The American Association of State Highway and Transportation Officials (AASHTO) increased the design strength for concrete reinforcing steels to 100 ksi for bridges and other structures, enabling highway engineers to start designing with higher-strength, corrosion resistant, MMFX2 rebar (AASHTO MP18 / ASTM A1035 Grade 100 [690 MPa]). This engineering advancement will reduce the costs of replacing our nation’s aging infrastructure and result in better built bridges and roadways by utilizing less steel, relieving costly rebar congestion issues, and providing a cost-effective, corrosion-resistant, rebar solution.

On 12 July 2012, AASHTO, through the Subcommittee on Bridges and Structures, updated the Load and Resistance Factor Design (LRFD) Bridge Specifications to permit public bridges and structures to be designed using high-strength reinforcing steels up to 100 ksi yield. The LRFD Bridge Specification is the standard used by state Departments of Transportation (DOTs) to set local bridge design codes.

AASHTO, made up of the chief transportation officers from the 50 states, the District of Columbia and Puerto Rico, is an international leader in setting technical standards for highway systems. AASHTO’s approval of the higher-strength steel standard was based on the finding and recommendations of the National Cooperative Highway Research Program (NCHRP) Report 679 released in 2011. The report states, "…using steel with this higher capacity could provide various benefits to the concrete construction industry by reducing member cross sections and reinforcement quantities, leading to savings in material, shipping, and placement costs. Reducing reinforcement quantities also would reduce congestion problems leading to better quality of construction." The NCHRP report provided AASHTO decision-makers with the necessary background and engineering basis, in the form of experimental and analytical studies, and recommended the application of high-strength rebar, specifically AASHTO MP 18 / ASTM A1035.

This change by AASHTO expands the opportunities for the nation’s DOTs to harness the higher-strength of MMFX2 rebar to design and build structures with 20% to 50% less steel and up to 60% lower labor costs. MMFX2 rebar, sold in North America by MMFX Steel Corporation of America and its distribution partners, had previously been limited in designs up to 75 ksi for bridge structures.

In addition to high-strength, MMFX2 rebar offers superior corrosion-resistance as previously recognized by AASHTO MP18. Use of uncoated, corrosion resistant, MMFX2 steel results in longer-lasting bridges and other structures without the problems and special handling requirements associated with coated rebar.

As the only 100 ksi strength rebar with enhanced corrosion-resistance, MMFX2 meets this new AASHTO standard. Not only can bridges be constructed more efficiently because of the higher strength, the structures will last over 100 years due to MMFX2 rebar’s superior corrosion-resistance. The most significant benefit will be for taxpayers through lower upfront construction and lifetime repair costs for infrastructure, and less disruption to traffic flow.