Whether you’re thinking of getting into the concrete contracting business or would simply like to understand a bit more about it from the outside looking in, it’s handy to know some key terms that are commonly used in the concreting world. Hence why our Melbourne concrete contractors have written up this glossary of concrete terms.
Agitator truck: An agitator truck has a large cylindrical concrete mixer on the back. This mixes the plastic concrete whilst it’s being transported to job sites. By keeping the concrete in constant motion, it guarantees that the concrete will not dry up and therefore rendering it useless.
Batching: The process where concrete is created through the use of all the other materials. Batching helps to ensure that the appropriate amount is being used for the job.
Bleed water: This is the excess water that is released from the concrete after it is placed. It forms on the surface and the degree of it is dictated by how good the mix is.
Bony/harsh mix: A concrete mix that lacks sand or cement. It commonly has a bony appearance and is difficult to place.
Broom finish: As the name suggests, the plastic concrete is finished by sweeping a broom in a single direction – giving it a rough, grooved finish.
Cement: A binding agent made up of elements such as silicon, iron and calcium.
Comprehensive strength test: A test which reveals how strong concrete through the use of a concrete cylinder.
Concrete pump: An on-site vehicle used for pumping concrete into forms.
Concrete cylinder: Commonly sized at 100mm by 200mm, a concrete cylinder is crafted on-site and used during a comprehensive strength test – as described in AS1012 (Methods of testing concrete).
Curing: A process that reduces bleeding and thus keeping the concrete as hydrated as possible whilst it sets. There are a few different methods that can be used whilst curing including spray chemicals and wet hessian. The ultimate goal here is to reduce shrinkage and avoiding any cracks in the concrete.
Expansion joint: An assembly that is used to separate concrete from other parts of a structure and allow for thermal expansion without the risk of cracking.
Finishing: The final product of the concrete.
Fly ash: A powdery material that is an alternative cement. Categorised as a pozzolanic material and considered a supplement that can strengthen concrete.
Formwork: A temporary mould that plastic concrete can be poured into to take a certain shape. It is taken down after the concrete has set.
Grano (Granolithic topping): Grano is primarily used for repairing concrete, surfacing floors and infills. It features a maximum aggregate size of 7mm and typically holds a textured finish.
Hydration: This occurs when you combine concrete with water. The more hydration occurs, the stronger the concrete will be.
Indirect tensile: A strength test that measures concrete’s resistance to being pulled apart. A concrete cylinder is again used for this test.
Kerb and channel: The kerb is the edge of the pavement and directs drainage. This concrete mix has a high sand content and a low slump – it is placed by a machine.
Kibble: A bucket that is lifted by a crane and is responsible for transferring the concrete from the agitator truck to where it needs to go.
Lean concrete: This concrete has a low cement content, making it weaker than regular content. It is commonly used to fill or as a sub-base for concrete pavements.
Lightweight: Low-density concrete that features polystyrene beads or aggregates that weigh less than usual.
Mass concrete: Mass concrete refers to the thickness – usually greater than 600mm thick – of the concrete. Special considerations should be made when dealing with this type of concrete as due to its thickness it’s more likely to have high thermal properties – increasing the chances of it cracking.
Mesh: Steel bars – or wires – that are welded together to form a mesh. It is used to improve tensile strength and also prevent cracking.
Microstrain: A unit of measurement that is used to define the maximum amount of time certain concrete should dry for whilst accounting for shrinkage.
Mix design: The step before concrete mixing. This is where Melbourne concrete contractors consider things like setting times, strength, bleeding, materials available, specific proportions and ratios, cost and customer satisfaction.
Mixing time: How long it takes to mix a load of concrete satisfactorily.
MPa (Megapascals): The metric unit used to measure concrete’s strength.
NCA (Non-Chloride Accelerator): A chloride-free chemical that speeds up the setting time for concrete.
No fines concrete: Concrete that features up to 10% of course aggregate and cement.
Pattern paving: This type of paving allows for patterns and colours to be created on the surface of the concrete and typically holds 10mm of aggregate as well as high sand content.
Plastic concrete: Concrete that has not completely set but is still able to be worked.
Polythene: Polythene is a thin plastic sheet that is placed on the ground where concrete is to be poured. This prevents any groundwater leakage into the concrete whilst it sets. It also prevents moisture loss. High levels of moisture loss can result in concrete cracking as well as a loss of strength.
Pozzolanic material: This is the correct term for materials such as silica fume or fly ash – otherwise known as supplementary cementitious materials. The chemical reaction caused by combining these materials with lime results in concrete being strengthened.
Precast concrete: Concrete that is cast and cured in a mould and then placed in its final position afterwards.
Prestressed concrete: This is a special type of concrete that can be used in the form of slabs or beams and is ideal for supporting structures. It is created with certain pressures in mind that will be forced upon it when the structure is complete. This allows our Melbourne concrete contractors to compensate for the pressures – since they know where they’ll be – by reinforcing those areas.
This means that it is overall a very strong and durable concrete mix and is typically used if larger spans of space are required between columns – such as in a commercial office building.
Reinforced concrete: Because concrete is typically lacking when it comes to tension, it can be reinforced with steel to improve its tensile strength and also limit cracking and shrinkage.
Reinforcement: The use of welded steel wire fabric or steel bars to help control cracking and reinforce the concrete structure.
(S) Special class: Specialised concrete that features particular properties that make them different from standard concrete.
Sand moisture test: This test involves drying out a small portion of sand to determine how much water it contains. Once this is done, the water content in the mixes can be adjusted appropriately.
SCC (Self-compacting concrete): Specifically designed concrete that flows freely and requires either little or no compaction.
Screeding: The levelling of freshly placed concrete.
Segregation: The process of separating fine and coarse aggregates in a concrete mix.
Set time: How long it takes for the concrete to set. Once set, its plasticity is lost, and it is unable to be worked with.
Shotcrete: A specialised type of concrete that is shot out of an air compressed nozzle. It is commonly used for constructing swimming pools and walls.
Shrinkage: This term relates to when the volume of concrete changes. When concrete is fresh, plastic shrinkage occurs from water loss – and when concrete has dried, dry shrinkage occurs from the hydration process.
Slag: A supplementary cementitious material that is produced in conjunction with iron in a blast furnace and is then quenched and ground.
Slag aggregate: Identical to a normal slag, excepted it is left to cool naturally instead of quenched. The final result is then crushed to form the aggregate.
Slump: A measure that is used to understand the consistency and workability of concrete.
SP (Superplasticiser): An additive that increases the workability of the concrete without sacrificing the strength of it.
SSD (Saturated surface dry): SSD is a state that a concrete surface must be brought to before a cement product is applied to it. To achieve this state, the concrete must be saturated with water to a depth of several millimetres – but the surface must be dry.
Topping: When concrete is laid over already existing concrete.
Type GB (General purpose blended cement): A type of blended cement that is formed by combining Portland cement and other materials such as fly ash, ground slag and/or silica fume. Further information can be found in Australian Standard AS3972 (General purpose and blended cements).
Type GP (General purpose Portland cement): A general-purpose and common type of cement – as laid out in AS3972. Portland cement is produced by grinding cement clinker.
Type HE (High early strength cement): Type HE cement develops strength much quicker than that of Type GP. Strength development is not to be confused with setting time.
Type LH (Low-heat cement): This type of cement generates less heat than usual during the hydration and hardening phases. It is useful for mass pouring or when early strength gain is not essential. Often features supplementary cementitious materials in the blend.
Type SR (Sulphate resistant cement): Provides extra protection if the concrete is set in an environment that contains large amounts of sulphate.
WR (Water reducer): A chemical that is added to a mix that reduces the amount of water needed. This can help control the setting time and maintain strength whilst using less cement.
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