BACKGROUND

1. Field

The disclosure of the present patent application relates to a treatment composition for steel rebar embedded in concrete, and particularly to an additive for reinforced concrete to help inhibit corrosion of the steel rebar, improve the workability of the concrete, and reduce water absorption/permeability in the concrete.

2. Description of the Related Art

Steel rebar is commonly used for the reinforcement of concrete. Typical manufactured steel rebar is often coated with black oxide (i.e., “mill scale”), which is a mixture of three phases of iron oxide, namely, wüstite (FeO) near the steel surface, magnetite (Fe3O4) above the layer of wüstite, and a top portion of the scale formed from hematite (α-Fe2O3). These layers of iron oxide develop cracks, since their coefficients of expansion and compaction due to changes in temperature differ to a more significant extent than those of the steel structure.

Rebars covered in mill scale, along with rust, are mistakenly considered to provide protection against corrosive attack on their surfaces when embedded in concrete. The presence of the mill scale actually accelerates corrosive reactions. This is due to the cracks that form in the scale, as well as the presence of unstable oxides of iron. Both the cracks and the unstable iron oxides are conducive to the formation of galvanic cells, which accelerate corrosive reactions in the rebar.

Due to the problems associated with mill scale, descaling of the rebar prior to its embedding in concrete may be performed. Although descaling improves general corrosion resistance of the rebar, and also increases the threshold chloride concentration for the onset of a corrosion pitting attack, the process of descaling (typically conducted on-site) is very expensive and time-consuming, and also requires cumbersome equipment. Other methods include surface coating, the use of corrosion inhibitors, and the application of cathodic protection. However, the compositions and methods involved for each of these techniques are not only expensive, but have a tendency to affect the quality of the concrete, as well as the bond strength between the concrete and the rebar. Thus, an additive for reinforced concrete solving the aforementioned problems is desired.

SUMMARY

The additive for reinforced concrete is a concrete additive for inhibiting corrosion of steel rebars in reinforced concrete, improving the workability of the cast concrete, and reducing water absorption/permeability in the cast concrete. The reinforced concrete may be a conventional reinforced concrete, such as that formed from a mixture of an aggregate, water, and cement, and has at least one steel rebar embedded in the mixture. The additive is added to the mixture prior to curing and casting. The additive may have, for example, a concentration with respect to the cement of between 0.25 wt % and 1.0 wt %. The additive includes a triazole and a non-ionic surfactant including a poly oxy ethoxylated product of the reaction between sorbitan and a fatty acid, i.e., an ethoxylated sorbitan ester. The triazole and the non-ionic surfactant are dissolved in the solvent.

The solvent may be, for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, water, or combinations thereof. The triazole may be, for example, 1,2,3-benzotriazole, tolyltriazole, or other triazole. Exemplary fatty acids include oleic acid and stearic acid. The non-ionic surfactant may be, for example, polyoxyethylene sorbitan monooleate (also referred to as polysorbate 80, and sold commercially as TWEEN® 80) or polyoxyethylene sorbitan monostearate (also referred to as polysorbate 60, and sold commercially as TWEEN® 60).

The weight-to-volume ratio of the non-ionic surfactant in the solvent may be between 50% and 90%. The concentration of the triazole with respect to the non-ionic surfactant and the solvent may be between 0.25 wt % and 25.0 wt %, and preferably between 2.5 wt % and 20.0 wt %, and more preferably between 5.0 wt % and 15.0 wt %.

These and other features of the present subject matter will become readily apparent upon further review of the following specification.

