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Glossary

A

Additives

Additives improve the properties of concrete: setting time, viscosity, porosity, mechanical resistance, etc. There are 9 families of additive: accelerators, retarders, plasticizers, flow promoters, air-entraining agents, anti-freezers, water-repellents and curing agents.

Aggregates

Aggregates are small rock fragments (0.08 to 80 mm) of mineral origin. Aggregates come in different types: maritime, fluvial and terrestrial. They may be sand, gravel or crushed gravel. Aggregates, mixed with water and cement, are essential for the production of concrete.

C

CO2

Carbon dioxide (CO2) is a greenhouse gas. It is produced by the combustion of organic compounds and the respiratory systems of animals and plants.

The cement industry naturally emits CO2:

  • 60% of emissions are due to the physical-chemical transformation of raw materials at high temperatures,
  • 40% result from the combustion needed to heat the cement furnace to 1500°C.
Cantilever

Cantilever refers to the section of a construction which extends into an overhang, i.e. beyond its supports. A cornice or a balcony, for example, are cantilevered constructions.

Cement

Cement is a hydraulic bonding agent which is obtained by heating, then grinding, a mixture of limestone and clay. Most cements are made from clinker and additives and are usually used in the form of a powder. Cement sets when mixed with water. Combined with sand and aggregates (sand or gravel), it turns into rock-hard concrete or mortar.

Cementitious

Called "cement additives", these minerals are used in varying proportions during the last phase of the cement production process. The additives make it possible to obtain a range of cements with different properties. They can be:

  • of natural origin, for example limestone or volcanic and sedimentary rock (pozzolanic rock),
  • of industrial origin, for example byproducts of the steel industry (slag from blast furnaces), the microchip industry (silica fume), and coal-fired power plants (fly ash).

The use of cementitious additives reduces CO2 emissions:

  • firstly, because using additives in cement production automatically reduces the proportion of clinker (the decarbonation phase of clinker production releases a lot of CO2),
  • secondly, because it uses industrial waste which would otherwise have been discarded and treated by the local authority.
Clinker

Clinker is the main ingredient in cement. These hardened granules are obtained by firing a mixture of approximately 80% limestone and 20% clay to a high temperature. Cement is obtained by grinding clinker and, in some cases, supplementing it with additives.

Cold bridge

Cold bridges are the areas within the building envelope which offer the least thermal resistance. They are therefore one of the major causes of a building being poorly insulated. Most frequently, thermal bridges are the junctions of partitions, the concrete shell-work, roller-shutter cases, etc.

Concrete

Concrete is a building material made by mixing water, aggregates and sand with a binding agent (usually cement) and, if necessary, with additives. This mixture is made on building sites and factories.

The characteristics of a concrete can vary greatly depending on the choice of cement and cement-aggregate ratio, the type of aggregate used, the inclusion of additives, etc. The way concretes are used and surface treated can also have an impact on their performance and appearance. So concrete is reconstituted stone and is sometimes referred to as "liquid stone".

D

Deck

Collection of components arranged side by side to form the floor of a walkway, footbridge, platform etc.

Ductility

Ductility refers to a material's capacity to be stretched or bent without breaking. A material which does not have this quality is fragile.

F

Fiber-reinforced concrete

Fiber-reinforced concrete contains an array of different fibers (polypropylene, metal, fiberglass, carbon, etc.) that create a reinforced mesh, improving the concrete's solidity and resistance to cracking. This is a rapidly developing approach to reinforcing concrete.

Fly ash

Fly ash is hydrophilic and can be used as a cementitious additive. The ash, which is collected from chimney filters in coal-fired power plants, is composed of vitreous silica, alumina, iron oxide and lime.

They can be used as a partial substitute for clinker and thus help to reduce CO2 emissions.

G

Geothermal heat pump

A geothermal heat pump takes advantage of the natural warmth of the ground below the frost line to heat spaces above ground, even though thermodynamic principles should result in this warmth being diffused when it comes into contact with cooler elements.

Granular stacking

Granular stacking is a technique which improves the compactness and resistance of concrete and reduces porosity. Granular stacking is achieved by replacing part of the water with fine and ultra-fine grains that fill in the spaces between larger grains. The result is more consistent, more fluid concrete which becomes more compact upon setting.

Gypsum

Gypsum is a construction material made by firing the gypsum mineral in a kiln and then grinding it. It can be used as a paste or as pre-fabricated boards. Mixed with water, it forms a gel that sets within a few minutes and then hardens. It is widely used for interiors: coatings, dry partitions, ceilings and wall linings in the form of tiles or plasterboard. It has several important properties: accoustic and thermal insulation, fire resistance, etc.

I

Industrial ecology

Industrial ecology is a new concept in environmental management. The idea is to improve the way environmental factors (energy resources, natural raw materials, etc.) are integrated into business strategies. Industrial ecology takes its inspiration from the cyclical way in which natural ecosystems operate. Just as nature goes through cycles of production, destruction and recycling, industrial waste from certain activities can serve as raw material or fuel for other industries.

L

Lime

Lime is a binding agent obtained from the calcination of limestone. Limes are divided into 2 categories depending on whether they are set by exposure to carbon dioxide (slaked lime) or to water (hydraulic lime).

Slaked lime is mainly used in traditional finishing plasters, pointing mortars and whitewashes. Hydraulic lime contains clay, giving it similar properties to cement and making it suitable for use as an undercoat or render.

M

Mortar

Mortar is a mixture of cement, sand (an inert component which provides body) and water, which may be complemented with additives, supplements and colored pigments. Unlike concrete, mortar does not include aggregates. It may be prepared on site or delivered from a mixing plant. Mortars are used for bonding (to join cut or molded elements), for cladding (waterproofing and dressing of walls and coverings, finishing of floors), and for a number of other purposes including jointing, rendering, insulating, sealing and plugging.

N

Nanotechnologies

All studies and processes that relate to the manufacture or modification of structures, devices and materials at the nanoscale, measured in nanometers 10(-9).

P

Photovoltaic cell

A photovoltaic cell is an electronic component which generates electrical tension (or voltage) when exposed to light and can therefore be used to produce electricity. These cells produce a constant current with an average voltage of 0.5V.

Plasterboard

Plasterboard panels are industrial building components. They are made in factories by locking a thin layer of gypsum and additives between two cardboard sheets to create thin panels. Plasterboard is put in place with screws or adhesive mortar. The panels can also be nailed or screwed to wooden or metal frames to dress interior walls and partitions.

Pozzolan

Pozzolan is named after Pozzouli, a region near Naples, Italy, which is rich in volcanic ash.

Natural pozzolan is a light siliceous mineral produced during basaltic volcanic eruptions. It contains silica, alumina and iron oxide (which gives it a red color), as well as lime and magnesium oxide. Pozzolan is used as a cement additive.

Artificial pozzolans with the same properties as natural pozzolans can be created by heating clays, basalts or schists.

Prefabricated concrete

An inconvenience of conventional concrete is its drying time, which slows construction on the building site and increases costs. Prefabricated or pre-cast concrete helps to speed up construction work. Concrete pieces (columns, beams or slabs) are formed and prepared in a workshop onsite or close to the site and then transported to the right location. This has the advantage of reducing the length of the construction phase and limiting the impact on local populations.

Prestressing

The technique of combining concrete's high level of resistance to compression with steel cables' resistance to traction, by placing them in permanent opposition. With resistance equal to a traditional reinforced concrete beam, a prestressed beam allows a significant increase in weight and a reduction in the cost of load-bearing structures.

Prestressing by post-tensioning

Post-tensioning is a prestressing technique, as opposed to prestressing by pre-tensioning. This procedure, also called "prestressing with cables", involves pouring concrete sections after placing tubular ducts into the mold. After the concrete has hardened, steel cable is passed through the duct and then tensioned. This technique is used for strong load-bearing elements (superstructures of art works, footbridges, very long or cantilevered beams, etc.)

Prestressing by pre-tensioning

Pre-tensioning is a prestressing technique, as opposed to prestressing by post-tensioning. This procedure, also called "prestressing with tendons", involves pouring the concrete after placing steel tendons into the mold. After the shuttering is removed, the tension of the tendons does not relax inside the concrete section. This technique applies to sections of limited dimensions (girders, sleepers, posts, etc.)

R

Rheology

This term is derived from the Greek words "rheo" (to flow) and "logos" (study). Rheology is the study of the flow (plasticity, elasticity, viscosity and fluidity) of deformable materials. In architecture, rheology is used to study the deformation of foundations. Other applications include the study of landslides in geophysics and the deformation of foundations in geo-mechanics.

 

S

Screed

A screed is a thin layer of mortar (15 to 50 mm) that is spread over a base layer of slabs, tiling, etc. It gives a flat surface and is generally covered by another material, such as floor tiling

Self-leveling concrete

A variant of self-placing concretes, self-leveling concretes have a specially formulated and graded composition to ensure a fluid spread. They form smooth-surfaced slabs with no need for vibration or float finishing (used to make a surface flat).

Self-placing concrete

Self-placing concretes are special, highly-fluid concretes which settle into place by gravity alone and do not, therefore, require vibration. They are designed to be poured into watertight formwork. Even without vibration they cover reinforcements perfectly and provide extremely smooth facing.

Slag

This mixture of lime, alumina and silica is produced when iron is smelted with coke in blast furnaces. Slag accumulates on top of the molten cast iron. If cooled quickly, its hydraulic properties are close to those of clinker. Slag takes longer to hydrate but it offers greater stability in corrosive conditions. It is, therefore, a suitable additive for cement and concrete so as to reduce CO2 emissions.

Superplasticizer

A superplasticizer is an additive that is mixed with concrete, mortar or grout just before the concrete is used. Its main purpose is to improve the workability of the mix. Its secondary role is to modify the setting or hardening time. Superplasticizers are sometimes called "fluidifiers".

Sustainable construction

Sustainable construction aims to limit the impact of buildings on the environment while enhancing their quality in terms of aesthetics, sustainability, durability and strength. Sustainable construction techniques apply across the entire lifecycle of a building, from the selection of initial materials to demolition and recycling.

Sustainable construction signifies in particular:

  • the use of recyclable materials to conserve natural resources,
  • the integration of renewable energy sources into a building's design,
  • the optimization of renewable energy sources.

T

Thermal inertia

This term designates the capacity of a material to accumulate and store calorific energy which can then be released over a period of time.

U

Ultra-high performance fiber-reinforced concrete

Ultra-high-performance fiber-reinforced concrete is an innovative construction material. The addition of metal fibers increases its resistance 6-fold compared to standard concrete and also increases its durability.

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