What is lightweight concrete masonry and is it suited for structural applications?
The standard for concrete masonry is ASTM C90, Specification for Load-bearing Concrete Masonry Units. C90 defines three weight classifications for masonry: lightweight is less than 105 pcf (1680 kg/m3), medium weight is defined as 105 to less than 125 pcf (1680 to 2000 kg/m3), and normal weight is 125 (or more) pcf (2000 kg/m3). (Properties are tested with methods outlined in ASTM C140, Test Methods for Sampling and Testing Concrete Masonry Units.) Because the block has a lower density, designers and specifiers may wonder if it has adequate compressive strength for structural applications and the answer is yes. Some lightweight aggregate (LWA) particles have hard shells while others have surfaces with open voids. Aggregate used to cast lightweight block is typically expanded shale, clay, or slate, but other materials are also available. Information about structural lightweight aggregate is available from the Expanded Shale, Clay, and Slate Institute. Many LWA are strong enough for stru
