There is no part of your house that is more critical than the foundation. The concrete is what everything else is built on; if it's compromised in any way, structures built on top of it will be unsafe. Concrete is the material used for foundations because of its strength. However, the strength of concrete is not static -- it can vary greatly depending on certain factors and how they are controlled during the construction process. In addition, concrete repairs are necessary for continued strength.
Quality of the Raw Materials
Concrete is primarily composed of cement, large and small aggregates, and water. The quality of each of these raw materials must be in line with what is recommended by professional bodies.
Cement, for example, comes in different types depending on the application. For a strong concrete foundation, the cement used should be intended for that application. Even the aggregates must be of the right size.
The quality of materials recommended may vary depending on environmental factors, soil quality, etc.
Correct Composition of Materials
The amount of water used depends on the amount of cement used. The amount of coarse aggregate in the mixture will affect the quantity of fine aggregate required. The cement and aggregate also share a similar relationship.
None of the components that go into making concrete are measured independent of the rest. When one component is increased or reduced in the mixture, it can drastically change the quality of the concrete. Therefore, the mixing ratio has to be predetermined depending on the desired strength.
When air is trapped in concrete, it causes a drastic reduction in strength; 10% trapped air results in around 30 – 40% reduction in strength.
Compaction of concrete is used to get rid of as much air as possible before the concrete hardens. Compaction must be done properly throughout the process to ensure as much air as possible is removed from the concrete.
The curing stage of concrete is usually the first 28 days after the concrete is poured. During this stage, the concrete will be gaining strength and permeability will be decreasing. In order for concrete to cure properly, it must be protected from loss of moisture during this period, and the temperature must also be kept within a certain range.
If the concrete is allowed to dry out, it will not achieve the desired strength, resulting in a weaker foundation. A higher curing temperature can quicken the process but the strength will be lower.
Finally, strength can only be maintained through good foundation repair. For example, hairline cracks in concrete can result in a major fracture in the foundation when weight is placed on the structure over time. It's best to keep in mind a good concrete contractor who knows how to work with concrete installation and foundation repair.