Materials scientist gives new life to old buildings with a geopolymer mortar
A growing number of steel-frame structures are using a new carbon-fiber-reinforced geopolymer mortar for cathodic protection (CP). The conductive mortar helps to carry an electrical current through the building’s frame, guarding against corrosion.
A new facility produces the mortar by the ton. “We set up a new geopolymer production facility in the Northwest of England that increases production capacity from experimental batch sizes of 100 kg to up to 10 tonnes per day,” says Graeme Jones, managing director of C-Probe Systems Ltd., Altrincham, England.
Jones developed the mortar with the help of Mott MacDonald and Sheffield Hallam University, Yorkshire. Mixing carbon fibers with an alkali-activated cementitious binder, or geopolymer, amplifies the mortar’s conductivity, says Jones. It has the side benefit of reducing shrinkage problems, which means that repairs—such as repointing—last longer than those done using conventional mortar.
“Because of the carbon fibers, the geopolymer is less susceptible to thermal and chemically induced damage than portland cement,” says Jones’ co-developer, Paul Lambert, Mott MacDonald head of materials and corrosion technology, and a visiting professor at the Centre for Infrastructure Management at Sheffield
Hallam University. The mortar is also environmentally friendly, notes Lambert, adding, “The carbon fibers are from recycled sources.”
Jones and Lambert developed the mortar to solve a problem that doesn’t go away. Heritage buildings, built with steel frames and masonry, were popular between the 1800s and 1950s. The frames are vulnerable to corrosion behind their stone cladding, which results in the degradation of the structure, says Jones. To arrest corrosion, CP is a necessary and proven technique.
Jones’ team uses a mixed-metal-oxide-coated titanium wire as the main anode to conduct a small anti-corrosion electrical current to the building’s steel frame. Jones’ mortar adds a new level of protection: The mortar covers and connects the anode wires, making the installation less invasive, he says.
The mortar has won awards from Fiatech, the International Concrete Repair Institute and the Leeds Sustainability Institute. The company is preparing to launch the product in other markets and for other uses, such as extending infrastructure longevity and as a seismic-damage protector and a fire-resistant anode.