Rust is a very extensive topic, there are many types and much attention must be paid to it, because neglecting this variable can cause many accidents, therefore, the steel in the open, exposed to rain, heat or cold, among Other conditions such as the case of reinforced steel under construction that I show you, must be evaluated to take the appropriate respective measures.

Oxidation is a reaction with negative potential, in this way it occurs spontaneously in any oxidizable metal, therefore, when it is left exposed, it begins to turn yellow and with time depending on it, it takes on a reddish-brown color.

The respective question would be, should you clean the steel bars with a steel brush before pouring with cement; When you observe the armed bars and touch them, you notice how a very soft brown powder comes off, common sense tells you that it is better to clean them with a wire brush, since if it is emptied with the oxide film it can remove the grip between the bar and cement.

In addition, if it is decided to clean it, it would take vital time and manpower to do it, it would be a tedious and laborious job, which translates into additional costs in the work.

To discern the matter, consult the American Standard ACI 318-14, in chapter 26 article 26.6.6.1.1, where it says:

“(b) reinforcement not pre-stressed with rust, flake, or a combination of both should be considered satisfactory if the minimum dimensions (includes the height of the ribs of the corrugation) and the weight of a sample cleaned by hand using a brush of steel wire meets applicable ASTM standards. ”

Furthermore, R26.6.1.28b) tells us:

“The specified limits of oxidation are based on the tests performed (kemp et al 1968) and on the review of previous tests and recommendations: Kemp et al (1968) provide guidance regarding the effects of oxidation and from flaking on the characteristics of corrugated rebar: Research has shown that a normal amount of oxide increases the bond between concrete and reinforcement. " Generally, through normal rough handling, loose rust is lost and can impair the bond between concrete and reinforcement.

This makes sense, since oxidation occurs at the molecular level and forms a very strong passive layer on the surface, thus creating irregularities on the surface, increasing roughness and improving the adhesion between the concrete and the reinforcement.

It is necessary to limit something, that the norm mentions the bars in a loose state, prior to being used; and when handling it, the powder mentioned above will be lost with handling in the reinforcement assembly; in my case the reinforcement is already assembled, there will be no more manipulation and in this sense the loose dust has to be removed, as specified by the norm.

In the impotent case that there are scales and greater corrosion, the reinforced reinforcement should be evaluated with ASTM A615 / A615M - 15th, Section 12: which mentions that there is a nominal section that is the theoretical section of the bar and that theoretical section has Some nominal characteristics, a weight, a nominal section or even a nominal mass, that bar can decrease its nominal section or it can reduce its nominal mass or nominal area up to 94%, if it exceeds that it must be rejected and if it is above it, accept it .

Good friends, it all depends on the conditions that your reinforcement element finds, in my case I will only clean them of that loose dust.