Handy Hints

Best Practises for Concrete Placement

Gecko Rocks range of exposed mixes will add value to your building project. The success of using this range of mixes depends upon planning and attention to detail and an experienced contractor should always be appointed to achieve the best results. Remember the trade skills employed are as important as the mix being supplied, don’t cut corners. The process is not just good luck on the day. As specialists in exposed aggregates we are aware of all factors that determine the final quality of the job and implement best practises to limit the risk of cracking.

To be sure you get the best result we have provided a list of best practises that are vital to the final finish and are included as standard in all our pricing.

Compaction
All areas are to be compacted prior to placement of concrete. Without compaction of the ground some sinkage may eventuate causing cracking of your exposed aggregate.

Reinforcement
If mesh is being used ensure that the correct cover is achieved, you don’t want to see mesh being exposed in the washing operation. We recommend mesh for all driveways and use mesh chairs to ensure that the mesh is correctly placed in the concrete with adequate concrete cover on top and bottom. 12mm deformed bar should also be placed at all internal corners to help avoid cracking.

Expansion
Exposed aggregates abutting brick work or other fixed surfaces should always have expansion foam separating the two materials. This allows for expansion and for the two materials to move independently, that is the concrete does not stick to the brickwork and result in cracking.

Area
Don’t try to do too much in one day. It’s easy to pour initially however chasing the concrete to achieve the desired level of exposure can often lead to an inconsistent appearance. Trying to pour too much in one day is often a result of a greedy contractor. If your job needs to be done in two days to achieve the best result then do it in two days.

Set Retarders
Consistency is everything, same day washing is not as effective as the use of a surface set retarder which allows the concrete to be exposed on the following day. Same day washing is reliant upon the skills of the contractor, it can be affected by differential setting times of the concrete, ambient temperatures, areas of shade etc basically the concrete has to be consistently hard to ensure an even level of exposure, if too soft the concrete can be overexposed this will result in an entirely different appearance of the finished surface. We use and recommend Rugasol C by Sika.

Pumping
As exposed mixes contain a higher percentage of coarse aggregate difficulties can be experienced in pumping such mixes. We only use pumps in most severe cases where wheelbarrows can not reach the site.

Joints
We recommend joint cutting with a diamond saw opposed to tooling in the joints as it is much neater. This must be done on the same day (using a soft cut machine) or early the next day to avoid cracking.

Washing off
This part of the process is often not considered when selecting a contractor. A poor job of washing off can mean you are left with stained walls and a patchy finish on your aggregate. All surfaces around the site should be kept wet when washing off to avoid any slurry sticking to them. During this process an area should be designated to catch the wet waste. This will normally mean digging a large hole to act as a reservoir or allowing it to run off into future garden beds. It can’t be allowed to run onto the road or into a neighbouring site. Where there is nowhere for the wet waste to go a wet vacuum and slurry bin will be used.

Sealers
When sealing exposed aggregate a solvent based sealer should be used. You have a choice of a matt or gloss finish though we recommend a gloss as it highlights the colour of the stones better. We use and recommend Crommelins Enhance Gloss.