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Carbon Leverage

By Don Marsh

Solidia Technologies approaches commercialization of its branded cement and concrete, trading hydration-based binding and curing methods for carbonation

LeadEarly testing of Solidia Concrete has centered on molded or extruded product, concrete masonry and hollowcore plank representing higher volume candidate markets. Plank cores enable accelerated curing, as they extend the surface area for carbon dioxide streaming beyond elements’ top and sides. The New Jersey headquarters and laboratory displays samples from the largest equipment investment: a Columbia Model 16 block & paver machine.

The green building movement’s embrace of materials and products bearing lower carbon footprint than heritage offerings has piqued the interest of parties outside traditional cement and concrete circles. Some are promoting solutions that lower portland cement requirements, but impart comparable performance in finished concrete; others are targeting cement and concrete materials’ calcium chemistry to make aggregates, slabs and structures that bear loads and function as permanent carbon dioxide sinks.

Piscataway, N.J.-based Solidia Technologies has refined a process converting a stream of CO2 to binding solids within a concrete matrix, after the gas has first been channeled for hardening and curing. On the heels of six years of laboratory work, capped with 2012–13 field trials, the company is approaching the commercial stage of an integrated value proposition: Solidia Cement + Solidia Concrete. The latter will debut primarily for zero or low slump precast products as staff investigates higher slump mixtures suited to conventional precast and cast-in-place conditions.

The Solidia Technologies business plan envisions licensing and royalty agreements with cement and concrete producers across the world. The company’s 50-member team spans scientists and engineers with wide connections in construction and building materials, plus extensive experience in new product and market commercialization, intellectual property, and simplified manufacturing. They are leveraging competencies in chemistry and kiln energy optimization for cement production, and fabrication and curing to deliver finished concrete with up to 70 percent less embodied carbon than portland cement alternatives.

A compelling carbon message is critical for the level of capital Solidia Technologies investors have committed in laboratory and production equipment, plus domestic and international research. Management acknowledges, however, that a reduced carbon factor and ticket on the green-building express will only carry so far. Beyond carbon math, the company looks to demonstrate how Solidia Cement and Solidia Concrete can equate to mixes that require less water and fewer, if any, admixtures than portland cement concrete; set on demand and only when exposed to CO2 gas streams; and, yield finished products with 4,000 psi to 8,000 psi compressive strength development in one day versus a week or more on conventional alternatives.

President and CEO Tom Schuler underscored the Solidia philosophy in a panel discussion earlier this fall during the World Business Council for Sustainable Development/Cement Sustainability Initiative 2013 Forum in Vancouver, B.C. “Sustainability is about competitiveness. Companies that don’t adopt sustainable technologies will struggle to compete,” he observed for the packed gathering, which included representatives from more than 20 of world’s top cement operators. “The [cement] industry must adopt sustainable technologies that can help generate profits—without relying on grants or carbon credits.”

“Sustainability must stand on its own two feet with commercially viable technologies,” he tells Concrete Products. “We have worked for years to understand the market and its challenges, and focus on processes that use the same raw materials in cement and concrete plants. Our technology fits within existing parameters of a broad span of producers from North America and Europe to Japan, China and Australia.”

Through much trial cement or concrete production and sample testing involving global, regional and independent producers, Schuler adds, “I haven’t found an industry working harder to improve its sustainability profile. Every company we’ve talked to is looking at carbon factors and energy consumption. We’re an intriguing option. We can bring something competitively priced to cement and concrete companies, which in turn can offer customers products of reduced carbon footprint.

“We have taken a complex technology and made it simple, not only to ease adoption around the world, but also to provide the construction and building materials industries a real competitive edge, with immediate cost savings, superior performance, and an enhanced sustainability profile.”

POWDER MILLING
The CO2 intensity label has accompanied cement producers and their concrete customers through much of the green building era and two-plus decades of global regulatory developments on greenhouse gas emissions. Portland cement’s carbon load owes to three production phases proceeding aggregate, clay and other raw material extraction: calcination, where CO2 is released when calcium carbonate-laden limestone is preheated with other finely graded, rotary kiln-bound feed to nearly 1,600°F; clinker, where materials and particles agglomerate into nodules, typically reaching 2,700°F; and, clinker grinding in electric power-hungry ball mills or vertical crushers.

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As material formulations and carbon dioxide curing processes were refined, Solidia Technologies equipped its laboratory with small-scale, commercial grade concrete plant equipment, including a ¼-yd. Sicoma mixer. The equipment has produced mixes with a wide variety of local aggregates, plus Solidia Cement (shown in clinker and finished states) produced from different kilns.

Solidia Cement derives from the same raw materials as portland cement, minus gypsum and bauxite, but with less limestone (about 50 percent versus 80 percent) and more silica sources; its clinker entails pyroprocessing at lower temperature than portland cement, and grinding to a Blaine number consistent with Type I powder. Where tricalcium silicate and dicalcium silicate constitute the bulk of the latter, Solidia Cement is chiefly simple calcium silicate compounds. The Solidia binding mechanism is a radical departure by portland cement standards: It joins fine and coarse aggregate with chemistry similar to hydraulic cement, using carbonation in lieu of hydration.

“Our calcium silicate compounds do not hydrate,” says Solidia Chief Technology Officer Nick DeCristofaro, Ph.D. “In portland cement concrete, water has two functions: It hydrates cement particles to bind fine and coarse aggregate and acts as plasticizer during mix production and placement. In Solidia Concrete, water also has two functions: Shaping and plasticizing the mix, then effecting the carbonation that substitutes for hydration.

“Water in our product dissolves gaseous carbon dioxide to form carbonic acid, which in turn helps dissolve calcium. As the carbonic acid migrates across the matrix, carbonate ions and calcium ions precipitate as calcium carbonate and crystallize in between coarse and fine aggregate. Like portland cement concrete, we observe reactivity with about 75 percent of Solidia Cement particles; the remaining ones function as ultra fine aggregate. The carbonate and calcium ionic bonds are tighter than those in calcium silicate hydrates found in portland cement concrete.”

The Solidia binding mechanism is independent of carbonation in existing concrete, which Portland Cement Association describes as a slow, nondestructive process where slabs or structures’ embedded moisture reacts with ambient CO2 and results in slight surface paste shrinkage and pH reduction. Once it is CO2-cured, Solidia Concrete will not carbonate to any further degree. The curing process used for the setting and hardening of Solidia Concrete, moreover, provides intrinsic corrosion protection for both embedded and exposed rebar. It is expected that this additional corrosion protection, when fully developed and implemented, will allow the use of steel reinforcement in all Solidia Concrete candidate applications.

CO2-activated binding is based on material synthesis technology developed at Rutgers, The State University of New Jersey, under Distinguished Professor Richard Riman, Ph.D., who founded the company and remains chief scientist. Vahit Atakan, who co-invented the technology as graduate student and research associate, is Solidia director of Research & Development. They originally weighed applications outside cement and concrete, but found the technology adaptable for calcium, carbon and silica.

Their reactive hydrothermal liquid phase densification (rHLPD) process uses a liquid solution to penetrate into the pores between the particles; react with the particles; and, create “bridges” between particles to lock them into place. In 2007, Solidia Technologies consolidated rights to cement and concrete-applied rHLPD through an exclusive licensing agreement with Rutgers. Including two recently issued U.S. patents, it covers a portfolio of 50-plus U.S. and foreign patents and patent applications. “Together, they teach a unique method that enables cement companies to cut their environmental footprint by operating at far lower kiln temperatures than the conventional method, and provide customers a new means for carbon sequestration in concrete,” notes Professor Riman.

PRECAST PREMIER
Solidia Technologies sited its northern New Jersey lab and office in an existing 26,000-sq.-ft. building—fittingly constructed of prestressed double tee wall members and concrete masonry. Beginning in 2008, technical staff adapted the rHLPD to cement and concrete, capping initial research by announcing alternative cement and concrete production methods at the 2011 Greenbuild International Conference. Since then, team members have conducted Solidia Cement production trials at overseas mills, powder returning to the Garden State in supersacks. The most recent milling took place at the world’s largest research rotary kiln in Weimar, Germany, netting 25 tons.

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In addition to product from the Columbia and Elematic machines, laboratory staff has tested the Solidia Concrete mixes’ suitability for aerated block, pervious slabs, plus strand- and grout-ready railroad ties. Team members are especially keen on the rate carbon dioxide-generated carbonic acid permeates the concrete matrix.

In 2012, the company began testing the cement in North American and overseas precast operations, aiming to gather production and performance data on prospective users’ wide variety of fine and coarse aggregate. Demonstrations entailed small batches and manufactured-concrete elements that could be staged in forms, beds or aluminum chambers for curing with CO2 gas. Most sample products have seen curing to design strength in under 24 hours, although mass and cross section can extend the window required for carbonic acid to fully migrate.

Field demonstration successes, coupled with management’s goal to expedite Solidia Cement and Solidia Concrete commercialization in a handful of higher volume precast applications, drove investment in a custom ¼-yd. Sicoma mixer with integral 12-ft. skip hoist; three-at-a-time Columbia Machine Model 16; Elematic hollow core extruder; and, two curing chambers—one fixed on the main lab floor, another mobile CDS container-style model—each fed industry-derived, waste CO2 through flexible, 6-in. diameter ducts.

Mixing, product machinery and curing equipment arrived at headquarters in early 2013, allowing Solidia Technologies to test commercial-grade block and paver unit, plus prestressed hollow core plank production on a small scale. The curing chambers accommodate 16-pallet transfer racks bearing 48 concrete masonry units, along with other molded products that can be handled by small capacity forklift. Four-foot hollow core plank, extruded on a 30-ft. long bed, is cured with a twin manifold charging tarps with CO2. In addition to block, pavers and plank, lab staff have fabricated large cubes and thick panels of aerated concrete, using primarily Solidia Cement and fine aggregate.

Cured Solidia Concrete sequesters CO2 at a rate equal to 5 percent of product, slab or structure weight. In hardened concrete, CO2 is about 1/1000th its volume in a gaseous state.

This year’s lab and field demonstrations have enabled Solidia Technologies to test fabrication and carbonation-style curing of additional precast members, including wet cast rail road ties, architectural panels and colored, decorative paving slabs. Domestic precasters who have observed the potential of Solidia Cement and Concrete—especially within their existing plant settings and using everyday fine and coarse aggregates, plus pigments on occasion—are eyeing the potential for offering products with the low carbon proposition, reduced permeability, and other performance aspects.

The New Jersey lab has a full inventory of specimen molds and testing devices to validate Solidia Concrete engineering properties per common ASTM test methods. Additional testing and validation have been secured through a new Cooperative Research and Development Agreement (CRADA) Solidia Technologies and the Federal Highway Administration announced this fall. With a three-year schedule, the CRADA is a mechanism for FHWA’s Turner-Fairbank Highway Research Center, McLean, Va., to test the potential of Solidia Cement and Solidia Concrete in durable, sustainable and cost-effective transportation infrastructure applications.

The first phase of the agreement will document Solidia Concrete’s compressive and flexural strength, freeze-thaw durability, and other basic properties, with initial findings expected in early 2014. A second phase holds potential for fabrication and testing of Solidia Concrete precast traffic barriers, sound walls, box culverts, bridge components, and pavement panels.

INVESTORS + LAFARGE
Development of lower carbon binder alternatives to pure portland cement has not been lost on investors, who look downstream to concrete—the second most utilized substance after water—and see worldwide shipments eclipsing $1 trillion amid building and construction to support urbanization across the globe.

Solidia Technologies is positioned as a disruptive business, one often forcing an industry to alter or rethink long-held practices. Leading its initial 2008 funding round was Kleiner Perkins Caufield & Byers, whose astute calls on AOL, Amazon and Google made it one of Silicon Valley’s premier venture capital firms. A second round in early 2012 brought additional funding participants, including Germany’s BASF Venture Capital, distant sister to Cleveland-based BASF Construction Chemicals; U.K. energy giant-backed BP Ventures; and, Bright Capital, the venture arm of Ru-Com Corp.

In September 2013, Solidia Technologies signed a partnership agreement with Paris-based Lafarge Group, which will assist in demonstrating feasibility of commercial-scale Solidia Cement production in the first half of 2014—likely at a Lafarge North America site. The two companies will collaborate to market the integrated cement and concrete technology as a new solution for precast operators.

The agreement dovetails a CO2 emissions reduction commitment across Lafarge Group. Thus far, the cement, concrete and aggregate giant has reduced emissions of the gas by 25 percent per ton of powder since 1990. Prior to the partnership, Solidia Technologies gained technical and market perspective from an Advisory Board of former Lafarge North America executives Peter Cooke and Wayne Lyons, among five total members.

Nearly two years into current funding, Solidia Technologies has begun a third round to carry its cement and concrete to commercialization. In presentations to strategic investors and funding prospects, Tom Schuler holds firm: “The key message here is how do you take an industry that is working hard to reduce its carbon factor and give it commercially viable technologies. We are promoting a differentiated product offering building and construction users the benefit of low carbon in the raw material and concrete production phases, and comparable performance to a higher carbon alternative they know well.”