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Ⅰ.Introduction
Waterproof mortar has become an essential material in modern construction, playing a critical role in ensuring structural durability, safety, and long-term performance. In many regions of the world, buildings are exposed to harsh environmental conditions such as heavy rainfall, high humidity, fluctuating temperatures, and groundwater intrusion. In these conditions, traditional cement-based mortars are often insufficient to prevent water penetration, which can lead to cracking, efflorescence, corrosion of reinforcement, and even structural damage over time.
Globally, the demand for high-performance waterproof mortars continues to grow across residential, commercial, and infrastructure projects. From basement walls and foundations to roofs, balconies, swimming pools, and water containment structures, waterproof mortars provide an indispensable barrier against moisture. In regions with tropical climates, frequent rains, or high groundwater tables, waterproofing is no longer optional—it is a critical requirement for building longevity and occupant safety.
Modern waterproof mortars achieve their performance through a combination of advanced polymer technology, chemical additives, and optimized mix designs, resulting in mortars that not only resist water penetration but also provide excellent workability, adhesion, and crack resistance. These attributes make waterproof mortars a preferred choice for architects, engineers, and contractors worldwide who aim to deliver durable, high-quality, and reliable construction projects.
By integrating specialized additives such as HPMC, RDP, hydrophobic agents, superplasticizers, and defoamers, manufacturers can produce waterproof mortars tailored to a wide range of applications and environmental challenges. This comprehensive approach ensures that buildings remain safe, functional, and visually appealing for decades, highlighting the strategic importance of waterproof mortar in the global construction industry.
Ⅱ.How Waterproof Mortar Achieves Waterproofing: Three-Layer Mechanism
(1) Mechanism 1 — Microstructure Densification
A major cause of water penetration in ordinary mortar is the presence of interconnected capillary pores. High-performance waterproof mortars improve internal compactness through:
– enhanced cement hydration
– reduced total porosity
– refining pore size distribution
– breaking capillary continuity
– reducing shrinkage cracking
(2) Mechanism 2 — Polymer Film Formation
When redispersible polymer powder(RDP) redistributes in water and cures with cement, it forms a flexible, continuous polymer film within the hardened matrix.
This film:
– seals pores & micro-cracks
– enhances flexibility & crack bridging
– increases adhesion to substrates
– withstands dynamic loads & temperature cycling
– forms a hydrophobic polymer
–cement composite
(3) Mechanism 3 — Hydrophobic Capillary Chemistry
Hydrophobic agents modify internal capillary walls by creating:
– siloxane crosslinked networks (Si–O–Si)
– stearate hydrophobic surfaces
– water-repellent molecular films
These reduce water absorption while retaining vapor permeability.
Ⅲ.Additive Mechanisms — In-Depth Technical Explanation
1.HPMC / HEMC — Cellulose Ether Mechanism Water Retention Mechanism:
HPMC forms a temporary hydrocolloid film in fresh mortar that holds free water, reduces evaporation, prolongs hydration, and ensures complete C-S-H development.
Reduction of Capillary Channels: HPMC prevents particle segregation, water bleeding, and non-uniform pore formation, resulting in a tighter microstructure.
Cracking Prevention: HPMC slows water loss, reducing early shrinkage and plastic cracking.
Enhanced Polymer Film Co-Formation: HPMC assists RDP dispersion and film uniformity.
2. Redispersible Polymer Powder (RDP) Polymer Film Formation:
RDP particles coalesce into a flexible film embedded within cement hydrates.
Crack Bridging: RDP increases elongation & tensile strength, absorbing
substrate movement.
Adhesion Enhancement: RDP improves bonding through polymer–C-S-H hybrid interfaces.
3. Silicone Hydrophobic powder
Introduce Silicone Hydrophobic powder into mortar, reduce water absorption by 50–90%, and maintain vapor permeability.
4. Polycarboxylate Superplasticizer (PCE)
PCE disperses cement particles, lowers water–cement ratio, increases C-S-H density, and reduces porosity, enhancing waterproofing.
5. Powder Defoamer
Defoamers eliminate air voids, improving compressive strength, compactness, and consistent waterproofing performance.
Ⅳ. Combined Mechanisms — How Each Additive Works Together
Additive | Main Waterproof Contribution |
HPMC | Water retention + pore refinement + cracking reduction |
RDP | Flexible waterproof polymer film + crack bridging |
SHP | Water repellency + capillary blocking |
PCE | Lower W/C ratio → densification |
Defoamer | Air void elimination → structural compactness |
When all additives are combined, mortar achieves:
70% porosity reduction
50% water absorption reduction
300% crack resistance improvement
100% adhesion improvement
This is why polymer-modified waterproof mortar is now a global standard.
Ⅴ. Reference Formulations
1. One-Component Rigid Waterproof Mortar
Raw Material | Dosage (wt%) |
Cement | 35–45% |
Quartz sand | 45–55% |
HPMC | 0.15–0.30% |
RDP | 3–6% |
SHP | 0.2–0.5% |
PCE | 0.1–0.3% |
Defoamer | 0.05–0.1% |
Features: high impermeability, low cost, suitable for basements, foundations, interior walls.
2. Flexible Waterproof Mortar (High Performance)
Raw Material | Dosage (wt%) |
Cement | 30–40% |
Fine sand | 35–45% |
RDP (flexible grade) | 10–20% |
HPMC | 0.2–0.35% |
SHP | 0.2–0.4% |
PCE | 0.1% |
Defoamer | 0.05% |
Applications: roofs, wet rooms, exterior walls, balconies, pools.
3. Crystalline Waterproof Mortar (Advanced Durability)
Raw Material | Dosage (wt%) |
Cement | 40–50% |
Sand | 40–50% |
Chemical crystalline materials | 2–5% |
HPMC | 0.1–0.2% |
RDP | 3–5% |
Defoamer | 0.05–0.1% |
Feature: self-healing micro-cracks.
Ⅵ. Reference Formulations
Waterproof mortar performance depends on a precise balance of additives, microstructural optimization, and polymer technology. HPMC, RDP, hydrophobic agents, PCE, and defoamers form an integrated system that provides dense matrix, flexible polymer waterproof layers, hydrophobic capillary surfaces, crack resistance, and long-term structural durability. With these technologies, waterproof mortar can meet global construction standards across diverse climates and applications.
TENESSY, as a global supplier of high-performance cellulose ethers, redispersible polymer powders, superplasticizers, and specialty hydrophobic agents, provides a complete additive solution for manufacturers and contractors seeking advanced waterproof mortars. With TENESSY’s tailored solutions, construction professionals can achieve consistent, reliable waterproofing performance while optimizing workability, durability, and cost-efficiency. TENESSY products are engineered to meet international quality standards, ensuring that your waterproof mortar formulations deliver excellence in every project, from residential basements to large-scale infrastructure.
With the right combination of TENESSY additives, manufacturers can confidently produce waterproof mortars that meet the demands of diverse climates and rigorous performance expectations, offering clients a proven solution for durable and long-lasting water resistance.
