Monday, 27 May 2013

Fun with concrete pavers and planter pots

Lately I've been experimenting with concrete and cement to create my own garden pavers and plant pots. Concrete and cement are fairly cheap products so if you screw up your paver its not like its a lot of money thrown away.

I've noticed that many people don't seem to know the difference between concrete and cement - many people think concrete is just dried cement. According to Wikipedia, concrete is made up of aggregate (such as small stones) and cement as a binder. So what is cement made from? Portland is the most common and is made by heating limestone (a source of calcium) with clay and grinding this product with a source of sulfate (source: Wikipedia). I always thought Portland cement was named after the US city, but apparently no, it is named after the English Isle of Portland.

If you are making plant pots/ planter boxes, its important to remember that the lime in the cement can damage your plants. To solve this problem, you'll need to either leave your finished pot out in the rain for a month to wash the lime away (or hose it down regularly over a month), or you could seal or paint the inside to protect the plant.

Rockery planter
I'm planning to build a rock garden and fill it with dry tolerant plants that can handle our sandy region (we're only a few days away from winter now, hence why our grass is actually green in the background). My rock garden will be made from a mixture of real rocks, cement planters and driftwood from the local beach.

For my first cement creation I mixed Portland cement with vermiculite (a light weight gardening additive) and water in a bucket with a garden trowel. The vermiculite gives it texture and makes the finished product lighter to work with. I cut some chicken wire and moulded it into a low cylinder shape and squashed down the front so that flowers could spill over that area.

The mixture should feel like cookie dough (not sloppy but not crumbling and dry). I squashed it flat in my palms (with rubber gloves on) and pressed it against the chicken wire frame, both inside and out, but leaving a hole at the bottom for drainage. This is what it looked like after 12 hours curing in the shade:
After drying completely.
I bought a parahebe (a native NZ plant that is commonly used in rockeries) and planted it in my cement creation. The green grass makes it difficult to see the plant, but it will stand out well once I surround it in rocks and succulents.

Stepping stones
To create some country garden style round stepping stones, I've used my laundry flexi-tubs as moulds. I've used concrete for these, partly because concrete is cheaper to buy (since the cement is mixed up with stones) and partly because the small stones add strength which is important for pavers since they take a lot of weight. Don't use quick-set concrete for pavers - buy the regular ready-mix concrete or it will dry before you get a chance to wrestle the mixture into the flexi-tubs.

Mix the concrete and water (according the instructions on the packet) in a bucket. You'll need enough mixture so that the pavers are about 4cm thick (about 1.5 inches). Make them a little thicker for high usage areas such as around a front door (mine were only used around the chicken coup to protect my boots from mud).
It is quite easy to remove the dried pavers from these flexi-tubs but to protect the tub you should spray the inside with either cooking oil or spray a mix of dish liquid and water inside. Tip the concrete mixture into your tub:
Grab the sides of the tub and give it a really good shake until the air bubbles rise to the top:
I left the two tubs in the shade of the garage for 24 hours (don't leave them in the sun to cure). If the weather is hot, cover them with plastic while they cure. 

This is what they looked like when I carefully tipped them out the next day. They dry to a lighter colour with time. Ideally you should apply concrete sealer to protect them from moss and other slippery plants that might grow on them with time. Avoid walking on them for about a week to give them time to harden.

Animal drinking trough
I made this trough to place under a shady tree so that the chickens could have a place to drink when they are out scratching in the garden (and the dog will probably drink from it too). I've filled it with water to wash out the lime taste, but apparently it won't harm the hens like it harms plants. Sealing the inside would protect it from slime growing at the bottom, but I don't really want to risk having chemicals in their drinking water.

I mixed vermiculite into my concrete mixture again (to add some texture and make it lighter), but its hardly even noticeable except around the rim.
The bottom and sides should be about 4cm thick (1.5 inches) for strength. I sprayed dilluted dish liquid into the flexi-tub and on the bottom and sides of the plastic bucket that I used to mix the concrete in. I poured all of the concrete mixture into the tub and then filled the bucket with water (to weigh it down and wash out the concrete mix). I then pushed the bucket into the concrete mix until it was 4cm from the bottom.
Try to get it as centred as possible to ensure that all sides are equal in thickness. Leave for at least 24 hours in the shade.
Using bought paver moulds
Our kitchen looks onto a herb garden that I'm currently building. I wanted to use "nice" pavers rather that just laundry tub pavers, so I bought these two moulds off an auction website. If you want to buy some just search "concrete mould" or "mold" in the US, also known as "forms". Many companies sell these online.
I've chosen a cobblestone look and a picture of NZ (note that pictures will be backwards). The instructions say to use cement only, rather than concrete, otherwise the picture will have air bubbles and flaws on it. I've chosen to pour cement in halfway up and then pour concrete to the top. That way the paver will be stronger (due to having aggregate at the bottom).

Concrete colouring agents are cheap to buy so we bought one to create a terracotta look for the herb garden pavers. I decided to experiment by mixing it up quite roughly to get a mottled look of part stone colour and part terracotta:

I made a couple more without the coloured powder:
Here are all the pavers ready to be placed around the garden:

1 comment:

  1. That is very cool, thanks for sharing this! I actually just recommended to a friend that he get a similar project like this done. I then told him to contact EP Henry at Roxbury because they did my project and I knew that they would do a good job for his.