Concrete block walls are some of the strongest walls available to the construction industry. However, they may experience many problems over their lifetime, such as cracking, leaking, separating and degradation of block materials. Most problems can get worse if they are not identified and addressed.
The materials used in making and installing concrete blocks are all subject to nature. The concrete blocks themselves are made from Portland cement and sand. The combination of these two materials creates porous surfaces on the concrete blocks that allow water penetration. The materials used for setting concrete blocks are similar to the materials used in making the blocks. Sand, water and mortar are used in combination to make a wet, pasty mix that bonds the blocks together, and can be subject to the same problems.
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Concrete blocks may break down over time because of exposure to the natural elements, including sun and freezing rain. Prolonged exposure to the sun will cause the blocks to expand and contract as they dry out, thus creating cracks and failures in the structural composition of the block. During the winter, when water penetrates the pores of the blocks and freezes, it also expands and cracks the blocks.
The mortar used to set concrete blocks can break down over time because of the same natural elements as the blocks themselves. One additional element may play into the mortar problems: human error. When a field worker mixes the mortar mix, exact calculations must be made. The correct ratio of mortar, water and sand must be applied in order for the mortar mix to effectively bond the concrete blocks. Too much sand makes the mortar joints flaky and prone to breaking; too much mortar makes the mix too sticky and prone to washout.
Often concrete block walls will crack because of settlement of the ground beneath the wall. This issue can be resolved by filling the cracks with hydraulic cement, which will expand and seal the cracks.
Because concrete blocks are porous, they will absorb large amounts of water if they are located beneath the soil line. Water enters the soil and penetrates the block pores, finally settling on the interior of the block wall. One way to combat this problem is to apply tar to the exterior of the block wall and water sealer to the interior of the wall.