Coniston Dam: The rehabiliation of a 50-year-old concrete dam affected by alkali aggregate reaction

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:192163

Read, P H ^[1]; Thomas, M ^[2]

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1. KST Hydroelectric Engineers, Ontario (Canada)
2. Univ. of Toronto, Ontario (Canada)

This paper discusses the rehabilitation of the Coniston main dam in Ontario, with particular emphasis on the alkali-aggregate reaction (AAR) related aspects of the investigation and the influence of these on the design approach adopted, including measures taken to allow for possible future expansion of the original gravity section concrete. The rehabilitation program was primarily undertaken to increase the stability of the gravity sections and log chute which did not meet current dam safety criteria. However, all parts of the structure were found to be affected by AAR and the downstream face of the gravity sections were severely deteriorated due to the combined effects of AAR and freeze-thaw cycles. Field and laboratory investigations were undertaken to determine the extent of deterioration of the dam structures and to assess the potential for continued deterioration. Based on the findings from these studies, a rehabilitation and upgrade strategy was developed which included removal of badly deteriorated concrete, placement of reinforced concrete liners (upstream and downstream), addition of mass concrete buttresses along the length of the gravity sections, replacement of the deck and epoxy injection of the cracked sluiceway piers. Particular attention was paid to the design of the new concrete mixes (to limit the supply of alkalis to the existing concrete) and to the relief of stress between the original concrete core and new concrete liners. The new gravity section liner was debonded from the core concrete to reduce the transfer of stress due to continued expansion of the core; furthermore, the reinforcement of the liner was designed to resist tensile stresses induced by future expansion. Consideration was also given to minimizing the ingress of water to the dam core in order to reduce the degree of saturation and likelihood of further AAR and freeze-thaw action.

• OSTI ID: 192163
• Report Number(s): CONF-9510182--
• Country of Publication: United States
• Language: English

Related Subjects

13 HYDRO ENERGY
CANADA
CHEMICAL REACTIONS
CONCRETES
DAMS
HYDROELECTRIC POWER PLANTS
HYDROXIDES
REPAIR
STRESSES
TESTING