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Excess Steel Reinforcement in Concrete Structures
Friday, March 24, 2017 9:36:31 PM Australia/Melbourne
Reinforced concrete allows you to vastly improve the strength and durability of buildings and other structures. Used in conjunction with formwork, you can produce concrete slabs and columns with increased precision. Slabs can be wider, thinner and more cost-efficient than ones produced from methods from the past.
The widespread application of reinforced concrete allows us to build faster and produce more complex structures than ever before. Though concrete has been around since the time of the Ancient Romans, the introduction of reinforced concrete turned it into a much more versatile, reliable material that is suited for a wide range of applications.
Rebars and reinforcing mesh help the concrete maintain its shape and withstand higher levels of stress. There is no doubt that using them is highly beneficial to construction work, but is it possible to use too much reinforcement?
Rebars and Concrete
Iron and concrete are a winning combination because they share similar thermal expansion rates. The alkalinity of concrete helps inhibit rust, and a little bit of give is provided by the high tensile strength of iron. The two materials simply bond well together.
The relationship between the two materials comes into play when you are trying to determine how many rebars you should be using in your project. The most common percentage of steel to concrete sections should be between 3% - 5%, though this varies depending on the application.
Excessive reinforcement occurs when you experience too much shrinkage, or if honeycombing occurs.
Shrinkage occurs if your aggregate has too much or too little water. The moisture levels in the mix affect the rate at which the concrete dries. If your mix is too wet or too dry, and you have too much reinforcement in place, cracking will occur as it hardens. Cracking happens because the reinforcement puts too much strain on the drying concrete, and it will not be able to accommodate the shrinkage.
Honeycombing, on the other hand, happens during the forming process. This is when concrete fails to pour between the gaps of the rebars, creating air pockets in the structure. To remedy this, you will need a smaller millimetre aggregate that pours into spaces more readily; alternatively, use fewer rebars.