We recently completed a patio/pool surround and house surrounds at Elanora. The customer chose to use an exposed aggregate mix, specifically Sodalite from Nucon.
Exposed aggregate – “Sodalite” from Nucon Southport
Sodalite is a white coloured concrete mix with primarily light brown stones. The stone in this mix was smooth and flat. Sodalite has a base cost of $550 + GST per cubic metre (material only). It was only available from the Nucon Southport plant.
In our photos here the concrete looks almost like a pale brown colour. When wet, the mix colour does look almost like a latte or coffee colour. The brown from the stone really contributes to this when wet and most likely will appear this way if a wet look sealer is applied.
When dry, the mix really lightens up and appears closer to a white colour. It can be rather glary on the eyes when in full sun. The customer on this job is going to install a fly over roof above their patio area.
Concreter’s Perspective
From the concreter’s perspective, Sodalite was a fast moving mix. In moderately hot November temperatures (high 20s, low 30s C) the mix was hard and ready to wash within 2 to 3 hours of the truck arriving on site.
The mix is rather “chalky” and doesn’t seem to rapidly bond to materials as much as regular concrete does, so washing tools and surfaces was easier with this mix compared to usual.
The white colouring does create a lot of staining if you wash off into a drain or guttered area and damming the drainage is absolutely necessary.
We barrowed this mix in as the job access was limited and pumping exposed aggregate mix is a risky endeavor, especially when it costs this much. The job was split into two pours to increase access to the work areas, provide wash areas for the 2 house surround areas, to remove the need for a concrete pump and the use of a “pump mix” and to make the pours more manageable overall.
This post will discuss area and how it applies to concreting. It will also explain how to calculate the area of different shapes which can be applied practically when working.
Area and Concreting
Almost everything in concreting is to do with area. We construct, or lay, “areas of concrete”. A concrete slab is an area where concrete is laid.
Many of the materials we use to construct concrete areas will be calculated or thought about in terms of area.
Understanding how to find the area of different shapes will make it faster, easier and more accurate to price, start and finish a concreting job.
Important
When we work out the area of a shape, we usually will talk about the area size in square metres.
square metres is written as: m2, m2 or sqm
Square
A true square’s area can be found by raising the value of square’s side Length by the power of 2.
Length^2
Rectangle
A rectangle’s area can be found by multiplying the rectangle’s Length by its Width.
Length * Width
Triangle
A triangle’s area can be found by multiplying the Base by the Perpendicular Height and then multiplying by 0.5
Math Tip
Multiplying by 0.5 halves a value.
Base * P. Height * 0.5
Circle
The radius of a circle is the distance from the center to the edge of the circle. It is half the value of the circle’s diameter.
A circle’s area can be found by multiplying Pi (3.14) by the circle’s Radius raised by the power of 2.
3.14 * Radius^2 or 3.14 * Radius * Radius
Trapezoid
A trapezoid is a square or a rectangle with 1 or 2 angled sides.
By understanding and using the trapezoid’s area formula it saves you calculating the triangles separately.
(Length + Width) * P. Height * 0.5
Examples
Waffle Pod – Square
A waffle pod is 110cm on both its length and width. The area that a waffle pod takes up can be found using the Area of a Square Formula.
Remember
If we square a number, it means we multiply it by itself.
This is also called raising by the power of 2 or to the power of 2.
When we write this operation, it looks like: ^2
We can raise to the power of different numbers as well. So to the power of is indicated by the ^ character.
On a calculator you will see a button that says xy.
This button is the to the power of button.
The “to the power of” button on Windows Calculator.
Length^2
Length = 110cm
Length^2
=110^2
= 12100cm2
Now change the Length into metres instead of centimetres...
Length = 1.1m
Length^2
= 1.1^2
= 1.21m2
The area of a 110cm waffle pod in square metres is 1.21m2
Viscrine (Black Plastic) – Rectangle
A roll of viscrine is 50m long. It folds out to be 4m wide. Let’s use the Area of a Rectangle Formula to find how much area a whole roll can cover:
The total area a full roll of viscrine will cover is 200m2
Mesh – Triangle
We are making someone’s driveway wider.
The shape will be a triangle and the mesh needs to be cut to suit the shape. The mesh size needs to be a triangle with one side 2.2m and the other side is 4.8m. Work out the area that the mesh piece will be:
Base * P. Height * 0.5
The Base will be the Length. The Perpendicular Height (P. Height) will be the Width. Therefore:
Base = Length, P. Height = Width
Length = 4.8m, Width = 2.2m
Base * P. Height * 0.5
= 4.8 * 2.2 * 0.5
= 5.28m2
The triangular piece of mesh will have an area of 5.28m2.
Exercises
1.
Your uncle wants to have a patio laid at his house. The area he wants to make the patio is a square shape with sides that are 6m.
What is the area of the proposed patio?
2.
Find the area of the shape shown above. Hint: you can use rectangle & triangle formulas, or use the trapezoid formula.
3.
The plan above shows a round-about. The inner circle has a 5m radius and the outer circle has a 15m radius. If we are going to concrete the roundabout (like a donut!) How many square metres will it be?
