For the design of masonry structural elements, there are two methods to verify masonry compressive strength: 1) unit strength method or 2) prism test method. In a prism test, an assembly of materials (masonry block, mortar, and grout) representative of the actual materials used on the project are tested for its compressive strength at 28 days or any designated test age. The unit strength method utilizes an empirical table based on masonry block strength and mortar type, per TMS 602 Section 1.4B.2.

Table 2 Summary (TMS 602 Section 1.4B.2):

1. Masonry, f’m=2000psi — Type S Mortar & masonry block strength of 2000psi
2. Masonry, f’m=2000psi — Type N Mortar & masonry block strength of 2650psi
3. Masonry, f’m=2250psi — Type S Mortar & masonry block strength of 2600psi
4. Masonry, f’m=2250psi — Type N Mortar & masonry block strength of 3400psi
5. Masonry, f’m=2500psi — Type S Mortar & masonry block strength of 3250psi
6. Masonry, f’m=2500psi — Type N Mortar & masonry block strength of 4350psi
7. Masonry, f’m=2750psi — Type S Mortar & masonry block strength of 3900psi
8. Masonry, f’m=3000psi — Type S Mortar & masonry block strength of 4500psi

For historical information of masonry block strength tests completed, please go to the CMU Block Strength Map. The information provided on the the website CMU Block Strength Map is for reference only, and should not be used in the actual design of structural masonry elements. The block strength for masonry element design must be verified by the CMU supplier for each specific projects.