Fechino Files: Reinforcing Bar

Words: Steven Fechino

I still like doing projects that are new to me. Learning as I go still has that pressure that makes “making sure you have it right” more fun than if I have done something 100 times.  

This article is not as much of a comparison as an introduction for those who haven’t seen the various reinforcing products.  

Steel reinforcing bars (Rebar) are commonly made from recycled steel, typically cars, random scrap metal, and even old washers and dryers, just to mention a few of the items that are melted into big chunks of steel called billets. The billets are then extruded several times to create the proper section (diameter) and then tied with the ribs and a number of bar diameters as identification. The ribs are used to reduce slippage within the concrete when placed in it. Reinforcing steel is easily identified by size by a number stamped into the side of the bar. The reinforcing steel is sized by 1/8-inch increments. A number three is 3/8-inch in diameter. A number five is 5/8-inch in diameter, and a bar that has a five stamped into the side is known as Number 5, and it is really that simple.  

Steel reinforcing bar has tensile properties, which means it can recover from small amounts of deflection (bending), shear loads, and even small amounts of rotation. Compressive strength, which is not typically a characteristic of reinforcing steel, is when the load is applied and stacked like pancakes. Reinforcing steel does not have an adverse thermal expansion. Therefore, it will blend easily with the concrete that it is placed within, again limiting the potential for thermal cracking (though this may be small) within the structure. Reinforcing steel in a bond beam is usually placed with rods parallel to each other because the individual units, once filled with grout, become a beam that supports the load of additional masonry above; the bond beam is designed to accept the compressive load of the masonry and control the deflection all while creating a horizontal feature that does not move so door and window frames can be successfully installed. Reinforcing steel is placed in a single wythe concrete masonry wall, and reinforcing steel is placed in increments of 8 inches to 48 inches depending on the wall thickness, wall height, application, and exposure. The vertical steel and the grouted cells offer the designer the ability to accept the lateral loading placed by wind loading, control the flexure of the wall, and offer the building owner a high-performing wall that has tremendous compressive strength.

Steel reinforcing steel does rust; I think we have all grabbed a piece of rebar on a wet day and found out how messy it can be; however, that mill scale that comes off on your hand actually is a limited protective “coating, but not really” that protects the steel short term. This protection is until its placement in a timely manner, and it is not stored outside or exposed to direct elements. Once the mill scale is disturbed, a small amount of rust can appear on the surface of the reinforcing steel.

Reinforcing steel that is used in a marine environment (seawater direct exposure) could exhibit rusting in under six months and continue throughout the life of the structure.

Recently I was part of a project on the beach in South Carolina and saw something that was new to me. Pink Reinforcing steel, or so I thought. As I looked closer it was a reinforcing bar made of Fiberglass. 

The product by name was #3 PINKBAR®, made by Owens Corning Infrastructure Solutions. So, the Pink stuff is fairly new to the industry; it does not weigh as much as steel, is rust-proof (something that works well on the coast), and is stronger by section than steel. This product is still undergoing long-term evaluations for durability in various construction applications. PINKBAR® is not made with recycled material and is still being evaluated for sustainability as a product. The good side of the product is that it has a lower impact on the environment because the maintenance and application of chemical surface coatings on the building can reduce pollution. My introduction was a great application (concrete placed directly on the beach where salt water is commonly present depending on storm surges) for the product, but it will not be my forever replacement for the steel reinforcing bar. Both the PINKBAR® and Steel Reinforcing bars are manufactured using complicated processes.  

Another great Reinforcing Bar that has been available for many years is Galvanized Reinforcing Steel. This product is reinforcing steel that undergoes a complicated chemical cleaning process. Once the steel is free from all contaminants, mill scale, dirt, oil, and anything else that would inhibit the galvanic bond, then the galvanizing process, or hot dipped, as a common term in our industry, begins. Galvanizing is the application of zinc in a large open tub heated to 830 degrees Fahrenheit. Zinc offers excellent corrosion ability when placed in concrete. The zinc that is the galvanized coating, if scratched, resulting in bare reinforcing steel, will actually corrode and electrochemically protect the underlying steel from corrosion.

Epoxy-coated reinforcing steel is a process that has been around since 1973. The “green rebar” is commonly used in Highway and bridge projects across the country because of its excellent resistance to salts and corrosion resistance. This product is typically not common in masonry applications, though it could be used.

All of the items that were discussed in this article were listed as an introduction to the product types and all have pros and cons, cost, application and availability differences. 

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