Ozinga cut the ribbon Oct. 13 on a slag cement mill in East Chicago, Ind., that it says can turn out 1 million tons of low-carbon cement a year, the largest plant of its kind in North America. The Mokena, Ill., concrete and materials company built the mill on the Lake Michigan shoreline with rail, truck and barge access, and it’s selling the output as a way to take carbon out of concrete without waiting on new chemistry.
Ozinga announced the opening the same evening. Ozinga says the project put more than 250 construction workers on site, many of them through Indiana-based, employee-owned Morrison Construction. Ozinga hasn’t disclosed what it spent.
What the East Chicago slag cement mill makes
The product is ground granulated blast furnace slag meeting ASTM C989, plus proprietary blends sold as CarbonSense under the ASTM C1157 performance spec. The grinding runs on a Gebr. Pfeiffer MVR 5300 C-6, a six-roller vertical mill that Concrete Products described at groundbreaking as one of the largest on the continent.
Raw slag is first processed at Ozinga’s Burns Harbor operation at the Cleveland-Cliffs steel mill, then moves to East Chicago for grinding. Indiana Harbor Belt Railroad connects the site to the Class 1 network. Ozinga says a single barge carries what 17 railcars or 75 trucks would.
Checking the low-carbon cement claims
Ozinga says its blends can cut embodied carbon by up to 80% compared with traditional portland cement mixes, and that the plant will offset more than 700,000 metric tons of CO2 a year once fully running. Both are company figures. “Up to” matters here: the reduction in a real mix depends on how much slag replaces cement, and most structural mixes don’t run at the top of that range, especially in cold-weather pours where early strength drives the schedule.
The offset estimate also rests on the mill running near capacity and the slag displacing portland cement that would otherwise have been used. The release doesn’t publish an EPD or show the math. Specifiers writing embodied-carbon limits into a project will want plant-specific EPDs before they count those tons.
Supply is the other limit. Slag is a byproduct of blast furnace ironmaking, and its availability tracks the steel industry. Tying this mill to one Cleveland-Cliffs furnace site gives Ozinga a steady source but not an expandable one.
Why domestic slag cement capacity matters
Ozinga’s pitch is as much about imports as carbon. Citing USGS, it says imports covered about 22% of U.S. apparent cement consumption in 2024. A Great Lakes grinding plant with rail and barge reach can compete with imported slag and clinker coming in through coastal terminals, the way Silvi is railing Grade 120 slag into the Southeast.
The plant is expected to support about 50 permanent union steelworker jobs across East Chicago and Burns Harbor. The measure that’ll count is how much CarbonSense shows up in Midwest ready-mix submittals next spring, and at what price against straight Type IL.