Conbextra CB: High Flow Grout for Void Fill Applications

Product Overview

Conbextra CB is a highly flowable, high-strength, non-shrink Class A cable bolting grout supplied as a ready-to-use dry powder. It is specifically designed for void fill applications, including cable bolt grouting, backfilling behind concrete tunnel segments, and general civil applications.

Key Features and Advantages

Conbextra CB offers several distinctive advantages for demanding grouting operations:

• High strength development allows early tensioning of cables, enabling efficient project timelines
• Gaseous expansion system compensates for shrinkage in the plastic state, maintaining structural integrity
• Early high strength development without requiring chlorides, ensuring durability and safety
• Excellent pumpability across both flowable and thixotropic consistencies, providing application flexibility
• RCS (Respirable Crystalline Silica) Hazard Free classification, with less than 0.1% RCS content, supporting worker safety

Product Composition and Description

Conbextra CB is formulated as a ready-to-use dry powder requiring the addition of a controlled amount of clean water and mechanical mixing in a high shear grout mixer to achieve the desired consistency. This pre-packaged format eliminates on-site mixing variations while maintaining precise quality control.

Technical Specifications and Properties

Compressive Strength

The product demonstrates excellent strength development across multiple testing intervals when mixed with different water additions:

Additional Properties

• Fresh Wet Density: 2100 kg/m³
• Pumping Life: 120 minutes
• Set Time: 7.5 hours
• Shelf Life: 36 months from date of manufacture (when stored in original, unopened bags)

Application Methods

Preparation

Prior to application, ensure that holes are clean and free from debris. Install cables carefully to prevent kinking of the breather tube. Position and secure the grout tube at the bottom of the hole. It is recommended to flush water through grouting lines and up the hole to provide lubrication and prevent water absorption into the strata.

Mixing Requirements

A forced-action mixer is essential for proper preparation. Mix for 3 to 5 minutes at slow speed (400/500 rpm) in an appropriately sized drum using equipment such as a 120/140mm helical mixing paddle fitted to a heavy-duty 1500W mixer. For larger quantities, a high shear vane mixer is required. Do not use a colloidal impeller mixer.

Water requirements per 20kg bag:

• Thixotropic consistency: 5.1 - 5.8 litres
• Flowable consistency: 5.8 - 6.8 litres

Fill the mixer with required water, start the mixer, then slowly add Conbextra CB powder. The entire bag contents should be slowly added and continuously mixed for 3 to 5 minutes until lump-free.

Placing Procedure

Continuous flow of grout is essential during placement. Ensure sufficient grout is available to completely fill the hole. Stop pumping when air ceases to bubble from the breather tube. Ensure the grout tube is folded and tied off to prevent seepage from the hole.

Yield and Supply

Each 20kg bag yields approximately 12 to 13 litres at the recommended consistency. Conbextra CB is made to order and supplied in 20kg moisture-resistant plastic bags, with product code FC501087-20KG. Minimum order quantity is 75 x 20kg bags with a lead time of 14-21 days.

Storage and Shelf Life

Conbextra CB has a shelf life of 36 months from the date of manufacture when kept in original, unopened bags. If stored in high temperature and high humidity locations, the shelf life may be reduced. Do not use if lumps appear in the product or loss of workability is experienced.

Safety and Documentation

A Safety Data Sheet (SDS) is available from the Fosroc website and should be read carefully prior to use, as application or performance data may change over time. In emergencies, contact any Poisons Information Centre (phone 13 11 26 within Australia) or consult a doctor for advice.

References

• [1] Fosroc_Conbextra_CB_TDS.pdf