING :12 pages
Link
NIOSHTIC No.
10003158
Abstract
In support of its objective to improve mine safety, the Bureau of Mines has searched for better materials and systems to anchor roof bolts. This report describes a study on the effects of mine waters upon accelerated gypsum, one of the materials under consideration. The accelerated gypsum dissolved at an appreciable rate relative to an assumed 10-yr life span of a roof bolt. Surface orientation, initial ion concentration of a dissolving solution, and flow rate of the solution had substantial effects on the dissolution rate. Factors such as water-cement ratio, accelerator content, wax capsule additions to the gypsum in cartridge-installed bolts, surface area, temperature, and curing duration had little effect. In an actual roof-bolt environment, dissolution will occur in static solutions to the solubility limit of gypsum ( 2g/l) and cease, resulting in minimal damage; but in flows of unsaturated solution as slow as 1 l per month, a loss of up to 10 pct will occur in 2 yr. Since miners cannot readily measure the flow or ion concentration of static- appearing water at every roof-bolt site, all such water must be assumed to be pure and flowing. It is recommended that gypsum- bonded roof bolts be confined to dry roofs only.
Publication Date
19830101
Document Type
IH; Report of Investigations
Fiscal Year
1983
NTIS Accession No.
NTIS Price
Identifying No.
RI 8814
NIOSH Division
ALRC;
Source Name
MISSING
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