Monday, September 5, 2011

High-Strength Steel Cheaper Overall Than Conventional Rebar

Courtesy Cary Kopczynski and Co. Once thought to be just a seismic product, high-strength rebar is paying off for general builders because they can use less steel reinforcement. However, it is not yet widely available. Related Links: When Does It Pay To Use Innovative Concrete Products?


High-strength rebar reduces overall building costs compared to traditional steel reinforcement, according to a new study from the Construction Industry Institute.

Compared to traditional rebar, typically rated at 60 kips per sq in., the high-strength variety, rated at 100 ksi, costs twice as much to buy up front. However, it reduces overall reinforcing steel by 14% to 49%, translating into a net cost reduction of 12% to 33%.

This calculation assumes a 100-ksi rebar cost of $1,200 per ton versus 60-ksi rebar's $600 per ton, with a labor cost of $710 per ton for both.

"The high-strength steel definitely seemed to be on the winning end," says David MacNeel, operations manager at Baker Concrete Construction. He is part of a team studying productivity for Austin, Texas-based CII. Researchers presented the results in Chicago on July 26 at CII's annual conference.

The team studied three recent innovations in concrete—modular formwork, self-consolidating concrete and high-strength reinforcement—and compared them to their traditional counterparts.

The advantages of high-strength steel, the team found, are reduced rebar congestion, reduced weight and increased design strength. The downsides are higher cost, brittleness, complex structural analysis and limited availability.

Only one supplier, MMFX Technologies Corp., Irvine, Calif., currently offers 100-ksi rebar, and not every building code yet accepts it.