Working on building or remodeling projects will frequently require you to deal with both cement and gypsum. These materials are mainstays in the field because they each have special qualities that make them indispensable for different kinds of work. Nevertheless, the key to getting the best outcomes is comprehending how they work together.
Although they can occasionally be used together, gypsum and cement aren’t always compatible. Issues such as poor adhesion, decreased strength, or even cracking over time can occasionally result from the mixture. You can avoid future headaches by knowing when and how to combine these materials, or when to avoid them altogether.
We’ll examine the compatibility of gypsum and cement in this post, delving into the science underlying their relationship and providing helpful advice for combining them in your projects. Regardless of your level of experience, this information will assist you in making well-informed decisions that will lead to a successful project.
- Using gypsum for cement production
- Ettringite or "cement bacillus"
- Sad consequences
- Use of a gypsum-cement mixture
- Conclusion
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Using gypsum for cement production
Cement is a material composed of several components, such as:
- clay rocks (loam, clay, clay shale, loess or loess-like loams);
- mineral rocks of the carbonate group (calcites, dolomites, limestone, chalk, marl).
Cement is made up of oxides of aluminum, silicon, magnesium, iron, and calcium, to name a few elements.
Natural materials are ground, dried, and combined in the cement-making process. The mixture is then heated to extremely high temperatures. The final clinker is ground once more, and this time the powder should be fine. Next, different modifiers and additives are added to the material to give it specific qualities.
All varieties of cement mixtures contain gypsum added to slow down the solution’s rapid setting, allowing the ready-to-use material to be transported the necessary distances. Furthermore, gypsum gives the solution more strength. The amount of gypsum that can be added to cement is strictly limited to 3–6% of the total volume.
Ettringite or "cement bacillus"
Is it feasible to combine gypsum and cement to create a universal solution that can be used to level a surface with obvious flaws in a single application and applied well in a thick layer? It is strictly discouraged to add gypsum or alabaster to the cement-sand mixture, even though dishonest private craftsmen use this method.
When cement’s aluminate components are combined with gypsum and water, ettringite, or calcium hydrosulfoaluminate, is the product. Ettringite was once referred to as "cement bacillus" because, as it becomes stronger, the crystals drastically expand in volume and obliterate the cement stone; this process is unavoidable.
In addition to happening during the solution’s preparation, hydration (the addition of water molecules) also happens when moisture is applied to a material, as would be the case when plastering a room with high humidity or outside.
Sad consequences
For rough plastering, dishonest contractors use a cement and gypsum mixture that is easy to apply in thick layers and solidifies fast. This enables you to finish work much more quickly because, in the absence of gypsum, the cement-sand mixture for concrete walls must be applied in layers and allowed to partially dry over several hours.
But, a dense network of microcracks covers such plaster very quickly—within one to five days. If the material is applied indoors to a red brick wall, it can be salvaged with a final coat of cement mortar that is free of facade putty or gypsum. This technology is not going to help with concrete walls.
When gypsum is mixed with cement and sand, the plaster hardens in a matter of minutes. However, because of the continuous chemical reaction, the plaster dries for a longer period of time and is exposed to the "cement bacillus."
Consequently, a layer of gypsum and cement plaster inside a dry room will not deteriorate for up to five years, but it will become unusable after the first winter when applied to the building’s facade. If you use metal mesh for reinforcement, it will rust quickly because the plaster absorbs moisture from the gypsum addition. The plastered wall will start to show signs of rust.
Use of a gypsum-cement mixture
In order to make plastering ceilings and upper slopes easier, gypsum was added to the cement-sand mixture prior to the widespread use of modifiers that can increase the adhesion of the solution. Because of this, the ceilings needed to be repaired on a regular basis because the plaster may start to crumble after a few years.
As long as pozzolanic additives—which include silica in an active form—are added to the mixture, cement and gypsum can be combined to create an effective binder. These materials can be man-made (acid blast furnace slag) or naturally occurring (flask, diatomite, tripoli). Ettringite cannot form because silica lowers the amount of calcium hydroxide present in the mixture.
Concrete is made with gypsum-cement-pozzolanic binder (GPVC). It is crucial to pay close attention to the component proportions when assembling it to reduce the possibility of "cement bacillus" causing damage to the material.
Knowing how gypsum and cement mix together when working with building materials is essential to preventing problems like structural deterioration or cracking. Both materials are frequently used in construction projects, but if they are mixed improperly, they may react differently to moisture and setting times, which can cause issues. The advantages and disadvantages of mixing cement and gypsum will be discussed in this article to assist you in making decisions about your projects.
Conclusion
The percentage ratio of gypsum to cement as well as the addition of silica have an impact on their compatibility. It is advised to use these binders alone, in their purest form, as a starting point for creating different building solutions when creating crafts out of gypsum and cement.
| Property | Gypsum | Cement |
| Setting Time | Quick setting, usually within minutes | Slower setting, takes several hours |
| Strength | Lower strength, more prone to moisture | Higher strength, more durable |
| Compatibility | Can cause expansion and cracking if mixed in large amounts with cement | Compatible in small amounts, but too much gypsum can weaken the mixture |
| Usage | Common in interior finishes like plaster and drywall | Used in construction for structural elements like foundations and walls |
Comprehending the properties and compatibility of gypsum and cement is essential when combining them in construction. Even though both materials are commonly used, their interactions with water and other substances differ, and if they are not handled properly, they may have unanticipated consequences.
Gypsum is perfect for finishing tasks because of its quick setting time. However, the two materials’ performance can be impacted when combined with cement, which hydrates differently and has a slower setting time. The secret is to pay close attention to the ratios and take the project’s particular needs into account.
In order to ensure that the finished mix has the appropriate strength and durability, additives are occasionally used to enhance the compatibility between gypsum and cement. The possibility of chemical reactions that could eventually erode the structure must also be considered.
You can use gypsum and cement together to create a strong and long-lasting result for your construction projects by taking these factors into consideration.
