Concrete vs Cement

Cement

What it is: A powder that binds the other materials. Mixed with water it reacts and hardens, gluing sand and stone into a rock-like mass. On its own it is an ingredient, not a finished product.

Use it for: Mixing your own concrete (with sand and aggregate), mortar (with sand) and render (with sand).

Which bags: General Purpose Cement, Builders Cement, Low Carbon Cement, Off White Cement and White Cement.

Concrete

What it is: Cement, water, sand and gravel or crushed stone. The sand and stone (the aggregate) make up most of it, up to about 80% of the volume; cement is only 10 to 15%. It starts soft enough to shape and sets hard enough to carry load.

Use it for: Footings, slabs, paths, posts and anything that has to carry weight.

Which bags: Rapid Set Concrete, PROSTRENGTH Rapid Set Concrete, Concrete Mix and PROSTRENGTH Extra Strength Concrete.

Concrete mix (bagged)

What it is: Cement, sand and aggregate already measured into the bag. You only add water and mix it in a barrow or mixer.

Use it for: Small jobs under about 0.1m3: posts, small footings, pads, mower strips and garden edges. Paths, driveways and slabs are usually a ready-mix truck job.

Which bags: Concrete Mix and PROSTRENGTH Extra Strength Concrete.

Rapid set concrete

What it is: Concrete with an added setting agent. Pour the water into the post hole, then the dry bag, and it starts to harden within 15 minutes. Never mix it in a barrow or bucket: it sets in the container.

Use it for: Fence posts, non-load-bearing pergola posts, clothes hoists and letterboxes. Not for structural work: for gates, load-bearing and sign posts, use PROSTRENGTH Rapid Set.

Which bags: Rapid Set Concrete and PROSTRENGTH Rapid Set Concrete.

Mortar

What it is: Cement and sand with no stone, mixed with water, often with hydrated lime added so it is easier to work and bonds better. It is the layer that holds bricks and blocks together, and a bed under fixtures and pavers.

Use it for: Laying bricks, blocks and stonework; bedding shower bases, toilet pans, pavers and garden edges; patching brickwork and render.

Which bags: Trade Mortar and Sand & Cement.

Render

What it is: A cement and sand mix spread over a wall as a finish, in coats of about 2 to 10mm. It works inside and out.

Use it for: Brick and block walls, blueboard and fibre cement sheet, feature walls and letterboxes. Colour it with an oxide, or use White or Off White cement for a light finish.

Which bags: General Purpose Cement and Low Carbon Cement.

Hydrated lime

What it is: Burnt limestone (quicklime) with water added, which makes it less caustic, though still strongly alkaline. An additive for cement and sand mixes.

Use it for: Mixing into sand and cement mortar and render to make it easier to work, hold its water and bond better. Also used in gardening and landscaping.

Which bag: Hydrated Lime.

Clay (fireclay)

What it is: Finely milled clay powder. Cement Australia also calls it fireclay.

Use it for: Making mortar and render easier to work when your sand is low in clay, as a filler, and for its refractory (heat-resisting) properties. It does not replace lime.

Which bag: Clay.

Gap sand

What it is: Fine sand with an added polymer. Swept into paver joints and misted, it binds the sand and helps keep weeds and insects out. It dries firm, not hard, so it is not a grout.

Use it for: Brick and block paver joints up to 3mm, including driveways and sloping sites. Not within 1m of a pool.

Which bag: Gap Sand.

Dried sand

What it is: Washed, factory dried sand with no additives, clean enough for bricklaying (it meets AS3700).

Use it for: Filling paver joints up to 3mm, and as the sand in your own mortar, render, concrete and grout mixes.

Which bag: Dried Sand.

Not sure which bag your job needs? Contact us with the job and its size, and we will match the product.

Bags suit small jobs. Cement Australia sizes it by how much concrete the job takes:

Under about 0.1m3: use bags of Concrete Mix.

From 0.1 to 0.5m3: mix your own with Builders Cement, sand and aggregate.

Over 0.5m3: ready-mixed concrete by truck, where access allows.

Paths, driveways and slabs are usually a ready-mix truck job.

In SA, bagged concrete is often called premix. Ready-mix usually means concrete delivered by truck.

For a sense of scale, the Concrete Mix page draws the small pad two bags make, the size that sits under a tap, a bin or an air-conditioner unit. Mixing your own? The proportions are in the mix ratio table. Setting posts? See bags per post hole.

Every bag in this guide is on our concrete and cement page, where you can compare the four bagged concretes and see which concrete suits which job. Order by the bag through Allmat, then click and collect from the Allmat yard or have it delivered to site with the rest of your order.

The product information on this page comes from Cement Australia's published product data sheets, safety data sheets and website (see each product's Documents section). It is general guidance only. Other manufacturers may give different advice for their own products, so always follow the instructions on the bag and the product's data sheet. Structural work, such as footings for buildings, must follow your engineer's design and the relevant Australian Standards.