Concrete Cracking and Internal Curing Agent SAP

2022-11-21
Concrete Cracking and Internal Curing Agent SAP

Keywords
Concrete cracking, internal curing agent, Super Absorbent Polymer, SAP

The internal curing agent is used to improve the shrinkage performance of concrete and reduce concrete cracking.

The internal curing agent of concrete refers to adding water-absorbing materials to the concrete to provide internal water sources. This type of water-absorbing materials can adjust and convert storage and water release functions according to external conditions.  The water-absorbing material in the concrete can continuously release water to the surroundings, replenish the water consumption inside the cement stone, and make the concrete have enough water for secondary hydration, thereby effectively reducing autogenous shrinkage.  The internal curing agent mainly includes superabsorbent resin and porous light aggregate.

Internal curing is a method of water supply and curing inside the concrete by using the water stored in materials with water absorption and water release functions.

Material types
Common internal curing materials include Super Absorbent Polymer (SAP), expanded perlite, lightweight porous ceramsite, etc. Among them, the water absorption and release properties of SAP are more in line with the needs of high-performance development of concrete.

Mechanism
The super absorbent polymer has a good water retention capacity, and the water will be released only under certain conditions. When SAP is added to the recycled concrete, as the cement hydration reaction proceeds, the ion concentration inside the concrete increases.  Under the effect of ion concentration difference, SAP will release water for the hydration of cement.

The action mechanism of SAP in cement slurry is mainly divided into two aspects: on the one hand, with the progress of cement hydration reaction, a large amount of free water is consumed, and when the internal humidity decreases, SAP gradually releases water under the action of humidity difference, alleviating  The phenomenon of internal drying acts as a reservoir; on the other hand, the release of SAP can rehydrate the unhydrated cement of the cementitious material, and can provide a steady stream of water for continuous hydration.  It has a good promotion effect on the hydration degree of cement slurry, which will make the interior of the structure more compact.