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Bridges & Special Structures Design

Underbridge inspection units (UBIUs) that reach from above deck to below.
Department of Transportation

Bridges & Special Structures Design

Concrete Deterioration of Prestressed Bridge Beams


Project Number: SPR-1703

Contract Number: 2016-0069 Z9

Status: Complete

Start Date: 03/01/2019

End Date 07/31/2022

Summary:

The mild to significant concrete deterioration observed on many prestressed concrete (PSC) beam bridges constructed in the 1970’s and 1980’s was suspected to be due to alkali-aggregate reactivity (AAR) and other material compatibility issues. The inventory analysis and field inspections identified a total of 136 I-beam bridges (~12% of the I-beam bridge population) with material related distress in the beams. An agency developed element (ADE) is recommended to document fascia beam conditions since the concrete deterioration was limited to the bottom flange of the fascia beams. Also, a collection of photographs is provided in the report; these can be included in inspection manuals to provide better clarifications on the types of cracks observed on PSC beams. Moreover, two staining techniques were evaluated to select a suitable method to detect alkali-silica reaction (ASR) in concrete. Only uranyl acetate is capable of providing reliable results to effectively identify ASR. For load rating of beams with concrete deterioration, one of the major challenges is to identify the ineffective stands in a section. For I-beams, it is recommended to use 2.5 in. crack depth for longitudinal cracks at the bottom flange when the crack width is less than 0.016 in. to identify the ineffective strands. Guidelines are provided to identify the ineffective strands in box beams. A Mathcad calculation sheet was developed to calculate input data for AASHTOWare BrR for flexural load rating of distressed box beams. The same Mathcad can be used as a stand-alone tool for load rating of box beams. Breathable penetrating sealants and surface coatings were identified through an experimental program to protect concrete beams. Protectosil® BH-N, SILACT® ATS-200, and Si-Rex 03 with Si-Primer performed better than the other products evaluated during this study.

 

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Michael Townley Rick Liptak Western Michigan University