Which material is primarily used to reduce heat of hydration and improve resistance to chemical attacks when added to concrete?

Which material is primarily used to reduce heat of hydration and improve resistance to chemical attacks when added to concrete?

• A. Slag (ground granulated blast-furnace slag).
• B. Fly ash only.
• C. Silica fume only.
• D. Lime putty.

Answer: (A)

Using supplementary cementitious materials can tame heat of hydration and boost durability. Ground granulated blast-furnace slag, when finely ground and blended with cement, reacts with calcium hydroxide to form additional cementitious products. This slows the rate of heat release during early hydration, reducing the peak temperature, and it also densifies the paste, making the concrete less permeable. The denser, less permeable matrix better resists chemical attacks from sulfates, chlorides, and other aggressive agents. Fly ash can also help lower heat and improve durability, but slag is particularly effective for chemical resistance due to its latent hydraulic reaction and pore-structure refinement. Silica fume mainly tightens the microstructure and increases strength, with less impact on heat reduction, and lime putty isn’t used in modern concrete for these purposes.

Using supplementary cementitious materials can tame heat of hydration and boost durability. Ground granulated blast-furnace slag, when finely ground and blended with cement, reacts with calcium hydroxide to form additional cementitious products. This slows the rate of heat release during early hydration, reducing the peak temperature, and it also densifies the paste, making the concrete less permeable. The denser, less permeable matrix better resists chemical attacks from sulfates, chlorides, and other aggressive agents. Fly ash can also help lower heat and improve durability, but slag is particularly effective for chemical resistance due to its latent hydraulic reaction and pore-structure refinement. Silica fume mainly tightens the microstructure and increases strength, with less impact on heat reduction, and lime putty isn’t used in modern concrete for these purposes.