Bond Wrench Testing

Bond wrench testing uses a lever to create a moment in a specific mortar joint. The mortar-unit bond fails at the location of maximum tensile stresses.

ASTM C1072

 

A bond wrench test frame ready to test a masonry prism.

Using the following applied loads and self weights, the moment and ultimately the stress in the mortar joint can be calculated.

Below shows a free body diagram of the mortar-unit interface under testing conditions.

The moment in the mortar joint is equal to the load P times the distance to the center of the brick plus the weight of the lever arm times its distance to the center of the brick. The stress state of the mortar joint can be calculated by combining the stress from the bending moment and the axial stress due to the load, weight of the lever arm and weight of a brick.

 

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