Before discussing the best concrete densifier, we need to explain what it is and how it works. Concrete densifiers provide extra strength and durability to a concrete floor. Polished concrete also uses densifiers to obtain the right texture. Understanding how the densifier bonds with the concrete and the chemical reaction that strengthens the concrete is essential in deciding on the right densifier to use. Bisley can also assist you in finding the best densifier for you.
How Do Densifiers Work?
Concrete consists of three components—cement, aggregate and water. If the mixture between the three is slightly off, the result is a weakened concrete mixture. Suppose there is too much water added during the hydration process. In that case, the concrete becomes weaker as the excess water evaporates, leaving cracks or large pores. The strength of the concrete is proportional to the porosity.
A densifier works through a chemical reaction between the silicates in the densifier and calcium hydroxide in the cement. The resulting calcium silicate hydrates fill the pores, strengthening and hardening the concrete by up to 50%. The densifier also reacts with another byproduct of the curing process, calcium carbonate, known as free lime or cement dust. In this way, the densifier keeps the concrete surface clean and free of cement dust. Densifiers also work as penetrating sealers, keeping the floor sealed and increasing abrasion resistance.
What Types of Densifier Are Available?
Four types of silicate densifiers are available, and we’ll discuss these.
Sodium silicate is the oldest and cheapest type of densifier. It doesn’t give the same finish as lithium and is not suitable for decorative concrete.
Potassium silicate works well on highly porous concrete floors. Still, it’s best to mix it with a lithium silicate for better bonding and higher strength, also sealing the slab.
Lithium silicate has smaller particles than either sodium or potassium mixes. The smaller particles give a higher penetration in harder concrete slabs and a higher silicate content per volume. The larger silicate particles of sodium or potassium silicates work better with low-strength concrete with more porosity.
Colloidal silica has the smallest particles and reacts better with concrete with admixtures like pozzolan resulting in less free lime. The reaction is also faster than any of the other types. The disadvantage of colloidal silica is that it doesn’t work well with lower strength slabs.
Using a densifier for a polished concrete floor has many benefits. These include sealing and protecting the floor from wear. To find the right one to use can be a little complicated. Generally, the best densifier to use is lithium silicate. A blend of lithium silicate and colloidal silica also works well for high-strength floors. You need to consider several different factors which will influence your final choice. The concrete’s initial strength and porosity and even the age of the slab can play a part. Whenever there is doubt, a lithium silicate should do the job and give you a good finish.
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