1. Seeding Method
- The selected aggregate is distributed on top of freshly screeded concrete surface
- Note: During hot weather it is helpful to pre-wet aggregate to cool it prior to placement to reduce rapid drying of the surface allowing for uniform finishing.
- A concrete tamp (jitterbug) or float is then used to even the concrete surface. It is important to float sufficiently to bring the cement paste to the surface, enabling the finisher to properly close the surface. The use of a tamp also enables the finisher to surround the placed aggregate without pushing it further down into the mix and away from the surface.
- Apply surface retarder using a low-pressure sprayer at a uniform rate of 150-200sf/gal. Product should be applied soon after the floating operation. If excess bleed water occurs, wait until puddles disappear prior to application.
- The retarding chemicals diffuse into the paste, due to the normal porosity of cement in the first hours of curing, and slow down the cement hydration reaction. During the next 16 – 72 hours of curing, the bulk concrete hardens except where the cement has been retarded. The retarded surface cement is then removed by water or sandblasting, revealing the aggregate in the concrete mix.
2. Homogeneous Method
- It is important to design a fairly plastic mix with an aggregate content of 65 – 70%.
- Rodding or striking the concrete surface is critical. This must be done in a sawing motion, which will remove the excess matrix and leave the aggregate at the surface.
- The floating operation should be minimal, just enough to bring the matrix around the aggregate.
- Apply surface retarder as soon after the floating operation as possible, using low-pressure sprayer at a uniform rate of 150 – 200 sf/gal. If excessive bleeding occurs, wait until the puddles disappear prior to application. Follow additional notes in the previous section.
- It is not necessary to cover the retarder due to the unique curing mechanism incorporated into the product. It is pigmented for easy use and when dry, normally 30 to 60 minutes after application, it will provide protection from intermittent rain.
- When concrete has cured, usually overnight, remove matrix to expose aggregate with high-pressure spray or with rinse and brush method. See note in previous section.
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