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A Shayan

Alkali-aggregate reaction (AAR) is a potentially deleterious process in concrete containing reactive aggregates, and can lead to varying degrees of cracking in structures, and differential movement and misalignment of concrete elements and mechanical installations. The rehabilitation of affected structures would require information on the extent of current damage and possibility of on-going damage that could be caused by AAR.

Information on the characterisation of concrete components of an AAR-affected dam and estimation of their future potential for further expansion and cracking are provided and repair options discussed in this paper.

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1998 Papers

1998 – Characterisation of AAR-Affected Concrete From Dam Structures for Rehabilitation Purposes
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A Shayan

Alkali-aggregate reaction (AAR) is a potentially deleterious process in concrete containing reactive aggregates, and can lead to varying degrees of cracking in structures, and differential movement and misalignment of concrete elements and mechanical installations. The rehabilitation of affected structures would require information on the extent of current damage and possibility of on-going damage that could be caused by AAR.

Information on the characterisation of concrete components of an AAR-affected dam and estimation of their future potential for further expansion and cracking are provided and repair options discussed in this paper.
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1999 Papers

1999 – Investigations on Canning Dam Concrete Gravity Structure and it’s Rehabilitation
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Ahmad Shayan, Robert J. Wark and John Waters

The Canning Dam concrete gravity structure located in Western Australia has shown an upward movement of 18.3 mm and lateral upstream movement of 14.2 mm over the past 15 years of monitoring. These movements have been associated with considerable cracking of the upper parts of the dam and the upper gallery. Investigations have shown that the cause of the cracking was a strong alkali-aggregate reaction (AAR) in the concrete, brought about by a deformed granitic rock. Extensive horizontal and vertical cracking in the upper part of the dam wall has necessitated the removal of the section above the floor of the upper gallery level, and construction of a new reinforced concrete section to act as head beam for post-tensioning of the rest of the dam wall.

A set of small diameter cores were taken from the various parts for diagnostic purposes, and a vertical core of 100 mm diameter was taken through the whole thickness of the wall for the determination of the strength properties, alkali content and residual expansion potential. Based on these, a post-tensioning stress of 1.5-2.0 MPa has been calculated for restraining the residual expansion of the concrete. The spillway bridge structure which is part of the dam wall has also shown mild signs of deterioration. The piers and abutment walls and the deck were surveyed for corrosion activity and extent of AAR. This work showed that the spillway bridge structure was sound and only needed maintenance. The performance of a triple blend concrete mix containing a high volume of fly ash (45%) and silica fume (5%) developed for the replacement of the old concrete is also discussed.
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2018 Papers

2018 – Dam Safety Management of Junction and Clover Dams: A Risk Based and Observational Approach
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Steven O’Brien, Christopher Dann, Timo Mantyvirta

Junction and Clover Dams are central spillway slab-and-buttress dams located in Victoria. Previous safety reviews and assessments of the dams concluded that neither dam met modern dam design standards and remedial works were recommended, including infilling the slab-and-buttress dams with mass concrete to sustain seismic loadings. These conclusions were based largely on the assessed seismic hazard at the site, the results of response spectrum analyses and observed conditions of the dams including alkali-aggregate reaction of the concrete. AECOM used current seismic hazard assessment techniques, conducted concrete investigations and testing, assessed long term surveillance monitoring results and used modern finite element techniques to demonstrate that no upgrade works were required at either dam resulting in a significant saving for AGL.
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2012 Papers

2012 – Reducing Uncertainties in Safety Assessments of Aging Dams through Site Specific Investigations
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Nicole Anderson, M. Tooley, N. Vitharana, D. Moore

There is a significant stock of aging concrete dams in Australia which do not meet the requirements of modern dam safety practices. Where no site-specific information exists, current practice requires unduly simplified, conservative assumptions to be made. In some cases, this results in theoretical dam failure for load conditions which the dam has already experienced and safely withstood.
This paper outlines a range of site-specific field and laboratory investigations undertaken to reduce uncertainties in the assessment of two concrete gravity dams. For one dam, a suite of lab tests was undertaken to determine the residual reactivity so that potential future Alkaline-Aggregate Reaction induced expansion can be incorporated into any upgrade design.
The main purpose of the investigations was to reduce inherent uncertainties surrounding the design assumptions for strength and uplift pressures. This in turn reduced uncertainties relating to the risk profile of the dams.
The findings of this investigation will be of interest to dam designers and owners faced with upgrading concrete dams where a single traditional assumption can result in the difference between no upgrade or an upgrade worth several million dollars.
Keywords: Concrete gravity dams, testing, upgrade, Alkali Aggregate Reaction, dam design guidelines.
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2010 Papers

2010 – INVESTIGATION OF TWO AGING CONCRETE GRAVITY DAMS IN SOUTH AUSTRALIA
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M. Tooley, N. Anderson, N. Vitharana, G. McNally, C. Johnson and D. Moore

There is a significant stock of aging concrete dams in Australia which would not meet the requirements of the current recognised dam safety practices applicable to concrete gravity dams.
In this paper, field and laboratory investigations undertaken for two concrete gravity dams are presented, these being Middle River Dam and Warren Dam both owned and operated by the South Australian Water Corporation. The field investigations included a comprehensive drilling program recovering core samples ranging in diameter from 61mm (HQ) to 95mm (4C), continuous imaging (RAAX) of the drilled holes and installation of piezometers. Geological logging of the holes and mapping of the unlined spillway were also undertaken. The laboratory program included the testing of concrete lift joints and concrete samples in direct tension, shear and compression.
Concrete in Middle River Dam is suffering from extensive Alkali Aggregate Reaction (AAR), and consequently a suite of laboratory testing is being undertaken to determine the current level of deterioration and residual reactivity so that potential future AAR-induced expansion can be incorporated into any upgrade design solution.
The main purpose of the study is to determine whether site-specific parameters can be used to re-assess the stability of these two dams as calculations, based on the current standards, have shown that the dams have exceeded the allowable factors of safety values at the storage water levels experienced to date.
The findings may be useful to dam designers and owners faced with the upgrading of concrete dams, where traditional assumptions can result in no upgrade or an upgrade costing several million dollars.
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Steven O’Brien, Christopher Dann, Timo Mantyvirta