You must have come across concrete with cracks in it or seen surfaces that break at the slightest impact. While there are several reasons for their weak structural integrity, one among them is using too much water. Some water is mixed into the cement until it forms into a paste. But, an excessive amount of water causes drying shrinkage, reduction in strength, cracks, scaling, reduced durability, and high permeability. A concrete water reducing admixture effectively reduces the water content while ensuring its consistency remains the same. It also increases the strength of the cement while reducing its consumption. If you have not heard of this product before, here are some things you ought to know about it.
What is a concrete water reducing admixture?
Concrete water reducing admixture is also known as concrete water reducers or water reducing agents. As the name suggests, they work to reduce the quantity of water in the concrete while maintaining its integrity. Construction professionals use two types of admixtures: high-range concrete superplasticizers and ordinary water reducing admixtures. Construction workers use water reducers either before or during the mixing process. However, their results depend on several factors, including the methods used for batching (measuring ingredients for the cement mix) and concreting.
How are they used?
As mentioned earlier, concrete water reducing admixtures will only provide the intended results if you properly use them. Most of the reducing agents are liquid and mixed with the concrete at the construction site. Some reducers, such as expansive agents, pigments, and pumping aids, are utilized in minor quantities after being measured in pre-measured containers. Their effectiveness will also depend on the mixing time, slump, type of cement, quantity, water content, and concrete’s temperature.
Different types of admixtures
You will usually come across four types of water reducing admixtures: SLS (sodium lignosulfonate), SNF (sodium naphthalene sulfonate), CLS (calcium lignosulfonate), and PCE (polycarbonate superplasticizer). Even though they are equally effective, they have varying characteristics and features.
SLS (sodium lignosulfonate)
SLS is the most common water reducing admixture found anywhere, with its primary raw material being lignin. When used in a mortar, it increases the concrete’s strength, fluidity, workability, and efficiency. It reduces the water consumption between 5% to 10% and carries out three functions: venting, dispersion, and initial hydration inhibition.
SNF (sodium naphthalene sulfonate)
Even though SLS is the most popular water reducing agent, SNF was one of the first lowering agents produced by scientists. It has a light yellow to dark brown color, depending on which SNF you choose. It has a high dissolving property and a high dispersion effect on various materials, including cement. Compared to SLS, it has a high water reduction rate of almost 25% and can reduce the amount of concrete used by 10% to 25%. It also contributes significantly to the cement’s strength and workability. A significant advantage is its high adaptability, as it works well with different kinds of cement and concrete admixtures. It is particularly suitable for steamed, fluid, natural curing precast, plasticized, and high-strength concrete.
CLS (calcium lignosulfonate)
CLS is suitable for concrete engineering, involving all things built with concrete. Besides absorbing and dispersing concrete, it also improves its physical properties. Engineers also use it to improve the concrete’s fluidity, workability, and efficiency. It also saves between 8% to 10% of the cement consumption while maintaining its slump and strength.
PCE (polycarbonate superplasticizer)
Polycarbonate superplasticizer is perhaps the most potent admixture you will ever find. It boasts a water reducing rate of about 45% and ensures minimum slump loss. PCE also provides the high workability of the concrete and drastically reduces the amount of shrinkage. It is eco-friendly and does not contain toxic elements such as formaldehyde.
Using a concrete water reducing admixture is the best way to reduce the cement’s water usage while improving its fluidity, workability, durability, and overall performance. However, you must know what type of admixture works best for your project and use one accordingly.