CONCRETE & CEMENT
DIY - Builders Mix & Cement
For the home handyman, small business person or the DIY'er, Oldfields have the products required for that concreting job.
Concrete is made from a combination of cement, water, sand and coarse aggregates.
| Cement | + | water | = | cement paste |
| Cement paste | + | sand | = | mortar |
| Coarse aggregates | + | mortar | = | concrete |
Builders mix is the most common coarse aggregate for concrete and is available from Oldfields by the trailer or truck load. Bags of Golden Bay Cement are also available.
You will find both these products at the Waingawa Weighbridge and the Te Ore Ore Yard - covering both ends of Masterton for your convenience.
If you require a special effect in your concrete, pebbles of varying sizes are available.
The basic formula for the cubic metres of concrete required is width x depth x length = m3. If you are unsure about the quantity, the operators at the Weighbridges can assist you.
Cracking in Concrete
Cracking is one of the the most common problems encountered when pouring concrete. There are a wide range of factors that can result in cracking, but there are some things that you can do to reduce the chances of it happening;
- Have the job well planned in advance
- Correct preparation of the sub-grade and slump (100mm max)
- Keep an eye on the weather forecast for extremes in temperature
- Moisten ground, use sun shades, pour early morning or evening to avoid additional heat
- Enough labour to quickly place, finish and cure the concrete
Remember, curing takes 7 days and it's not a drying process, but a series of chemical reactions between the cement and water present in the mix. Drying out can be minimised by keeping the poured surface damp, especially during hot weather. Ponding or spraying water can help reduce drying.
Possible Causes of Cracking
These are some of the possible causes of cracking in concrete that you might have laid.
| Type | Plastic | Thermal | Drying |
| Appears | Same day | Within first few days | Perhaps weeks/months later |
| Where | anywhere but short in length | along weak spots | along weak spots |
| Cause | evaporation of water was too quick | difference in concrete and outside temperatures | drying period too long |
| Prevention | slow the evaporation process down | reduce restraints to movement | correctly positioned movement joints |
Ready Mix for DIY
WHY USE READY MIX
Many a DIY'er asks themselves this question. Can there be anything better than standing over a mixer for hours, shovelling builders mix and cement; some loads a bit too wet, and some a bit dry?
Using ready mixed concrete has its advantages;
- better quality - instead of 20 barrow loads of "never-the-same" concrete, one truckload of consistently mixed concrete arrives on the job
- mixed to required grade - not sure just what proportions to mix in for that job? Ready mix can be ordered specifically for the job you have to do.
- no wastage - No more leftover piles of builders mix lying around when the jobs done. Order what you need, and the surplus goes back with the truck
- minimum mess - Hand mixing can be messy, concrete the job and not your drive or backyard with spills from the mixer and barrow
- less labour - Box up for the pour, get the truck in, finish it off, then stand back and admire your work. No more hours of back breaking shovelling to mix up individual loads
- delivery when required - get the job done when you're ready and still have time left over in the day.
Here are some examples of projects where using ready mixed concrete makes good sense;
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Slabs |
for garage and sheds slabs where the area can be large, ready mix will give you a consistent mix, and save time |
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Paths |
paths for landscaping or access can be done quickly and easily with ready mix concrete |
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Garden Sheds |
the larger the area to pour, the bigger the advantage in using ready mixed concrete |
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Fences |
for footings, nibs, of a large number of posts, ready mix can be used for constructing your fence |
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Garden Edges |
tidy up those garden edges with concrete. Usually a smaller amount of concrete is required, but get the job done faster with ready mix |
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Retaining walls |
where grade, quality and strength are important, ready mix concrete will meet you needs when building retention walls |
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Garage foundations |
pour those footings in a fraction of the time it would take hand mixing |
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Drives |
when you have a large area to cover, ready mix make sense to get that driveway poured and still have enough time in the day to finish it just the way you want |
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Pools |
not a job to be undertaken with a mixer and barrow - special sprayable concrete is most likely what is needed to build that backyard pool |
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Ponds |
if your subsoil isn't suitable for water retention, the alternative to a plastic pond liner is concrete |
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Fire Wall |
the right mix, and grade will be required to build an approved firewall |
WHAT CHOICES DO I HAVE?
- Plain concrete - a standard finish
- Ground concrete - where the surface has been ground to a smooth finish
- Scribed concrete - where a pattern has been scribed or stamped in to the finished surface
- Exposed aggregate - where aggregate is added to the finished surface, and later exposed by washing
- Coloured concrete - dyes are added or applied to colour the concrete
There are several ways of introducing colour to the concrete:
- Integral - where the colour is added to the concrete at the ready mix plant
- Dry Shake method - where the colour is applied to the surface of the freshly placed concrete and is then trowelled into the surface.
- Staining - where the colour is applied to the hardened concrete
WHAT INFORMATION DO I NEED TO HAVE WHEN I RING TO ORDER?
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You will be asked to ring again on the morning of delivery to confirm order. |
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More Information: Cement and Concrete Assn of NZ
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