An admixture is a chemical additive incorporated into concrete mixtures to improve its natural properties. As a major player in construction, concrete ensures a sturdy and durable building. Understanding admixtures, their purposes, and the effective casting tips may help a construction worker a lot.
To learn more about admixtures, types, and purposes, let's look at the information below.
What Is an Admixture?
A concrete admixture is an additive put into concrete during the mixing. Its purpose is to change the properties of concrete to fit the needs of a particular job. It can also save on construction costs.
In general, admixtures are divided into two types, namely:
- Mineral admixture (additive): mixed in during stirring or casting.
- Chemical admixture: mixed only during stirring.
Concrete Admixture Types
Admixtures have several different types and functions. The types of admixtures are as follows:
1. Accelerating Admixture
An accelerating admixture is an additive that speeds up the bonding and early strength development. It primarily helps shorten the drying time and allows the concrete to reach early strength more quickly.
2. Water-reducing Admixture (WRA)
A water-reducing admixture is an additive that reduces the use of water. It can help the concrete achieve the desired consistency without changing the water-cement ratio.
Adding WRA produces concrete with a higher slump value, making it easier to pour, mix, and compact. This improves the workability of the concrete without reducing the amount of cement.
Therefore, concrete with WRA has greater compressive strength than concrete without WRA. WRA doesn't have much water in the mix, increasing the density and bond strength between cement particles.
In addition, the use of WRA also offers several advantages, such as:
- Improves the workability.
- Reduces water demand.
- Increases the compressive strength.
- Enhances concrete resistance to cracks and shrinkage.
- Improves surface finishing.
WRA is commonly used in various construction applications, such as foundations, floor slabs, beams, columns, structural walls, roads, sidewalks, and stairs.
Read also: The Usage of Reinforced Concrete for Construction
3. Water Reducing and Retarding Admixture (WRRA)
Water-Reducing and Retarding Admixture is a concrete additive that has two main functions. First, WRRA can reduce the water required to achieve the desired concrete consistency. With WRRA, concrete can be made with less water without reducing workability.
Secondly, WRRA can inhibit concrete bonding. This means the concrete will have a longer hardening time for placement and compaction.
There are advantages to using WRRA admixture in concrete, such as increased strength and durability, reduced cracking, and improved workability. In this regard, WRRA is often used in construction projects that require high-quality concrete and long hardening times.
4. Retarding Admixture
Retarding Admixture is the type of additive that slows down the bonding process. It means that concrete takes longer to work, especially in hot weather. Even so, the use of Retarding Admixture offers several advantages, such as:
- Concrete doesn't set too quickly; there is enough time to compact it perfectly, minimizing air voids and increasing the strength.
- Slower-hardening concrete allows well-calculated transport to the casting site, eliminating the issue of the concrete hardening too fast.
- You have more time to pour and shape the concrete according to the design, resulting in a neater and more precise finish.
Read also: Knowing the Importance of Concrete Treatment
5. Water Reducing, High Range Admixture (HRWR)
Water Reducing, High Range Admixture is a concrete additive that can reduce water requirements by up to 12% or more. This water-saving additive will produce concrete with the same consistency, albeit with less quantity, resulting in more durable and stronger concrete.
6. Water-reducing and Accelerating Admixture (WRAA)
Water-reducing and Accelerating Admixture is a concrete additive that helps reduce the water required in the concrete mix without sacrificing its workability. It allows you to achieve the desired concrete mix consistency with less water usage.
WRAA also accelerates the initial bonding and hardening process, allowing the concrete to dry faster and improve its strength for time-constrained construction projects.
7. Water-Reducing, High Range Retarding Admixture (WRHR)
Water Reducing, High Range Retarding Admixture is an additive that reduces water demand and slows down the bonding and hardening process. Compared to ordinary concrete, WRHR uses 12% less water to achieve the same consistency, resulting in more durable concrete.
WRHR uses two elements, a superplasticizer, and a binding time delay. The superplasticizer improves the workability of the concrete, making it easier to pour and compact.
The bond time delay, on the other hand, slows down the process of concrete bonding and hardening. The process gives you extra time to complete the job, especially when space and time are limited.
Purposes of Using Admixture
After knowing concrete admixture types, it's time to understand the purpose of it. Here are the explanations:
1. Accelerator
Accelerators generally contain compounds like NaNO3, CaCl2, and Ca(NO3)2. Their main function is to accelerate the chemical reaction between cement and water in the concrete mix. It evokes a rapid hydration reaction where the cement particles bind together and form a solid structure.
However, the use of chloride (CaCl2) as an accelerator can potentially corrode the reinforcing steel in concrete. Therefore, it's recommended to use nitrate (NaNO3) to avoid such a problem.
2. Water Reduction
Adding admixtures to concrete mixes can help reduce water demand without changing the viscosity of the mix. It can help you achieve higher compressive strengths without diluting the mix.
Additionally, admixtures make it possible to produce concrete with the same compressive strength using a thinner mix. Pouring concrete becomes easier, especially concrete with complex structures or those with limited access.
3. Retarder
Retarders are chemicals that slow down the bonding, allowing the concrete to remain in a workable state during transportation and pouring.
Some commonly used retarders are sugar, sucrose, glucose, citric acid, and tartaric acid. Proper use of retarders can help ensure optimal concrete quality and construction results.
Kesimpulannya, admixture adalah salah satu komponen penting dalam dunia konstruksi agar infrastruktur beton menjadi lebih kuat, kokoh, dan tahan lama. Pemahaman mengenai admixture dan fungsinya merupakan kunci untuk mendapatkan hasil konstruksi yang maksimal.
In conclusion, admixtures are one of the important components of strengthening concrete infrastructure and realizing a sturdier and more durable building. Understanding admixtures and their functions is key to achieving optimal results.
If you are under construction, choosing high-quality cement is an obligation. In this case, Semen Merah Putih continues to innovate and present products equipped with advanced admixture technology.
We are committed to providing optimal construction solutions for professionals and people with our concrete and Portland Composite Cement products to realize stronger and more durable buildings.
Contact us for more information about Semen Merah Putih products and get the best construction solution for your project.
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