Saturday, August 8, 2009

Concrete Methods - Adding Reinforcement

One of the most important factors to consider when pouring, forming and placing concrete is what kind reinforcement is needed, if any is needed at all. Recent technologies in concrete mix designs have made many more available and cost effective solutions to your reinforcement needs. Some times all that is needed is an engineered mix for simple floors, patios, driveways, porches and slabs. However, larger structures that support greater weights require more reinforcement and are required by general building codes.

Depending on the structure you are making will be what determines the type of reinforcement needed. Concrete walls require the use of steel rebar. Usually the sticks of rebar are tied together based on an engineered plan. Building codes, structural design and an engineer usually determine how much is needed and how it should be placed in the concrete. The larger the area to support usually means the higher amount of rebar as well as the grade (diameter of rebar or rebar size). Smaller flatwork pieces like residential flat work usually only require an engineered bag mix of concrete, or simple wire mesh. Wire mesh concrete reinforcement is often used when placing a boiler heat system in a driveway for example. This wire mesh must be set just right so as not to puncture the tubes when pouring concrete and to eliminate protruding wire from the concrete slab.

Thicker walls and floors will almost always require mats of rebar (rebar sticks tied together vertically and horizontally in specific lengths and spaced properly based on what it supports). This reinforcement is usually tied to footings that have been poured with sticks of rebar placed into and protruding upward or leaning into the floor to connect the mats together. Reinforcement can be bought pre-bent or bent on site based on need. The reinforcement is usually throughout the entire structure including columns. The higher up and the more to support the more reinforcement and concrete is needed, both in quantity and grade size. Improper placement of reinforcement, lack of reinforcement, incorrect type of reinforcement and inadequate sizing causes weakness, structural damage and protrusion from the structure. Most buildings require an a building inspector to pass off whether or not the proper amount, size, type and placement is correct. Hiring a contractor who is qualified to do it right is very important.

Once the size of the reinforcement is determined how much of it is needed to support the structure you are building? These requirements usually come in the form of an engineered plan stating the bare minimum needed. If you are not sure, hire an engineer to review your needs. They usually state the type that is needed as well. Structures that are exposed to water elements usually require that they be epoxy coated. This epoxy coating is usually a thin layer of epoxy that the rebar is coated with to protect the bar or mats from rusting and give it longevity.

Because reinforcement can get expensive, modern technology is trying to focus on ways to place reinforcement directly into concrete mixes, by the use of engineering mix designs. Engineers are researching the use of graphite in the mix to bond it together and provide reinforcement as well as other chemicals. Progress is advancing at a rapid pace and many different mix types are available. Some builders and engineers require these mixes on jobs in addition to steel reinforcement. They usually require testing of the strength of the mix by pouring core samples to test at a later date to make sure it is not defective. If the strength test is not met to the required standard, it must be removed and replaced until it passes. If reinforcement is not inspected by a building inspector prior to pouring concrete, the building inspector can require you to remove the entire structure and start all over, or bring an imaging device to the job site and ex-ray the structure to see if it was properly placed. Usually great costs are associated with both of these. Concrete is expensive to do over, so it is important to follow building codes and requirements when installing rebar to make sure it is done right the first time.

Concrete reinforcement is an important step when considering the longevity of a structure. In my experience I haven't met a single person or company who wanted to waste their money on buildings or structures that aren't going to last. Too little reinforcement can cause severe structural failure and damage that can be expensive and dangerous. Which, is not worth it in the long run.

Wall Repairs

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