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1960 house - "shale block" info

1960 house - "shale block" info

1960 house - "shale block" info

I am working on a house from 1960 and the original drawings call for "shale block". I assume this is lightweight CMU - does anybody have some original literature they can share, or suggested design values? Google has failed me.


RE: 1960 house - "shale block" info

"Shale block" are no different than than any other block that must meet the requirements of ASTM C90 (loadbearing concrete masonry units) and are probably higher due to the premium the have historically demanded. It is just an aggregate that meet the ASTM requirements.

The expanded aggregates (shale, slate, clay) are are produced by firing to achieve expansion and better thermal and fire resistance properties, while maintaining the necessary strength.

Engineer and international traveler interested in construction techniques, problems and proper design.

RE: 1960 house - "shale block" info

Thanks, concretemasonry! I was hoping you'd see this and share your wisdom.

RE: 1960 house - "shale block" info

slta...you are correct. It is a lightweight CMU. As CM noted, it is expanded shale using a process called "sintering".

RE: 1960 house - "shale block" info

Not all lightweight CMUs are made from "cintering" (burning and expanding at 2000F+ on a traveling grate), but some are made using lightweight aggregate that consists of a raw aggregate that is pelletized and fired in a rotary kiln to created the expansion and fusion into rounded aggregate units that is usually crushed to the appropriate size for the needed gradation. The process is dictated by the locally available raw materials to make an acceptable aggregate.

Many old and not now readily available concrete block were made from cinders that were a by-product of uncontrolled burning coal (trains, mills. etc.) were waste materials in the long gone past (cinder block).

The spherical uncrushed aggregates are very strong and durable and have been used on highway bridges because of the lower weight and strength'


Engineer and international traveler interested in construction techniques, problems and proper design.

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