Can Mold Grow on Concrete?

Concrete is one of the most common construction materials in the world due to its strength, affordability, stability, and flexibility. It is a highly versatile construction material that can be used from residential buildings to large-scale infrastructure. However, the growth of mold on concrete can lead to structural damage and health problems.

Surface moisture, high humidity, and warm temperatures such as 70 degrees and above can cause mold to grow on concrete. Mold growth occurs in concrete surfaces that are in shaded areas that do not get enough sunlight. The porousness of concrete is also a great incubator for mold due to its ability to absorb moisture.

There are different types of mold but all of them need moisture to grow. Mold growth can occur when that moisture accumulates on building materials. This article will explain which, where, and how mold can grow on concrete. It will also explain how mold can affect the structural integrity of concrete and how mold growth can be avoided.

What are Molds?

Molds are part of the kingdom of Fungi and thrive in places with humid and moist places such as soil, plants, and decaying matter. They can be found anywhere as long as there is moisture and oxygen.

Molds reproduce through spores, which can be transported by air, water, or insects. Mold spores are usually 2 to 10 micrometers in size and can be found in both indoor and outdoor air.

Use of Concrete

Concrete is a widely used building material. It is made up of three basic components: water, aggregate (rock, sand, or gravel), and Portland cement. The major uses of concrete are the following:

  • Residential Buildings

Small and large-scale residential buildings are made with concrete using traditional or modern form-work as a construction method.

  • Commercial Buildings

Commercial buildings are built with concrete as it is a more economic and safer option than other construction materials.

  • Streets, Pavements, or Driveways

Streets, pavements, and driveways that are made with concrete are more durable and strong than those that are built with asphalt.

  • Foundations

Reinforced Cement Concrete is usually used in the construction of the foundation of high-rise or low-rise buildings.

  • Fences

Due to the development in the precast concrete industry, the quality of concrete fences has improved. The use of concrete in fence construction has resulted in the creation of beautiful and more attractive designs in fences.

  • Concrete Bridges

Concrete, when reinforced with steel, offers strength, durability, and endurance which makes it the best solution for constructing bridges. Pre-stressed concrete, post-stressed concrete, self-compacted concrete are types of concrete that can be applied in the construction of bridges.

Molds That Can Grow on Concrete

Mold comes in different shapes, colors, and sizes but all of them need water or moisture to grow. Excessive moisture in buildings or on building materials allows mold growth to occur, especially when that moisture remains unaddressed. The following are some types of mold that can grow on concrete:

  • Black Mold (Strachybothrys Chartarum)

Strachybothrys Chartarum, also known as “black mold”, is a type of mold that can grow on concrete. Stachybotrys has a mucous-like texture and appears black or dark green. It thrives on areas that regularly experience dampness and humidness.

As it is a toxigenic type of mold, exposure to Strachybothrys Chartarum can cause allergic reactions and flu-like symptoms.

  • Acremonium

Acremonium is a toxigenic mold that usually cultivates in areas where condensation from humidifiers, cooling coils, window sealants, and drain pans accumulate within residential buildings.

At first, it appears as a patch of moist mold and slowly develops into a fine powdery substance. Acremonium usually appears as pink, grey, white, or orange in color.

  • Alternaria

Alternaria is a type of mold that grows in areas where dampness usually occurs. It is part of the common mold species that typically appear as a result of water damage to a home or building. It is a smooth-textured mold that appears with either brown or dark green hairs. It appears as a velvet-textured mold with brown or dark green hairs. It is commonly found in areas with showers, bathtubs, and sinks.

How Does Mold Grow on Concrete

Unlike organic materials like wood, concrete cannot act as a source of food for mold. There are no elements in the properties of concrete that are appropriate for mold growth. However, walls and surfaces that are made with concrete can accumulate organic materials like moisture, algae, bacteria, salts, dust, pollen, dirt, dead skin, and other particles which mold can feed on.

Concrete is also a poor insulator. Sudden or gradual changes in temperature can cause condensation to form on a concrete surface. This elevated surface moisture provides an environment for the mold to grow.

Additionally, its porousness allows moisture to seep inside and trap organic materials as well as absorb moisture. The ability of concrete to absorb moisture slowly can hide water damage for a long time before it becomes noticeable. Once a small part of concrete has started to absorb moisture, it starts that spread and creates a higher level of moisture across a large area.

Effects of Mold on Concrete

Mold can damage the structural integrity and aesthetic value of concrete. Mold can leave stains that discolor the concrete and are very difficult to remove. This is an issue when concrete is used for decoration or when it is used in a location that visible to people.

The structural integrity of concrete can also decrease when the acid that mold produces degrades concrete over time. Constant repairs and expensive damages can result from an unchecked mold infestations.

Removing Mold on Concrete

Removing mold growth on concrete is a simple process. Concrete is extremely durable and can tolerate various methods of mold removal.

The process of removing mold on concrete in a large area calls for professional services. It usually requires the use of fungicide and physical removal of the mold. Mold spores are killed and deactivated using fungicide. However, staining and discoloration can remain on the surface. The staining and discoloration can be addressed with HEPA vacuuming, scrubbing, steam cleaning, sandblasting, etc. 

If the area for mold removal is relatively small, mold can be easily removed using household disinfectants such as:

  • Hydrogen Peroxide – Hydrogen Peroxide kills mold, lightens stains, and does not produce toxic gases or residue. However, it eliminates mold slower than chlorine bleach and removes color from the surface it is applied on.
  • Baking soda (Sodium Bicarbonate) – When applied on a porous surface, baking soda absorbs moisture from these surfaces and inhibits mold growth.
  • Borax (Sodium Borate) –The high levels of pH in borax stops the development of mold. However, in terms of effectiveness in removing mold, borax works better than baking soda.

Lastly, provision of adequate ventilation and wearing of protective gear or equipment like gloves and eye protection must always be practiced when removing mold.

Preventing Mold on Concrete

Mold growth in concrete is preventable. Temperature and relative humidity levels control are major factors in preventing mold growth. Relative humidity levels are lower in warm temperatures so humidity levels in indoor areas with concrete surfaces should be kept below 60 percent – at best, between 30 and 50 percent.

Ventilation should also be improved. A dehumidifier can be used to help pull moisture from the air and keep the area dry. Standing water should also be avoided and removed from the premises of a concrete surface because it can produce moisture. Lastly, periodic cleaning and use of HEPA air filters can help stop the development of mold growth and prevent it from occurring.