Define Internal Curing
When a concrete mixture is internally cured, a component that acts as a curing agent is introduced to it. It is possible to use saturated porous aggregates or superabsorbent polymers as the curing agent.
Define Superabsorbent Polymers
Concrete can also be internally cured by using superabsorbent polymers. If SAP comes into contact with water, it swells and becomes gel like. A superabsorbent polymer swell between 20 and 2000 times its own mass in water. Upon contact with other ionic substances, such as salt, the superabsorbent polymers release the absorbed water.
Workflow of Internal Curing
An internal curing of concrete depends on three main parameters: the volume of water supplied by lightweight aggregate, it’s desorption properties, and the spacing between lightweight aggregates.
Water Volume
Chemical shrinkage and auto shrinkage determine the volume of lightweight aggregate required. Water is required from lightweight aggregate by the difference between these two elements.
Desorption Properties
Curing internally requires large, well connected pores in the internal reservoir, which are larger than those found in cement paste.
The cement paste’s capillary pores are refined during cement hydration, and their radius is smaller than that of lightweight aggregate pores. As a result, water can flow more easily between the aggregate and cement paste.
Spacing
In hydrating mixtures, water movement determines the spacing of lightweight aggregates. It is recommended to use a greater quantity of lightweight aggregate if the mixture is highly impermeable.
Water in lightweight aggregates can travel up to one mm, so most of the cement paste will remain intact. Moisture movement within a mixture is affected by the amount of lightweight aggregate substituted for normal weight aggregate.
Purpose of Internal Curing
Lightweight aggregates such as expanded shale, slag, pumice, perlite, and clay are suitable for internal curing instead of normal strength aggregates.
It is important to note that internal curing of concrete does not replace surface curing, but it works in conjunction with it to produce better concrete. By using it, you can compensate for poor, plain concrete that commonly occurs on construction sites, and for rainy weather conditions that may negatively impact the strength development of concrete.
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