In order to achieve a desired level of exposure for your chosen aggregate mixture finish the concrete has to undergo one of a few on site processes. In this article we wish to provide you with a general overlook of how the finishes are achieved and what goes in to the process, as well as ways we can be environmentally friendly throughout the process to ensure minimal impact on the environment.
From choosing the best aggregate mixture and a delivery date the next step is to then deliver the mix to the site via a process of combining the aggregate with concrete mixture in a liquid state ready to be spread and leveled. The mixture is delivered via a concrete mixing transport truck that aims to keep the concrete in a liquid state whilst thoroughly mixing through the aggregate within the concrete. This technique is used by the majority of aggregate concrete suppliers as it allows for such an even spread of aggregate to concrete whilst still able to be poured, spread and leveled for driveway jobs that are typically quite substantial.
As soon as the trucks deliver the concrete on site in its liquid form it gets poured within the boundaries of the driveway whilst workers push the concrete within the defined area to ensure an even spread and level finish. At an appropriate time within the curing process the concrete gets either acid washed or blasted with air or sand to expose the aggregate accordingly. The blasting technique has been developed over the years and now employs the use of an environmentally friendly catching process that collects any waste created as the machines are used.
Another way of achieving the exposed aggregate finish typically used for smaller areas is the process of pouring concrete in a liquid state, having it spread and leveled within the driveways boundaries before seeding the aggregate mixture evenly across the concrete surface. Once there is sufficient spread of aggregate across the concrete it gets bullfloated, this process pushes the aggregate pebbles into the concrete evenly and as the concrete cures from a liquid to a solid state the pebbles set adding strength to to the surface.
Once the concrete is set into a solid state it goes through a process of abrasive blasting via the use of sand mixed with either a water or air system that causes the solidified and strengthened concrete to erode, stripping it back to the desired grade of abrasion. As result of the blasting technique the aggregate will loose its shine and gloss and appear in a matt finish, this is sometimes desired however not always and should definitely be noted.
When considering what amount of exposure you desire for the aggregate, know that there are four levels of abrasion. The levels start at minimal blasting that provides a sandpaper like feel and appearance, and get progressively more abrasive with light and medium with heavy blasting being the most exposure providing quite a coarse textured finish.
Mike Baxter, Epping VIC