Pocketformer with Reverse Tapered Ledge for Post-Tension Corrosion Control
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Solution Overview
Problem
In encapsulated post-tension concrete reinforcing systems, the unsheathed tendon tail length often exceeds the capacity of the grease cap, leading to moisture ingress and potential corrosion, especially after grout filling, making it difficult and costly to correct.
Innovation Solution
A pocketformer with a tapered body and a grout ring that leaves a reverse tapered ledge, combined with a tail gauge for precise measurement and a pocket cap for sealing, ensures the tendon tail is within acceptable length, preventing moisture entry and facilitating effective sealing and grout retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tendon tail is allowed to extend beyond the grease cap capacity, then the installation process is simpler, but moisture ingress and corrosion risk increase
Solution Approach 1:
The pocketformer is inserted into the anchor base before concrete pouring to pre-establish the pocket structure. The reverse tapered ledge is formed in advance during pocket formation, creating a pre-prepared sealing surface that will later receive the grease cap and prevent moisture ingress, thus resolving the contradiction between installation simplicity and corrosion resistance
Solution Approach 2:
The reverse tapered ledge acts as an intermediary element between the pocketformer and the grease cap. It provides a dedicated sealing surface that receives the grease cap, creating a moisture barrier that protects the tendon tail while maintaining installation simplicity through the standardized pocketformer design
2Reliability
If grout filling is performed after tendon installation, then the pocket is sealed, but the tendon tail length control becomes difficult and costly to correct
Solution Approach 1:
The tail gauge is used to measure and control the tendon tail length before grout filling is performed. This preliminary measurement ensures the tendon tail is within acceptable length limits prior to sealing, making it easier to correct any length issues before the pocket is filled with grout, thus resolving the contradiction between sealing reliability and manufacturing ease
Solution Approach 2:
The tail gauge provides feedback on the tendon tail length during the installation process. This feedback mechanism allows operators to adjust the tendon tail length before grout filling, ensuring proper length control while maintaining sealing reliability through the reverse tapered ledge design that accommodates the measured tail length
3Device complexity
If a standard pocketformer is used without modification, then the device complexity is low, but the grout retention and sealing effectiveness are insufficient
Solution Approach 1:
The pocketformer is segmented into functional components: the main body that forms the pocket, the reverse tapered ledge that provides sealing engagement, and the interface with the anchor base. This segmentation allows each component to perform its specific function optimally while maintaining overall device simplicity, resolving the contradiction between low complexity and high sealing effectiveness
Solution Approach 2:
The reverse tapered ledge is a localized feature on the pocketformer that provides enhanced sealing engagement with the grease cap. This local quality enhancement focuses the sealing function at a specific location, improving grout retention and sealing effectiveness without requiring complex modifications to the entire pocketformer structure
Data Source
AI summary
A pocketformer includes a pocketformer body having a tapered exterior surface. The exterior surface has at least one portion along a length thereof of substantially constant diameter. The pocketformer body has a feature for engaging an anchor base in a concrete structure prior to pouring concrete and a grout ring having a substantially constant inner diameter substantially equal in diameter to the at least one portion. The grout ring has an exterior surface shaped to cause retention of the grout ring in set concrete.