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What Efflorescence Is And How To Remove It

Efflorescence On Brick Wall

What Efflorescence Is And How To Remove It

by | Sep 11, 2021

Your house may not just be aesthetically damaged by the white staining spread all over your concrete wall but also structurally compromised. You therefore need to know when to call the professionals before your brick and slabs begin to spall off. Demand for fancy finishing and decorations in modern concrete housing projects is on the rise. As a result, there is an increase in the variety of designs and shapes of concrete decoration products in the market. Most of these products are made of cement and are susceptible to a phenomenon known as efflorescence, which affects both the aesthetic and structural integrity of your house.

What Is Efflorescence?

Simply put, efflorescence is defined as salt or white powder on brick or concrete surfaces. Most concrete load-bearing structures like bridges and building decoration materials like bricks, wallboards and tiles among others are made of cement, lime, sand, mortar, clay and admixtures. These materials contain salts such as chlorides, calcium carbonate, manganese oxide, sodium carbonate, sodium sulfate, potassium sulfate and potassium carbonate.

In the presence of water, these salts are dissolved and left as white deposits on the surfaces of your concrete structures as water evaporates. Sometimes, salts such as chlorides are present in the environment around your concrete structures. When they dissolve in water and are absorbed in the porous concrete structures, the chloride ‘poison’ dissolves the cement stone. These porous structures may also clog internally as they absorb these salts creating internal pressure and subsequent structural damage.

This deposition of dissolved salts either outward or inward of concrete structures is known as efflorescence. Efflorescence may compromise the structural integrity of your building or simply stain your brick wall and become an eyesore. Even though efflorescence is a typical surface phenomenon manifested as a white powder on the concrete or brick surfaces, it can sometimes form as yellow or brown stains on these surfaces.

The Two Types Of Efflorescence And How They Are Formed

There are two categories of efflorescence depending on the formation process. While the formation process that brings about the two categories of efflorescence vary, three conditions must be fulfilled for both. The first condition is that soluble salts must be present. In most cases, efflorescence salts include calcium carbonate, potassium sulfate and sodium sulfate. Water must also be present to dissolve these salts. Sometimes mix water is a source of magnesium, potassium or sodium salts which contribute to efflorescence potential. As a third condition, the concrete material or brick must be porous to provide a pathway for the movement of the solution. Permeability of the concrete matrix determines the efflorescence potential.

1. Primary Efflorescence

Primary efflorescence results when salt deposits emerge from within concrete, brick or masonry work and is deposited on the brick or concrete surface as white, yellow or brown powder. The salts are dissolved by the excess mix of water used during the manufacture of the concrete material and is precipitated on the surface by carbonation or evaporation. Primary efflorescence is more of aesthetic concern than structural concern as it only leads to staining of concrete and bricks. It normally happens during the first 48-72 hours of manufacturing concrete or laying bricks.

2. Secondary Efflorescence

Secondary efflorescence results from external sources of water like rain or condensation that dissolves external salts in the surrounding or salts present in the concrete material or brick. While movement of the solution is outward during the process of primary efflorescence formation, it is inward during secondary efflorescence formation. As the solution travels inwards, the salts dissolve cement used in the manufacture of concrete or brick. These salts also clog pores as they move inside these porous concrete materials creating internal pressure. Eventually this causes brick spalling. Secondary efflorescence is therefore a structural concern as it compromises the integrity of a building.

How To Cure Concrete Products To Prevent Efflorescence

Efflorescence is a problem that has for long been associated with manufactured concrete products, bricks, cement content, mix water, water/cement ratios, curing conditions, permeability and the construction industry in general. Optimising these parameters during the manufacture of concrete products and when mixing cement and other admixtures would lead to products that are less susceptible to efflorescence. This article outlines the best practices for preventing efflorescence in cement-based concrete products like bricks, firetops, wallboards, tiles and slabs among others. The guiding principle in attempting to avoid efflorescence in concrete products is to eliminate the conditions which are mentioned in this article as necessary for efflorescence formation.

Reducing Salt Levels

Softening mix water to reduce various levels of salts helps to prevent potential efflorescence. Using special admixtures that will bind salts to the concrete in the presence of water helps to protect concrete structures from efflorescence.

Reducing Permeability

It is recommended that you keep water/cement ratios low to reduce the porosity of the cement matrix. Another way to make cement matrix less permeable is by using water-repellent or pore-blocker admixtures to eliminate the pathways that would aid movement of dissolved salts within the concrete or brick. Plasticising admixtures are also used to achieve reduced permeability of cement matrix and sometimes carbon dioxide is forced into the concrete matrix so as to form efflorescence below the surface. This reduces porosity and blocks pathways for formation of primary efflorescence.

Avoiding Excess Mix Water

Appropriate water and cement ratio not only yields less porous cement matrix but also eliminates excess mix water that would aid in dissolving salts. This is very important in preventing primary concrete or brick efflorescence as no excess water is available to precipitate salts on the surface. Adding fatty acid mixtures and calcium stearate dispersion (CSD) to the batching process yields a water repellent concrete structure. Concrete products should also be protected from external water sources as much as possible. This would help to prevent secondary efflorescence which has been established to have an impact on structural integrity of concrete products.

How To Get Rid Of Efflorescence From Concrete Or Brick Surfaces

The method you use for efflorescence treatment or removal from concrete or brick surfaces depends on the length of time the white powder has been on your wall, bricks or any concrete surfaces. It is easier to remove concrete efflorescence by simply washing or wet scrubbing the surface if the powder is fresh. A dilute solution of household white vinegar and water can be used to remove efflorescence if they have not stayed longer on the brick or concrete surfaces. However, if the salt has stayed on your concrete or brick surface for long, you may need to use any or a combination of the following methods to get rid of the efflorescence.

  • You will need a stiff brush to scrub the tough build up and debris from your wall, bricks or concrete products
  • Overstayed efflorescence may require that you use chemical efflorescence treatment. Sulphuric acid can be used to remove efflorescence from concrete surfaces
  • The most effective way that guarantees a complete removal of efflorescence from your concrete structure is using pressure wash

The best solution in preventing efflorescence from your building or construction materials is to remove the source of water.

Type Of Efflorescence That Requires Professional Removal Services

When you have salt on your bricks or concrete structure that cannot be removed by simple washing or scrubbing, it is time to call a professional. This is because in such scenarios you definitely need chemical treatment or pressure wash to get rid of the efflorescence from your concrete. These two methods need experience and are labor intensive. Thus, due to the chemicals that may be needed to remove efflorescence from your building, it is advisable to engage professional efflorescence removers.

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