Waterproof Cement: What to Know Before Use?

Written By Adam Paul - Waterproofing Expert

Regular cement is not a waterproof material. Cement is a permeable material, and it tends to pass moisture and air through the cement. Hence cement bases products such as mortar, plaster and concrete are also not waterproof. But cement is a highly water resistant material. In order to waterproof the cement, you should install a waterproofing membrane internally or externally of the cement based products.

Cementitious waterproofing and waterproofing cement are two types of cement. Waterproof cement is used to stop heavy leaks from the water source, while cementitious waterproofing is used on the surface as a coating to stop the water dampness and wetness on the structure.

The waterproofing capability of the cement can be improved by adding agents and water-repellent chemicals. In order to make cement 100% waterproof, additional waterproofing treatments are needed. Among cement types, hydraulic cement is waterproof, while rubber cement is not waterproof. The most used cement boards are also not waterproof, but they are highly water resistant.

Waterproofing cement is not flexible, and it consists of a minimum of (37.9 Mpa) of strength after 28 days. The setting time of the waterproof cement is between 2-5 minutes. When you use it you should apply it within that period to prevent setting. You should mix the waterproof cement 3 to 5 parts to 1 part of water, and it should apply within 2-5 minutes. You can apply waterproof cement on both active leaks and inactive leaks by using a trowel. A waterproof cement will last long 5-10 years if it is not damaged by heavy impacts, improper mixing application, free-thaw cycles, exposure to harsh chemicals and settling of the structure.

You can use waterproof cement on heavy water leaking occurs areas such as bathrooms, swimming pools, water tanks, foundations, concrete roofs and terraces. You should not apply waterproof cement on higher temperature areas, flexible structures, thin applications, over the paint and other coating and as a waterproofing membrane on the surface.

Is Cement Waterproof?

Regular cement, which is known as Portland cement, is not a waterproof material but it is a highly water resistant. Cement is a permeable material that allows moisture and air to pass through the cement. It is mixed with aggregate to form a solid and tough mixture of concrete, plaster, and mortar. All of these compound materials are not even waterproof.

The waterproofness of cement and its mixture depends on the material's permeability. The permeability depends on the porosity, porous size, water pressure, temperature and fluid properties. In order to reduce the permeability and improve the waterproofing capability of cement based products, they should be waterproofed internally or externally.

What are the Differences between Waterproof Cement and Cementitious Waterproofing?

Waterproofing cement is not 100% waterproof. It is highly water resistant and is designed to withstand higher compression strength. Those are used to stop water leaking through a higher leak rate.

Cementitious waterproofing is a 100% waterproof coating that is used to stop water leaking form the water source. Cementitious waterproofing can be applied as a coating and is suitable to prevent damping and wetness of the structure.

What Types of Cement Waterproof?

The waterproofing cement types are made by adding waterproofing agents and water repellent chemicals. These repellents and chemicals form high water resistance cement. Below are the most used waterproof cement types.

These are the most used waterproof cement

1. Rapidset water stop hydraulic cement
2. Quikrete hydraulic water stop
3. Kwixset waterproof cement
4. Demtite waterproofing cement
5. Drylok hydraulic cement
6. BASF master seal 583

In order to make 100% waterproof cement, additional waterproofing treatments or admixtures are needed.

Is Hydraulic Cement Waterproof?

Yes, hydraulic cement is waterproof. Hydraulic cement is specifically designed to set and harden by using a chemical reaction with water. When it hardens, it forms a strong and durable seal that is resistant to water and moisture, which makes it an excellent choice for repairing leaks and sealing cracks in concrete and masonry structures. Hence, it can be used under water construction or for those constantly exposed to wet weather conditions.

Is Rubber Cement Waterproof?

Rubber cement is not 100% waterproof. It is a water resistat material. When it is exposed to water or moisture, its adhesiveness and properties can weaken over time. Therefore it is not recommended for long-term waterproofing solutions.

Rubber cement is a type of cement that is made of adhesives such as elastic polymers mixed with solvents such as acetone, hexane, heptane or toluene. It has a higher flexibility; hence it can be used for moving and vibrating structures.

Is Cement Board Waterproof?

The cement board is not a waterproof material. Cement boards are highly water resistant. Hence when it is wet, it will not deteriorate over time. Cement boards can seep the excess water. Therefore, you should install an exterior waterproofing barrier to make the cement board waterproof.

Is Waterproof Cement Flexible?

Not all waterproof cement is flexible. The flexibility of the waterproof cement depends on the material mixed with it. Some waterproof cement has a limited flexibility, while acrylic based modified waterproofing cement has a higher flexibility. Waterproof flexible cement is highly recommended for a structure that has small substrate movements such as temperature fluctuation and structure settlements.

What is the Strength of Waterproof Cement?

The compressive strength of waterproof cement mortar is based on the ASTM C109 and ASTM C191 test methods. According to that, waterproof concrete consists of a minimum of 5500 psi (37.9 Mpa) of strength after 28 days. The strength of waterproof cement motar is increased as below.

1. After 1 hour of setting time, compressive strength should be between 0-300 psi (0-2.06 Mpa)
2. After 3 hours of setting time, compressive strength should be between 300-1000 psi (2.06-6.9 Mpa)
3. After 8 hours of setting time, compressive strength should be between 1000-2000 psi (6.9-13.8 Mpa)
4. After 24 hours of setting time, compressive strength should be between 2000-3000 psi (13.8-20.68 Mpa)
5. After 28 days of setting time, compressive strength should be more than 5000 psi ( 34.47 Mpa)

What is the Setting time for Waterproof Cement?

The setting time of the waterproof cement is between 2-5 minutes after mixing it with water. This means you should apply waterproof cement to the substrate within 2-5 minutes after mixing it. The setting time depends on the amount of water, cement, moisture content, temperature, finess of the cement and the gypsum content in the cement. The lower setting time for waterproofing cement will reduce its workability. It can waste the material without use.

When you use waterproof cement, do not mix all of the cement and water together. Mix the sufficient amount you can apply within the above period.

Where Can You Use Waterproof Cement?

Waterproof cement can be used in a variety of applications where water resistance is required.

Basements: Waterproof cement can be applied for basement floor and wall waterproofing in order to prevent water seepage into the basement.

Bathrooms and kitchens: Waterproof cement is applied on the bathroom floor, walls, shower walls, kitchen, countertops, and sink areas where the areas tend to expose higher amounts of water.

Swimming pools: Waterproof cement is used in the construction of swimming pools to prevent water leakage. How to waterproof new swimming pool helps you to apply cement waterproof in the newly constructed swimming pool.

Water tanks: Waterproof cement is used for the water tanks to prevent water leaking from the tank walls and floors. How to waterproof water tank guide helps you to apply cement waterproofing on the water tank surface.

Foundations: Waterproof cement is used in the foundation to prevent water from seeping into the building from the ground.

Concrete roofs and terraces: Waterproof cement is used to prevent water seepage leakage and prevent water damage through the concrete roofs, slabs and terraces to prevent the water damage. How to waterproof a concrete roof is a helpful guide for you to apply waterproofing on the concrete roofs and terraces.

How to Mix Waterproof Cement?

You can mix waterproof cement by following the below method

1. Take 3-5 part of waterproof cement and 1 part of water by weight. (Proportion can be varied with the manufacturer brand)
2. Then, pour the water into the cement container and start the mixing process. Do not put the cement into the water.
3. Then mix it thoroughly until the mixture becomes putty heavy troweling consistency.
4. Then, it is applied to the leaking paths within 3-5 minutes of mixing time.

You should not mix too much cement and water due to its lower setting time. It tends to waste material without use.

How to Apply Waterproof Cement?

You can apply waterproof cement on both active leaks and inactive leaks.

What Tools Need to Apply Waterproof Cement?

1. Chisel
2. Trowler
3. Electric mixture
4. Spactual
5. Wire brush
6. PPC equipment (eye protection, rubber gloves, and dust mask)

How to Prepare Surface for Waterproof Cement?

1. Before applying waterproof cement, you should prepare the surface by cleaning it.
2. The area to be patched should be cleaned thoroughly using a wire brush, pressure washer or any cleaning equipment.
3. Then, chisel the patch path to the shape of the inverted “V” until the loose, crumbled, deteriorated masonry is removed.
4. Then, clean the notch using water to remove the masonry debris

How to Apply Waterproof Cement for Active Leaks?

1. Mix and wait 1 minute until the mixture becomes warm
2. Then, apply the waterproof cement to the patched area
3. Then, hold it in place for 3-5 minutes until it is completely set and has a sufficient bond to stop the flow of water.
4. You should make the patch area smooth during this time.

How to Apply Waterproof Cement for Inactive Leaks?

1. First, you should thoroughly soak the area to be applied
2. Then, apply the waterproof cement to the prepared area using a knife or trowel
3. Let the mixture set and prepare the surface as smoothly

How Long is a Waterproof Cement Last?

Waterproof cement can last for about 5-10 years. The durability of the waterproof cement can reduced by poor construction practices, incorrect mixing and application, and exposure to harsh environmental conditions like extreme temperatures, high humidity, or aggressive chemicals.

Where Should You Not Use Waterproof Cement?

You should not use waterproof cement in the areas below. These areas tend to damage the waterproofing cement to damage.

Higher temperature areas: You should not use waterproof cement on higher temperature areas such as fireplaces and furnaces as it can degrade or crack under such conditions.

Flexible structures: You should not use waterproof cement on flexible structures vibration structures. This causes to to crack the waterproof cement layer.

On thin applications: Waterproof cement is not ideal for very thin applications as it may crack.

Over paint or other coatings: Waterproof cement may not adhere properly to surfaces coated with paint, oil, or other substances.

As a standalone waterproofing solution: Waterproof cement does resist water penetration, it may not be enough to completely waterproof a structure, especially under high hydrostatic pressure. Hence, you should use a waterproof barrier as an extra waterproof solution.

How to Damage Waterproof Cement Layer?

Waterproof cement can be damaged due to below 5 ways. Those can crack the waterproof cement and tend to leak the water through the sealed area.

Heavy impact on waterproofing cement: Heavy impact or pressure can cause cracks or chips in the cement layer.

Improper mixing and application: Waterproof cement can be damaged easily If the cement is not mixed or applied correctly, it can lead to weaknesses in the cement layer that may cause it to fail over time.

Freeze-Thaw cycles: Waterproof cement can be damaged in colder climates when the water seeps into tiny cracks in the cement, freezes, and then expands, causing the cracks to widen. Repeated freeze-thaw cycles can cause significant damage over time.

Exposure to harsh chemicals: Waterproof cement can be damaged by certain cement. This causes the degradation or weakening of the cement barrier.

Settling of structures: Waterproof cement can be damaged by the ground structure settling.

Exposure to higher temperature: Waterproof cement can be damaged to when the cement is exposed to extreme temperature and temperature fluctuations.

Is Concrete Waterproof?

Concrete is not a fully waterproof material. Solid concrete consists of impervious and porous substances. These substances absorb water and other liquids over time. When the porous are saturated with water, concrete tends to seep the water through the concrete layer. This can lead to damage to concrete by cracking, erosion, and damage to the reinforcement. The concrete waterproofing guide helps you prevent water leaking from concrete in any construction structure.