FAQs

Cement is the binding agent in concrete, normally the most active component, and usually the most costly. Its selection and proper use are important in obtaining the balance of properties required for a particular concrete mixture and in minimising the cost of that mixture. An understanding of the properties of the available cements and their influence on the properties of the concrete is important for the proper selection and use of these materials. Such understanding requires some familiarity with the chemical and physical characteristics of the cement and of their influence on cement performance.

Although the terms cement and concrete are often used interchangeably, cement is actually an ingredient of concrete.  Concrete is basically a mixture of aggregates and paste.  The aggregates are sand and gravel or crushed stone; the paste is water and Portland cement.  Portland cement is not a brand name, but the generic term for the type of cement used in virtually all concrete.  Cement comprises from 10 to 15 percent of the concrete mix, by volume.  Through a process called hydration, the cement and a portion of water react and harden, binding the materials into a rocklike mass.

General Purpose (Portland) GP For general use in all types of building and construction

General Purpose Blended (GB) For general use in all types of building and construction.  Early rates of strength gain may be lower than those of Type GP, and curing may be more critical for full strength development.

High Early Strength (HE) Where early strength is a critical requirement (eg for the early stripping of formwork), in very cold weather, in repairs to concrete structures.

Low Heat (LH) Where rise in concrete temperature must be limited to avoid thermal stress (eg in mass concrete construction or in very hot weather).  Where moderate resistance to some forms of chemical attack is required.

Shrinkage Limited (SL) Where limiting the drying shrinkage of concrete is necessary for crack control, in road pavements and bridge structures.

Sulfate Resistant (SR) Where high resistance to sulfates is required, eg in sulfate-bearing soils and groundwaters.

White and Off-White In the production of architectural concrete and concrete products.  Normally complies with requirements of AS 3972 for Type GP, GB or HE cement.

Coloured In the production of concrete products, concrete paving and similar applications.

Masonry Mortar in brick, block and stone masonry construction.  Unsuitable for use in structural concrete.

Oil-well Grouting gas, oil and other deep bore holes and wells.  Normally complies with the relevant specification of the American Petroleum Institute.

High Alumina Cement (HAC) Where high early strength and/or resistance to very high temperatures are required (eg refractory concrete and factory floors).

(Sourced from Standards Australia Guide to Concrete Construction)

Aggregates form up to 80% of the volume of concrete and are therefore an important constituent.  At one time they were considered to be inert fillers but we now know that their properties can significantly affect the performance of the concrete in both its plastic and hardened state.  Some types of aggregates used are sands, gravels and rocks (crushed or uncrushed) and there are also manufactured aggregates available.

The glue gains the properties from a chemical reaction that occurs between the cement and the water.  This chemical reaction is called Hydration.  It requires a favourable temperature and the presence of water to proceed.

Concrete is described in two different states – Plastic & Hardened State.  After mixing, the concrete is in a plastic state, which enables it to be moulded into various shapes.  In this state it cannot carry any load.  As the concrete sets, it moves to the hardened state.

This is the ratio of the total water in the concrete to the cement content.  With concrete that has Fly ash or Slag in it, the cement component is the cementitious component that includes the cement plus those ingredients.  The amount of water used in the calculation includes water from all sources and not merely the water added during batching. Aggregate and fine aggregate in particular can contain a significant quantity of water.  The w/c ratio is calculated from the weights of the materials, eg Concrete with 300kg of cement and 180 litres of water has a w/c ratio of 0.6 (i.e. 180÷300 = 0.6).

The term 'cement' is used to describe a range of binding materials, the most common of which are known as hydraulic cements. These have the ability to react with water and harden, to produce a strong, durable product.

The first civilisations to use this type of cement on a large scale were the Babylonians and Ancient Egyptians. They mixed lime, clay and water, or lime, gypsum and water to make concrete and mortar. This was used for structures including the Great Pyramid built some 4500 years ago.

The Romans provided the first major advance on this technology. They found that when lime was mixed with a type of volcanic sand found in the neighbourhood of Mount Vesuvius, at a place called Pozzuoli near Naples, and mixed with water, a strong cement was produced.  This was combined with pumice and other aggregates to produce the concrete for aquaducts, harbours and buildings including the Colosseum in Rome (80AD).

In Australia, Portland cement was first produced in 1882 at Brighton, in South Australia.

Clinker production involves the quarrying or dredging of raw materials which are then crushed and ground to a smaller size and once blended in the correct proportions are burned at high temperature in a kiln.  The resulting material is cooled in a controlled manner and is called clinker.

The clinker is ground to a fine powder with gypsum being added.  This fine powder is the cement that is used in concrete.

There are three types of Supplementary Cementitious Materials used in Australia – Fly Ash, Ground Granulated Blast Furnace Slag (GGBFS) and Amorphous Silica (Silica Fume). SCM's are by-products from other industries that can partially substitute for cement in concrete, and help to improve the performance of the concrete.

Supplementary cementitious materials have been used in building construction for many years.  The original term used to describe these materials was pozzolan.  Pozzolans are rich in silica and/or alumina and these oxides combine with lime in the presence of water to form compounds that are virtually identical to the compounds in hydrated Portland cement.

The particulates (dust) separated from the flue gases from black coal burning power stations is called fly ash. 

The fly ash is generally captured by electrostatic precipitators or other particle filtration systems eg: fabric filters

The waste material removed in the operation of blast furnaces in the smelting of iron ore.

Naturally occurring deposits or Silica Fume which is very fine particulate matter collected in the refining of silicon metal.

SCM’s are wastes or by-products from other industries and are available at lower cost than Portland cement.  The materials are waste products and it is difficult to find practical, economic and environmentally sensitive ways to dispose of them.  It is of great benefit to the environment to utilise such waste materials.  SCM’s generally have a positive influence on both the plastic and hardened concrete properties.

Lime is commonly derived from limestone through calcination (burning at high temperature) the limestone converts into a highly caustic material called Quicklime. Through the addition of water, slaking, that  material becomes less caustic, but still alkaline and is called hydrated lime.

Limestone is a general term embracing carbonate rocks or fossils; it is composed primarily of calcium carbonate or combinations of calcium and magnesium carbonate with varying amounts of impurities, the most common of which are silica and alumina.  Cement Australia operates limestone mines near the  Gladstone (Qld) and Railton (Tas) cement manufacturing facilities.

MPa is the metric unit for pressure or stress called megapascal (MPa). The term is used in concrete as the common unit for compressive strength. If you have a project which requires a defined strength of concrete - i.e. 20MPa to set the posts for a raised deck - then its time to call in the experts and have concrete delivered from a ready mixed truck – it’s the only way to guarantee the structural strength in the concrete.

You may also see concrete requirements expressed as 'N20/10' - this is where N means normal class concrete, 20 refers to 20MPa of strength and 10 refers to it containing a maximum aggregate size of 10mm.

General Purpose Cement (or GP Cement) is straight cement. GP cement is manufactured from Portland cement clinker, gypsum and limestone.  GP cement is used in all types of building and construction. Our General Purpose Cement exceeds the requirements specified in Australian Standard AS3972 for Type GP cement.

Builders Cement (or General Purpose Blended (GB) cement) contains both GP cement and a nominal mass of fly ash. Concrete made with Builders Cement delivers improved workability, later-age strength, enhances the durability performance of concrete and provides a lower carbon footprint. Early rates of strength gain may be lower than GP cement and curing may be more critical for full strength development. Builders Cement is used in all types of building and construction. Builders Cement is a uniform blend of Portland cement and Fly Ash that exceeds the requirements specified in Australian Standard AS 3972 for Type GB cement.

When you need a light or pastel coloured finish for your cement-based job, use Off White or White Cement as your base product and select the palest sand you can find.

The bulk density is the mass of the material related to a specific volume and for cement is normally expressed as “kilograms per cubic metre”. The bulk density reflects the volume taken up by the cement plus any air trapped between the particles. The relative density or specific gravity is the weight of the material particles themselves and for cement, this density is typically 3.11. When used in concrete, the space around the cement particles is taken up by water so there is no air around the particles and the bulk density is not important. The weight of the particles and their volume is important so the relative density value is used in concrete mix calculations. The bulk density of bagged GP cement is approximately 1000-1300kg/m3 and Builders cement is approximately 1000-1250kg/m3.

As we source our raw materials locally the  aggregate and sand sizing will vary across different regions of Australia. 

Approximate size is -

Aggregates: 7mm-14mm
Sand:          <5mm

If you are chasing specific information by product, please feel free to contact us.

Approximately 110 x 20kg Concrete Mix bags are required.

A bag of 20kg Mortar Mix will lay 20 house bricks or 10 masonry blocks with a 10mm mortar joint if mixed correctly.  Always read and follow the instructions on the back of the bag.

It is important to follow the coating manufacturers’ directions for curing or drying times before painting. 

The surface can generally be painted with water based paints after 14 days.  For oil based paints being applied to a masonry surface, it is necessary to cure the surface for 5 days and then wait for 28 days before applying the paint.

Yes. Before any cement based coating or render can be applied correct surface preparation of the substrate is essential. Any paint and residue from other coatings will prevent an effective bond and it is recommended that they be removed.

The ambient temperature can affect the setting times of all types of concrete. If the temperature is less than 10^oC, wait until the day becomes warmer and if its over 35^oC then postpone the job until it is cooler.

“Pointing”, raking or finishing  mortar joints should occur only once the mortar has become firm to touch.

It is important to moisten the surface and edges of the concrete for up to 7 days. This provides a continuous supply of moisture to enable the hydration process to continue to enhance strength development and surface hardness. Curing will ensure that a hardened, abrasion resistant surface is developed and the risk of surface dusting is reduced.

Protection should start as soon as the final surface finish is produced and not the next day. 

This can also be achieved by covering the slab with black plastic. Care should be taken to ensure that covering the slab does not mark the freshly poured concrete. Protection of coloured concrete slabs must be considered. If polythene sheets are in direct contact with the concrete variable colour of the surface due to hydration staining may occur and this is not possible to correct at a later stage. 

Alternatively, mist spray the slab at least twice daily for up to 7 days as it is important that the slab does not dry out before the cement has fully hydrated.

The ready to use Sand & Cement product from our "Just add water" range should be used for gaps greater than 3mm.  You can either sweep it in dry and then use a hose to mist the product or mix it wet and use a trowel to fill the joints.

Watch this video clip to see the right consistency for concrete.

Watch this video to see how to mix it and the right consistency you need for best results.

Watch this video to see how to use Rapid Set Concrete when setting a post.

This depends on the specific product:

• Concrete products refer to the directions on the bag for the clean water ratio
• Mortar and Sand & Cement add 3.5 litres of clean water per bag
• Rapid Set Sand & Cement add 3 litres of water per bag
• Render It™ and Roof Tile Bedding Mortar add 4 litres of water per bag

Remember - too much water ruins good concrete, mortar and render!

One bag of Render It™ covers 2.5m² at 5mm thickness.

Ensure that you mix the Render It™ with exactly 4 litres of clean water to achieve a workable mix.  Only mix as much render as you can apply within 30 minutes. Discard any render not applied within 30 minutes and mix a fresh batch.

One bag produces enough mortar to lay 3 linear metres of ridge or hip tiles.

Plasticiser was developed to make mortar more workable or more “plastic”.  Plasticisers that are based on a water reducing admixture action may improve strength, whereas excessive use of plasticisers that entrain air will reduce strength and bond.

TIP – A simple way to tell the difference between a plasticiser and a water reducing admixture is to shake the container. If the liquid produces a froth that does not quickly dissipate, then it is an air entraining product.

Cement is a dry product and is free flowing whereas damp sand tends to clump together. Cement tends to lie flat on the shovel and has less volume than the sand. Using a shovel does not ensure that materials are measured equally and it is recommended that proportions of raw materials are measured with a container such as a bucket.

Always use an accurate measure to add your water too as the most common mistake made when mixing concrete, render or mortar is to add to much water.

Too much water ruins the strength of concrete, mortar and render.

Hardened concrete, mortar and plaster can be damaged at high temperatures. It is recommended that a product called Cement Fondue (aka Ciment Fondu) is used.  This product is a High Alumina Cement and is available from specialty cement suppliers. 

Cement Australian strongly recommends that unless you are experienced in using specialty cement products you should seek technical advice before using these products.

If you’re looking to mix your own concrete at home, add Cement Australia Builders Cement to your sand and aggregate for a more creamy, easy to work concrete that will give a really smooth surface finish.

Gap Sand has an added polymer which assists to bind the sand together to inhibit weed growth and insect infestation. Dried Sand is a sand that contains no additives that can be used as an infill between pavers.  Both products are used to lock pavers into place.

*Dried sand particle size will vary .

One 20kg bag covers approximately:

• 3.5 square metres for brick shaped pavers spaced at 3mm.
• 12 square metres for 400mm x 400mm x 50mm square pavers spaced at 3mm.

These products are not recommended for use in paving when the gaps are wider than 3mm.  Cement Australia’s Sand & Cement is recommended for these applications.

Use our handy Calculator to work out how much sand you will need for your paving project.

Due to the splashing of water in a pool area it is not advisable to use Gap Sand to lock pavers into place within 1 metre of the pool edge. It is better to use Sand & Cement to fill the gaps between these pavers.

Ensure that the pavers are dry and sweep the Sand & Cement into the joints and tamp it down into the joints.

Remove any excess sand with a dry brush and then wet the paved area with a light mist spray. Ensure that pools of water do not form on the surface or the Sand & Cement will be dislodged from the gaps and your pavers will not be held firmly in position.

For concrete made for paths & driveways, mix 1 part Cement Australia Builders Cement with 2 parts sand and 3 parts aggregate.  Approximately 16 x 20kg bags of Builders Cement are required per cubic metre of finished concrete.

Rapid Set Concrete contains cement, sand and aggregate and an additive which causes an initial hardening to happen within 15 minutes of water being added.

In warm temperatures, this hardening is accelerated and can be as fast as 5 minutes!

Never mix Rapid Set Concrete in a vessel like a bucket or a wheelbarrow as it will set hard and ruin it before you can remove the product.  Rapid Set Concrete is designed to be added to clean water in the hole that you wish to fill with concrete.

For concrete made for foundations or footings, mix 1 part Cement Australia Builders Cement with 3 parts sand and 3 parts aggregate.  Approximately 13 x 20kg bags of Builders Cement are required per cubic metre of finished concrete.

This process is referred to as the placing and finishing of the concrete and there are four steps:

1. Screeding  - which is the initial levelling of the placed concrete using a straight length of wood, aluminium straight edge or a portable power screed for larger jobs.
2. Bleed water accumulation  - where the concrete is left for 1 to 2 hours after screeding to allow bleed water to accumulate on the surface and then to evaporate.
3. Final floating  - occurs when the bleed water has evaporated and the top surface is firm to touch and is completed with a wooden or magnesium float.
4. Final trowelling  - occurs when the concrete surface becomes firm and is often carried out in several passes at intervals of 30 minutes where the concrete receives its final surface finish.

One way to tell if you have used too much water in your Cement Australia Mortar Mix is that the mortar squeezes out from between the brick or block joint as soon as you place a brick or block on the bed of mortar.

Always use a batch of wet Cement Australia Mortar Mix within 1 hour of mixing.

Do not try to re-temper old mortar by adding more water as this will reduce the strength of the mortar.  Dispose of any spilt mortar thoughtfully.

Cement Australia has worked with roofing professionals to develop a mortar mix specifically designed for bedding ridges, barges, and apexes. Roof Tile Bedding Mortar is a ready to use, consistent product which performs equally well in warm and hot temperatures.

One bag, when mixed correctly with 4 litres of water, beds 3 linear metres of ridge or hip tiles.

Yes, simply add 4 litres of clean water and slowly add the Render It™ product mixing it thoroughly with a spade or shovel.

If multiple batches of render are required to complete your job, it is worthwhile considering using a heavy duty drill and stirring attachment to make mixing easier and more consistent across batches.

Yes, add one small jar of oxide per bag of Render It™. Be sure to accurately measure both the oxide and the water to reduce colour variation between batches.

Tip: Ensure your ratio percentage is based on the cement content only, as oxide will not colour sand or stone.

The Cement Australia range of oxides contains contemporary colours. 

Cement Australia Render It™ Multisurface gives you all the convenience of a premixed product manufactured to trade standard with additives that allow you to apply this product in a one part system ranging in thicknesses from 2mm to 10mm in a single application.

Always plan to complete your rendering project in the early morning before the surface to be rendered is in full sun.

Where render has been applied to a masonry surface, to prevent cracking it is vital keep the rendered surface moist for a period of time. Spray the surface with a hose on mist spray 24 hours after the wall is finished and repeat this for 5 days in the early morning and evening.

It is not advised to cure render that has been applied to blueboard or fibre cement sheeting.
 

It is recommended that for a light colour shade 2% of oxide is added for the weight of cement in the mix, 4% for a medium colour and 6% for a dark colour. For example, 63 grams of oxide would be added to a 20kg bag of Mortar to achieve a light colour shade.  It is important to note that no more than 10% oxide loading should be added to the cement content as the pigment reaches saturation. 

It is recommended that a test panel be prepared before completing the actual job. Allow the test panel to dry for a week to assess the final colour as fresh concrete always dries to a lighter colour after it has been laid.

For convenience, add one small pot of oxide per 20kg bag of Cement Australia Render It™ product.  

Check out the current oxide colour range.

Colour variation can be caused by changes in the amount of water added to the mix, cement type and colour, change in aggregate colour or sizing, curing temperature, incorporation of admixtures, finishing of the concrete surface and inaccurate weighing of raw materials including the oxide. It is recommended that the same source of raw materials is used for the entire project.

When using Cement Australia oxides to colour your own mix, premix the oxide with the sand or aggregates for 15 seconds before adding the cement. After adding the cement thoroughly mix again for at least 20 seconds before adding the water.

We have a broad range of bagged products which are primarily packaged in 20kg bags with some variations.  Our bagged product is available from hardware and landscape suppliers and for larger orders, we will arrange delivery.  

Bulk cement is delivered to your site in pneumatic tankers and you will require a silo for storage of the product.

Our pneumatic tankers cover the entire country, employing various configurations including singles, B-doubles and even triple road trains that can carry up to 70 tonnes per load. We are also able to offer re-locatable 120 m3 capacity road super-tankers that satisfy local-site storage demands for large projects.

To meet the highest level of service that our customers demand, our modern fleet of prime movers and tankers are despatched 24hrs per day to locations as far south as Hobart and to the remotest parts of North Queensland and the Northern Territory.

As part of our commitment to the highest standards of operational safety, Cement Australia operates a rigorous fleet replacement programme, has NHVAS mass and maintenance accreditation and employs a comprehensive driver selection, induction and training programme.

Cement Australia also utilises “ISO” intermodal containers for road/rail distribution of product. This form of transport is a vital part of our long distance haulage strategy and allows "direct to door" deliveries to customers through the transfer of the “ISO” intermodals from rail to road. “ISO” containers are in operation, linking depots, terminals and customers. Our rail freight service is further complemented by our investment in large numbers of conventional rail tankers.

In conjunction with various rail service providers, Cement Australia also utilises an extensive range of dedicated rolling stock for the delivery of cement, fly ash, coal, limestone and other raw materials at our various terminal and cement manufacturing facilities.

For more information, please contact Customer Interface Team on 1300 236 368.

SDS can be found here.

Always wear the correct protective clothing when handling any product containing cement as it is an alkaline substance in a fine powder form:

• Gloves - to guard against skin irritation
• Face mask - to prevent dust inhalation
• Eye protection - to prevent dust from getting into eyes
• Long pants and sleeves - to guard against skin irritation
• Safety boots - to prevent injuries to your feet when handling heavy items or using potentially hazardous tools

Always separately wash clothes that may be splashed with cement-based products at the end of each day.

A 20kg bag of cement based product requires 2 people to lift it safely.

Manual handling of bagged products without due care and attention could result in personal injury. Prior to handling it is recommended that appropriate consideration be given to the task. Where possible, all manual handling of bagged products should utilise load-shifting equipment, such as a wheelbarrow or trolley, or at a minimum be undertaken as a 2 person team lift. 

When loading a wheelbarrow, always place the bulk of the load over the wheel to lessen the effort required and reduce the strain on your back.

When lifting bagged products, both you and your team lift partner should protect your back – especially lifting bags in and out of your vehicle. Keep your lower back straight and use your leg muscles to lift, keeping your head up and do not pivot on your spine. When lowering the product, use your leg muscles and don’t bend your back.

If product gets into the eyes, irrigate the eyes with plenty of water for 15 minutes and seek medical attention. 

If any products are inhaled, vacate the dusty area immediately and seek medical attention if symptoms persist.

If product comes into contact with skin, wash thoroughly with clean water.

Please refer to the Safety Data Sheet (SDS) for each product prior to use.

Cements may cause respiratory, skin and eye irritation. Wet cement can be irritating and corrosive to the eyes and skin and may cause skin sensitisation (dermatitis). Repeated inhalation of the dust containing crystalline silica may cause bronchitis, silicosis (scarring of the lung) and lung cancer, and the risk of scleroderma.

Always protect yourself with the correct Personal Protective Equipment (PPE).

The recommended shelf life of cementitious products such as Grey Cement and Lime is approximately 6 months from the date of manufacture. It is recommended that Off White Cement is used within 3 months of manufacture. These timeframes are based on the understanding that the product has been stored unopened and off the ground away from moisture.  Cementitious products are recommended to be stored indoors out of the weather and with the pallet wrap always maintained around the product. It is essential to ensure that stock of this product type is rotated with the oldest pallet always used first.

If you have to store bagged cement products at home, make sure you keep them off the ground and fully protected from the weather.  

The recommended shelf life of Grey Cement based products is approximately 6 months from the time of purchase. It is recommended that any product made with Off White Cement is used within 3 months of purchase.

Once you’ve opened a bag of cement based product, it is recommended  to use the contents that same day and discard any remaining product.

If a cement based product appears to be hard then you need to dispose of the bag and source a fresh bag as it has likely been exposed to moisture and has reacted with the water.

In order to improve its recyclability, Cement Australia has removed the plastic inner lining within the packaging of a number of its "just add water" blended products, making these bags suitable for recycling as a paper waste.  

However, in order to maintain product integrity, cement and cement blend products still contain a plastic liner inside the packaging and these should be disposed of as general waste.

If in doubt, please check the back of the bag as packaging suitable for recycling will be clearly marked with the recycling symbol. 

For Bulk supply or Retailers please refer to our Credit page. If you require further assistance please call our Customer Interface Team on 1300 236 368 (1300 CEMENT).

For consumers of our packaged products please use the Find a stockist function on our website to locate your closest retailer.

For Retailers, please call our Customer Interface Team on 1300 236 368.

By calling our Customer Interface Team on 1300 236 368.

Contact Holcim on 131 188 or Hanson on 132 662