A detailed explanation of the differences between waterproof mortar and ordinary mortar.-RDP/VAE

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Waterproof mortar and ordinary mortar are two types of materials with different uses, formulations, and properties. The core difference between them is that the primary function of ordinary mortar is to transfer loads and level surfaces, while the primary function of waterproof mortar is to form a dense barrier to prevent water penetration.

Different Core Composition and Formulation Approaches

This is the basis of all the differences between the two.

Ordinary Mortar: The basic composition is "cementitious material + aggregate (sand) + water". Based on the type of cementitious material, it is mainly divided into:

Cement Mortar: Used in humid environments or for masonry and plastering requiring high strength.

Lime Mortar: Used in dry environments and areas where high strength is not required.

Mixed Mortar:  Fly ash, etc., is added to cement or lime mortar to improve workability and reduce costs.

The core principle is to adjust the mix ratio to meet the strength and workability (flowability and water retention) requirements.

Waterproof Mortar: Based on ordinary cement mortar, it significantly improves impermeability by introducing specific functional components. There are two main technical approaches:

Adding Waterproofing Agents/Admixtures:  Adding ferric chloride, water reducers, etc., to ordinary mortar to block and densify the capillaries within the mortar. The mix ratio is similar to ordinary cement mortar, but the performance requirements are higher.

Adding Polymers: This is the mainstream approach for high-performance waterproof mortar, i.e., polymer-modified cementitious waterproof mortar. It adds polymer emulsion (such as acrylic emulsion) or redispersible latex powder to the cement and sand. The polymer forms a flexible film, interweaving with the cement hydration products to create a denser, highly adhesive, and somewhat flexible structure. Its performance standards (such as bond strength and impermeability pressure) are far higher than mortars with admixtures. Typical mix ratios include: polymer waterproof adhesive: cement: sand = 1:2:4, or liquid material: powder material = 1:3.3.

Core Characteristics and Performance Requirements Differ Significantly

Different formulations directly lead to vastly different performance.

Ordinary Mortar:

Performance Focus: Strength and workability.

Bonding Strength: Primarily serves load-bearing and adhesion purposes; standard requirements are relatively basic.

Water Impermeability: No specific requirements; its inherent water impermeability is very weak.

Flexibility: Basically rigid, with poor resistance to deformation and cracking of the substrate.

Waterproof Mortar:

Performance Focus: Water impermeability and bonding strength.

High Water Impermeability: This is its fundamental characteristic. For example, polymer cement waterproof mortar requires a water impermeability pressure of no less than 1.5 MPa, far higher than ordinary mortar.

High Bonding Strength: Must be firmly bonded to the substrate to prevent water leakage. Polymer waterproof mortar requires a bonding strength greater than 1.2 MPa.

Certain Flexibility: The polymer components give it a certain deformation capacity, enabling it to resist the propagation of micro-cracks.

Weather Resistance and Durability: Usually required to withstand freeze-thaw cycles, alkali resistance, etc., resulting in a long service life.

Detailed Comparison of Uses and Applicable Scenarios

Performance determines the use; the application scenarios of the two are distinctly different.

Ordinary Mortar:

Masonry Mortar: Used for bonding bricks, stones, blocks, etc., to form load-bearing or enclosing masonry.

Plastering Mortar: Used for leveling, finishing, and protecting the base layer of walls, floors, and ceilings. For example, mixed mortar is commonly used for plastering concrete beams and columns.

Core Scenarios: Almost all structural masonry and surface leveling and decoration of buildings, but not in areas requiring high waterproofing.

Waterproof Mortar:

Key Feature: Specifically used in areas with standing water, dampness, or requiring moisture protection.

Typical Applications:

Underground Engineering: Basement side walls, base slabs, and roof slabs.

Water-related Structures: Swimming pools, water tanks, canals, sewage treatment tanks.

Wet Areas in Buildings: Walls and floors of kitchens, bathrooms, and balconies.

Exterior Wall Waterproofing: Can be used as a waterproof layer or moisture barrier.

Others: Tunnels, granaries, roofs, etc., as waterproof and moisture-proof layers.

Special Requirements for Construction and Maintenance

Ordinary Mortar: The base layer needs to be pre-wetted to prevent rapid water loss. Emphasis should be placed on smooth troweling, and the curing time is usually shorter (e.g., around 7 days).

Waterproof Mortar:

Base Layer Treatment: Requires higher standards; the base must be firm, clean, and thoroughly wetted but without standing water.

Construction Process: Usually requires layered application (e.g., two to three layers), with each layer approximately 1-2 mm thick, and a clear requirement for the total thickness (e.g., not less than 3 mm for floors). Joint areas require reinforced treatment.

Curing: Crucial. After construction, rapid water loss must be avoided.  Water spraying or covering with damp cloth is required for curing, and the curing time is usually not less than 14 days.

Environment: Construction temperature is generally required to be between 5-35℃, and construction should be avoided during rainy, snowy, or windy weather.

How to Choose: Summary and Suggestions

First, consider the function: For load-bearing masonry or surface leveling/smoothing → choose ordinary mortar. For actively preventing water penetration → choose waterproof mortar.

Secondly, consider the environment: For non-structural partition walls or plastering in dry indoor areas, ordinary mortars such as lime mortar can be used to save costs. For damp areas (such as bathroom walls, basements) or areas directly exposed to water, waterproof mortar must be used.

Thirdly, consider the performance level: For waterproofing projects, polymer cement waterproof mortar usually has superior performance (water resistance, adhesion, flexibility) compared to ordinary waterproof mortar with additives, making it suitable for more critical or demanding areas.

Finally, verify the qualifications: When choosing waterproof mortar, pay attention to the product's standards (e.g., JC/T 984-2011) and ensure it is suitable for your specific application.