Weatherproofing Mortar, Cement and Concrete: Techniques for Resilient Construction

Mortar, cement and concrete are prone to damage and deterioration when exposed to harsh weather conditions. Finding ways to weather-proof these materials is important for creating resilient, long-lasting structures. We explore various techniques and methods for waterproof concrete, mortar and cement projects.

The article explains why these materials are vulnerable to weathering factors like freezing temperatures, excess moisture and salt exposure. We also discover top tips on how to effectively weatherproof these materials for an extended lifespan. By examining these techniques, you will gain valuable insight into the durability of concrete-based materials. 

What are the weatherproofing challenges with aggregates?

While weatherproofing concrete materials is critical for durability, it also comes with several challenges. From concrete paving slabs to roof tiles and wall foundations, below are the key issues to think about. 

1. Prone to cracking

Ready mix mortar, cement and concrete are porous materials containing microscopic pores that allow water and chemicals to seep in. This makes them prone to cracking and deterioration. Applying silane or siloxane-based sealers to exterior brick and concrete surfaces creates a waterproof barrier. It keeps moisture from penetrating pores while still allowing vapour transmission.

2. Exposure to moisture

The chemistry and composition promote reactions when exposed to moisture and air that can weaken the structure over time. Incorporating admixtures with tiny air bubbles in concrete mix improves freeze-thaw resistance. It provides space for water to expand without cracking the material. 

3. Degrading sealant

Many standard weatherproofing techniques like grout sealant and coatings degrade and lose effectiveness as the concrete ages. Using an optimal water-to-cement ratio in concrete and mortar mix ensures proper curing and strength development.

4. Limitations with surface treatments

They cannot prevent damage from moisture wicking through thick structural concrete elements, making complete weather-proofing difficult. Allowing concrete to cure slowly and completely over several days or weeks allows full hydration of the cement mixture.

5. Unsuitable for large areas

Due to cost and labour, it is often not feasible to apply specialised weatherproofing treatments throughout very large buildings. Combining Portland cement with lightweight aggregates that repel water, such as expanded shale or slate, produces concrete with greater water resistance.

6. Maintenance issues

Ongoing maintenance of weatherproofing treatments is necessary but not always practical long-term. A saw-cut joint relieves stresses from movement and drying shrinkage to control where cracks occur. As a result, this prevents uncontrolled cracking.

7. Porous concrete materials

Overcoming the inherent porosity and reactivity of concrete materials poses a significant challenge for enhancing weather resistance. Proper site grading and drainage away from foundations keep excessive moisture away from concrete. It avoids damage from pooling water.

How to apply surface treatments

Proper application of weatherproofing treatments is crucial for maximising performance. The right techniques allow coatings to fully bond to surfaces such as concrete floors or walls. Key application methods include the following. 

1. Fully coat surfaces

Use a rotary drum coater to even coat all surfaces. This handles large volumes efficiently compared to manual spraying. It ensures all areas are covered versus pile coating.

2. Apply before mixing

Coat aggregates 1-2 days before concrete mixing to allow proper curing. This prevents bond degradation compared to applying right before mixing.

3. Use spray application

Utilise pressurised spraying nozzles to apply a fine mist coating. Sprayers provide better control over thickness and uniformity than brushing. The thin layer prevents bleed-off or pooling versus roller applications.

4. Add silane/siloxane

Apply an active silane/siloxane concentrate using low-pressure spraying. Higher active concentration improves water repellency compared to dilute formulations. Low pressure prevents excess that can impact strength.

5. Heat treatment for adhesion

Pass coated aggregates through a rotary kiln heated to approximately 148-205°C (300-400°F). Heating enhances chemical bonding to the aggregate for permanent hydrophobic properties rather than just a surface coating.

6. Allow proper curing

Let coatings dry for the manufacturer’s recommended time before concrete mixing. The set time is usually 1-3 days. This allows reactions to fully occur for proper adherence and performance.

Can you use eco-friendly weatherproofing solutions?

There are some emerging options for more environmentally friendly weatherproofing treatments for concrete aggregates. Below is an overview of various eco-friendly solutions to consider.

• Bio-based oils: Plant-derived oils like soybean, linseed and palm can be effective sealers. This is because they soak into pores and repel water.
• Sodium silicate: Also known as water glass, it is made from sand and plant ash silicates. They chemically react with aggregates to reduce moisture.
• Lithium silicate: Overall, lithium-based silicate solutions provide good water repellency.

Eco-friendly aggregate treatments are an emerging option. However, you should weigh the pros and cons before you begin the weatherproofing process.

Learn more about eco-friendly mortar, cement and concrete practices with our article.

How long do weatherproof aggregates last?

When properly treated and maintained, weatherproofing mixed mortar, cement and concrete can significantly extend the lifespan and durability of these building materials. However, the expected lifespan depends on several factors.

For exterior structural concrete treated with penetrating sealers, lifespans of 10-30 years can be expected. High-quality silicone or silane-based treatments often last 15-25 years. Acrylics and cheaper options may only last 5-10 years.

Mortar joints with water-repellent admixtures can maintain effectiveness for over 20 years. But cracks must be properly repaired to prevent water intrusion that deteriorates the joints.

Ready mix cement made with waterproofing compounds can maintain internal water repellency for the full lifespan of the concrete. This is typically over 50 years for properly placed and cured concrete not subject to structural issues.

Exposed horizontal surfaces will weather faster. They require reapplication of toppings and sealers every 5-8 years. Sheltered vertical façades may only need resealing every 15-20 years. As a result, harsher climates accelerate deterioration.

What is the future of weatherproofing aggregates?

While current weatherproofing options for concrete, cement and mortar mixes have limitations, several promising trends are emerging for enhancing weather resistance. In the future, we could see the following.

• Self-healing concrete: Microcapsules of sealants or bacterial spores are added to concretes that automatically repair cracks and seal against moisture. This provides ongoing passive protection.
• Nanomaterials: Adding nano-silica, carbon nanotubes and other nanoscale materials can dramatically improve the density, durability and water-repellency of concrete.
• Advanced polymers: New hydrophobic polymers are being developed that have superior bonding to cementitious materials to provide long-lasting water repellency, even in harsh climates.
• Smart concretes: Concretes with self-sensing abilities to detect strain and moisture ingress are being researched. This would allow quicker repair work before major damage occurs.
• Improved testing: Advanced modelling and simulation methods are being used to study and optimise the weathering resistance of cementitious mixes under different conditions.
• Green solutions: As outlined above, more sustainable water repellents and mineral-based sealers with lower environmental impacts will become available.