Retaining wall contractors, much like John Wassmer Construction, are often called to the scene of a collapsed retaining wall only to find the wall in question was made of concrete blocks. The reason for the collapse is always evident. By the very nature of the application, retaining walls are intended to bear loads coming from behind them where the ground they are designed to retain is.
Design of Concrete Walls
When we study the concrete block, the design itself can tell us a lot about why they fail when stressed from the side. As with any hollow device, they are strongest when the load is brought to bear from top to bottom when set in their normal installation orientation. The manner in which the concrete block is most commonly used, to build walls for buildings, the majority of the load is placed on top, pushing toward the ground, where a poured concrete foundation bears the load.
A simple test of the block strength is possible by taking a standard framing hammer and hitting the side walls of the block. With very little effort, the walls will burst and the block is no longer of any use.
Segmented Retaining Wall Blocks vs. Concrete Blocks
Compared to concrete blocks, the segmented retaining wall block is solid and made of a high density concrete. Using the same hammer as before, you can easily wear yourself out before you bust the block. You can break off the corners and round off the edges, but it takes a chisel and sledge hammer to do any real damage. Another problem with concrete blocks is their ability to absorb water. We are all familiar with the expansion strength of water when it freezes so we can understand that a retaining wall, one that is in constant contact with the earth behind it, would be wet most of the time. This cannot be said for the wall of a building that is protected from the rain on the outside and is open to the air on the inside.
There is always an Alternative Solution
When the temperature goes below freezing for a long enough period of time to freeze the ground, it will also freeze the water in the blocks supporting your retaining wall. Though it may take a few years, depending on the number of freezes you have each year, eventually cracks will begin to form in both the blocks and the mortar used to hold them together.
Segmented retaining wall blocks are impervious to water. They can be put in a water bath for several years and will never absorb the water any deeper than an eighth of an inch. The high density of the concrete is too tightly packed to allow water to enter the bond. Freezing will have no more effect than a hot day on these blocks.