Glossary

Absorption – (1) The process by which a liquid (water) is drawn into and tends to fill permeable pores in foamed concrete. (2) The amount of water absorbed by a material under specified test conditions, commonly expressed as a percentage by mass of the test specimen.

Accelerating admixture – Admixture that speeds the rate of hydration of hydraulic cement, shortens the normal time of setting, or increases the rate of hardening, of strength development, or both, of foam concrete.

Addition – see Batching

Admixture – Material, other than water, aggregate, and hydraulic cement, used as an ingredient of foam concrete and added to the batch immediately before or during mixing to change the characteristics of foam concrete or its matrix.

Aggregate – Granular mineral material such as natural sand, manufactured sand, air-cooled blast-furnace slag, Fly ash, vermiculite, pumice or perlite.

Air-content – Total volume of air voids, both entrained and entrapped, in foam concrete. Entrained air adds to the durability of hardened foam concrete, reducing weight of the foam concrete and workability of fresh mixtures.

Air entrainment – Intentional introduction of air in the form of minute, disconnected bubbles (generally smaller than 1 mm) during mixing of foam concrete to improve desirable characteristics such as cohesion, workability, and durability.

Air void – Entrapped air pocket or an entrained air bubble in foam concrete. Entrapped air voids usually are larger than 1 mm in diameter; entrained air voids are smaller.

Air Curing – A type of curing process, wherein foam concrete is cured under ambient air temperature, pressure and humidity.

Alkali-aggregate reactivity / Alkali–Silica Reaction (ASR) – Production of expansive gel caused by a reaction between aggregates containing certain forms of silica or carbonates and alkali hydroxides in foam concrete.

Autoclaved Aerated concrete – Also known under the brand name "Ytong", "Hebel” or "Siporex" can only be produced in special plants. AAC is produced using quartz sand, calcined gypsum, lime (mineral), fly ash, Aluminium powder and/or cement and water are used as a binding agent. Aluminum powder reacts with calcium hydroxide and water to form hydrogen. The hydrogen gas foams and doubles the volume of the raw mix creating gas bubbles up to 3mm (⅛ inch) in diameter. When the forms are removed from the material, it is solid but still soft. It is then cut into either blocks or panels and placed in an autoclave chamber for 12 hours. This steam pressure hardening process gives AAC its high strength and other unique properties.

Base mix – The cementitious mortar comprising cement, water, filler and chemical admixtures into which foam is incorporated to produce foam concrete.

Batching – Process of weighing or volumetrically measuring and introducing into the mixer the ingredients for a batch of foam concrete.

Blast-furnace slag – Nonmetallic byproduct of steel manufacturing, consisting essentially of silicates and aluminum silicates of calcium that are developed in a molten condition simultaneously with iron in a blast furnace.

Bleeding – Separation of mixing water from cement paste in fresh mix caused by the settlement of the solid materials in the mixture

Blended hydraulic cement – Cement containing combination of portland cement, pozzolans, slag, and/or other hydraulic cement.

Bulking – Increase in volume of a quantity of sand when in a moist condition compared to its volume when in a dry state.

Carbonation – Reaction between carbon dioxide and a hydroxide or oxide to form a carbonate.

Cellular Concrete or Cellular Lightweight Concrete – See Foam Concrete

Cement – See Portland cement and Hydraulic cement.

Cement paste – Constituent of foam concrete, consisting of cement and water.

Cementitious material (cementing material) – Any material having cementing properties or contributing to the formation of hydrated calcium silicate compounds. When proportioning foam concrete, the following are considered cementitious materials: Portland cement, blended hydraulic cement, fly ash, ground granulated blast-furnace slag, silica fume, and rice husk ash.

Chemical admixture – See Admixture.

Chemical bond – Bond between materials resulting from cohesion and adhesion developed by chemical reaction.

Clinker – End product of a portland cement kiln; raw cementitious material prior to grinding.

Chloride (attack) – Chemical compounds containing chloride ions, which promote the corrosion of steel reinforcement. Chloride deicing chemicals are primary sources.

Coalescence – The joining of two or more bubbles in the foam. (Because larger bubbles have a tendency to rise to the surface, coalescence can lead to segregation and reduced strength.)

Coarse aggregate – Natural gravel, crushed stone, or iron blast-furnace slag, usually larger than 5 mm (0.2 in.) and commonly ranging in size between 9.5 mm and 37.5 mm (3/8 in.to 1 ½ in.).

Cohesion – Mutual attraction by which elements of a substance are held together.

Collapse (Foam) – In foam concrete, foams collapse due to film rupture caused by shear force of raw materials while mixing in the concrete mixer, while agitation, compaction & pumping. To keep foam from collapsing, it is essential to choose right type of mixer and pump, which reduces the shear force of raw material induced to the foam and avoid compaction.

Colored foam concrete – Foam concrete containing white cement and/or mineral oxide pigments to produce colors other than the normal gray hue of traditional gray cement foam concrete.

Compaction – Process of inducing a closer arrangement of the solid particles in freshly mixed and placed concrete, mortar, or grout by reduction of voids, usually by vibration, tamping, rodding, puddling, or a combination of these techniques. Also called consolidation, compaction or vibration or rodding should not be done in foam concrete as it can break down the air bubbles.

Compatibility – The situation where there is no adverse interaction between foam and chemical admixture that reduces the stability of the foam in the mortar.

Compressive strength – Maximum resistance that foam concrete will sustain when loaded axially in compression in a testing machine at a specified rate; usually expressed as force per unit of cross sectional area, such as megapascals (MPa) or pounds per square inch (psi).

Concrete – Mixture of binding materials and coarse and fine aggregates. Portland cement and water are commonly used as the binding medium for normal concrete mixtures, but may also contain pozzolans, slag, and/or chemical admixtures.

Consistency – Relative mobility or ability of freshly mixed foam concrete to flow. (See also Slump and Workability).

Construction joint – A stopping place in the process of construction. A true construction joint allows for bond between new concrete and existing concrete and permits no movement. In structural applications their location must be determined by the structural engineer. In slab on grade applications, construction joints are often located at contraction (control) joint locations and are constructed to allow movement and perform as contraction joints.

Contraction joint – Weakened plane to control cracking due to volume change in a concrete structure. Joint may be grooved, sawed, or formed. Also known as a "Control joint.”

Corrosion – Deterioration of metal by chemical, electrochemical, or electrolytic reaction. Corrosion products can contribute to the expansion of metals, which can build up and cause cracking and eventually lead to the destructive spalling of concrete.

Creep – Time dependant deformation of concrete, or of any material, due to a sustained load.

Curing – Process of maintaining freshly placed foam concrete moist and at a favorable temperature for a suitable period of time during its early stages so that the desired properties of the material can develop. Curing assures satisfactory hydration and hardening of the cementitious materials.

Damp-proofing – Treatment of foam concrete to retard the passage or absorption of water, or water vapor.

Delayed ettringite formation (DEF) – This reaction, which occurs at temperatures in excess of 65°C, involves the decomposition and reformation of primary ettringite in the presence of moisture: it generates disruptive expansive forces in the concrete matrix.

Density – Mass per unit volume; the weight per unit volume in air, expressed, for example, in kg/m3 (lb/ft3).

Durability – Ability of foam concrete to resist weathering action and other conditions of service, such as chemical attack, freezing and thawing, and abrasion.

Drying – Process aimed to remove moisture in the foam concrete using elevated temperature (around 50 Deg. Celsius) in a hot chamber. Drying & curing are totally different process, whereas the former is used to remove the water and the later is used to gain the strength of the concrete. Drying is not necessary in foam concrete manufacturing except if the ambient temperature is below 20 Deg Celsius, which is detrimental to remove the moulds or forms for precast elements manufacturing.

Early stiffening – Rapidly developing rigidity in freshly mixed foam concrete. It is caused either by false setting or flash setting. Severe false setting in cement may cause difficulty from a placing and handling standpoint. It is most likely noticed where concrete is mixed for a short period of time in stationary mixers and transported to the forms in trolleys, as on some paving jobs, and when concrete is made in an on-site batch plant. Cements with severe false setting usually require slightly more mixing water to produce the same consistency, which may result in slightly lower strengths and increased drying shrinkage. Early stiffening resulting from flash set, depending on severity, can cause a cement to fail the applicable time of setting requirement. Addition of gypsum prevents flash setting of concrete.

Entrapped air – Irregularly shaped, unintentional air voids in fresh or hardened foam concrete 1mm or larger in size.

Entrained air – Spherical microscopic air bubbles – usually 10 µm to 1000 µm in diameter – intentionally incorporated into foam concrete to reduce weight and/or improve workability.

Epoxy resin – Class of organic chemical bonding systems used in the preparation of special coatings or adhesives for foam concrete or as binders in epoxy-resin mortars and concretes.

Ettringite – Needle like crystalline compound produced by the reaction of C3A, gypsum, and water within a Portland cement concrete. Ettringite is the mineral name for calcium sulfo-aluminate (3CaO•Al2O3•3CaSO4•32H2O), which is normally found in Portland cement concretes. Calcium sulfate sources, such as gypsum, are intentionally added to Portland cement to regulate early hydration reactions to prevent flash setting, improve strength development, and reduce drying shrinkage. Most of the sulfate in the cement is normally consumed to form ettringite at early ages. The formation of ettringite in the fresh, plastic concrete is the mechanism that controls stiffening. At this stage, ettringite is uniformly and discretely dispersed throughout the cement paste at a submicroscopic level. Ettringite formed at early ages is often referred to as "primary ettringite.” It is a necessary and beneficial component of Portland cement systems.

Expansion joint – A separation provided between adjoining parts of a structure to allow movement.

Exothermic heat – The chemical reaction between cement & water, known as the hydration process, is an exothermic reaction. That is, heat is liberated during both the setting & hardening process of the concrete. The amount of heat liberated is primarily a function of the amount of cement in the mix, the temperature of the concrete at the time of placing & the degree of insulation provided by the formwork in which the concrete is cast. A number of factors influence both the rate of temperature gain & the peak temperature attained. See also Heat of Hydration.

Foam Concrete – Foam Concrete also known as Cellular Lightweight Concrete (CLC), is a lightweight product, produced by initially making a slurry of Cement, Fly ash or Sand, Water, which is further mixed with the addition of pre-formed stable foam in an unique Foamed concrete mixer under ambient conditions. In foam concrete, the density control is achieved by substituting macroscopic air cells for all or part of the fine aggregate. Normal-weight coarse aggregate is usually not used but lightweight aggregates, such as pumice or perlite, both fine and coarse, can be utilized in cellular concrete. The mixture is either poured or pumped into assembled moulds of blocks or form-work of reinforced structural elements or poured onto flat roofs or voids for thermal insulation or filling. The foam imparts free flowing characteristics to this slurry due to ball bearing effect of foam bubbles enabling it to easily flow into all corners and compact by itself in the moulds/forms without requiring any kind of vibration or compaction. The moulds are then demoulded after 6 to 8 hours depending on the ambient temperature and humidity. The blocks removed from the moulds are sent for cutting into different sizes required by the market and then stacked for curing. The curing can be moist curing or vapour curing. For moist curing, the blocks are kept wrapped in polythene sheets by pouring water everyday for atleast 14 to 21 days and then dry it for another 7 days to develop the strength of the blocks and to reduce drying shrinkage. See also Vapour Curing.

Foaming agent – A foaming agent is a material that facilitates formation of foam such as a protein, surfactant or a blowing agent. A surfactant, when present in small amounts, reduces surface tension of a liquid (reduces the work needed to create the foam) or increases its colloidal stability by inhibiting coalescence of bubbles.

Foam Generator – Equipment used to generate foam using foaming agent, water & air. It primarily consists of air compressor, water pump, foaming agent pump & foam lance.

Foam Lance – Part of foam generator through which foam is generated and added to cement slurry. It is a pipe made of either plastic or metal which is filled with specialized ingredients to produce uniform foam bubbles.

Foam stability – The ability of foam to resist collapse into solution.

Fibers – Thread or thread like reinforcing material ranging from 0.05 to 4 mm (0.002 to 0.16 in.) in diameter from 10 to 150 mm (0.5 to 6 in.) in length and made of steel, glass, synthetic (plastic), carbon, or natural materials.

Fiber concrete – Concrete containing randomly oriented fibers in 2 or 3 dimensions through out the concrete matrix.

Fine aggregate – Aggregate that passes the 9.5 mm (3/8 in.) sieve, almost entirely passes the 4.75 mm (No. 4) sieve, and is predominantly retained on the 75 µm (No. 200) sieve.

Finishing – Mechanical operations like screeding, consolidating, floating, troweling, or texturing that establish the final appearance of foam concrete surface.

Fire resistance – That property of a building material, element, or assembly to withstand fire or give protection from fire; it is characterized by the ability to confine a fire or to continue to perform a given structural function during a fire, or both.

Flexural strength – Ability of foam concrete to resist bending.

Flowability – The ability of foam concrete to flow under its own weight. See also Rheology.

Fly ash or Pulverised Fuel Ash (PFA) – Residue from coal combustion, which is captured from flue gases, and is used as a pozzolan or cementing material in foam concrete.

Form work – Temporary supports for keeping fresh foam concrete in place until it has hardened to such a degree as to be self supporting (when the structure is able to support its dead load). As foam cement can flow like a liquid, tight fitting forms can prevent materials from leaking.

Freeze-thaw resistance – Ability of foam concrete to withstand cycles of freezing and thawing. (See also Air entrainment and Air-entraining admixture.)

Fresh foam concrete – Foam concrete that has been recently mixed and is still workable and plastic.

Grading – size distribution of aggregate particles, determined by separation with standard screen sieves.

Grout – Mixture of cementitious material with or without aggregate or admixtures to which sufficient water is added to produce a pouring or pumping consistency without segregation of the constituent materials.

Hardened foam concrete – Foam concrete that is in a solid state and has developed certain strength.

Heat of hydration – The temperature rise generated by hydration. See also Exothermic Reaction & Hydration (Foam concrete has excellent insulation properties and so a significant rise in temperature rise can be reached through curing and retained for several days. The temperature rise can be moderated by the use of PFA as a partial replacement for Portland cement)

High-density foam concrete – Foam concrete of very high density; normally in the range of 1000 Kg/m3 to 1600 Kg/m3, designed to take greater loads.

High-strength foam concrete – Foam concrete with design strength of at least 20 MPa (2,900 psi).

Hydrated lime – Dry powder obtained by treating quicklime with sufficient water to satisfy its chemical affinity for water; consists essentially of calcium hydroxide or a mixture or a mixture of calcium hydroxide and magnesium oxide or magnesium hydroxide, or both.

Hydration – In foam concrete, the chemical reaction between hydraulic cement and water in which new compounds with strength-producing properties are formed.

Hydraulic cement – Cement that sets and hardens by chemical reaction with water, is capable of doing so under water. (See also Portland cement.)

Imperial units – See US units

Isolation Joint – Separation that allows adjoining parts of a structure to move freely to one another, both horizontally and vertically.

Joint – See Construction joint, Contraction joint, Isolation joint, and Expansion joint.

Kiln – Rotary furnace used in cement manufacture to heat and chemically combine raw inorganic materials, such as limestone, sand and clay, into calcium silicate clinker.

Lightweight aggregate – Low-density aggregate used to produce lightweight (low-density) concrete. Could be expanded or sintered clay, slate, diatomaceous shale, perlite, vermiculite, or slag; natural pumice, scoria, volcanic cinders, tuff, or diatomite; sintered fly ash or industrial cinders.

Lightweight concrete – See Foam Concrete.

Lime – General term that includes the various chemical and physical forms of quicklime, hydrated lime, and hydraulic lime. It may be high-calcium, magnesium, or dolomitic.

Masonry – Foam concrete or conventional concrete masonry units, clay brick, structural clay tile, stone, terra cotta, and the like, or combinations thereof, bonded with mortar, dry-stacked, interlocking blocks or anchored with metal connectors to form walls, building elements, pavements, and other structures.

Masonry cement – Hydraulic cement, primarily used in masonry and plastering construction, consisting of a mixture of portland or blended hydraulic cement and plasticizing materials (such as limestone, hydrated or hydraulic lime) together with other materials introduced to enhance one or more properties such as setting time, workability, water retention, and durability.

Mass concrete – Cast-in-place foam concrete in volume large enough to require measures to compensate for volume change caused by temperature rise from heat of hydration and/or ambient temperature in order to keep cracking to a minimum.

Meta-kaolin – Highly reactive pozzolan made from kaolin clays. The calcination temperature required to produce meta-kaolin is typically in the range of 600–800 °C.

Metric units – Also call System International (SI) Units. System of units adopted by most of the world by the 21st Century. These include but are not limited to: (1) length millimeters, meters, and kilometers; (2) area-square millimeters and square meters; (3) volume-cubic meters and liters; (4) mass-milligrams, grams, kilograms, and megagrams; and (5) degrees Celsius.

Mineral admixtures – See Supplementary cementitious materials.

Modulus of elasticity – Ratio of normal stress to corresponding strain for tensile or compressive stress below the proportional limit of the material; also referred to as elastic modulus, Young’s modulus, and Young’s modulus of elasticity; denoted by the symbol E.

Moist-air curing – Curing with moist air (no less than 95% relative humidity) at atmospheric pressure and a temperature of about 23 degrees C (73 degrees F).

Mortar – Mixture of cementitious materials, fine aggregate, and water, which may contain admixtures, and is usually, used to bond masonry units.

Mortar cement – Hydraulic cement, primarily used in masonry construction, consisting of a mixture of portland or blended hydraulic cement and plasticizing materials (such as limestone, hydrated or hydraulic lime) together with other materials introduced to enhance one or more properties such as setting time, workability, water retention, and durability. Mortar cement and masonry cement are similar in use and function. However, specifications for mortar cement usually require lower air contents and they include a flexural bond strength requirement.

Moulds – A shaped cavity used to give a definite form to foam concrete. It is used to make foam concrete in different shapes, form, design or pattern

Normal weight concrete – Class of concrete made with normal density aggregates, usually crushed stone or gravel, having a density of approximately 2400 kg/m3 (150 lb/ft3). (See also Lightweight concrete and High-density foam concrete.)

No-slump concrete – Conventional Concrete having a slump of less than 6 mm (1/4 in.).

Overlay or Screeds – Layer of foam concrete or mortar placed on or bonded to the surface of an existing pavement or slab. Normally done to insulate the roof or floor for both thermal and sound insulation.

Pavement backfilling (concrete) – Highway, road, street, path, or parking lot sub-surfaced with foam concrete. Although typically applied to surfaces that are used for travel, the term also applies to storage areas and playgrounds.

Permeability – Property of allowing passage of fluids, vapours or gases

Pervious concrete (no fines or porous concrete) – Concrete containing insufficient fines or no fines to fill the voids between aggregate particles in a concrete mixture. The coarse aggregate particles are coated with a cement and water paste to bond the particles at their contact points. The resulting concrete contains an interconnected pore system allowing storm water to drain through the concrete to the sub-base below.

pH – Chemical symbol for the logarithm of the reciprocal of hydrogen ion concentration in gram atoms per liter, used to express the acidity of alkalinity (base) of a solution on a scale of 0 to 14, where less than 7 represents acidity, and more than 7 alkalinity.

Plastic cement – Special hydraulic cement product manufactured for plaster and stucco application. One or more inorganic plasticizing agents are interground or blended with the cement to increase the workability and molding characteristics of the resultant mortar, plaster, or stucco.

Plastic density – The density of freshly placed foamed concrete: it can be determined by measuring the weight of material in a container of known volume.

Plasticity – The property of freshly mixed cement paste, concrete, mortar, grout, or plaster that determines its workability, resistance to deformation, or ease of molding.

Plasticizer – Admixture that increases the plasticity of portland cement concrete, mortar, grout, or plaster.

Plastic shrinkage cracks – It can happen when moisture evaporates from the slab while the concrete is still "plastic" - that is, wet and workable. This typically happens under extremely hot, dry, and windy conditions, leaving short, parallel cracks (6 inches to 3 feet long) at right angles to the wind. Plastic shrinkage cracks can allow water to enter an overlay or screed, where it may freeze, causing further deterioration. It is best to pour early in the day or wait until conditions improve. You can also use set retarders to slow hydration, and some batch plants may offer ice as a replacement for part of the mix water.
Plastic viscosity – Material characteristic associated with the energy required to sustain a reasonable rate of flow of material.
Popout – Shallow depression in a foam concrete surface resulting from the breaking away of bubbles due to internal pressure.

Portland blast-furnace slag cement – Hydraulic cement consisting of: (1) an intimately inter-ground mixture of portland-cement clinker and granulated blast-furnace slag; (2) an intimate and uniform blend of portland cement and fine granulated blast-furnace slag; or (3) finely ground blast-furnace slag with or without additions.

Portland cement – Calcium silicate hydraulic cement produced by pulverizing Portland cement clinker, and usually containing calcium sulfate and other compounds. (See also Hydraulic cement.)

Portland cement plaster – A combination of Portland cement–based cementitious material(s) and aggregate mixed with a suitable amount of water to form a plastic mass that will adhere to a surface and harden, preserving any form and texture imposed on it while plastic. See also Stucco.

Portland-pozzolan cement – Hydraulic cement consisting of an intimate and uniform blend of Portland cement or Portland blast-furnace slag cement and fine pozzolan produced by intergrinding Portland cement clinker and pozzolan, by blending Portland cement or Portland blast-furnace slag cement and finely divided pozzolan, or a combination of intergrinding and blending, in which the amount of the pozzolan constituent is within specified limits.

Pozzolan - Siliceous or siliceous and aluminous materials, like fly ash or silica fume, which in itself possess little or no cementitious value but which will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.

Precast foam concrete – Foam concrete cast in forms in a controlled environment and allowed to achieve a specified strength prior to placement on location.

Quality control – Actions taken by a producer or contractor to provide control over what is being done and what is being provided so that applicable standards of good practice for the work are followed.

Ready-mixed foam concrete (RMFC) – Foam concrete manufactured at a batching plant for delivery to a location in a fresh state using specialized delivery trucks.

Recycled foam concrete – Hardened foam concrete that has been processed for reuse, usually as an aggregate.

Reinforced foam concrete – Foam concrete to which tensile bearing materials such as steel rods, fibers or metal wires are added for tensile strength.

Relative density – A ratio relating the mass of a volume of material to that of water; also called specific gravity.

Relative humidity – The ratio of the quantity of water vapor actually present in the atmosphere to the amount of water vapor present in a saturated atmosphere at a given temperature, expressed as a percentage.

Retarder – An admixture that delays the setting and hardening of concrete.

Rheology – The study of the flow of matter, primarily in a liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force. Foam concrete’s workability is related to the rheological properties of the fresh cement paste. In foam concrete, before addition of foam, sufficient water should be added (water-cementitious ratio of between 0.4 to 0.5) to ensure the stability of foam. If the mix is dry or only optimum water as that of normal concrete (water-cementitious ratio less than or equal to 0.35) is added, the foam breaks up by the compression of the cement paste.

Scaling – Disintegration and flaking of a hardened foamed concrete surface, frequently due to repeated freeze-thaw cycles and application of deicing chemicals.

Screed – See Overlay.

Sealed curing – Curing through the use of an air and watertight film. (Where curing in water is used, foamed concrete absorbs varying amounts of water.)
Segregation – The separation of foam from the mortar, by various interactions between the components, producing variations in composition and density with pour depth. Segregation of foamed concrete in the fresh state can be detected through foam rising to the surface of the mix (noticeable in a ready-mix truck or in recently poured concrete), or by the formation of a separate paste/sand mortar at the bottom of the mixer (noticeable when mixing).

Set – The degree to which fresh concrete has lost its plasticity and hardened.

Shaping Phase – Part of foam concrete precast plant that consists of moulding, de-moulding, cutting and in-facility transport and handling.
Shear force (in Mixer) – Any real fluids moving along solid boundary will incur a shear stress on that boundary. In the mixer (See Turbine Pan Mixer), when the foam concrete is mixing, it undergoes shear force on the boundary of the mixer when the mixing arm rotates. This helps in faster and uniform mixing of foam with the cement slurry. If this shear force it too high (when the mixer rotates too fast), the bubbles break-up and loss of volume in foam concrete can be observed. If the shear force is too low (when the mixer rotates too slow), the foam will not mix with the slurry and so inconsistent density of foam concrete can be observed.

Shrinkage – Decrease in either length or volume of a material resulting from changes in moisture content, temperature, or chemical changes.

Shrinkage cracks – See Plastic Shrinkage Cracks.

Silica fume – Very fine non-crystalline silica which is a byproduct from the production of silicon and ferrosilicon alloys in an electric arc furnace; used as a pozzolan in foam concrete.

Slag cement – Hydraulic cement consisting mostly of an intimate and uniform blend of ground, granulated blast-furnace slag with or without portland cement or hydrated lime.

Slump – Measure of the consistency of freshly mixed foam concrete, equal to the immediate subsidence of a specimen molded with a standard slump cone.

Slurry –Thin mixture of an insoluble substance, such as portland cement, slag, or sand, with a liquid, such as water.

Soil cement – Mixture of soil and measured amounts of portland cement and water compacted to a high density; primarily used as a base material under pavements; also called cement-stabilized soil.

Sound Insulation – process of soundproofing an enclosed space, such as a room. This type of insulating activity is usually employed when there is a need to keep sound from filtering into or out of the space

Specific gravity – See Relative density.

Stucco – Portland cement plaster and stucco are the same material. The term "stucco” is widely used to describe the cement plaster used for coating exterior surfaces of buildings. However, in some geographical areas, "stucco” refers only to the factory-prepared finish coat mixtures. (See also Portland cement plaster.)

Sulfate attack – Most common form of chemical attack on concrete caused by sulfates in the groundwater or soil manifested by expansion and disintegration of the concrete.

Superplasticizer (plasticizer) – Admixture that increases the flowability of a fresh foam concrete mixture.

Supplementary cementitious (cementing) materials – Cementitious material other than portland cement or blended cement. See also Cementitious material.

Surfactant – A material that affects the properties of an interface between air and liquid such that it provides a thermodynamically stable environment for foam.

Tensile strength – Stress up to which concrete is able to resist cracking under axial tensile loading.

Thermal conductivity – Material characteristic indicative of the ease of heat transfer through a material. It is basically the measurement of insulating capability of the material.

Thermal Insulation – The reduction of heat transfer (the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.

Thixotropic – Chemistry of fluids and gels having a viscosity that decreases when a stress is applied, as when stirred. Certain gels or fluids that are thick (viscous) under static conditions will flow (become thin, less viscous) over time when shaken, agitated, or otherwise stressed

Turbine Pan Mixer – Type of mixer in which the mixing action comes from the rotating blades, which are scientifically designed to push the material from the inside to the outside of the chamber and back again, whilst lifting and folding it, mixing the foam concrete fully in a few revolutions.

Unit Weight – Density of fresh concrete or aggregate, normally determined by weighing a known volume of concrete or aggregate (bulk density of aggregates includes voids between particles).

US Units – Units of length, area, volume, weight, and temperature commonly used in the United States during the 18th to 20th centuries. These include, but are not limited to (1) length-inches, feet, yards, and miles; (2) area-square inches, square feet, square yards, and square miles; (3) volume-cubic inches, cubic feet, cubic yards, gallons, and ounces; (4) weight–pounds and ounces; and (5) temperature-degrees Fahrenheit.

Vapour Curing – Curing with moist air (no less than 95% relative humidity) at atmospheric pressure and a temperature of about 70 degrees C (158 degrees F).

Vibration – High frequency agitation of freshly mixed concrete through mechanical devices, for the purpose of consolidation. Vibration is not needed and should not be done in foamed concrete to avoid segregation.

Volume change – Either an increase or a decrease in volume due to any cause, such as moisture changes, temperature changes, or chemical changes. (See also Creep.)

Viscosity – a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal concept of "thickness". For example, honey has a much higher viscosity than water.

Water absorption – See Absorption.

Water to cementing (cementitious) materials ratio – Ratio of mass of water to mass of cementing materials in concrete, including portland cement, blended cement, hydraulic cement, slag, fly ash, silica fume, calcined clay, meta-kaolin, calcined shale, and rice husk ash.

Water to cement ratio (water-cement ratio and w/c) – Ratio of mass of water to mass of cement in foamed concrete.

Water reducer – Admixture whose properties permit a reduction of water required to produce a concrete mix of a certain slump, reduce water-cement ratio, reduce cement content, or increase slump. Water reducer should not be used in foamed concrete as it affects the stability of the foam.

White portland cement – Cement manufactured from raw materials of low iron content.

Wire Cutting / Sawing – A flexible tool for cutting precast foam concrete elements. It is cost effective and creates less wastage than other alternative methods.

Workability – The property of freshly mixed foamed concrete, mortar, grout, or plaster that determines its working characteristics, that is, the ease with which it can be mixed, placed, molded, and finished. (See also Slump and Consistency.)

Yield – Volume per batch of concrete expressed in cubic meters (cubic feet). Also defined as difference between the target and actual plastic density.

Yield value – Minimum stress required to initiate flow.

Zero-slump concrete – Concrete without measurable slump (see also No-slump concrete).