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What chemicals to use on concrete stains

What chemicals to use on concrete stains

While water is usually enough to remove dirt from concrete, you often need the help of chemicals to clean tough stains. From oil and grease to rust and graffiti, chemical cleaners will make the task of cleaning concrete much easier. 

Many contractors will recommend spraying the stain with the cleaning agent and leaving it to soak for about 15 minutes before using a high-pressure water spray to wash it away. Concrete is slightly alkaline because of the lime in the cement, so we suggest using an alkaline cleaning agent rather than an acidic one.

Oil and grease stains

One of the most common types of concrete stain is caused by oil. Parking lots, roads, pavements and garage floors are all victims of dripping oil from vehicles. Workshop and industrial floors can also suffer from grease stains. The best way to clean these surfaces is to use an alkaline degreaser with hot water.

The degreaser will improve the removal rate of these stains by emulsifying the oil and grease. The hot water will help to lift the oil from the concrete surface. Using a high-pressure water jet will also help to remove the tough stains in the pores of the concrete surface. Alkaline degreasers can also be used to clean soot and soil stains too.

Rust stains on concrete walls

Rust stains can either have a golden-brown appearance or a blue-green colour. They commonly occur on concrete walls around exposed pipes, metal brackets and bolts. Heavy rust stains can sometimes penetrate deep into the wall.

The golden-brown stains occur when steel oxidises and rusts, whereas the blue-green markings happen around copper water pipes. The best cleaning agents to use for these stains are the ones that contain oxalic acid. This chemical helps to break down the metals in the rust stain and make it easy to wash away with a hose or a water jet.

Graffiti on concrete walls

Graffiti on a wall can be very difficult to remove. The type of spray paint used will determine how much effort you need to clean it off. The best way to remove paint stains is to use a chemical stripper that contains a citrus-based solvent, methylene chloride or potassium hydroxide.

The citrus-based solvents are the least aggressive and safest cleaners, which is good for your concrete wall but not as effective at removing graffiti as the other two chemicals. Cleaning agents that contain potassium hydroxide are the best for paint stains. Spray them on the wall and allow it to soak for several hours before spraying the wall with a high-pressure hose. You will also need to spray an acid neutraliser on the wall after the cleaning process to protect the concrete from acid damage.

Another method of cleaning graffiti from a wall is to use a special attachment fitted to a water jet nozzle that feeds sand into the water stream. This essentially sandblasts the paint off the wall. While this method is safe and clean, it can damage the surface of the wall.

These tips will help you remove the most common types of stains from your concrete floors and walls. Water and a cleaning chemical will always give you the best results, but it is important to know what type of cleaning agent to use for each stain.


LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 


LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.


At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.


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