Date of Award

6-1999

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. J. Bret Bennington

Second Advisor

Dr. Eliot Atekwana

Third Advisor

Dr. George Guthrie

Fourth Advisor

Dr. Alan Kehew

Access Setting

Masters Thesis-Open Access

Abstract

Secondary minerals, predominantly carbonates, forming under concrete structures have received attention in terms of their possible role in the degradation of their hosts. δ13C and δ18O analyses of several calcium carbonate growths collected from bridges in Michigan and New York were performed. The δ13C and δ18O values clustered around -24.7 ± 1(PDB) and 13.7 ± 1(SMOW) ‰, respectively. A positive δ18O- δ13C correlation suggests kinetically driven precipitation involving atmospheric CO2• 14C activities determined for select samples support the theory that atmospheric CO2 is involved in the formation of these deposits. The δ18O values indicate that the oxygen in the deposits is in part derived from atmospheric CO2. In addition, select samples were dated using the disequilibrium between 266Ra and 210Pb, on the assumption that some amount of 226R is incorporated and there was no initial 210Pb. The ages ranged from the 3.8 to 64 years, not unreasonable based on the actual age of the bridge. If true, this provides a means to date calcite minerals found in concrete structures.

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