Abstract: A sheet 100 of water-soluble material such as polyvinyl alcohol comprises a plurality of individual, sealed pockets 110, each containing concrete admixture. The sheet is cut to size and attached to the interior of a formwork structure 200 with, for example, PVA glue. After concrete is poured into the formwork, covering the sheet 100, the sheet dissolves, releasing the admixture onto the surface of the concrete as it sets. In another arrangement, a sealed container 300 formed from a water-soluble material contains concrete admixture. The external wall of the container has a plurality of regions 320 where a thickness of the wall is reduced. The container is attached to interior walls of a formwork structure 200 or to reinforcing bars inside a formwork structure. After concrete is poured into the formwork, submerging the container, the container dissolves, with the thinner regions dissolving sooner, releasing the admixture into the concrete.

Abstract: A sheet 100 of water-soluble material such as polyvinyl alcohol comprises a plurality of individual, sealed pockets 110, each pocket containing concrete admixture. The sheet is cut to size and attached to the interior of a formwork structure 200 with, for example, PVA glue. After concrete is poured into the formwork, covering the sheet 100, the sheet dissolves, releasing the admixture onto the surface of the concrete as it sets. In another arrangement, a sealed container 300 formed from a water-soluble material contains concrete admixture. The external wall of the container has a plurality of regions 320 where a thickness of the wall is reduced. The container is attached to interior walls of a formwork structure 200 or to reinforcing bars inside a formwork structure. After concrete is poured into the formwork, submerging the container, the container dissolves, with the thinner regions dissolving sooner, releasing the admixture into the concrete.