Supplementary cementitious material (SCM)
A reactive material such as fly ash, slag, or silica fume used to replace part of the portland cement in a mix, improving durability and lowering carbon footprint.
What does supplementary cementitious material (scm) mean?
SCMs are not inert fillers; they react with the byproducts of cement hydration to form additional binder, densifying the paste and reducing permeability. The common tradeoff is slower early strength gain in exchange for higher long-term strength and better resistance to chlorides, sulfates, and alkali reactivity. Availability has tightened as coal plants close, pushing the industry toward limestone blends and alternative pozzolans.
In practice
An SCM mix that tests lower at an early age and finishes slower in cool weather is behaving normally, not failing.