Causes of Concrete efflorescences

What Is Efflorescence In Concrete | Concrete Efflorescence | What Causes Efflorescence7 min read

What Is Efflorescence In Concrete?

Efflorescence in concrete surface means the whitish or grayish tint-colored powder is shown in the concrete surface. It consists of crystalline salt and deposits on the concrete and remains on the surface of the concrete after evaporation of water. In addition, special care is required for treating concrete efflorescence.

What Is Efflorescence In Concrete
Concrete Effloresces

The following various types of salts are present in the concrete efflorescence,

  • Calcium Sulphate: Calcium Sulphate is a common salt that is a source of brick.
  • Sodium Sulphate: Sodium Sulphate is often seen in brick cement reactions.
  • Potassium Sulphate: Potassium Sulphate salts are noticeably seen in many cement brick reactions.
  • Calcium Carbonate: It is discovered in mortar or baking concrete.
  • Sodium Carbonate: It is frequently seen in cement mortar.
  • Potassium Carbonate: It is generally found in mortar like sodium carbonate.
  • Vanadyl Sulphate: This salt is found in brick.
  • Manganese Oxide: Manganese oxide is often visible in brick.

Read More: Sand Finish Concrete | 10 Types of Sand Finish Concrete | Top Concrete Sand Finish | Sand Washed Concrete


Why does Efflorescence occur on concrete surfaces?

The following are the Causes of Concrete efflorescence;

Generally, one or more ingredients of concrete may have salts contained. A High water-cement ratio, makes concrete more porous and that allows movement of salt solution and water. An inadequate amount of curing may be leaving the product un-hydrated near the surface of the concrete.

Moisture is allowed salts and transported to the concrete surface where they accumulate as water evaporation. Exposure to rainwater and other water sources.

The evaporation of water rate is slow then salts are permeating on the concrete surface. More variability of concrete during making concrete, curing concrete, and compaction of concrete in that water can permeate more easily through the concrete.


How to Repair concrete surfaces affected by efflorescence?


Method-1- By Using Hard Brush

In concrete surface deposits, soluble slats or concrete efflorescence can be removed easily with a hard stiff bristle broom or brush. But in some cases, the result is not satisfactory dry brushing then, scrub with clean water and lightly rinse out the surface of the concrete.

An insoluble salt deposited such as white in color, hard, scaly, or crusted cannot be removed by lightly cleaning water so that used a high-pressure water jet for cleaning efflorescence.                                                                           


Method-2-By Using Dilute acid Solution

This dilute acid solution application is more effective in most cases and in some cases, this may be the only way as discussed below,

Extreme care is required for handling chemical solutions, when diluting hydrochloric acid always add the acid to the water never the reverse. Used only diluted chemical solution or acid to clean the surface of the concrete.

The recommended proportion is 1:20 1 part of hydrochloric acid to 20 parts of water. Alwayssurface is making saturated using water before applying this diluted acid solution.

When before applying the solution, ensure that the surface is moist but without any fee water being present.  This applied chemical solution should be allowed to react on the concrete surface for 10 to 15 minutes.

The surface was rinsed lightly and scrubbed with clean water. Repeat the washing process at least twice or until all traces of the chemical solution have been removed.

Washing the surface with acid or chemical solution may cause variation in color and surface texture. Before applying the whole surface patch test should be required.

When chemical or acid rinsing is applied on the color finish surface at that time you should dilute the solution to 2% means 1 part of acid by 50 parts of water.

Properly followed the safety criteria while working with a chemical solution in this procedure. Ensure that the working areas have properly ventilated. Avoiding the direct touch between steel and acid while treating concrete efflorescence.

Read More: Can You Pour Concrete Over Concrete | How to Pour Concrete Over Existing Concrete 


How to prevent efflorescence in concrete?

The following steps are used for preventing the concrete efflorescence,

Generally used, little soluble salts are present in the ingredients of concrete. Use concrete ingredients containing as little soluble salt as possible.

Use Waterproofing admixture in concrete for reducing the permeability of concrete and cement mortar. Use Denser concrete again for reducing permeability, this may help to increase the shrinkage.

Use cement lime and sand mortar no stronger than required for the application for minimizing possible soluble salt levels. A Lime free from calcium sulfate salt.

Avoid premature drying, Installing a vapor obstacle for preventing the movement of moisture from the sub-grade to the surface of the slab. Using class F fly ash for fixing a considerable amount of calcium hydroxide in the concrete.

The application of coating layers and sealers can avoid moisture or surface water from the slab. The used plastic membrane inside the slab for entering groundwater, site drainage water, rainwater, etc.

Use a sufficient amount of aggregate, sand, cement, and sand which contains very less amount of salts present on it. Applying to coat for preventing efflorescence on the concrete surface.

So that using water repellents, acrylic, and silicone coatings remove the concrete efflorescence. The coating layer will absorb the water across a masonry surface and prevent efflorescence.

Also, warm water and white wine vinegar is eliminating the efflorescence.

The following three steps are used for coating;

Rinsing of concrete surface

For Rinsing, concrete surfaces used clean water. If the washing concrete surface is outdoors then you can use a hose to spray down the surface and if the concrete surface is indoors then also you can use a spray bottle filled with clean water for rinsing the surface thoroughly.

Apply the solution

The spray cleansing solution onto the building surface or concrete surface and allow it to sit for several minutes. When you did not see the result then apply multiple coats of the cleaning solution to the surface.

Again Rinsing the concrete surface

Last time rinse the concrete surface with clean water and then clean the surface with a dry cloth. Ensure the concrete surface is dry for minimizing the risk of ongoing efflorescence.

Read More: Concrete Core Test | Concrete Core Test Procedure | Concrete Cores | Concrete Core Sample


FAQs:

What is Concrete Efflorescence?

Efflorescence in concrete surface means the whitish or grayish tint-colored powder is shown in the concrete surface.  It consists of crystalline salt and deposits on the concrete and remains on the surface of the concrete after evaporation of water. In addition, special care is required for treating efflorescence.

How to Repair concrete surfaces affected by efflorescence?

Method-1- By Using Hard teeth Brush
Method-2-By Using Dilute acid Solution

How to prevent efflorescence in concrete?

Generally used, little soluble salts are present in the ingredients of concrete. Use concrete ingredients containing as little soluble salt as possible.

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