Nitobond SBR: Water Resistant Polymer Additive - Technical Details and Specifications

Product Overview

Nitobond SBR is a modified styrene butadiene rubber emulsion supplied as a ready-to-use white liquid bonding agent. It is specifically designed to improve the qualities of site-batched cementitious mortars and slurries, enhancing their performance across multiple construction applications.

Key Characteristics

Composition and Properties

Nitobond SBR is resistant to hydrolysis, making it ideal for both internal and external applications in conjunction with cement-based materials. Being cementitious in nature, mortars produced with Nitobond SBR are alkaline and provide protection for embedded steel reinforcement.

Single Component Formulation

The product is supplied as a single component liquid that can be easily gauged as required, eliminating the need for complex site mixing procedures beyond standard mortar preparation.

Primary Applications

Nitobond SBR is used for:

• Concrete repair mortars - Improving and bonding fresh materials to existing concrete surfaces
• Cementitious floor toppings and screeds - Enhanced durability and adhesion
• Waterproof renders - Highly resistant to freeze/thaw cycling
• Cementitious slurries - For patching, repair work, and various toppings
• Tile bonding mortars - Improved adhesion and waterproofing properties
• Slurry prime coats - For permanently immersed and submerged applications including ponds, pools, and water retaining structures

Mechanical Properties

The following properties were measured for a 3:1 sand:cement mortar containing Nitobond SBR (4 litres per 20kg cement) at 28 days air-cured in accordance with BS 6319:

These properties demonstrate that Nitobond SBR significantly enhances the mechanical performance of cementitious materials.

Key Advantages

• Excellent bond to concrete, masonry, stonework, plaster, and blockwork surfaces
• Improved tensile and flexural properties allowing thinner applications compared to standard mortars
• Enhanced cohesion and workability of cementitious mortars
• Waterproof repairs, renders, and toppings that are highly resistant to freeze/thaw cycling
• Improved chemical resistance through reduced permeability, helping to resist attack by aggressive chemicals, acid gases, and water
• Easy single-component application with no complex mixing requirements

Application Specifications

Thickness Requirements

Nitobond SBR mortars can be applied at varying thicknesses depending on application location:

• Horizontal applications: Up to 40mm thickness in single applications
• Vertical applications: Up to 15mm without formwork; greater thicknesses possible with formwork
• Overhead applications: Thickness dependent on substrate profile
• Minimum thickness: Not less than 6mm

Design Criteria

• Mortars can be built up in layers for applications exceeding standard single-application thresholds
• Formwork with properly sealed faces facilitates achieving required build-up thickness up to 40mm
• The thickness achievable without formwork is largely dependent on the substrate profile and repair area configuration

Environmental and Chemical Properties

Freeze/Thaw Resistance

Nitobond SBR mortars provide high resistance to freeze/thaw cycling through improved waterproofing properties, making them particularly suitable for exterior and weather-exposed applications.

Chemical Resistance

The addition of Nitobond SBR to cement mortars reduces permeability and therefore helps reduce the rate of attack by:

• Aggressive chemicals
• Acid gases
• Water infiltration

This property enhancement is critical for long-term durability in challenging environmental conditions.

Water Resistance

As a slurry prime coat mixed with sand and cement, Nitobond SBR creates a waterproof bonding primer suitable for permanently immersed and submerged applications, ensuring protection in water-exposed environments such as ponds, pools, and internal tank systems.

Environmental and Safety Data

VOC Content: 29 g/litre

The product is supplied with comprehensive Safety Data Sheets available from the Fosroc website, which should be read carefully prior to use as application or performance data may change over time.

Typical Mix Designs

Nitobond SBR is versatile and accommodates various mix designs:

1. Patching and repair mortar: 20kg GP Cement + 60kg sharp sand + 4 litres Nitobond SBR + 3 litres water (Yield: 38 litres, 6-40mm thickness)
2. Heavy-duty floor screed: 20kg GP Cement + 30kg crushed rock + 30kg sharp sand + 2.5 litres Nitobond SBR + 2.5 litres water (Yield: 37 litres, 10-40mm thickness)
3. Render: 20kg GP Cement + 60kg sharp sand + 2.5 litres Nitobond SBR + 2.5 litres water (Yield: 37 litres, 6-9mm thickness)
4. Bonding mortar for tiles: 20kg GP Cement + 50kg sharp sand + 4 litres Nitobond SBR + 3 litres water (Yield: 33 litres, 6-40mm thickness)

Slurry Prime Coat Formulation

For submerged applications, Nitobond SBR is prepared as a slurry primer consisting of:

• 1 volume Nitobond SBR
• 1 volume clean water
• 3 volumes fresh cement

This slurry provides essential priming before applying waterproofing membranes such as Nitoproof 410 in permanently immersed conditions.

References

• [1] Fosroc_Nitobond_SBR_TDS.pdf
• [2] Fosroc_Nitoproof_410_TDS.pdf