Conbextra CB - High Flow Cementitious Grout for Void Fill Applications

Product Overview

Conbextra CB is a highly flowable, high-strength Class A grout supplied as a ready-to-use dry powder. It is specifically formulated as a non-shrink cable bolting grout designed for void fill applications. The product combines excellent flow characteristics with rapid strength development, making it suitable for demanding grouting operations.

Key Features and Advantages

Conbextra CB offers several distinctive advantages for cable bolting and void fill applications:

• High strength development that allows early tensioning of cables, enabling faster project scheduling
• Gaseous expansion system that compensates for shrinkage in the plastic state, ensuring complete void filling
• Early high strength development without requiring chlorides, providing durability and safety
• Excellent pumpability over both flowable and thixotropic consistencies, offering application flexibility
• RCS (Respirable Crystalline Silica) Hazard Free classification, containing less than 0.1% RCS, ensuring worker safety

Primary Applications

Conbextra CB is ideally suited for:

• Backfilling behind concrete tunnel segments in underground construction projects
• Bottom-up cable bolt grouting applications where controlled placement and early strength are critical
• General civil applications requiring void filling with high flow properties

Product Specifications

Physical Properties

Conbextra CB exhibits the following properties when tested at 23°C:

Compressive Strength Development

The product demonstrates progressive strength gain across different water additions:

Supply and Yield

• Supplied as: 20kg moisture-resistant plastic bags (made to order)
• Product Code: FC501087-20KG
• Minimum Order Quantity: 75 bags (20kg each)
• Lead Time: 14-21 days
• Typical Yield: Approximately 12-13 litres per 20kg bag at recommended consistency

Mixing Requirements

Mixing Equipment

A forced-action mixer is essential for proper preparation. Recommended equipment includes:

• 120/140mm helical mixing paddle
• Heavy-duty 1500W mixer
• Mixing speed: 400-500 rpm (slow speed)
• For larger quantities: high shear vane mixer

Important Note: Do not use colloidal impeller mixers, as these do not produce uniform grout consistency.

Water Requirements

Water requirements vary based on desired consistency:

• Thixotropic: 5.1 - 5.8 litres per 20kg bag
• Flowable: 5.8 - 6.8 litres per 20kg bag

Mixing Procedure

1. Fill the mixer with required water first
2. Start the mixer
3. Slowly add Conbextra CB powder to prevent lump formation
4. Continuously mix for 3 to 5 minutes until lump-free
5. Ensure uniform consistency throughout

Application Instructions

Preparation

• Ensure all holes are clean and free from debris
• Install cable carefully to avoid kinking the breather tube
• Position and secure the grout tube correctly at the bottom of the hole
• Recommend pre-flushing grouting lines with water to provide lubrication and prevent water absorption into strata

Placing Process

• Continuous flow of grout is essential throughout the application
• Ensure sufficient grout is available before starting to prevent interruptions
• Stop pumping when air ceases to bubble out of the breather tube
• Fold and tie off the grout tube after completion to prevent seepage

Cleaning

• Remove Conbextra CB from tools and equipment immediately after use with clean water
• Cured material can be removed mechanically using appropriate equipment

Storage and Shelf Life

Conbextra CB has a shelf life of 36 months from the date of manufacture when kept in original, unopened bags. Storage conditions should meet the following requirements:

• Store in dry conditions
• Keep original packaging unopened
• Do not use if lumps are present in the product
• Do not use if loss of workability is experienced (requiring excessive additional water)
• High temperature and humidity environments may reduce shelf life

Safety and Health Information

Health and Safety Considerations:

• A Safety Data Sheet (SDS) is available from the Fosroc website
• Read both the SDS and Technical Data Sheet carefully prior to use
• Application or performance data may change over time
• In emergency situations, contact any Poisons Information Centre (phone 13 11 26 within Australia) or seek medical advice

Technical Classification

Conbextra CB meets Class A grout classification, indicating:

• High strength performance characteristics
• Reliable and predictable behavior in grouting applications
• Suitable for structural and demanding applications

References

• [1] Fosroc_Conbextra_CB_TDS.pdf
• [2] Fosroc_Conbextra_Deep_Pour_TDS.pdf