• The most evident issue with many existing SCMs is that while they can reduce a significant amount of Portland cement in construction, they cannot replace it entirely—thereby preventing the possibility of a net zero-emission concrete. Senate Bill 596 (SB 596), passed in September 2021, requires the California Air Resources Board (CARB) to develop a comprehensive strategy to achieve net-zero emissions for cement used within California by 2045.54 The legislation also set an interim goal of 40 percent below 2019 levels by the end of 2035. In order to achieve these goals and California’s broader emissions goals, either new SCMs which are able to replace Portland cement entirely or carbon capture technology must be developed and implemented. Realistically, both strategies will have to be used in concert to achieve decarbonization.

54 SB 596, Greenhouse gases: cement sector: net-zero emissions strategy. Available at: