A

Abrasion Resistance – A term that is used to describe how well a surface resists being worn away by friction or rubbing.

Accelerator – A type of admixture used to speed up the rate of stiffening or hardening of concrete.

Admixture – A chemically developed ingredient added to concrete, other than water, cement, or aggregate, that is used to modify certain characteristics or reactions as they take place within the mix. Chemical admixtures exist for different purposes in powder or fluid forms.

Aggregate – A granular mixture of materials comprising elements such as sand, stone, rock, gravel, or other particles.  Aggregate is commonly used as part of a concrete mix to improve structural performance.

Air Content – A reference to entrained, or entrapped air in concrete, usually expressed as a percentage of total volume.  See Air Entrainment.

Air Entrainment – The intentional creation of air bubbles in concrete, the purpose of which is to increase the durability of the hardened concrete, particularly in the face of temperature changes.

B

Bleed through – The dispersal of colour from an underlying surface.

Bleed water (bleeding) – A form of segregation involving water rising to the surface of fresh laid concrete.  Bleeding can interfere with finishing operations.

Bonding agent – An adhesive agent, also known as a primer, that is used to increase the adherence of coatings or toppings to an existing surface, or bond new concrete to old.

Broadcast – The physical process of hand-casting a dry-shake colour, hardener, or other dry material across fresh concrete, overlays, or coatings.

Bull float – A flat-based tool used to flatten, or smooth, fresh laid concrete slabs.

Bush hammer – The description applied to a range of tools, ranging from hand held hammers to larger machine tool carrying rows of conical, or pyramid-shaped points used to roughen or profile a concrete surface.

C

Cast in place – Refers to the final part of a process involving concrete that is often prepared in advance off-site, then transported in a ready-mix, unhardened state, then placed and finished on site.

Cementitious – Refers to a material containing cement-like characteristics, or properties.

Chalking – Usually refers to the degradation of a coating or overlay, resulting in the presence of loose surface dust.

Compressive Strength – The maximum compressive stress, under a progressively applied load, which concrete or cementitious overlay materials are capable of sustaining.

Control Joint – Also known as a Contraction Joint, this is a tooled groove in a concrete slab designed to avoid high stresses with the structure and control the location of cracking.

Cracks, moving – Cracks in concrete that are still moving, or active. Often they are structural in nature and continue through the entire depth of the concrete.

Craze Cracks – Also known as crazing, this is the presence of random, hairline surface cracks caused by shrinkage.  This type of cracking is cosmetic in nature and therefore no indicator of damage to structural integrity.

Crusting – A condition arising with concrete that dries too quickly, causes for which might include exposure to winds or high temperatures.

Curing – A methodology for maintaining a satisfactory hydration and hardening process for concrete after laying.  Typically this involves the creation of a temporary greenhouse-like environment immediately surrounding the concrete, designed to ensure the desired properties are allowed to develop.  This process ensures moisture is returned to the concrete should it begin to dry too quickly.  The first 24 hours is the most important with curing, although for best results we recommend a curing period of 28 days.  That said, rare is the contractor or client willing to maintain a temporary environment for this length of time.

D

Decorative Aggregate – Naturally occurring stones, which might be considered particularly eye-catching, such as granite or quartz, added to a concrete mix then exposed as part of a mechanical concrete polishing process.

Decorative Concrete – A term used to describe concrete that has been prepared, or treated in a particular fashion, that is perceived to have enhanced the appearance of the concrete surface.

Densifier – A concrete densifier is a chemical hardener.  It is applied to concrete surfaces to fill pores and instigate a reaction that hardens the surface and enhances surface shine.  The densifier brings about surface uniformity and is a popular tool for rescuing soft or damaged concrete.

Diamond Grinding – This generally refers to the mechanical process used by contractors to grind and hone a concrete surface, as part of a full polished concrete process.  This involves the use of mechanical equipment with diamond-segmented abrasives attached.  The process starts with coarse diamond abrasives, transitioning to increasingly finer grits until the desired level of sheen is achieved.

 

E

Edger – A tool used to provide a clean, finished edge to a concrete installation.

Efflorescence – Salt deposits which form on a concrete surface arising when certain conditions combine to cause a reaction with the concrete.

Exposed Aggregate – A decorative surface formed by removing the surface layers from a concrete slab.

F

Finishing – A description for any of the processes, such as compacting, levelling or smoothing, which lead to the finished properties and look of the concrete slab.

Flexural Strength – Refers to the ability of concrete to withstand bending without incurring structural failure.

Float Finish – Refers to the finish achieved after bull floating.

Floor Polisher – Generally refers to a walk-behind machine tool operated by a polished concrete contractor.

G

Glass-Fibre Reinforced Concrete (GFRC) – A lightweight concrete mix containing glass-fibre, designed to offer greater tensile strength.

Grind and Seal – This is the nae for a process which is sometimes misrepresented as a full mechanical polished concrete polishing process.   It is a shorter process, which can yield similar looking, but less durable results.  The process focuses on the elimination of surface scratches in the concrete, before the application of a topical (or surface) sealer, a chemical solution designed to offer a degree of protection from scratching, wear and tear.  This process involves only a limited amount of grinding with specialist machine tools, compared to a full polished concrete process.

Grinding – The process of concrete surface preparation using rotating diamond abrasives that remove layers from the concrete surface, usually in readiness for further honing and polishing.

Grout – A mixture of cementitious materials and water used to fill small holes.

H

Hand float – A smaller version of a bull float, generally useful for floating along the perimeters, or working in tight spots.

Hard-troweled finish – Surface finish achieved using a steel blade trowel.

Hydration – The process by which cement and water react during hardening.

I

Integral colour – Colouring that is premixed into concrete before placement.

Iron oxide – Pigmentation used to colour decorative toppings or coatings.

J

Joint – A deliberately placed gap, or groove, sometimes referred to as a Control Joint, designed to alleviate the build up of stress across concrete sections and control the location of cracks arising from such stresses.

Joint filler – A compressible material intended to prevent debris gathering in the joints.

L

Laitance – A gathering of loose particles caused by the upward movement of water through the concrete slab, which must be removed prior to any decorative work, such as concrete polishing, or coating.

M

Microtopping – An ultra-thin, yet durable decorative topping, sometimes chosen as an alternative to a full mechanical polished concrete process, or sometimes used to rescue a concrete slab which is of insufficient quality for a full polished concrete process to be applied.

Mix Design – Refers to the make-up of a cement mix, sometimes referred to as the concrete matrix.

N

Neutralise – The process of returning concrete to its proper pH condition.

O

Overlay – A bonded layer that is placed on concrete surfaces, for restorative, or decorative purposes.

P

Penetrating sealer – Designed to provide invisible protection to repel water and resist staining.

Permeability – Refers to the ability of a liquid or gas to penetrate concrete.

Pigment – Particles capable of adding colouring or opacity to another mass, or compound.

Plastic – Refers to a particular condition of freshly mixed concrete when it is capable of being shaped, framed or moulded.

Plasticity – Refers to the ease with which a cement, or cementitious compound can be shaped, framed or moulded.

Polished Concrete – A finish attained by means of special mechanical machine tools fitted with diamond-impregnated abrasive disks (similar to sandpaper).   There is a variety of finishes which can be achieved by means of this process, depending upon the desired degree of shine and smoothness.  The resulting surface is low-maintenance.

Portland Cement – The most common type of cement in general usage throughout the world, commonly used in the production of concrete.  Comes in a fine powder which hardens when mixed with water.

Power floating – Power floating is a finishing process applied after concrete is poured, once it is hard enough to take the weight of the machine (power float) used to carry out the work.  Power floating done correctly, at the right time, with the right tools by the right professionals, should result in a flat, hard, durable surface.

Primer – A coating applied to a concrete surface to improve the bonding or adherence of subsequent coats.

R

Ready-mixed concrete – Concrete that’s prepared prior to being transported to the location where it is required for use.

Rebar – Also known as Reinforcing Bars, come in a variety of sizes.  These are ribbed steel bars installed within a concrete structure to provide additional strength.

Reinforced concrete – Tension resistant concrete containing embedded Rebar or welded wire mesh.

S

Sandblasting – A high velocity cleaning method, which fires sand at the surface to be cleaned using compressed air.

Scaling – Refers to flaking found on a concrete surface, often caused by freezing and thawing.

Sealer – A liquid based chemical applied to seal and protect a concrete surface.

 

Shotblasting – Refers to an abrasive blasting method.

Skim Coat – A thin overlay.

Slump – A form of measurement that refers to the consistency of freshly mixed concrete.

Static cracks – Hairline surface cracks (see Craze Cracks).

Strike off – A levelling process applied to fresh laid concrete.

T

Trowel – A hand tool used to compact the concrete surface and provide a smooth, flat finish.

Trowel Finish – The smooth or lightly textured surface finish achieved by troweling.

Translucent Concrete – Refers to concrete installations with light-emitting qualities.  Thanks to advancements in technology there is now a variety of ways in which this can be achieved.

V

Volatile organic compounds (VOCs) – Chemical compounds which vaporise at room temperature, some of which are hazardous to health if inhaled.

W

Water-cement ratio – The ratio of water to cement in a concrete mixture.

Water Reducer – Chemical admixture products added to concrete prior to pouring, designed to reduce water content, increase strength and reduce permeability, with the purpose of achieving increased durability.

Wet Polishing – A concrete polishing process that uses water to cool the diamond abrasives whilst polishing, although not that commonly used, most likely due to the amount of slurry produced in the process.

White Cement – Suitable for general purpose concrete, mortar, render or screed, commonly used for its reflective qualities.

Workability – The ease with which concrete or other cementitious materials can be mixed, placed, and finished.

Working Time – Refers to the amount of time available to work with concrete or other cementitious materials before beginning to set.

X

Xylene – A highly flammable common solvent.