|Concrete Basics – A concrete batching plant for ready-mix concrete trucks>|
When you ring up the concrete supply company they will want know a few things, apart from the obvious where you live and when you want it.
- How much you require in cubic metres. This is in increments of 0.2cuM. So on a small job you may order 0.8cuM or a larger job 3.4cuM.
- What the concrete is to be used for. Footpath, house slab, footings etc. A footpath will probably use what we call a paving mix, with a maximum aggregate size of 10mm where a driveway will be thicker and 20mm will more likely be used.
- The strength of the concrete. On say a house slab, you will have on your drawing or in the specifications somewhere “Concrete class N25”. The different classes denote the strength of the concrete, so N25 will be normal class, that has a normal workability and has a compressive strength of 25MPa or around 3600 pounds per sq inch after 28 days. (It’s not 25MPa when your pour it, but it will be after the normal testing period of 28 days) Concrete gets stronger as it gets older.
- Placement method. The concrete batcher will want to know how you will be getting the concrete to the job.
|Concrete Basics – The mix for pumping is generally more liquid and contains a greater percentage of fines and cement slurry, to allow it to be pumped.|
- Concrete that is pumped will be designed for pumping, the batcher will then want to know the pumping company and the two will liaise with each other. Usually the pumper will radio the batcher so that the transit mixer will arrive just when the pump is set up.
- Placing straight out of the mixers shoots. Easy and quick if you can get the truck close to the job
- Wheelbarrow, not so easy and definitely not so quick. If it is a few cubic metres and is going to be slow the batcher may give you more retarder in the mix to give you more time to work it.
- On a large pour with more than one truck he may want to know the interval to send the trucks. Back to back or half hour intervals.
Another consideration with transit mixer trucks is the size. Quite often it is possible to get a small Mini-Mix type truck capacity 1.6 cuM around the back of a house, when a larger truck would mean a tough wheelbarrow job or a pump hire.