Q: Our project calls for lightweight concrete block. Aren't heavyweight concrete block stronger and better to use?

A: Heavyweight block may be slightly stronger than lightweight block, but ASTM C 90, Standard Specification for Hollow Load-Bearing Concrete Masonry Units, requires both types of block to have the same minimum strength. And both types of block can be used in any type of construction.Lightweight units are more fire resistant, more sound resistant, and provide more insulation. Because they're lighter, they also are easier to lay, which means masons can lay more of them in a day--as much as 10% more. Lightweight block also cost a few cents less per block. A Denver concrete block producer charges 4 cents per block more for heavyweight block.However, because lightweight block are more porous than heavyweight block, they may be more susceptible to water penetration and freeze-thaw damage. This is perhaps why in the Northeast and Great Lakes states, heavyweight block are used more than lightweight block. Nationally lightweight block are used as much as heavyweight block (see map). Source: 1987 Market Planning Statistical Survey, National Concrete Masonry Association, 2302 Horse Pen Road, Herndon, VA 22070.