What is the difference between lightweight, mediumweight, and normalweight blocks?
ASTM C90 specification for load-bearing concrete masonry units defines lightweight as concrete less than 105 lbs per cu. ft., mediumweight as concrete between 105 and 125 Ibs per cu. ft. and normalweight as concrete of 125 lbs per cu. ft. or more. The aggregate used to make lightweight blocks is usually expanded shale, expanded clay, pumice, or some similar type of open-cell material. By its nature such aggregate is porous and will allow some moisture penetration. ASTM C90 sets the maximum rate of absorption at 18 lbs per cu. ft. for lightweight, 15 lbs per cu. ft. for mediumweight, and 13 lbs per cu. ft. for normalweight. Most TRENDSTONE® and TRENDSTONE PLUS® units are normalweight.
