Glossary

A

Abrasive Aggregate

An aggregate used to increase the abrasiveness of a concrete slab.

Absolute volume

The total volume of concrete occupied. This is found by dividing the weight of each ingredient by its gravity, times by the weight of one cubic foot of water.

Absorption

The absorption of water, usually shown as a percentage of the dry weight.

Absorption loss

Until the aggregate is fully saturated, water losses can occur.

Accelerators

A material added to a concrete mix to either speed up or reduce the setting time. Examples include: calcium chloride, aluminium sulfate or other acidic materials.

Accessories

Items such as shoring, scaffolding, frames and forms all used when placing concrete.

Admixture

A mixture that is not an aggregate, cement or water, that is added to the mix in order to make certain modifications e.g. plasticity, curing time or air entrainment. The admixture is commonly referred to as accelerators, plasticizers or water-reducing agents.

Aggregate

A mixture of particles that makes up around 75% of concrete. This can include materials such as, crushed stone, rock and sand. This helps improve the structural performance of the concrete, including the flow and formation.

Aggregate testing

Tests performed on aggregates to determine the chemical and physical properties of it. For instance, absorption, abrasion and soundness tests are some of the most common ones carried out.

Apron

Concrete that extends from the entrance of a building, particularly used for vehicular traffic e.g. at an airport or hangars.

Architectural concrete

Either structural or non-structural concrete that will be permanently exposed so needs to therefore be uniform and aesthetically pleasing. This type of concrete is often cast in a mould and has a patterned surface.

Asphalt

A black petroleum residue that is often used as a roofing material, for lining walls of reservoirs, swimming pools and for resurfacing roads. It can be either in solid or liquid form, depending on the temperature, and should not be confused with tar - as it is a similar looking substance.

B

Ballast

A mix of coarse materials, such as sand and stone, which is laid as a base underneath concrete.

Base course

A layer of a certain thickness that is formed on the sub-base of a pavement. This is laid in order to distribute loads, provide drainage and even minimise frost.

Batch

The quantity of concrete produced from one mixing operation i.e. one batch of concrete.

Bedding

A base that has been specifically prepared for either masonry or concrete.

Bond

The cement paste and aggregate joining together.

Brace/bracing

An accessory whereby one end of the brace is attached to the form and the other is anchored to the ground. The brace offers temporary support for aligning vertical concrete formwork.

Butterfly

A small hand-held tool used to finish concrete curb and gutter work.

C

Calcium chloride

A common chemical, calcium chloride is an additive used as a catalyst to speed up the curing time of ready-mix concrete.

Casting

The pouring of a liquid material into a mould that can physically change its form as it solidifies.

Casting Bed

A fixed form whereby permanent, pre-cast concrete forms are created.

Cement

A fine, grey powder that when mixed with water will harden and create concrete.

Cement-aggregate ratio

The ratio of cement mix to aggregate mix. This is measured in weight or volume.

Cement content / cement factor

An amount of concrete contained in a unit volume. This is usually expressed in pounds, bags per cubic yard or barrels.

Cement mixer

A container with a rotary motion used to mix all the concrete ingredients together. This can either be electrically powered or manually operated.

Cement mixtures

Cement mixtures are a ratio of cement: sand: aggregates and different quantities can be mixed to achieve different consistencies:

• Rich

  1: 2: 3

  Often used for roads and waterproof structures.

• Standard

  1: 2 ½: 4

  Often used for reinforced work, such as floors, roofs, sewers and conduits.

• Medium

  1: 1 ½: 5

  Often used for foundations, piers, walls etc.

• Lean

  1: 3: 6

  Often used for mass concrete work, stone masonry or large foundations.

Cement types

Different types of cement that can be mixed, including:

• Type: normal

  Suitable for many residential construction purposes but should not be exposed to extreme temperatures or high sulfate soils.

• Type II: Moderate

  Suitable for use in drainage structures where sulfate concentrations are higher than average.

• Type III: High Early Strength

  Suitable for when strong concrete is required quickly e.g. replacing old forms.

• Type IV: Low Heat

  Suitable for when the amount of heat generated during curing needs to be kept to an absolute minimum, and when strength is not needed straight away e.g. for dams.

• Type V: Sulfate Resisting

  Suitable only for where construction is exposed to severe sulfate action e.g soils with high alkali levels.

Cementitious

A material that is not cement but that shares the same properties of cement e.g. Portland cement and lime.

Concrete

A building material that consists of a mineral (commonly sand or gravel) and a binding agent (cement), a chemical additive and water. It is a popular material used mainly in construction, road building, airports, factories and bridges.

Concrete block

A hollow masonry unit that is larger than the size of an average brick.

Consistency

The plasticity of fresh concrete. This is usually measured by the consistency of the slump.

Curing

The hardening of concrete or other wet materials. This is the final process to laying concrete and happens when water evaporates. The weather conditions, mix proportion, size and shape of the concrete can all affect the length of time it takes to cure e.g. lean mixtures can take 3 weeks but rich mixtures only a few days.

D

Dampproofing

A method used to repel water on concrete, stone or masonry. This prevents surfaces from absorbing liquid, such as rainwater.

Dowel lubricant

Lubricant applied to a dowel, placed in slabs to allow movement in the joints.

Dry concrete

Concrete with a low water content. It is a stiffer mixture, ideal for placing on sloping surfaces.

Drying shrinkage

The reduction of moisture in concrete.

E

Edger (edging trowel)

An edging trowel tool used to finish the edges and corners off of fresh concrete.

Expansion joint

A divider that allows the surface to expand and usually consists of a fibrous material. This is placed in between concrete slabs to allow movement.

Exposed aggregate finish

Washing away the cement and sand mixture from the top layer of aggregate. A technique used regularly on driveways and patios.

F

Face forms

Concrete forms used to create curb profiles. They are attached to the curb and gutter by hooking to the division plate.

Fiber reinforced concrete

A type of concrete that has fibres added to the mix. The fibres can be made from stainless steel, carbon or glass.

Fine aggregate

Aggregate made up of very fine particles. The particles are so fine, they can pass through a ½ inch sieve and number four sieve.

Finishing

This involves the compacting, smoothing and leveling of fresh concrete in order to create the desired look.

Flexible forms

Metal forms made from spring steel, used for shapes such as islands, curbs and other similar forms.

Footing

The concrete foundation of a structure that supports the load and distributes the weight of the building evenly over the ground. The footings are always wider that the actual structure.

Form

A structure or mold used for temporary support and containment of concrete while it gains sufficient strength to self-support.

Foundation

The substructure, including the footings, below the ground floor of the building.

Foundation waterproofing

High quality moisture protection used for below-grade exterior concrete and wall damp-proofing. It has the consistency of black tar.

G

Glass Fiber Reinforced Concrete (GFRC)

A thin material often laminated to a plywood and used in wall systems. It works in a similar fashion to concrete but does not perform quite as well.

Grade

Refers to the existing level or surface of the grounds to a building. For instance, a road’s incline or decline presented as an average that is either above grade, below grade or on grade.

H

Hardener

This encourages the curing process of concrete.

High-pressure steam curing

Also known as autoclave curing, this is a method of using steam to cure cement products in an autoclave with temperatures between 340°F and 420°F.

Honeycomb

Method by which concrete is poured into foundation forms, leaving behind voids that create a honeycomb appearance.

I

Initial set

A certain amount of stiffening of the cement mix. The amount is indicated in hours and minutes that is required for the cement to stiffen sufficiently.

Initial stress

This refers to the stresses that occur before any losses happen.

J

Jitterbug

A concrete tamper tool designed to depress aggregates in concrete mixes. It helps to bring sand and cement grout to the surface of the slab.

Joint

Two or more building materials are joined together. The two materials can be held together either by cement, mortar or glue to name a few examples.

K

Kelly Ball

A tool to help judge the consistency of fresh concrete. This can be used as an alternative method to slump testing.

Keyway forms

Similar to straight forms but with drilled holes along the centre with a bolted keyway (which can be detached when straight forms are needed). This is commonly used to pour keyed slabs with.

Kiln

An oven, furnace or an enclosure of some kind to either harden, bake, char or burn various materials.

L

Lift

A single layer of concrete.

Line

Nylon string used as a guide to set the concrete to grade.

M

Mason

Someone who builds stones, brick and concrete units.

Masonry cement

A mixture of mortar, sand and water. This is classed as a Portland cement that helps make mortar more workable.

Mass concrete

Any large volume of concrete with dimensions vast enough to require certain measures are taken in order to cope with the heat generation.

Mixer

A piece of equipment used for blending two or more materials together that is used to manufacture concrete.

Mortar

A combination of cement, sand and water, used for masonry work.

Mud

A slang term used in place of cement or mortar.

N

Neat cement

Hydraulic cement that is not hydrated.

No-fines concrete

Concrete mixture made up from coarse aggregates only.

Non-air-entrained concrete

Concrete that has not been subject to either air-entraining admixtures, nor air-entraining cement.

O

Outside radius

The outside area of a bend.

Over vibration

Heavy use of vibrations during placement to segregate fresh concrete.

P

Paving

Typically masonry materials that are laid down on the ground to make an even surface.

Plain concrete

Concrete that has not been reinforced, or only reinforced for shrinkage.

Plastic consistency

A condition of concrete whereby it will sustain deformation time and time again, in any direction.

Plasticity

This property of concrete will determine how easy or hard it is to mould, in terms of how strong its resistance is.

Pre-cast concrete

Concrete that is cast into shapes using reusable forms. This can be transported easily as it is fully cured.

Pre-mixed concrete

Concrete that is ready-mixed.

Pump mix

A special concrete (usually a small rock aggregate mix) that is used in a concrete pump.

R

Reactive aggregate

Aggregates that contain substances that are reactive with products of Portland cement. This can result in harmful cracking, staining or expansion.

Ready-mixed concrete

Concrete that is already mixed before being delivered to a construction site, so it is ready for placement straight away.

Refractory concrete

Concrete suitable for use at high temperatures.

Reinforced concrete

Concrete that is reinforced with steel bars. This type of concrete is more able to withstand any tension.

Release agent

A substance used to avoid concrete from bonding to a surface i.e forms.

Retempering

Adding water to concrete that has stiffened - however this is not usually recommended as it can affect the strength of the concrete.

S

Scaling

Breaking off the hardened surface of concrete.

Screed

Following the pouring stage, the concrete needs to be levelled off. This includes scraping off any excess concrete above the plane.

Shrinkage

A decrease in volume via drying or chemical changes.

Slab

Concrete pavement that is used in driveways, basements and garages.

Slag

A hydraulic cement that is the product of the reduction of iron ore to iron.

Slump test

This test is widely carried out to determine the plasticity of concrete. A sample of concrete is taken, if the concrete flattens in a pile 4” high, then it has an 8” slump. If more water is added to the concrete mix, then the strength of the concrete decreases but the slump increases.

Spauling

Surface sections of the concrete either peel or chip away. This is due to the overuse of salt or an inferior concrete mix.

Stripping

Removing the formwork from concrete.

Sub-base

A layer of aggregate material laid underneath a stone base.

T

Temper

Introducing water to the cement mix to produce the right consistency.

Transit-mixed concrete

Concrete that has been mixed on the back of a truck during transportation.

Trowelling

The smoothing and compacting of fresh concrete, using a trowel.

Truck mixer

A mixer able to mix concrete on the back of a lorry during transportation.

V

Vibrating screed

A vibrating machine that helps level out fresh concrete.

Vibration

Either pneumatic or electric agitation of fresh concrete via high frequency impulses.

W

Water-cement ratio

Proportion of water (only that absorbed by aggregates) to cement, in a concrete mixture. This is stated as a decimal by weight e.g. 1:2:4 is 1 cubic foot of cement, 2 cubic feet of sand and 4 cubic feet of gravel.

Water-reducing agents

This material can help make freshly mixed concrete more workable, without adding more water to the mixture. Similarly, it can maintain the workability of the concrete by reducing the amount of water present in the mix.

Weep screed

A tool that is used to help extract moisture from concrete.

Wetting agent

A substance that facilitates the wetting of solid surfaces and the penetration of liquids.

Y

Yard

The measurement of concrete e.g. 1 cubic yard is 27 cubic feet or 3’ x 3’ x 3’.

Yield

The volume of freshly mixed concrete.

Z

Zero slump concrete

Concrete mix that has very little water, so no slump is created.