Climate Action Team Sub-Groups
FAQ / Resources
Q: What is calcination?
A: Calcination is the process of converting limestone (CaCO3) into calcium oxide (CaO) by releasing carbon dioxide (CO2) in the presence of heat.
Q: How is cement made?
A: Cement is made out of raw limestone and other minor components. The raw limestone is quarried, crushed, ground with other minor components, heated in cement kilns to form clinker, and finely interground with small amounts of gypsum. Read more about how cement is made.
Q: How is concrete made?
A: About 70 percent of the concrete produced in California is produced at a batch plant. The remaining concrete is used mostly in pre-fabricated structures such as precast. In addition to cement, the other basic ingredients of concrete include aggregate (coarse and fine), water and air. When water is mixed with cement, a chemical reaction occurs which hardens the cement, and holds the rocks and sand together, to make concrete.
Q: What is the difference between concrete and cement?
A: Cement is the glue which holds the sand and stones together, whereas concrete is the mix of all the following ingredients: cement, aggregate, water and admixtures. Cement is made at cement plants, where raw limestone is quarried, crushed, heated in cement kilns to form clinker, and finely interground with small amounts of gypsum. On the other hand, concrete is typically made at batch plants where concrete constituents are placed at the right proportion in a concrete trucks to be delivered to job sites.
Q: How are greenhouse gases (GHG) created in cement production?
A: During cement production, GHG is created by using fuels to heat the cement kiln as well as through the process of limestone calcination (where CO2 is a by-product).
Using environmentally-friendly fuels, making cement kiln production efficiency improvements, using a small amount of interground limestone in the mix, and blending cement with Supplementary Cementitious Materials (SCMs) help to reduce GHG emissions.
Q: What is GHG intensity factor?
A: GHG intensity factor is the amount of GHG released for each amount of cement production. The current GHG intensity of cement plants in California is 0.86 tons of CO2 per ton of cementitious materials. This number should be used to determine the carbon dioxide intensity of cement imported to California to guarantee these imports have at most the same intensity of California cements.
Related links: Universal GHG emission standards
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