We are requesting guidance regarding field load testing of reinforcing dowels intended to be installed in accordance with Hilti HIT RE 500-V3 (ESR-3814).
The specified installation consisted of #6 reinforcing bars embedded 9 inches into the edge face of an existing 14-inch-deep concrete footing. Structural Notes required core-drilled and roughened holes with Hilti HIT RE 500-V3 adhesive.
Construction photographs show a grey-colored adhesive surrounding the reinforcing bars prior to later observations of red-colored Hilti adhesive at the exposed face. We understand Sikadur 31 Hi-Mod Gel LPL may have been used during the original installation. To our knowledge, Sikadur 31 Hi-Mod Gel LPL is not evaluated for reinforcing bar anchorage in this application, and we are unaware of any Hilti-approved procedure for installation of HIT RE 500-V3 into, over, around, or in conjunction with previously placed Sikadur 31 Hi-Mod Gel LPL.
Our firm has requested load testing of the installed bars. The Owner is concerned that testing may damage the existing footing concrete.
Please advise:
• Recommended proof-load level for a #6 reinforcing bar with 9-inch embedment.
• Whether proof loading is appropriate for this installation condition.
• Recommended hold period and acceptance criteria.
• Whether a successful proof test can be considered representative of an ESR-3814-compliant installation.
Thank you for your assistance.
813-786-9494
elmer@longandassociates.com
Hi Elmer,
Thank you for reaching out. Hilti would not recommend the installation of HIT-RE 500 V3 in conjunction with previously installed alternative adhesives. HIT-RE 500 V3 must be installed per the published Operating Instructions to be considered an ESR-3814 compliant installation. Please see the below information for guidance on proof loading/pull testing. Hilti would be unable to support the installation of anchorage that falls outside of our published test data/ ESR-3814.
The manufacturer does not specify or require on-site evaluation. On-site evaluation is typically specified by the engineer on the project, by job specific requirements, or by requirements of the authority having jurisdiction. However, the snippet below shows the revised section of ICC-ES AC308, which discusses the proof loading program necessary for adhesive anchors that require continuous special inspection. Hilti adhesive anchors only require periodic special inspection. Thus, Hilti does not need to have continuous special inspection in their ICC-ES reports. The referenced section below provides a helpful guideline for engineers considering on-site evaluation.
13.3.4Proof loading program- Where required, a program for on-site proof loading, that is, proof loading program, to be conducted as part of the special inspection shall be established by the engineer or design professional of record and shall conform to the following minimum requirements.
- Frequency of proof loading based on anchor type, diameter, and embedment.
- Proof loads by anchor type, diameter, embedment, and location.
- Acceptable displacement at proof load.
- Remedial action in the event of failure to achieve proof load or excessive displacement.
Unless otherwise directed by the engineer or design professional of record, proof loads shall be applied as confined tension tests (4.7.2.3). Proof load levels shall not exceed the lesser of 67 percent of the load corresponding to the nominal bond strength as calculated from the characteristic bond stress for uncracked concrete modified for edge effects and concrete properties or 80 percent of the minimum specified anchor element yield strength (Ase,N * fya). Maintain the proof load at the required load level for a minimum of 10 seconds.
R13.3.4Proof loading programs are traditionally included in the contract documents to enhance the quality control for safety-related anchor installations. Significant latitude is given to the engineer of record in determining the parameters of the proof loading program, which will depend in large part on the type, size, and quantity of anchors being installed.
For adhesive anchors, the nominal bond strength can be referenced in Section 17.4.5.1 within ACI 318-14 Chapter 17 Anchoring-to-Concrete provisions. Per AC308 Section 13.3.4 above, the nominal bond strength can be calculated using a basic bond strength that utilizes a characteristic bond stress for uncracked concrete conditions, τuncr, which can be referenced from the product Evaluation Services Report for the applicable condition considering drilling condition, concrete condition, and temperature range. The basic bond strength of a single adhesive anchor can be referenced in Section 17.4.5.2 within ACI 318-14 Chapter 17.
For mechanical anchors, a similar approach could be utilized evaluating either nominal concrete breakout strength (ACI 318-14 Section 17.4.2.1) or nominal pullout strength (ACI 318-14 Section 17.4.3), whichever controls for the application. The test should be performed as an unconfined test (in lieu of a confined test for adhesive anchors). Proof load levels should not exceed the lesser of 67 percent of the controlling nominal strength (taking into consideration any nearby edge distances or anchor spacings) or 80 percent of the calculated steel yield strength. For all cases, proof load levels should not exceed 80 percent of the calculated steel yield strength.
The final decision for testing and alterations to the anchor system design is typically made by the engineer on the project. For additional information, please reference ASTM E3121/E3121M Standard Test Methods for Field Testing of Anchors in Concrete or Masonry.
Regards,
Katelyn