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Section 2: Voids Due to Honeycombing

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Description

Honeycombing in concrete members can result from either of the following:

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  • Forms not being sufficiently secure or tight, allowing mortar to leak out during casting operations. The grout leakage can lead to pockets of air voids between coarse aggregate.
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  • Lack of consolidation due to unworkable concrete mixes or inadequate vibration.
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Investigating Honeycombed Regions

The biggest cause for concern when voids occur on the exterior portions of members is that additional, unseen defects could exist on the interior portions. Honeycombing due to lack of proper consolidation is of particular concern, especially in the portions of precast concrete members that are highly congested with prestressing strands and mild reinforcement.

Prior to considering repair options, explore the voids to check for additional damage. The areas around the voids should be chipped to sound, undamaged concrete. However, do not chip out concrete around prestressed strands before discussing with the Engineer.

Occasionally Contractors ask to use Nondestructive Evaluation (NDE) to investigate the severity of honeycombing when it appears to be severe and the Engineer is considering rejection. Most of the available technology (e.g. Impact Echo and Pulse Velocity) cannot effectively show whether small voids exist along congested prestressing strands or mild reinforcement. Although the Contractor may propose to use NDE, it is up to the Engineer to determine whether it is acceptable. Generally NDE requires destructive verification testing, which is oftentimes not an option in highly congested concrete, such as the bottom flanges of prestressed girders.

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Repairing Honeycombed Regions

After the honeycombed regions have been removed, the damaged area should be evaluated and defined per Section 1 of Chapter 2 unless the damage is too severe to consider acceptance of the member. An appropriate repair material and method can be selected once the damage is categorized as minor, intermediate, or major.

At a minimum, remove defective material, patch, and finish as required in Section 420.4.13 of the Standard Specifications for Ordinary Surface Finish.

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