Manufacturing traditional cement for concrete is responsible for a sizeable (~8%) portion of overall global CO2 emissions. Meanwhile, anthropogenic global warming is driving the need for housing structures capable of withstanding hurricane-force winds and wildfires. The cement technology company Eco Material Technologies (South Jordan, Utah; www.ecomaterial.com) is developing a technology that could have an impact on both challenges.
In a collaboration with construction company HIVE3D (Houston, Tex.; www.hive3dbuilders.com), Eco Material is using its low-carbon, geopolymer-type cement to build 3D-printed houses at a development near Austin, Tex. The material, known as PozzoCEM®, is a mixture of fly ash that has undergone a proprietary chemical and physical pre-treatment process. The resulting product is a powdered glue material that can substitute for ordinary Portland cement (OPC), and can be pumped through specially designed 3D printing heads at construction sites. HIVE3D assembles the housing walls by applying PozzoCEM one layer at a time.
A co-product of coal-based power generation made primarily from silicon dioxide, aluminum oxide and iron oxide, fly ash has been incorporated into cement for decades to displace a portion of the OPC, and to enhance cement’s long-term durability properties. Eco Material has been working on ways to increase the proportion of OPC that can be substituted with fly ash, from 20% up to 50% or more. PozzoSlag®, an existing product from the company, has been in commercial use for more than a decade of proven concrete applications.
The PozzoCEM material has several significant advantages that make the 3D printing possible. One is an extremely fast cure time, which allows each layer to bond and harden with sufficient strength within an hour, making the 3D printing process time-efficient. Another is its carbon footprint. Since the fly-ash-treatment process requires much less heat than that needed for making OPC, and because PozzoCEM does not involve the CO2-releasing calcium-carbonate-to-calcium-oxide reaction found in OPC, the carbon footprint of the PozzoCEM material is about 93% lower than that of OPC, says Danny Gray, Eco Material’s executive VP of strategy and business operations.
Currently, PozzoCEM’s cost is significantly less than specialty cements serving the same 3D-printing applications, and the company leaders say the cost will improve further as volume usage expands in advanced applications such as concrete housing. Regular OPC is not suitable for 3D-printing applications.