Results of an investigation with Arizona State University (ASU) School of Sustainable Engineering and the Built Environment have prompted Ontario-based advanced nanomaterials producer HydroGraph Clean Power Inc. to commence testing of its admixture-grade graphene with major North American cement and concrete interests. HydroGraph graphene aggregate products (fractal graphene, FGA-1; reactive graphene, RGA-1) are part of the carbon nano-particle family, where single layers of carbon atoms bond in a planar lattice pattern. FGA-1 and RGA-1 have three to nine layers in the shape of platelets, whose sides measure about 20-50 nanometers—three decimal points right of cementitious material particle diameters.
Graphene can be processed and engineered to deliver strength, hardness and conductivity at inordinately higher multiples of steel, diamond, copper and aluminum. ASU investigators confirmed HydroGraph graphene products’ potential in mortar mixes dosed at 0.02 percent to 0.04 percent by weight of binder. Measured against portland cement paste control specimens, mixes bearing FGA-1 and RGA-1 powders exhibited a) up to 70 percent higher early and 15 percent higher 28-day compressive strengths; b) total porosity and critical pore size reduction; and, c) double the yield stress. At miniscule volumes properly dispersed throughout a cement-based matrix, the hydrophilic graphene platelets form optimal bonds with calcium silicate hydrate products and suggest portland cement substitution in mortar or concrete mix designs at 10-15 percent rates.
“Compared to other suppliers working with graphene products formed at micrometer scale, we are truly at nanoscale,” says HydroGraph CEO Kjirstin Bruere, who holds a master’s in Material Science and Engineering from ASU. “Nanoscale graphene in mortar or concrete mixes creates cement particle nucleating sites to speed curing and strength development and impart additional density in the hardened state.” Internal research, along with cement and concrete producer round robin testing, she adds, will shed additional light on the FGA-1 and RGA-1 platelets’ capacity to expedite and broaden cement hydration—ultimately enabling lower binder factors in mix designs. HydroGraph and ASU chemists are focusing on the hydration function of hydrogen and oxygen atoms in FGA-1 and RGA-1 molecules, whose base is COOH.
“As the global cement and concrete industry looks to lessen its carbon footprint, HydroGraph will be part of the solution,” adds Chief Science Officer Ranjith Divigalpitiya, who co-authored “New Generation Graphenes in Cement-Based Materials: Production, Property Enhancement, and Life Cycle Analysis,” a recently published ACS Sustainable Chemistry and Engineer Journal report. “Our 99.8 percent pure graphene is manufactured with a sustainable, repeatable process that has the lowest carbon footprint of all graphene producers. The net effect is better for the environment.”
LESS IS MUCH MORE
Cement and concrete industry testing coincides with HydroGraph’s commercial scale production ramp up of near-pure (carbon > 95 percent) graphene platelets, their surface area characteristics astonishing when compared to cementitious material particles. The ultra-low FGA-1 and RGA-1 dosages in the ASU investigation reflect the inordinately small platelet sizing—hovering 1/1,000th of portland cement particles’—and astronomical surface area (> 1,000 times typical cementitious materials) that HydroGraph attains through a production process dubbed “detonation synthesis.”
The company’s Hyperion reactors yield ultra-fine graphene platelets from high purity acetylene, a hydrogen and carbon-bearing gas (H2C2) produced in methane (C4H4) cracking facilities. An electrode ignites the extremely volatile gas, ripping apart the acetylene molecules in equal proportions. After an 11-microsecond phase where temperatures spike north of 4,200°F, the molecules recrystallize into the graphene platelets, which forms the aggregates in FGA-1 and RGA-1. After extensive testing and early production at a Manhattan, Kan. facility, HydroGraph is proceeding to commercial scale with modular Hyperion reactor models equipped for annual output of 10 metric tons. The units occupy less than 10 square feet each and can be grouped in efficient clusters depending on feedstock volume and target production levels.
“Hydrograph’s graphene, which is manufactured through scalable and cost-, energy- and carbon dioxide-efficient detonation synthesis, can be of huge benefit to the engineering and environmental performance of concrete and cement,” concludes ASU College of Built Environment Professor Narayanan Neithalath, “New Generation Graphenes” co-author. — HydroGraph Clean Power Inc., London, Ontario, www.hydrograph.com
