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Glossary of terms

Click on the terms listed below to see their descriptions.

Accelerators

Material additives used to accelerate, or reduce, the setting time of concrete causing it to harden faster. Accelerators often include calcium chloride, or aluminum sulfate or other acidic materials.

Admixture

A material, other than aggregate, cement, or water, added in small quantities to the mix in order to produce some desired modifications, either to the physical or chemical properties of the mix or of the hardened product. The most common admixtures affect plasticity, air entrainment, and curing time. These admixtures are often referred to as plasticizers, superplasticizers, accelerators, dispersants, and water-reducing agents.

Aggregate

A mixture of sand, rock, crushed stone, expanded materials, or particles that typically compose 75% of concrete by volume improve the formation and flow of cement paste and improve the concrete's structural performance

Agitator truck

Vehicle designed to take ready-mixed concrete and deliver it ready to be used at a construction site. The truck bed contains a large barrel or drum that is used to continuously roll or agitate the concrete mixture keeping it from solidifying before use.

Block Fill

Is when concrete is to be used to fill the voids in concrete blocks. The mix is the same as a cavity fill, with a small aggregate size of 7mm and a slump of 120mm to allow the concrete to flow between the blocks.

Cavity Fill

Is when concrete is to be used to fill the void between 2 courses of bricks. This is usually required as a retaining wall or when the wall will be used to support another structure on top of it. Blockfill mixes have a small aggregate size of 7mm and a slump of 120mm to allow the concrete to flow between the brickwork.

Cement

A material composed of fine ground powders that hardens when mixed with water. Cement is only one component of concrete. The gray powder is the "glue" in concrete.

Concrete

Concrete is a hardened building material created by combining a mineral (which is usually sand, gravel, or crushed stone) a binding agent (natural or synthetic cement), chemical additives, and water. It is an excellent material to be used in road building, bridges, airports, factories, waterways and other construction projects. Concrete is the mixture of cement, sand, gravel, and water used to make garage and basement floors, sidewalks, patios, foundation walls, etc. It is commonly reinforced with steel rods (rebar) or wire screening (mesh).

Concrete finish

A description of the smoothness, texture, or hardness of a concrete surface. Floors are trowelled with steel blades to compress the surface into a dense protective coat. Paving is usually trowelled with a spin or stippled finish which provides a non slip finish.

Concrete Slab

Regularly referred to as a Slab which is a concrete slab for a new house. Usually has a deeper edge beam and beams throughout the slab which is embedded into the ground.

Concrete transporting

The process of moving the concrete mixture from the central plant, or mixing location, to the construction site. Transporting device is a agitator trucks to get to the job site. Whilst onsite the concrete can be moved via buckets, wheelbarrows, conveyors, and a concrete pumping.

Curing

Curing typically occurs through the evaporation of water or a solvent, hydration, polymerization, or chemical reactions of various types. It is the final process, after placing and compacting, that ensures the concrete will set to its desired strength. The length of time is dependent upon the type of cement, mix proportion, required strength, size and shape of the concrete section, weather and future exposure conditions. The period may be 3 weeks or longer for lean concrete mixtures used in structures such as dams or it may be only a few days for richer mixes. Favourable curing temperatures range from 20° to 30° Celius. Design strength is achieved in 28 days.

Exposed aggregate finish

A method of finishing concrete which washes the cement/sand mixture off the top layer of the aggregate. It is often used in driveways, patios and other exterior surfaces.

Fly ash

A byproduct produced by coal-burning power plants that contains aluminosilicate and small amounts of lime. When combined with lime in a hydrothermal (using hot water under pressure) process, cement can be produced. It is a concrete admixture.

Foundation

Is a when a trench is dug into the ground which is then filled with concrete once rebar is inserted. The depth and width of the foundation will vary depending on soil types but in most cases will have a depth of 600mm and a width of 350mm, you should always check your plans or consult an engineer to check what is required for your site.

MPa

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. 20mpa is commonly used for footpaths, 25mpa for driveways and 32mpa for suspended slabs.

You may also see concrete requirements expressed as 'N20/14' - this is where N means normal class concrete, 20 refers to 20MPa of strength and 14 refers to it containing a maximum aggregate size of 14mm.

Mix

A general term referring to the combined ingredients of the concrete.

Mud

Slang term for cement or mortar.

Paving

Is a broad term when it comes to concrete, it can be a driveway, footpath or for when pavers are laid over top.

Plasticizer

An agent used to increase the fluidity of fresh cement with the same cement/water ratio improving the workability and placement of the cement. Is used to obtain a high slump without the addition of so much water.

Post-tensioning

A method of pre-stressing reinforced concrete in which tendons are tensioned after the concrete has hardened.

Pump mix

Requires the concrete to be a different mix to regular concrete so that the concrete is pumpable. Generally, the mix has smaller rock aggregate than regular concrete mix.

Ready-mixed concrete

Concrete that is batched or mixed at a central plant before it is delivered to a construction site and delivered ready for placement. It is also known as transit-mixed concrete since it is often transported in an agitator truck.

Rebar

The reinforcing bar-ribbed steel bars installed in foundations, concrete walls, slabs are put in place concrete structures designed to strengthen concrete. Rebar comes in various thickness' and strength grade. The term rebar is short for reinforcing bar.

Screed

To level off concrete to the correct height during a concrete pour. The screeds come in different sizes which can be purchased from bunnings or any garden supply centre.

Set retarders

Agents used to delay, slow down, the setting of concrete.

Shotcrete

Mortar or concrete pneumatically projected at high velocity onto a surface. Also known as concrete spraying. Commonly used for pools and retaining dirt on a battered wall.

Slump

The "wetness" of concrete. A 60 slump is dryer and stiffer than a 100 slump. In most cases the normal slump for concrete is 80.

Slump test

This is a test to determine the plasticity of concrete. A sample of wet concrete is placed in a cone-shaped container 30cm high. The cone is removed by slowly pulling it upward. Once the cone is removed the concrete will fall slightly. The wetter the concrete the more it falls, therefore having a higher slump. If more water is added to the concrete mix, the strength of the concrete decreases and the slump increases.

Straightedge

A rigid and straight, piece of wood or metal used to strike off or screed a concrete surface to the proper grade, or to check the flatness of a finished grade.

Superplasticizer

A concrete admixture that makes wet concrete extremely fluid without additional water. These agents perform the same function as a plasticizer, but are composed of different materials.

Truck mixer

A concrete mixer capable of mixing concrete in transit when mounted on a truck chassis.

Vibration

Energetic agitation of freshly mixed concrete during placement by mechanical devices, either pneumatic or electric, that create vibratory impulses of moderately high frequency that assist in evenly distributing and consolidating the concrete in the formwork. Available for hire from most hire companies.