SET-RETARDING AND HYDRATION CONTROL

A retarder is a retarder mainly composed of organic salts. Its retarding effect is achieved by the hydrogen bonding between the hydroxyl groups adsorbed on the surface of cement particles and the O2- on the surface of hydration products, as well as the hydrogen bonding with water molecules to form a stable solvation water film on the surface of cement particles, thereby inhibiting the hydration process of cement and achieving a retarding effect. Retarders are mainly used in concrete engineering that requires concrete to maintain plasticity for a longer period of time and needs to slow down the rate of hydration heat release.

Set-Retarding

• Definition: Set-retarders are admixtures added to concrete or cement to delay the setting time. This is useful in hot weather conditions or for large projects where extended working time is needed.
• Function: They work by interfering with the chemical reactions that cause the cement to harden, mainly by delaying the formation of C-S-H (calcium silicate hydrate) gel.
• Applications: Improve workability, allow longer transportation periods, and facilitate delayed finishing.

Hydration Control

• Definition: Hydration control involves managing the chemical reactions between water and cement particles to optimize setting and hardening processes.
• Methods: Using inhibitors like set-retarders, adjusting water-to-cement ratio, or employing specific curing techniques.
• Importance: Proper hydration control ensures desired strength, durability, and workability of concrete.