Masonry Anchor Testing: Why Concrete Rules Don't Apply

The standards gap

Australia has no Standard for designing post-installed anchors in masonry. AS 5216:2021 covers anchors in concrete only. The industry defers to EOTA TR 054:2016 (which replaced ETAG 029) for European guidance, and to AEFAC TN05 Volume 4 for Australian guidance on testing anchors in masonry substrates.

This gap means there is no code-based design methodology to calculate masonry anchor resistance from first principles. Site-specific testing, starting with ultimate testing to establish capacity, followed by proof testing to verify installation quality, is the primary basis for engineering design in masonry.

Why masonry behaves differently

Masonry is a composite material made of discrete units (bricks, blocks, stones) bonded by mortar joints. This creates behaviour that is fundamentally different from concrete:

• Brick pull-out (tension): : The entire brick unit is extracted from the surrounding mortar joints. The anchor capacity is governed by the shear strength of the mortar bed and perpend joints, not the brick unit strength.
• Brick push-out (shear): : A shear-loaded anchor pushes the brick through the opposite face of the wall. This failure mode is unique to masonry and does not occur in concrete.
• Mortar joint failure: : The anchor bond fails along the mortar joint interface, which is typically the weakest plane in the masonry.
• Hollow section effects: : Internal voids in hollow blocks reduce the effective bond area and can prevent the adhesive from forming a continuous bond around the anchor.

These masonry-specific failure modes can produce capacities well below the values published by anchor manufacturers, because those published values are typically derived from testing in concrete or solid substrates.

Why unconfined testing is essential

AEFAC TN05 Volume 4 recommends unconfined test configuration for masonry. The reason is straightforward: in a confined setup, the reaction frame bears on the masonry surface near the anchor, which restrains the mortar joint failure mechanism and prevents brick pull-out from occurring.

The result is artificially high test capacity that does not represent in-service performance. The anchor passes the test but may fail in service because the mortar joint failure mode, which the test restrained, is the actual governing mode.

The variability problem

Australian masonry varies enormously:

• Clay brick compressive strength ranges from 5 MPa to over 100 MPa
• Mortar grades span from heritage lime mortars to modern polymer-modified mixes
• Block construction includes lightweight aggregate, dense concrete, and autoclaved aerated concrete
• Heritage masonry may contain rubble fill, inconsistent mortar joints, and deteriorated lime mortar

This variability makes it impossible to rely on generic published data. Testing in the actual project masonry is the only reliable method for establishing the capacity the structure will deliver.

Testing approach for masonry

ATA recommends the following approach for masonry anchor applications:

• Conduct ultimate testing first to establish the anchor-masonry system capacity in the actual substrate
• Distribute test locations across representative masonry conditions including unit, mortar joint, and unit-joint interfaces
• Test in unconfined configuration per AEFAC TN05 Volume 4
• Follow ultimate testing with proof testing of production anchors to verify installation quality
• Derive proof loads from the project-specific ultimate test results, not from manufacturer data developed for concrete

References

• AEFAC TN05 Volume 4, Guidelines for Site Testing of Anchors: Testing in Masonry
• EOTA TR 054:2016, Design Methods for Anchorages with Metal Injection Anchors for Use in Masonry
• AS 5216:2021, Design of post-installed and cast-in fastenings in concrete