Silica Fume Modified Grouts for Corrosion Protection of Post-Tensioning Tendons


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Title: Silica Fume Modified Grouts for Corrosion Protection of Post-Tensioning Tendons

Author(s): Ulrich Diedrichs and karl Schutt

Publication: Special Publication

Volume: 114


Appears on pages(s): 1173-1196

Keywords: cement pastes; corrosion resistance; hydrothermal reactions; differential thermal analysis; grout; injection; microstructure; plasticizers; porosity; post-tensioning; pressure; vessels; strength; prestressing steels; silica fume; Materials Research

Date: 5/1/1989

A feasibility study on the performance of silica-fume modified cement grouts for corrosion protection of post-tensioning tendons was conducted. It began with laboratory tests on flow behavior and strength development. Subsequently, the proven mixtures were mixed and grouted under site conditions using a turbo mixer. The results and experiences were compared with results obtained with conventional neat cement grouts tested parallel. Additionally, corrosion protection behavior was studied with grouted tensioned prestressing steel samples, and grouting of post-tensioning tendons of a prestressed cast-iron pressure-vessel 1:5 scale model were performed. Because the tendons of the PCIV during service are exposed to 130 C, the investigation of the various hardened grouts relevant for corrosion protection and their alteration due to long-term exposure to elevated temperatures and high humidity were included. The results showed that silica-fume modified grouts exceed the conventional neat cement grouts in view of flow behavior, bleeding, density, processing time, etc. The dosing, mixing, and injection of silica fume grouts under site conditions caused no specific problems. Even some advantages may be reported. However, silica fume grouts require more care in mix proportioning and selection of appropriate superplasticizers.