The integrity of modern concrete structures is often compromised by an unexpected adversary: rust. Steel reinforcement bars (rebar) embedded within concrete are susceptible to corrosion, leading to premature structural failures. Bridges, continually exposed to moisture and de-icing salts, are particularly vulnerable. In the United States, approximately one-third of bridges require repair or replacement, with projected costs nearing $400 billion over the next decade.
Traditional methods to combat rebar corrosion include epoxy coatings and additional concrete layers designed to delay water infiltration. However, these measures often provide only temporary relief. The most effective solution to prevent rust is the use of stainless steel rebar, but its high cost has limited widespread adoption.
Allium Engineering, a forward-thinking startup, offers a cost-effective alternative by encasing standard rebar in a thin layer of stainless steel. This innovative approach aims to extend the lifespan of bridges from the typical 30 years to an impressive 100 years. Samuel McAlpine, co-founder and CTO of Allium, emphasizes that even a minimal stainless steel coating can provide corrosion resistance lasting centuries.
The company’s stainless steel-clad rebar has already been implemented in infrastructure projects, including a bridge deck replacement on U.S. Highway 101 in Mendocino County, California, and an upcoming project on Interstate 91 in Massachusetts. Additionally, Allium’s rebar has been utilized in a commercial boatyard in Key West, Florida.
For heavily trafficked bridges, engineers often specify stainless steel rebar despite its cost being approximately five times that of conventional rebar, justifying the expense to avoid major disruptions. For less critical structures, epoxy-coated rebar is commonly used, costing 25% to 50% more than uncoated rebar. However, epoxy-coated rebar requires careful handling and maintenance, adding indirect costs.
Allium positions its stainless-clad rebar as a superior alternative to epoxy-coated rebar, aiming to match or even undercut its price. CEO Steven Jepeal notes that Allium’s rebar reduces handling complexities and eliminates the need for additional concrete layers intended to protect against corrosion. This reduction could decrease cement usage by up to 20%, promoting more sustainable construction practices.
The manufacturing process involves cladding 7,000-pound steel billets with stainless steel, which are then rolled to the desired thickness. This method ensures a consistent stainless steel layer of approximately 0.2 mm, sufficient to prevent corrosion within concrete environments.
By integrating this innovative rebar into bridge construction, Allium Engineering offers a durable, cost-effective solution to the pervasive issue of rebar corrosion, potentially transforming infrastructure longevity and maintenance practices.
