Fireproofing

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Spray gypsum-based plaster fireproofing being installed. Fireproofing.jpg
Spray gypsum-based plaster fireproofing being installed.
Circuit integrity fireproofing of cable trays, using calcium silicate boards. Promat signum tray cladding 1.jpg
Circuit integrity fireproofing of cable trays, using calcium silicate boards.
Damaged spray fireproofing made of rockwool, cement and admixtures at a Toronto car dealership; 28 December 2013. Damaged fibrous spray fireproofing toronto.png
Damaged spray fireproofing made of rockwool, cement and admixtures at a Toronto car dealership; 28 December 2013.

Fireproofing is rendering something (structures, materials, etc.) resistant to fire, or incombustible; or material for use in making anything fire-proof. [1] It is a passive fire protection measure. "Fireproof" or "fireproofing" can be used as a noun, verb or adjective; it may be hyphenated ("fire-proof").

Contents

Applying a certification listed fireproofing system to certain structures allows them to have a fire-resistance rating. The term "fireproofing" may be used in conjunction with standards, as reflected in common North American construction specifications. An item classed as fireproof is resistant in specified circumstances, and may burn or be rendered inoperable by fire exceeding the intensity or duration that it is designed to withstand.

Markets

Applications

History

Asbestos was one material historically used for fireproofing, either on its own, or together with binders such as cement, either in sprayed form or in pressed sheets, or as additives to a variety of materials and products, including fabrics for protective clothing and building materials. Because the material was later proven to cause cancer in the long run, a large removal-and-replacement industry has been established.

Endothermic materials have also been used to a large extent and are still in use today, such as gypsum, concrete and other cementitious products. More highly evolved versions of these are used in aerodynamics, intercontinental ballistic missiles (ICBMs) and re-entry vehicles, such as the space shuttles.

The use of these older materials has been standardised in "old" systems, such as those listed in BS476[ full citation needed ], DIN4102[ full citation needed ] and the National Building Code of Canada.

Fireproofing of structural steel

In a building fire, structural steel loses strength as the temperature increases. In order to maintain the structural integrity of the steel frame, several fireproofing measurements are taken:

Historically, these masonry encasement methods use large amounts of heavy materials, thus greatly increasing the load to the steel frame. Newer materials and methods have been developed to resolve this issue. The following lists both older and newer methods of fireproofing steel beams (i-beams): [5]

Alternative methods

Intumescent spray fireproofing product has expanded. Unitherm2.jpg
Intumescent spray fireproofing product has expanded.

Among the conventional materials, purpose-designed spray fireproofing plasters have become abundantly available the world over. The inorganic methods include:

The industry considers gypsum-based plasters to be "cementitious", even though these contain no Portland, or calcium aluminate cements. Cementitious plasters that contain Portland cement have been traditionally lightened by the use of inorganic lightweight aggregates, such as vermiculite and perlite.

Gypsum plasters have been lightened by using chemical additives to create bubbles that displace solids, thus reducing the bulk density. Also, lightweight polystyrene beads have been mixed into the plasters at the factory in an effort to reduce the density, which generally results in a more effective insulation at a lower cost. The resulting plaster has qualified to the A2[ clarification needed ] combustibility rating as per DIN4102.[ full citation needed ] Fibrous plasters, containing either mineral wool, or ceramic fibres tend to simply entrain more air, thus displacing the heavy fibres. On-site cost reduction efforts, at times purposely contravening the requirements of the certification listing, can further enhance such displacement of solids. This has resulted in architects' specifying the use of on-site testing of proper densities to ensure the products installed meet the certification listings employed for each installed configuration, because excessively light inorganic fireproofing does not provide adequate protection and, thus, could be in violation of the listings.

Proprietary boards and sheets, made of gypsum, calcium silicate, vermiculite, perlite, mechanically-bonded composite boards made of punched sheet-metal and cellulose-reinforced concrete have all been used to clad items for increased fire resistance.

An alternative method to keep building steel below its softening temperature is to use liquid convection cooling in hollow structural members. [7] This method was patented in the 19th century although the first prominent example was 89 years later. [8]

Substandard

Penetrations of structural beams. The installation is incomplete, as the beams are not yet treated with fireproofing. If left as-is, they would collapse in a fire, resulting in openings in the fire separation wall. Beampenseal.jpg
Penetrations of structural beams. The installation is incomplete, as the beams are not yet treated with fireproofing. If left as-is, they would collapse in a fire, resulting in openings in the fire separation wall.

Money can be saved fraudulently by using apparently suitable fireproofing that is not built to the required standard. Such fraud can be prevented when documentation is required and checked to ensure that all installed configurations meet the certification standards. Possible cases include:

Work staging

Spray fireproofing products have not been qualified to the thousands of firestop configurations, so they cannot be installed in conformance of a certification listing. Therefore, firestopping must precede fireproofing. Both need one another. If the structural steel is left without fireproofing, it can damage fire barriers and a building can collapse. If the barriers are not firestopped properly, fire and smoke can spread from one compartment to another.

Traffic tunnels

Traffic tunnels may be traversed by vehicles carrying flammable goods, such as petrol, liquefied petroleum gas and other hydrocarbons, which are known to cause a very rapid temperature rise and high ultimate temperatures in case of a fire (see the hydrocarbon curves in fire-resistance rating). Where hydrocarbon transports are permitted in tunnel construction and operations, accidental fires may occur, resulting in the need for fireproofing of traffic tunnels with concrete linings. Traffic tunnels are not ordinarily equipped with fire suppression means, such as fire sprinkler systems. It is very difficult to control hydrocarbon fires by active fire protection means, and it is expensive to equip an entire tunnel along its whole length for the eventuality of a hydrocarbon fire or a BLEVE.

Concrete exposed to hydrocarbon fires

Concrete cannot, by itself, withstand severe hydrocarbon fires. In the Channel Tunnel that connects the United Kingdom and France, an intense fire broke out and reduced the concrete lining in the undersea tunnel down to about 50 mm.[ citation needed ] In ordinary building fires, concrete typically achieves excellent fire-resistance ratings, unless it is too wet, which can cause it to crack and explode. For unprotected concrete, the sudden endothermic reaction of the hydrates and unbound humidity inside the concrete generates pressure high enough to spall off the concrete, which falls in small pieces on the floor of the tunnel. Humidity probes are inserted into all concrete slabs that undergo fire testing to test for this, even for the less severe building elements curve (DIN4102, ASTM E119, BS476, or ULC-S101). The need for fireproofing was demonstrated, among other fire protection measures, in the European "Eureka" Fire Tunnel Research Project, which gave rise to building codes for the trade to avoid the effects of such fires upon traffic tunnels. Cementitious spray fireproofing must be certification-listed and applied in the field as per that listing, using a hydrocarbon fire test curve such as the one used in UL1709. [9]

Fireproof vaults

Fireproof vaults to protect important paper documents are usually built using concrete or masonry blocks as the primary building material.[ citation needed ] In the event of a fire, the chemically-bound water within the concrete or masonry blocks is forced into the vault chamber as steam, which soaks the paper documents to keep them from igniting.[ citation needed ] This steam also helps keep the temperature inside the vault chamber below the critical 176.7 °C (350 °F) threshold, which is the point at which information on paper documents is destroyed.[ citation needed ] The paper can later be remediated with a freeze drying process if the fire is extinguished before internal temperatures exceed 176.7 °C (350 °F).[ citation needed ] An alternate less expensive and time-consuming construction method is using dry insulating material.[ citation needed ]

This vault construction method is sufficient for paper documents, but the steam generated by concrete and masonry structures will destroy contents that are more sensitive to heat and moisture. For example, information on microfilm is destroyed at 65.5 °C (149.9 °F) (a.k.a. Class 150)[ citation needed ] and magnetic media (such as data tapes) lose data above 51.7 °C (125.1 °F) (a.k.a. Class 125).[ citation needed ] Fireproof vaults built to meet the more stringent Class 125 requirement are called data-rated vaults.[ citation needed ]

All components of fireproof vaults must meet the fire protection rating of the vault itself, including doors, HVAC penetrations and cable penetrations. [10]

See also

Related Research Articles

Vermiculite Hydrous phyllosilicate mineral which expands significantly when heated

Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and commercial furnaces can routinely produce this effect. Vermiculite forms by the weathering or hydrothermal alteration of biotite or phlogopite. Large commercial vermiculite mines currently exist in the United States of America, Russia, South Africa, China, and Brazil.

Mortar (masonry)

Mortar is a workable paste which hardens to bind building blocks such as stones, bricks, and concrete masonry units, to fill and seal the irregular gaps between them, spread the weight of them evenly, and sometimes to add decorative colors or patterns to masonry walls. In its broadest sense, mortar includes pitch, asphalt, and soft mud or clay, as used between mud bricks. The word "mortar" comes from Latin mortarium, meaning crushed.

Plaster General term for a broad range of building and sculpture materials

Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "render" commonly refers to external applications. Another imprecise term used for the material is stucco, which is also often used for plasterwork that is worked in some way to produce relief decoration, rather than flat surfaces.

Drywall Panel made of gypsum, used in interior construction

Drywall is a panel made of calcium sulfate dihydrate (gypsum), with or without additives, typically extruded between thick sheets of facer and backer paper, used in the construction of interior walls and ceilings. The plaster is mixed with fiber, plasticizer, foaming agent, and various additives that can reduce mildew, flammability, and water absorption.

Building material Material which is used for construction purposes

Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand and wood, even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.

This page is a list of construction topics.

Shotcrete

Shotcrete, gunite, or sprayed concrete is concrete or mortar conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique, first used in 1914 invented by engineer, Heidar Rizouki. It is typically reinforced by conventional steel rods, steel mesh, or fibers.

Steel frame Building technique using skeleton frames of vertical steel columns

Steel frame is a building technique with a "skeleton frame" of vertical steel columns and horizontal I-beams, constructed in a rectangular grid to support the floors, roof and walls of a building which are all attached to the frame. The development of this technique made the construction of the skyscraper possible.

Structural steel is a category of steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, sizes, chemical composition, mechanical properties such as strengths, storage practices, etc., are regulated by standards in most industrialized countries.

An intumescent is a substance that swells as a result of heat exposure, thus leading to an increase in volume and decrease in density. Intumescents are typically used in passive fire protection and require listing, approval, and compliance in their installed configurations in order to comply with the national building codes and laws.

Precast concrete

Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, cast-in-place concrete is poured into site-specific forms and cured on site. Precast stone is distinguished from precast concrete using a fine aggregate in the mixture, so the final product approaches the appearance of naturally occurring rock or stone. More recently expanded polystyrene is being used as the cores to precast wall panels. This is lightweight and has better thermal insulation.

A firestop or fire-stopping is a form of passive fire protection that is used to seal around openings and between joints in a fire-resistance-rated wall or floor assembly. Firestops are designed to maintain the fireproofing of a wall or floor assembly allowing it to impede the spread of fire and smoke.

Passive fire protection

Passive fire protection (PFP) is an integral component of the components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, such as by fire-resistant walls, floors, and doors. PFP systems must comply with the associated listing and approval use and compliance in order to provide the effectiveness expected by building codes.

A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for purpose.

Fiber-reinforced concrete (FRC) is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers – each of which lend varying properties to the concrete. In addition, the character of fiber-reinforced concrete changes with varying concretes, fiber materials, geometries, distribution, orientation, and densities.

A building joint is a junction where building elements meet without applying a static load from one element to another. When one or more of these vertical or horizontal elements that meet are required by the local building code to have a fire-resistance rating, the resulting opening that makes up the joint must be firestopped in order to restore the required compartmentalisation.

History of structural engineering

The history of structural engineering dates back to at least 2700 BC when the step pyramid for Pharaoh Djoser was built by Imhotep, the first architect in history known by name. Pyramids were the most common major structures built by ancient civilizations because it is a structural form which is inherently stable and can be almost infinitely scaled.

Types of concrete concrete technology used in building construction

Concrete is produced in a variety of compositions, finishes and performance characteristics to meet a wide range of needs.

Penetrant (mechanical, electrical, or structural)

Penetrants, or penetrating items, are the mechanical, electrical or structural items that pass through an opening in a wall or floor, such as pipes, electrical conduits, ducting, electrical cables and cable trays, or structural steel beams and columns. When these items pierce a wall or floor assembly, they create a space between the penetrant and the surrounding structure, which can become an avenue for the spread of fire between rooms or floors. Modern building codes generally require a service penetration firestop to seal the openings around penetrants, in order to restore the fire-resistance rating of the parent assembly.

Structural clay tile

Structural clay tile describes a category of burned-clay building materials used to construct roofing, walls, and flooring for structural and non-structural purposes, especially in fireproofing applications. Also called building tile, structural terra cotta, hollow tile, and clay block, the material is an extruded clay shape with substantial depth that allows it to be laid in the same manner as other clay or concrete masonry. In North America it was chiefly used during the late 19th and early 20th centuries, reaching peak popularity at the turn of the century and declining around the 1950s. Structural clay tile grew in popularity in the end of the nineteenth-century because it could be constructed faster, was lighter, and required simpler flat falsework than earlier brick vaulting construction. Each unit is generally made of clay or terra-cotta with hollow cavities, or cells, inside it. The material is commonly used in floor arches, fireproofing, partition walls, and furring. It continues to be used in Europe to build fire-resistant walls and partitions. In North America the material has largely been replaced by concrete masonry units.

References

  1. Oxford English Dictionary 2nd ed
  2. Allen 2009, p. 885
  3. Allen, Edward; Iano, Joseph (2009). Fundamentals of building construction : materials and methods. Iano, Joseph. (5th ed.). Hoboken, N.J.: Wiley. p. 884. ISBN   9780470074688. OCLC   209788024.
  4. Allen 2009, p. 878
  5. 1 2 3 Allen 2009, p. 459
  6. 1 2 3 4 5 6 7 8 Allen 2009, p. 460 - 463
  7. Fisher, Arthur (May 1970). Water-Filled Columns Keep Building Frames Cool in Fires. Popular Science. Retrieved 27 Jan 2012.
  8. see U.S. Steel Tower
  9. National Fire Protection Association 232 "Protection of Records"