Nicholson performed structural repair and instrumentation installation on six of the piers on the David D. Terry Lock and Dam that were damaged by alkali-aggregate reaction (AAR) which is a reaction between a highly alkaline cement paste and non-crystalline silicon dioxide. This reaction can cause expansion of the altered aggregate, leading to spalling and loss of strength of the concrete. Nicholson installed 12, 74-foot-long bar anchors with a design load of 237 kips.
Oriented coring and geophysical fracture characterization of each anchor location allowed for individual anchor design/installation to resist further expansion of the concrete due to AAR while installation of specially designed titanium extensometers allow for precise monitoring of the structure. Extensive crack mapping at and below the waterline was undertaken prior to grouting of each pier.
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