A test specimen built on site using the exact same bricks or concrete blocks, mortar, and grout as the actual wall. Inspectors cure these stacked assemblies in controlled conditions and then crush them in a testing machine to determine the specified compressive strength of the masonry. Testing a complete assembly gives a much more accurate picture of structural capacity than testing the mortar or blocks individually.
Heard on the job
The lab results just came back on the grout prisms we poured last week, and they easily cleared the three thousand psi requirement.
Insider tip
Always build prisms on a flat, level surface where they will not be bumped or disturbed during their initial curing period.
Also heard as
- masonry prism
- test prism