What is a primary purpose of using supplementary cementitious materials in concrete besides meeting workability requirements?

• A. To avoid emissions
• B. To increase early strength
• C. To improve color
• D. To increase water demand

Answer: (A)

Supplementary cementitious materials are used to replace part of the cement in the mix, which reduces the amount of cement that needs to be produced. The big payoff is environmental: less cement means lower CO2 emissions from cement manufacturing, along with benefits like improved long-term durability and reduced heat of hydration. These environmental and durability gains are the main reasons for using SCMs beyond achieving workable consistency. Other effects, like color changes or altered water demand, are secondary and vary with the materials used, and early strength can be affected in different ways depending on the SCM and dosage.