Positive Reinforcement

It is believed that iron and wood reinforcing bars were first used in masonry construction in Rome around 1 AD, where pozzolan cement was developed by combining powdered hydrated lime with volcanic ash and sand from Mt. Etna. After the fall of the Roman Empire, the techniques for making this type of cement were largely lost for almost 1,000 years as builders through the Middle Ages opted for more traditional materials like stone. It wasn't until the mid-1700s that widespread concrete use began to emerge. Reinforced concrete was invented in France in the mid-1800s, and the modern iteration of rebar was born.

Today, rebar is available in various types, including carbon steel, stainless steel, and composite bars made of glass or carbon fiber, fortifying the strength and durability of concrete structures. The reinforcing features of rebar have allowed for the design of larger and more complex architecture than ever before. While concrete remains strong under compression, it lacks the ability to effectively withstand tensile forces, or the maximum stress that a material can withstand while being stretched or pulled before breaking. Rebar provides the necessary tensile strength to concrete structures, allowing them to endure bending, twisting, or stretching forces.

It stands to reason then, that rebar durability is critical to the longevity of the massive concrete structures all around us. The manufacturing process involves several steps to transform steel into the reinforcing bars that are essential for concrete construction. The process begins with melting down recycled scrap steel, which can be carbon or alloy, into liquid form. Once the steel is melted, it is pulled through small round openings and the semi- liquid steel is formed into long, thin rods. After shaping, manufacturers create deformations on the metal to ensure it will properly bond to the concrete structure. Rebar is most often coat less standard concrete reinforcing products like couplers, dowel baskets, and wire mesh using the same ASTM A775 or A934 powders used for rebar coatings. That line was expanded in 2019 to more efficiently coat large wire mesh and dowel baskets. While the custom coating division focuses on parts using A775 or A934 powders, it has the capability to coat any product that follows a traditional powder coating process and can fit within a 10-foot by 2-foot by 25-foot fabricated to proper specifications in manufacturing locations using specialty shears and benders prior to being shipped to a jobsite. While unfinished steel is the most common form of rebar, some construction jobs require more specialized types, such as epoxy coated, galvanized, or stainless steel, to prevent corrosion from prolonged exposure to elements such as saltwater.

Reshaping Rebar
According to Simcote CFO and co-owner David Simmet, rebar coating systems were first developed for corrosion protection in the 1970s by repurposing epoxy technology used for protective pipe coatings. “While some pipe coaters had dabbled in coating reinforcing steel, no one else had embraced this technology as their core business,” David says.

David’s grandfather, John Simmet, tried to convince his employer to build an epoxy coating line to serve this growing market, but to no avail. Convinced it was a burgeoning market with tremendous upside, John founded Simcote in 1978 in St. Paul, MN, as one of the first companies to fabricate and epoxy coat reinforcing steel. Less than a decade later, Simcote expanded with a second plant in Marion, OH. In 2012, they built a custom powder coating line at the Marion location, extending its capabilities beyond reinforcing steel to window. In 2022, they began building a third, $17 million, 67,000 square foot facility in Sedalia, MO, to better serve the central U.S. with epoxy coated rebar. That facility is scheduled for completion before the end of the year.

Now owned by a third generation of the family, David says the company continues to uphold their core values of safety, quality, respect, integrity, and teamwork, taking pride in partnering with their vendors and customers to provide long-term, sustainable corrosion solutions.

Rebar Resilience
David points out that epoxy powder coating falls within a similar scope as traditional powder coatings. Ultimately, the process involves a steel grit blasting of the rebar, preheating of the substrate using an induction heater, electrostatic powder coating, and in some situations an oven cure. David says their rebar coating lines use a “short gel” epoxy, which gels and cures within several seconds, eliminating the need for oven curing, as induction heating gets the product hot enough to gel the epoxy all the way through. “The epoxy doesn’t need to flow very far since the powder guns can cover the entire surface evenly and there aren’t many nooks and crannies in straight rebar that the coating needs to flow into,” David explains. He continues, “On the other hand, our custom coating line uses ῾long gel’ products, which gel and cure in under a minute. Since those products have more complex geometries, the powder needs time in a cure oven to liquify and flow into areas that aren’t hit as directly with the powder guns.”

He emphasizes that special consideration should be made to blast the rebar to the required surface quality, heat it to the proper temperature for powder adhesion and cure characteristics, coat it to the appropriate thickness, and fabricate and store it using the proper equipment and padding to prevent damage to the epoxy.

ASTM A775 and A934 powders are designed for the concrete reinforcing industry as a corrosion protection element, with A775 powders formulated with flexibility to fabricate post-coating. According to David, “Many of the standards and certifications created for this space are developed by the Concrete Reinforcing Steel Institute and most of the epoxy coaters are members of Epoxy Interest Group.” He adds, “Simcote is one of the few companies that provide epoxy coating for rebar, custom products, and rebar fabrication including epoxy coated spirals. Our coated products are commonly used in structures such as bridges, parking ramps, commercial buildings, dams, and wastewater treatment facilities.”

While the process of epoxy coating is similar to traditional powder coatings, there are a few distinct differences. “The primary difference versus some other applications,” David says, “is that this is a functional powder coating for corrosion protection and is coated to a thickness of 8-10 mils, which is fairly thick compared to traditional powder coating for decorative applications.” He continues, “In addition, powder that meets the specifications of ASTM A775 is designed to be fabricated after coating, so the powder finish is flexible enough to bend along with the steel as it is cut and bent into the shapes needed for different projects.”

Look no further than coiled rebar to recognize the importance of ductility after coating. Coiled rebar is used primarily for automated production equipment due to its versatility and efficiency. Rebar coils offer easier handling, transportation, and storage compared to straight rebar. This makes it a convenient option for projects that require a large amount of reinforcing material that can be quickly and easily deployed. Additionally, coiled rebar can be used to create consistent diameter spiral and hoop shapes, which are essential for certain types of concrete reinforcements. David says to coat rebar coils, they straighten the coils prior to going through the coating process, then take advantage of the flexible characteristics of an A775 epoxy coating, recoiling at the end of the process.

David shares that even with deep experience in their industry, Simcote became a PCI member to stay up to date on best practices within the greater powder coating industry. Using information learned through events and workshops, they have implemented processes that work well within their company and have discovered vendors that can provide solutions to the unique demands of the powder coating process. “The Powder Coating 101 and 202 Workshops have been helpful as ways to train new employees in the powder coating process and to have additional outside training on performance management,” David says.

After three generations, Simcote remains committed to continually perfecting their craft. That will keep my mind at ease as I’m driving home this evening.

Troy Newport is publisher of Powder Coated Tough.