Does the use of retarders affect the hardening shrinkage of concrete?

1. Retarder is a commonly used admixture used to extend the setting time of concrete. In summer construction, adding an appropriate amount of retarder can make fresh concrete maintain good plasticity for a long time.

2. The retarder is a surfactant that only plays a physical adsorption and dispersion role in concrete. It does not directly participate in the cement hydration reaction and generates new substances. Therefore, it has a certain effect on concrete within a certain dosage range. The final strength has no direct impact, but because it delays the setting time of concrete, it affects the early strength of concrete to a certain extent. However, the later strength can generally catch up with or exceed the concrete without retarder.

With the rapid development of commercial concrete today, retarder plays a very important role. As people’s understanding of retarder continues to deepen, the application of retarder will become more and more extensive, especially when producing large-volume concrete that needs to reduce the instantaneous hydration heat of cement and delay the peak hydration of cement. Agents are indispensable.

The speed of concrete setting and hardening depends on the speed of hydration reaction. Adding a retardant will slow down the cement hydration reaction, lengthen the concrete setting time, and the related concrete properties will also change accordingly. When the retarder dosage is too large, the cement reaction time is too long, resulting in unreacted cement core, which directly leads to the reduction or even loss of concrete-related properties. When the dosage is too small, the retarder does not play a corresponding role and the concrete retardation fails. When retarder is used together with other admixtures, certain properties of concrete will be strengthened and better adapted to engineering applications.

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