Cement is a fine powder, most commonly portland cement, that reacts with water to form the paste that binds sand and stone into concrete.
Cement is a small share of concrete by volume but the largest source of its carbon. Making it requires heating limestone to very high temperatures, which releases carbon dioxide both from the fuel and from the limestone itself. Cement production is widely estimated at around 7 to 8 percent of global CO2 emissions, which is why lower-carbon binders matter for parking structures. See embodied carbon.
Common types
- Portland cement in several types for general use, moderate or high sulfate resistance, and high early strength.
- Portland-limestone cement, often called Type IL, which replaces some clinker with ground limestone and is now widely used in the U.S.
- Blended cements that include slag, fly ash or other supplementary materials.
Lowering cement carbon in a garage
- Use portland-limestone or blended cements.
- Replace part of the cement with slag, fly ash or other supplementary materials.
- Specify strength at 56 days instead of 28 where the schedule allows.
- Ask for environmental product declarations to compare mixes.
The Parkonomics view
A parking structure is mostly concrete, and concrete carbon is mostly cement. Choosing the binder is one of the biggest climate decisions an owner makes, and it is usually made by default.
Related terms: Concrete, Embodied Carbon, Environmental Product Declaration, Carbon Footprint, American Concrete Institute, Sustainability