Is it possible to concrete rusty reinforcement and how will this affect the structure of the house
Jan 19, 2021
The armature does not ask for food and you can stock up on it long before the start of construction. But any metal tends to rust, especially when stored outdoors. And here many have a question: "Is it possible to use rusty reinforcement for the foundation and how will this affect the strength of the house?" Whether or not it is possible - read on.
If you start looking for an answer to this question on the Internet, you will definitely stumble upon the "expert" sites of sellers of rust converters. They will hint to you that rusty is bad and will tell you how to clean the fittings to a shine with miraculous means. These are the tricks of marketers, you don't need to believe in them too much.
Rust + cement = glue effect
Portland cement contains from two to four percent iron oxides. High-quality cements based on blast-furnace slags include up to ten percent of these oxides. What does this mean?
Rust reacts with iron oxides during the mixing of cement into concrete. This provides the effect of gluing the reinforcement to the concrete over its entire surface.
And also a raid of rust indicates the absence of factory technological lubricant on the metal, which just reduces the adhesion of the rod to concrete. The fittings are rusty, but in moderation you can not be afraid!
Rebar rusting categories
But this measure needs to be defined somehow. For this purpose, the head of the NIIZhB valves laboratory, Doctor of Technical Sciences, Professor S.A. Madatyan developed a document in which he classified and described the types of rust. There are four of them.
- Light coating of rust, which does not change the color of the steel, does not change its weight and properties. This coating resembles dust and is easily peeled off.
- A dense coating of rust, evenly distributed over the entire surface of the reinforcement. It changes the color of the steel, but practically does not change the weight of the reinforcement and the section of the rod. This layer can be easily removed with a rag or metal brush. Rust of the second category will fly off when the concrete solution vibrates in the structure.
- Rust stained. It appears locally from the ingress of water. It is easily removed with the simplest cleaning agents and also does not change the cross-section and properties of the reinforcing bar.
- Surface corrosion of steel. After removal, it leaves deep foci of corrosion on the metal. Reduces the section and weight of the reinforcement; reduces the properties of the metal. Here you need to understand: corrosion is not rust. Rust is plaque and corrosion is destruction of metal!
According to this document, reinforcement covered with rust of the first, second and third categories can be used in concrete structures without any restrictions and pre-treatment. In concrete, the metal enters an alkaline environment with limited oxygen access and rust stops. The use of such fittings will not in any way affect the strength characteristics of the house.
The fourth category must be examined by specialists and issued a permit for the use of each individual batch. But here we are talking about critical areas and large construction sites.
Reinforcing bars with fourth grade rust should not be used in low-rise construction. For example: in foundations, ceilings, and in general, in any structures that work in bending and tension. It can stand for a long time, if you're lucky. But it may not be able to stand it, which will lead to the destruction of the structure. It's not worth the risk.
Throwing out, of course, such building material is not necessary. Corroded rods will also find their use on the farm. Nothing terrible will happen if you reinforce the screed or garden paths with them.
Fifth category: rot
But NIIZhB did not take into account one more category of reinforcement corrosion and we will take responsibility for creating and describing it. The fifth category can be called: "the armature on the ad is cheap." It is simple to describe it: when hit with a hammer, pieces and flakes of rust fly off from it. It's rubbish. Place it in the metal reception, not in the concrete structure.
There are even folk methods for removing rust from obviously "rotten" fittings using a solution of phosphoric acid. But you need to understand: an external defect can be removed even from the Titanic, which has been under water for a hundred years. But only this will not restore the properties of the metal.
Do you process reinforcement before concreting? Write in the comments!
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