Gypsum concrete

Last updated
Phosphorgypsum-based concrete with sawdust aggregate Kipsbetoon.jpg
Phosphorgypsum-based concrete with sawdust aggregate

Gypsum concrete is a building material used as a floor underlayment used in wood-frame and concrete construction for fire ratings, sound reduction, radiant heating, and floor leveling. [1] It is a mixture of gypsum plaster, Portland cement, and sand. [1]

Contents

Gypsum concrete is sometimes called gypcrete by construction professionals, [2] [3] as a generic name in common usage (but not in law), but that is an alteration of Gyp-Crete, a Maxxon trademark for its brand of gypsum concrete. [4] Other common brands of gypsum concrete include Levelrock [5] (from US Gypsum) and Firm-Fill. [6]

Composition

US patent 4,444,925 lists the components of Gyp-Crete® as atmospheric calcined gypsum, sand, water, and small amounts of various additives. Additives listed include polyvinyl alcohol, an extender such as sodium citrate or fly ash, a surfactant such as Colloid defoamer 1513 DD made by Colloids, Inc., and a fluidizer based on sodium or potassium derivatives of naphthalene sulfonate formaldehyde condensate. One example mix is shown below. [7]

ComponentAmountApproximate Percentage
Atmospheric calcined gypsum80 lbs24%
Polyvinyl Alcohol0.45 lbs 1 0.14%
Extender22.27 gr 0.00098%
Fluidizer108.8 gr0.0047%
Sand150-200 lbs57%
Water6.5-8.5 gal19%

The purpose of the polyvinyl alcohol is to prevent the surface of the concrete from becoming dusty. While the exact mechanism is not known, it is thought that as the concrete sets, water migrates to the surface, bringing with it fine, dusty particles. When the water evaporates, the dusty particles are deposited on the surface. It is thought that the polyvinyl alcohol prevents the dusty particles from migrating upwards with the water. [7]

The mix is prepared on site using a specialized truck. The truck contains a tank for water, a mixing tank, a holding tank, a pump, and a conveyor for the sand and calcined gypsum. A hopper for the sand and gypsum is mounted externally on the vehicle. [8]

To prepare the mix, the sand and calcined gypsum are added to the hopper and mixed. Most of the required water is added to the mixing tank, then the sand and calcined gypsum are mixed in. Once all the sand and calcined gypsum have been mixed in, the rest of the water is added until the proper consistency is attained. Finally, the additives are mixed in and the whole batch of concrete is moved to the holding tank to be pumped out into the required area via long hoses. A small sample is taken from the batch and set aside so that the set-up time can be observed and adjustments can be made to the amount of additives so that the timing is correct.

Once the mix has been poured, little leveling, if any, is needed. The mix should be smoothed gently with a flat board, such as a 40” 1x4. This helps to concentrate the calcined gypsum at the surface. [8]

Previous formulations

US patent 4,075,374 lists the by-weight formulation as 10 parts pressure calcined gypsum, 38-48 parts sand, and 4-10 parts water. 0.03 to 0.1 parts of a latex emulsion, such as Dow Latex 460, were also added. To prevent foaming, a defoamer such as WEX was added to the latex at a concentration of 0.2%. It was stated that gypsum calcined at atmospheric pressure produced poor results due to it having flaky particles, and that gypsum calcined under a pressure of 15-17 psi produced better results because it had denser, crystalline particles. [8]

Later it was found that this original formulation expanded too much and in some instances floors cracked. US patent 4,159,912 describes changes made so that the expansion was greatly reduced. In that formulation, 5-8% of Portland cement was added to reduce the expansion. The latex emulsion and antifoaming agent were no longer necessary as the concrete was strengthened by the Portland cement. It was found that atmospheric calcined gypsum could be used for the majority of the calcined gypsum if it was ball milled to change the texture. The proportion of sand was also changed, so that it was in a 1:1.3 to 1:3 ratio with the calcined gypsum. This resulted in a runnier mix, but the set up time was not changed. [9]

Advantages and disadvantages

Gypsum concrete is lightweight and fire-resistant. A 1.5-inch slab of gypsum concrete weighs 13 pounds per square foot versus 18 pounds per square foot for regular concrete. [10] Even though gypsum concrete weighs less, it still has the same compressive strength as regular concrete, based on its application as underlayment or top coat flooring. [11] A 7-man work crew can lay 4–6 times as much gypsum concrete in a work day as regular poured Portland cement. This is due to the ease of leveling the very runny gypsum concrete versus normal concrete. In addition, if the wooden subfloor is first coated in a film of latex, the adhesion between the subfloor and the concrete is much better than the adhesion obtained with “normal” concrete. A further benefit is that nails can be driven through the cement into the subfloor without it chipping. [8] The cost of gypsum concrete is comparable to regular concrete, ranging from $1.75 per square foot to $6.00 per square foot. [12] Regular concrete ranges from $2.50 to $4.50 per square foot. [13]

History

In the late 1940s, copper tubing and Portland concrete were used to install radiant heat flooring. The copper tubes would be laid out around the ground and then the Portland concrete could be poured to cover the tubing and make an even base for the floor. However, this practice fell out of use in the United States within 15–20 years because the Portland concrete was too corrosive on the copper tubing. In the 1980s Gypsum concrete again became widely used in the United States for radiant heat flooring as cross-linked polyethylene (PEX) tubing could be used with Gypsum concrete for radiant heat flooring without concern for corrosion on the PEX tubing. [14]

Notes

1. ^ The table in the patent lists the PVA content as 0.45 grains (0.00002%). Later on, it is stated that the PVA should be in a 1:0.005625 ratio with the calcined gypsum. This yields a PVA content of 0.45 lbs (0.16%).

Related Research Articles

<span class="mw-page-title-main">Concrete</span> Composite construction material

Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.

<span class="mw-page-title-main">Portland cement</span> Binder used as basic ingredient of concrete

Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th century by Joseph Aspdin, and is usually made from limestone. It is a fine powder, produced by heating limestone and clay minerals in a kiln to form clinker, grinding the clinker, and adding 2 to 3 percent of gypsum. Several types of portland cement are available. The most common, called ordinary portland cement (OPC), is grey, but white portland cement is also available. Its name is derived from its resemblance to Portland stone which is quarried on the Isle of Portland in Dorset, England. It was named by Joseph Aspdin who obtained a patent for it in 1824. His son William Aspdin is regarded as the inventor of "modern" portland cement due to his developments in the 1840s.

<span class="mw-page-title-main">Floor</span> Walking surface of a room

A floor is the bottom surface of a room or vehicle. Floors vary from simple dirt in a cave to many layered surfaces made with modern technology. Floors may be stone, wood, bamboo, metal or any other material that can support the expected load.

Flooring is the general term for a permanent covering of a floor, or for the work of installing such a floor covering. Floor covering is a term to generically describe any finish material applied over a floor structure to provide a walking surface. Both terms are used interchangeably but floor covering refers more to loose-laid materials.

<span class="mw-page-title-main">Mortar (masonry)</span> Workable paste which hardens to bind building blocks

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 those used between mud bricks, as well as cement mortar. The word "mortar" comes from Old French mortier, "builder's mortar, plaster; bowl for mixing." (13c.).

<span class="mw-page-title-main">Grout</span> Building material

Grout is a dense fluid that hardens used to fill gaps or as reinforcement in existing structures. Grout is generally a mixture of water, cement, and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting sections of precast concrete, filling voids, and sealing joints such as those between tiles. Common uses for grout in the household include filling in tiles of shower floors and kitchen tiles. It is often color tinted when it has to be kept visible and sometimes includes fine gravel when being used to fill large spaces. Unlike other structural pastes such as plaster or joint compound, correctly mixed and applied grout forms a water-resistant seal.

<span class="mw-page-title-main">Building material</span> Material which is used for construction purposes

Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings and other structures, like bridges. 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.

<span class="mw-page-title-main">Plasticizer</span> Substance added to a material to make it softer and more flexible

A plasticizer is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture.

<span class="mw-page-title-main">Efflorescence</span> Migration of a salt to the surface of a porous material

In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or occasionally in another solvent. The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.

Underlay may refer to flooring or roofing materials, bed padding, or a musical notation.

<span class="mw-page-title-main">Autoclaved aerated concrete</span> Lightweight, precast building material

Autoclaved aerated concrete (AAC) is a lightweight, precast, cellular concrete building material, eco-friendly, suitable for producing concrete-like blocks. It is composed of quartz sand, calcined gypsum, lime, portland cement, water and aluminium powder. AAC products are cured under heat and pressure in an autoclave. Developed in the mid-1920s, AAC provides insulation, fire, and mold-resistance. Forms include blocks, wall panels, floor and roof panels, cladding (façade) panels and lintels. It is also an insulator.

<span class="mw-page-title-main">Plasterwork</span> Construction or ornamentation done in plaster or a similar material

Plasterwork is construction or ornamentation done with plaster, such as a layer of plaster on an interior or exterior wall structure, or plaster decorative moldings on ceilings or walls. This is also sometimes called pargeting. The process of creating plasterwork, called plastering or rendering, has been used in building construction for centuries. For the art history of three-dimensional plaster, see stucco.

<span class="mw-page-title-main">Cement board</span> Backing board used in building construction

A cement board is a combination of cement and reinforcing fibers formed into sheets, of varying thickness that are typically used as a tile backing board. Cement board can be nailed or screwed to wood or steel studs to create a substrate for vertical tile and attached horizontally to plywood for tile floors, kitchen counters and backsplashes. It can be used on the exterior of buildings as a base for exterior plaster (stucco) systems and sometimes as the finish system itself.

<span class="mw-page-title-main">Earthen floor</span>

An earthen floor, also called an adobe floor, is a floor made of dirt, raw earth, or other unworked ground materials. It is usually constructed, in modern times, with a mixture of sand, finely chopped straw and clay, mixed to a thickened consistency and spread with a trowel on a sub-surface such as concrete. Once dry, it is then usually saturated with several treatments of a drying oil.

<span class="mw-page-title-main">Wood flooring</span> Product manufactured from timber that is designed for use as flooring

Wood flooring is any product manufactured from timber that is designed for use as flooring, either structural or aesthetic. Wood is a common choice as a flooring material and can come in various styles, colors, cuts, and species. Bamboo flooring is often considered a form of wood flooring, although it is made from bamboo rather than timber.

<span class="mw-page-title-main">Magnesium oxide wallboard</span>

Magnesium oxide, more commonly called magnesia, is a mineral that when used as part of a cement mixture and cast into thin cement panels under proper curing procedures and practices can be used in residential and commercial building construction. Some versions are suitable for general building uses and for applications that require fire resistance, mold and mildew control, as well as sound control applications. Magnesia board has strength and resistance due to very strong bonds between magnesium and oxygen atoms that form magnesium oxide crystals.

<span class="mw-page-title-main">Types of concrete</span> Building material consisting of aggregates cemented by a binder

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

<span class="mw-page-title-main">Self-leveling concrete</span>

Self-leveling concrete has polymer-modified cement that has high flow characteristics and, in contrast to traditional concrete, does not require the addition of excessive amounts of water for placement. Self-leveling concrete is typically used to create a flat and smooth surface with a compressive strength similar to or higher than that of traditional concrete prior to installing interior floor coverings. Self-leveling concrete has increased in popularity as the degree of flatness and smoothness required for floor covering products has increased, with vinyl goods becoming thinner and floor tiles becoming larger, for example.

Limestone Calcined Clay Cement (LC3) is a low-carbon cement developed by the École Polytechnique Fédérale de Lausanne (EPFL), Technology and Action for Rural Advancement (TARA), Indian Institute of Technology (IIT) Delhi, IIT-Bombay, IIT-Madras, and the Central University of Las Villas (Cuba). The cement can reduce carbon dioxide emissions (CO2) related to manufacturing by 30% as compared to ordinary Portland cement. In 2014, the LC3 project received 4 million CHF in Research and Development funding from the Swiss Agency for Development and Cooperation (SDC).

<span class="mw-page-title-main">Nanoconcrete</span>

Nanoconcrete is a form of concrete that contains Portland cement particles that are no greater than 100 μm and particles of silica no greater than 500 μm, which fill voids that would otherwise occur in normal concrete, thereby substantially increasing the material's strength. It is also a product of high-energy mixing (HEM) of conventional cement, sand and water which is a bottom-up approach of nano technology.

References

  1. 1 2 Grady, Joe (2004-06-01). "The finer points of bonding to gypsum concrete underlayment". National Floor Trends. Retrieved 2009-09-21.
  2. Blackstone, Victoria Lee (2021-11-21). "Repairing Cracked and Crumbling Gypcrete Floors". Hunker. Retrieved 2024-03-26.
  3. "Concrete or Gypcrete?". JLC-Online Forums.
  4. "Gyp-Crete® - Maxxon". Maxxon, Inc. Retrieved 2024-03-26.
  5. "Underlayments & Toppings". USG Corporation. Retrieved 2024-03-26.
  6. "FIRM-FILL® Gypsum Concrete floor underlayments". Hacker Industries, Inc. Retrieved 2024-03-26.
  7. 1 2 Feldman, J. G. (1984) U.S. Patent No. 4,444,925 . Washington, DC: U.S. Patent and Trademark Office.
  8. 1 2 3 4 Jorgenson, C. R., et al. (1978) U.S. Patent No. 4,075,374 . Washington, DC: U.S. Patent and Trademark Office.
  9. Jorgenson, R. M. (1979). U.S. Patent No. 4,159,912 . Washington, DC: U.S. Patent and Trademark Office.
  10. Silberstein, Eugene (2004). Residential construction academy: HVAC. Residential Construction Academy Series. Cengage Learning. p. 467. ISBN   978-1-4018-4901-6 . Retrieved 2009-09-21.
  11. "gypsum concrete". Kinzler Construction Services. Archived from the original on 16 September 2013. Retrieved 8 December 2013.
  12. "Archived copy" (PDF). Archived from the original (PDF) on 2013-12-13. Retrieved 2013-12-08.{{cite web}}: CS1 maint: archived copy as title (link)
  13. "Concrete Prices - How Much Does Concrete Cost? - The Concrete Network". www.concretenetwork.com.
  14. "History of Radiant Heat and Gypsum Concrete". www.gypsum-newyork.com.