The cement manufacturing industry is the major consumer of gypsum, which is added to the clinker in a percentage of 3–5 wt%,.
- 1 How much gypsum should I use?
- 2 What is the minimum thickness of gypsum plaster?
- 3 Can we eat gypsum?
- 4 Is gypsum as strong as cement?
What is the percentage of gypsum?
Gypsum: an old product with a new use Gypsum is calcium sulfate (CaSO 4 ). Refined gypsum in the anhydrite form (no water) is 29.4 percent calcium (Ca) and 23.5 percent sulfur (S). Usually, gypsum has water associated in the molecular structure (CaSO 4 ·2H2O) and is approximately 23.3 percent Ca and 18.5 percent S (plaster of paris).
Gypsum fertilizer usually has other impurities so grades are approximately 22 percent Ca and 17 percent S. Gypsum is sparingly soluble (the reason wallboard gets soft but does not immediately dissolve when it gets wet, at least if only damp occasionally). Gypsum is the neutral salt of a strong acid and strong base and does not increase or decrease acidity.
Dissolving gypsum in water or soil results in the following reaction: CaSO 4 ·2H 2 O = Ca 2 + + SO 4 2- + 2H 2 O. It adds calcium ions (Ca 2 +) and sulfate ions (SO 4 2-), but does not add or take away hydrogen ions (H+). Therefore, it does not act as a liming or acidifying material.
How much gypsum is added in OPC?
Gypsum is added 3% to 4% in ordinary portland cement and reduced by 2.5% in Quick setting cement. UPPSC AE Final Result Out on 1st December 2022.
How much gypsum should I use?
General Application Rates – If you decide that your garden will benefit from gypsum, you can plan on applying about 20 pounds for every 100 square feet of garden space. Lawns require much less, about four pounds per 100 feet. The best time of year to apply gypsum is in the fall.
- However, the majority of gardeners lay it down in the spring before planting.
- Gypsum should be added to the garden at least once a year.
- While also, keeping in mind that it will take several years to build up your soil levels to an amount that will make a big difference.
- Additionally, keep in mind that gypsum doesn’t supply many plant nutrients.
Thus, a healthy garden will still need a generous dose of organic fertilizer.
How much gypsum should I add?
How Much Gypsum to Add to Soil? It is important to know how much gypsum to add to your soil to prevent the mineral from removing any vital elements. For example, for a home garden, it is best to spread approximately 40 pounds of gypsum per one thousand square feet of soil area.
What is the minimum thickness of gypsum plaster?
Plastering Solutions – Cement Plaster vs. Gypsum Plaster Author: Admin Date:08/06/2018 Plastering is associate ancient building technique to cover the exposed surface and provides protecting surface against penetration of rain, alternative atmospheric agencies like vermin and improves the looks of the structure and provides decorative effects. Cement Plaster:
Cement plaster is a homogeneous mixture of Portland cement and sand with water. The sand and cement are mixed at the site in different ratios.
It is used on both internal as well as external surfaces.
The thickness of cement plaster should not be less than 10 mm. The Thickness of cement plaster may vary and it depends on the surfaces to be covered and its plumb and texture.
It has more or less same thermal conductivity as gypsum.
Cement plaster is basically weak in tension and flexural strength and hence prone to cracking. Most of cracking happens due to shrinkage, which is quite common.
Cement plaster is not 100 % permeable to water vapor. In the bathroom or in the kitchen it will lead to the formation of condensation on the walls and as consequences mould, fungi will develop and also floor will become slippery due to moisture.
Pre-Curing and Post-Curing are necessary for cement sand plaster.
Cement plaster needs an enormous amount of water during its curing period. The site becomes dirty due to it and also needs more time for works.
Cement plaster up to 200 to 300 C acts as refractory material and resists fire but later it becomes brittle and cracks and falls and loses bond with wall.
It has more or less same acoustics properties.
It cannot be applied on the smooth surface.
Cement plaster is not a rust inhibitor.
The mixture of the sand and cement is to be done on site in different ratios.
After sand cement plaster, POP punning is required for the better and leveled surface finish.
The space looks smaller and unattractive as it is dark grey in color.
Development of shrinkage cracks is quite frequent in cement plaster.
Density of cement plaster is higher than gypsum plaster; hence the load on the building is increased as compared to gypsum plaster and needs water to attain strength.
Cement plaster is comparative gives a rough finish.
Minimum 24hr. of interval between coats of interior Portland cement plaster. After a 48-hours period finished coat plaster may be applied to interior cement base coats.
Percentage of wastage is higher during application.
The application of cement plaster is time-consuming process hence increases the project cost.
However, per square feet cost of cement plaster is less than gypsum plaster due to higher cost of gypsum.
In gypsum plaster, gypsum is used as a binding material instead of Portland cement. It does not need sand and is ready to use.
Can be used only in internal walls and ceilings. And it cannot be used in wet areas like a toilet, bath, kitchen, wash area, etc.
The thickness of undercoat of gypsum plasters are generally 11 mm thick for walls and 8 mm thick for ceiling and finish coat plaster is 2 mm thick.
Gypsum plaster has low thermal conductivity and good thermal properties and ensures energy and power saving.
Gypsum plasters exhibit high tensile and flexural strength. They are less prone to cracking.
Gypsum plaster is not affected by insects and does not nourish mould growth of fungal. They pose no health hazards and are therefore frequently specified in hospitals and clinics.
Gypsum plaster requires no water curing and should be permitted to dry out as quickly as possible. Gypsum plaster requires no curing which saves up on all that water.
Gypsum is non-combustible and contains a high content of crystal water. In the event of a fire, it acts as a barrier and will protect the block work, concrete and steel.
Gypsum as a binder is used in the manufacture of acoustic tiles and plasters, a contributory factor to the absorption of air borne sounds.
Due to the nature and structure of gypsum, it exhibits excellent bonding properties hence is applied in a single coat on RCC ceilings, internal bare-brick walls, AAC blocks and concrete columns.
It can be applied on smooth as well rough surfaces.
Gypsum Plaster is the perfect rust preventive agent and also inhibits corrosion of electric metal fittings, pipes etc. Metal lathing embedded in gypsum plaster will not corrode or rust and serves durable and long life.
Gypsum plaster is pre-mixed and available in easy to handle bags. Only addition of water is required. A single coat application is resulting in less wastage of time, labour and material.
Gypsum plaster provides a smooth interior finish for ceiling, walls and is ideal back ground for good quality paints and wallpaper finishes.
The room space looks large and beautiful as gypsum plaster is pure white in color.
Gypsum plasters do not shrink like cement during the drying out and hardening process.
Gypsum plaster is light in weight and total strength is achieved in air.
Gypsum plaster is easily workable for excellent finish. It gives smooth finish compatible to receive all type of paints. Various surface textures and surface hardness can be obtained.
Setting time of gypsum plaster can be controlled. Time between two successive coats is very small.
Percentage of wastage is nominal during application.
The application of gypsum plaster is time saving process, thus decreases the project cost.
Gypsum plaster is costlier than cement plaster for same thickness.
Gypsum plaster is advisable when compared to cement plaster as it gives better-desired finish and performance. Gypsum plaster is also advisable where river sand/natural sand is not easily available for the construction. Good quality gypsum is not available everywhere and hence costly. : Plastering Solutions – Cement Plaster vs. Gypsum Plaster
What Colour is gypsum?
Gypsum is a pale, gray, veiled white with a red undertone.
Can gypsum replace cement?
As Gypsum has proved itself as a pozzolonic material it is used for replacement of cement in the concrete mix.
What is the chemical name of gypsum?
18.104.22.168 Setting Reaction of Calcium Sulfate – Gypsum is the name given to a mineral categorized as calcium sulfate mineral, and its chemical formula is calcium sulfate dihydrate, CaSO 4 ⋅ 2H 2 O. However, a broader definition includes all the calcium sulfates, including calcium sulfate hemihydrate, CaSO 4 ⋅ 0.5H 2 O, which is known as plaster or plaster of Paris (POP). Figure 6, Polymorphism of calcium sulfate. Calcium sulfate dihydrate and II-type calcium sulfate anhydrous, which has no solubility in water, can be taken as ore. When calcium sulfate dihydrate is heated, β- or α-form calcium sulfate hemihydrates are formed, as shown in eqn,
- I CaSO 4 ⋅ 2 H 2 O → CaSO 4 ⋅ 0.5 H 2 O + 1.5 H 2 O The β-form calcium sulfate hemihydrates, whose density is 2.64 g cm −3, are formed when CaSO 4 ⋅ 2H 2 O is heated dry at round 120–130 °C.
- In contrast, the α-form, whose density is 2.76 g cm −3, are formed when CaSO 4 ⋅ 2H 2 O is heated hydrothermally at round 130 °C.
At 190 °C, CaSO 4 ⋅ 0.5H 2 O loses water and becomes calcium sulfate anhydrous, III-type α-CaSO 4 and β-CaSO 4, Calcium sulfate anhydrous taken as natural ore is stable. However, the calcium sulfate anhydrous formed by heating at 190 °C transforms to its hemihydrates easily by reacting with the humidity in the atmosphere.
Further heating to 400 °C results in nonsoluble calcium sulfate anhydrous. The setting and hardening reaction of calcium sulfate hemihydrate is a phase transformation from calcium sulfate hemihydrates to calcium sulfate dihydrate, and is known as a dissolution–precipitation reaction, as shown in eqns and,
II αCaSO 4 ⋅ 0.5 H 2 O+ 1.5 H 2 O → CaSO 4 ⋅ 2 H 2 O + 17.2 J mol − 1 III βCaSO 4 ⋅ 0.5 H 2 O + 1.5 H 2 O → CaSO 4 ⋅ 2 H 2 O + 19.3 J mol − 1 In this exothermal dissolution–precipitation reaction, the solubility of CaSO 4 ⋅ 0.5H 2 O and CaSO 4 ⋅ 2H 2 O plays a very important role ( Figure 7 ). Figure 7, Solubility of α- and β-calcium sulfate hemihydrate and calcium sulfate dihydrate against temperature. For example, the solubility of α-form calcium sulfate hemihydrate, CaSO 4 ⋅ 0.5H 2 O, and calcium sulfate dihydrate, CaSO 4 ⋅ 2H 2 O, is 0.92 g/100 ml and 0.2 g/100 ml at 20 °C as shown in eqns and, respectively.
- Therefore, when CaSO 4 ⋅ 0.5H 2 O is mixed with water, Ca 2+ and SO 4 2 − ions, which are equivalent to 0.92 g CaSO 4 ⋅ 0.5H 2 O, are formed in 100 ml solution.
- If CaSO 4 ⋅ 2H 2 O does not exist, the solution will be stable, that is, at equilibrium with CaSO 4 ⋅ 0.5H 2 O, and no further reaction occurs.
However, CaSO 4 ⋅ 2H 2 O exists, and its solubility is 0.2 g/100 ml at 20 °C, as shown in Figure 7, IV CaSO 4 ⋅ 0.5 H 2 O ⇄ Ca 2 + + SO 4 2 − + 0.5 H 2 O V CaSO 4 ⋅ 2 H 2 O ⇄ Ca 2 + + SO 4 2 − + 2 H 2 O This means that the solution that is at equilibrium with CaSO 4 ⋅ 0.5H 2 O is supersaturated with respect to CaSO 4 ⋅ 2H 2 O.
- Therefore, Ca 2+ and SO 4 2 −, which are equivalent to ∼0.72 g CaSO 4 ⋅ 2H 2 O, will precipitate as CaSO 4 ⋅ 2H 2 O crystals.
- The precipitation of Ca 2+ and SO 4 2 − ions from the liquid results in the undersaturation of the solution to CaSO 4 ⋅ 0.5H 2 O, thus leading to a further dissolution of CaSO 4 ⋅ 0.5H 2 O.
In the actual reaction, the concentration of Ca 2+ and SO 4 2 − ions does not vary with time and is relatively constant. Anyway, this dissolution–precipitation reaction forms rod-like CaSO 4 ⋅ 2H 2 O crystals, and the interlocking of these rod-like CaSO 4 ⋅ 2H 2 O crystals forms the set mass, as shown in Figure 8, Figure 8, Scanning electron microscopic image of set calcium sulfate hemihydrate. As shown in Figure 7, the difference between the solubility of CaSO 4 ⋅ 0.5H 2 O and CaSO 4 ⋅ 2H 2 O becomes smaller with the increase in temperature. As a result of the smaller difference, CaSO 4 ⋅ 0.5H 2 O does not set at high temperatures of around 100 °C.
- Due to the crystal growth of calcium sulfate dihydrate, shown in Figure 8, the plaster exhibits setting expansion, as shown in Figure 9, where setting expansion and absorption expansion are plotted against time after the mixing.
- Setting expansion is caused by the crystal growth of calcium sulfate dihydrate, as explained earlier.
On the other hand, absorption expansion or hygroscopic expansion is observed when the plaster is immersed in aqueous solution during its setting process. The different expansion is explained by the surface tension of water on the crystal surface. When the plaster is allowed to set in the atmosphere, the surrounding water is reduced, and the growing gypsum crystals impinge on the surface of the remaining water, whose surface tension inhibits outward crystal growth. Figure 9, Example of setting and absorption expansion of plaster. In contrast, if water is supplied during the setting process, the gypsum crystals can grow further. For absorption expansion, the additional water provided must be presented to the plaster during the setting.
This is significantly different than the addition of more water to the premixed plaster. The setting reaction of the plaster is affected by the additives or by contamination. Some proteins and biological macromolecules are known to retard the setting reaction by preventing full hydration of the hemihydrate, inhibiting seed crystal formation, and forming complexes with the seed crystals.20,22,24 Contamination of the calcium sulfate with proteins may increase the setting time to 200 min.25 Also, the set plaster dissolves more quickly in the presence of blood.
To minimize the setting retardation and accelerated dissolution, setting accelerators such as NaCl, Na 2 SO 4, KCl, and K 2 SO 4 are used. However, preset calcium sulfate should be used if the setting cannot be guaranteed. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780080552941000295
Can we eat gypsum?
As a soil additive to improve crops such as alfalfa, corn, cotton, wheat, and peanuts. Gypsum is used in brewing beer, and to control the tartness and clarity of wine. As an ingredient in canned vegetables, flour, white bread, ice cream, blue cheese, and other foods. “> A primary ingredient in toothpaste. “> To simulate snow storms in movies and television programs. “>
A non-toxic mineral, gypsum can be helpful to humans, animals, plant life, and the environment. While the majority of gypsum produced in North America is used to manufacture gypsum panel products or building plasters, gypsum can also be used:
As a soil additive (sometimes called land plaster) to improve the soil’s workability and receptivity to moisture, and to overcome the corrosive effect of alkalinity. Gypsum specifically benefits such crops as alfalfa, corn, cotton, wheat, and peanuts where substantial amounts of sulfate sulphur are required. As an additive to turbid water, particularly ponds, to settle dirt and clay particles without injuring aquatic life. As a food additive. Gypsum (calcium sulfate) is recognized as acceptable for human consumption by the U.S. Food and Drug Administration for use as a dietary source of calcium, to condition water used in brewing beer, to control the tartness and clarity of wine, and as an ingredient in canned vegetables, flour, white bread, ice cream, blue cheese, and other foods. As a color additive for drugs and cosmetics. A primary ingredient in toothpaste.
Historically, gypsum played an important role in the entertainment industry. Before the era of computers and high-tech special effects, film and television producers would drop “showers” of gypsum in front of the cameras to simulate snow.
What is the hardness of gypsum?
The Mohs’ hardness scale was developed in 1822 by Frederich Mohs. This scale is a chart of relative hardness of the various minerals (1 – softest to 10 – hardest). Since hardness depends upon the crystallographic direction (ultimately on the strength of the bonds between atoms in a crystal), there can be variations in hardness depending upon the direction in which one measures this property.
One of the most striking examples of this is kyanite, which has a hardness of 5.5 parallel to the 1 direction ( c -axis), while it has a hardness of 7.0 parallel to the 100 direction ( a -axis). Talc (1), the softest mineral on the Mohs scale has a hardness greater than gypsum (2) in the direction that is perpendicular to the cleavage.
Diamonds (10) also show a variation in hardness (the octahedral faces are harder than the cube faces). For further information see articles from the American Mineralogist on microhardness, the Knoop tester, and diamonds, Mohs’ hardness is a measure of the relative hardness and resistance to scratching between minerals.
Other hardness scales rely on the ability to create an indentation into the tested mineral (such as the Rockwell, Vickers, and Brinell hardness – these are used mainly to determine hardness in metals and metal alloys). The scratch hardness is related to the breaking of the chemical bonds in the material, creation of microfractures on the surface, or displacing atoms (in metals) of the mineral.
Generally, minerals with covalent bonds are the hardest while minerals with ionic, metallic, or van der Waals bonding are much softer. When doing the tests of the minerals it is necessary to determine which mineral was scratched. The powder can be rubbed or blown off and surface scratches can usually be felt by running the fingernail over the surface.
One can also get a relative feel for the hardness difference between two minerals. For instance quartz will be able to scratch calcite with much greater ease than you can scratch calcite with fluorite. One must also use enough force to create the scratch (if you don’t use enough force even diamond will not be able to scratch quartz – this is an area where practice is important).
You also have to be careful to test the material that you think you are testing and not some small inclusion in the sample. This is where using a small hand lens can be very useful to determine if the test area is homogenous.
|Diamond||10||Zaire 1 cm.14 carats|
|Corundum||9||variety ruby, India 6 cm.|
|Topaz||8||Mursinsk, Russia, 5cm across Seaman Museum specimen|
|Quartz||7||variety amethyst, Guerro, Mexico 16 cm.|
|Orthoclase||6||Orthoclase (white) on quartz, Baveno, Italy Orthoclase crystal is 3 cm tall. Seaman museum specimen.|
|Apatite||5||Durango, Mexico. Crystal is 7.5 cm. tall. Seaman museum specimen.|
|Fluorite||4||Elmwood mine, Tennessee 2.5 cm. (note phantom)|
|Calcite||3||Elmwood Mine, Tennessee 8 cm. (twinned)|
|Gypsum||2||Wyoming 12 cm. Note “fishtail” twin on left|
|Talc||1||Rope’s Gold Mine, Michigan (green) 4 cm. across talc mass|
Why is hardness important? The effects of high hardness are important in many fields. Abrasives are used to form and polish many substances. Diamonds are an important mineral component in cutting tools for the manufacturing of metals and other substances, forming dies for the drawing of wires, and for cutting cores in oil wells and mineral exploration.
- Emery – a variety of corundum, is used in many abrasive products that do not require the hardness (or expense) of diamond tools.
- Garnets were used as an abrasive in sandpaper.
- Talc is an extremely soft mineral that has been used in bath powders (talcum powder).
- Mineral harness is also important in sedimentary rocks.
Harder minerals tend to be able to travel longer distances down river systems. Quartz can often undergo several cycles of erosion, transportation and lithification ( change of sediments to rock). Zircons are persistent minerals in the environment and can often tell geologists the types of rock that were the original source rock for metamorphic or sedimentary rocks. Niagara Falls, New York
Is gypsum as strong as cement?
What Benefits Does Plastering Offer? – Plastering offers multiple benefits to walls and ceilings. Both external and internal plastering is essential to lend the required strength and support. Plaster serves as a protective cover on stones and bricks and extends durability to ceilings as well as walls.
- Plastered walls are also protected against climate damage including rain, heat, and humidity.
- It is also easier to repair plastered walls in case if they get damaged in any way! Plastering also helps the levelling of the surfaces, and such walls are also finish-friendly as different finishes can be applied to it to enhance its look and appeal.
Your home could also be less polluted as plastered walls tend to attract and create less dust. Different materials are used for plastering, but the most commonly used plastering materials are cement and gypsum, The answer to which material is best for your home will depend on an analysis of the advantages and disadvantages of each. Cement plaster is made by mixing cement, sand, and water, usually, the ratio of cement and sand is 1:4. The thickness of plaster depends on the surface to be plastered and could be around 12 to 20 milliliters. Sometimes, plasticizers are also mixed in the plaster to protect walls from parasites.
- The best thing about cement plaster is that it can be used both for external as well as internal plastering.
- Cement plaster is the best bet when it comes to plastering exterior walls because it is moisture-resistant and will protect the wall against climate changes as well as environmental pollution.
Moreover the durability factor in cement plaster makes it the ideal choice for internal plastering too. Cement strengthens the walls, especially the hollow-concrete blocks. Also, when it comes to electrical fittings and wiring, cement plaster will not develop cracks and offer a sturdy base for drilling and holding it together.
Cons: The surface after cement plastering tends to look uneven and rough. Hence, it will require an additional process to achieve a smooth finish. Often, POP is applied to the plastered walls to give it a smooth finish. Cement-plastered walls and ceilings require water curing for about a week. Without the process, the surface will not gain strength and may soon develop cracks.
Over time, surfaces may even shrink causing hairline cracks. It is a ready-made plaster and is used after mixing it with water. It is white in colour and powder in form. The thickness varies for wall and ceiling plastering, for the wall it could be around 11 millimeters while for the ceiling, the thickness is just about 8 millimeters.
Gypsum plaster is also heated at specific temperatures to get different types of plasters. Pros: Unlike cement plaster, gypsum plaster does not require punning or any special process to achieve smoothness on the surface. Thus, it saves costs and time. Cement plaster has to be prepared manually but gypsum plaster is available in ready form.
Hence, preparing it is much easier and convenient. Gypsum plaster does not expand or contract with time; hence shrinkage does not happen. Gypsum plaster is extracted from gypsum rock and later dehydrated to obtain the powder form. The biggest advantage is that gypsum plaster can be recycled and reused many times.
- It saves a lot of time because it dries very fast and you can start your painting work within 72 hours of plastering.
- A great benefit of gypsum-plastered walls is that its thermal conductivity is low and hence is adept at keeping your home cool during summers and warm during winters.
- The high resistant nature to fire and mould protects your walls and ceilings for a long time.
- The main disadvantage of gypsum plastering is that it is suitable only for interior plastering.
- It is not moisture-resistant and hence unsuitable for damp areas such as bathrooms, basements, balconies or kitchens.
One needs to be careful when working with gypsum plaster when the plastering and painting work is completed. Being relatively soft in its property, gypsum plaster tends to break or develop cracks easily when drilling into the walls for electricals, wall hangings, wiring, etc. Both have pros and cons, but when it comes to exterior plastering, nothing beats cement plaster. For interior plastering, gypsum plaster is often preferred especially as it dries quicker and is easy to prepare and level. There are also other reasons for choosing gypsum plaster.
It saves time and cost because it does not require water curing, unlike cement plaster. Depending upon the place of construction, water may not be available at all or may be very expensive. Gypsum plaster also dries faster, so there is no waiting time required to start painting and other work. Since gypsum plastered walls have a good finish, you needn’t spend additional time and money on extra smoothening of the finishes.
The Role of Gypsum in Cement and its Effects in Construction
Also, gypsum is often preferred by developers as part of the interior plastering as it saves cost, Cement plaster has to be prepared with the right ratio of sand and cement, any ingredient in excess and you will not be able to get the right plaster texture.
When you use gypsum plaster, all you have to do is mix it with enough water. Gypsum plaster is also a green product as it can be recycled and reused. At times walls plastered with cement may develop cracks or shrinkage after a few months, but gypsum plaster remains fault-free for a longer time. It doesn’t mean it is stronger and durable than cement.
When a comparison is made, gypsum plaster seems to earn more favourable points. However, when it purely comes to durability, cement plaster is better in the long run, If you are looking for expert advice on how to get your home done up, get in touch with Hipcouch today! Get Interior Designing Cost Calculators Interior Design Tips, Guides to help you make Smart Choices for your Interiors & Decor without filling up your email inbox! : Gypsum Plaster vs Sand Cement Plaster: What Are They & Which One’s The Better Bet?
What are two uses of gypsum?
Uses in construction – Gypsum has multiple common uses and has been considered the “” in construction because of its many uses in the industry. Gypsum is widely used to manufacture wallboards that are used to cover walls and ceilings. It’s also used to make plaster which is used in the construction of homes as well as mixed into a patching compound for wallboard repair.
What percentage of gypsum should be added to the cement clinker?
The cement manufacturing industry is the major consumer of gypsum, which is added to the clinker in a percentage of 3–5 wt%,.