Terra CO2 has begun extensive testing of a zero-carbon concrete made from rock and sand to replace Portland cement, the company says.
The company uses available silicate-based igneous rock, such as basalt and granite, or unconsolidated sediments like sand and gravel to produce Opus Zero, a zero-clinker cement that does not require any mining or activities that produce carbon emissions, according to Terra CO2. The feedstock comes from existing aggregate mines where the company can set up its plants.
The announcement of the testing, which is expected to occur throughout 2024, follows Terra’s 2022 application of its Opus SCM supplementary cementitious material in the Minnesota Road Research Facility (MnROAD) pavement test track. Terra delivered 20 tons of Opus SCM, which the company says produced 70% lower carbon-dioxide emissions and 90% lower nitrous-oxide and nitrogen-dioxide emissions than Portland cement. The concrete mixture had the highest substitution of Portland cement at 35% of the other products tested, Terra says.
The Opus Zero product, Terra says, would go further – a 100% replacement of Portland cement.
To produce its cement mix, Terra uses a proprietary low-carbon and low-NOx reactor to turn rock and sand into a glass powder suitable for blending in cement products. The process and materials replace the use of fly ash used in traditional cement, which leads to heavy carbon emissions.
The Opus Zero product can be produced at the same plant that makes the Opus SCM. Terra says production of its Opus SCM is under agreement to be deployed across the U.S. by construction materials companies, and it can be seamlessly integrated with current infrastructure. The product was recently used in the construction of a Porsche dealership in Houston.
The Opus Zero product to be tested eliminates carbon emissions “by using just one-fifth of the calcium equivalent of conventional cements,” the company says.
The company reports that early results of testing Opus Zero have been promising by meeting or exceeding specifications for strength.
"By launching the full-scale trials of Opus Zero, we're setting new benchmarks for environmental responsibility and material performance in construction," says Terra CEO Bill Yearsley. "Our Opus Zero alternative to legacy cement has been in development since day one at Terra, and we are excited to begin full concrete trials as a final step toward commercial readiness. The trials mark a significant milestone in our mission to build a sustainable future for all."
