Hydrogen Embrittlement Testing of Concrete Screws

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Title: Hydrogen Embrittlement Testing of Concrete Screws

Author(s): Anthony J. Lamanna

Publication: Materials Journal

Volume: 114

Issue: 01

Appears on pages(s): 15-19

Keywords: anchors; concrete screws; durability; hydrogen embrittlement; induced cracking

Date: 1/1/2017

Abstract:
Concrete screw anchors can be susceptible to stress-induced hydrogen embrittlement cracking because they are case hardened and often coated. Hydrogen attack can result in decreased tensile ductility and decreased fracture stress at the root, which is where the threads meet the core. Currently, Acceptance Criteria 193 (AC 193) requires that two types of tests are conducted to qualify screw fasteners for stress-induced hydrogen embrittlement cracking under service conditions: 1) Method A, which is a test subjecting a concrete screw installed in concrete to a sustained tensile load while in an aggressive environment; and 2) Method B, which is a bending test on the threaded portion of the fastener while in an aggressive environment. This study examines Method A and Method B qualification test data obtained from three manufacturers for five different diameters and 11 different lengths. The comparison of the test results for the two methods shows that Method B is a redundant test, resulting in no additional safety or information beyond that gained from Method A.