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How to waterproof concrete structures

How to waterproof concrete structures

Waterproofing concrete structures can help to protect them from the weather and keep them in optimal condition. This is especially important in areas prone to flooding, heavy rainfall and constant ocean vapour. Water can penetrate concrete over time and affect its strength, so waterproofing is a good way to keep a building strong.

There are numerous ways to waterproof a concrete structure. Contractors can apply paints and bitumen felts to the exterior of the building, or they can use concrete admixtures to prevent water from penetrating the surface of the structure. For optimal waterproofing results, the design, workmanship and building materials should conform to the correct standards and codes of construction.

Concrete waterproofing admixtures

Certain admixtures make concrete impermeable to water and moisture. These chemicals can be added to the concrete or plaster batch during mixing. They reduce water permeability in the concrete by reducing the size and number of pores in the surface. They also line the surface with hydrophobic materials that prevent the absorption of water.

These admixtures react with the calcium hydroxide in the cement to create a hydrophobic layer. Examples of waterproofing admixtures include animal fats, stearic acid and some vegetable oils. These admixtures can also be mixed with plaster to line the surface of a wall. This acts like a layer of waterproof paint that repels rain, standing water and mist in the air.

Waterproofing concrete with bitumen coating

Another way to make concrete structures waterproof is to place a layer of bitumen on the exterior surface. The concrete first needs to be cleaned and sanded to give the bitumen a rough surface to stick to. Contractors should pour hot bitumen (about 1.5kg per square metre of concrete) onto the surface and spread it evenly. 

Once the first coat had dried and cooled, the second coating (1.25kg per square metre) is applied in the same manner. Immediately after the application of the second coating, contractors should spread sand over the surface. This is then left to dry and cool. The sand will give the surface a non-slip texture and improve the durability of the bitumen.

Certain concrete structures need to be waterproofed internally, such as concrete tanks and reservoirs that will store certain chemicals and liquids. Waterproofing a concrete structure will maintain its strength in the face of exposure to water and other liquids. It will prevent concrete rot and protect a building from heavy rains, flooding and salt moisture from the ocean.


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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