Conbextra BB92 Ultra-High Performance Grout: Technical Details, Specifications, and Features

Product Overview

Conbextra BB92 is an ultra-high performance cementitious grout supplied as a ready-to-use dry powder specifically engineered for structural grouted connections in critical infrastructure applications. The product is primarily designed for wind turbine and wind turbine foundation installations, with additional applications in oil and gas installations.

Product Description

Conbextra BB92 is formulated to create a free-flowing precision grout when mixed with a controlled amount of clean water. The product is engineered to deliver reliable, long-term performance in the challenging environmental and operational conditions typical of the wind energy and oil and gas sectors. It functions as a mechanically powered grout product that requires strict adherence to specific procedures regarding mixing, placing, curing, and storage to ensure optimal performance and structural integrity of grouted connections.

Packaging and Yield

The product is available in dry powder form in bags with documented sizes of both 20kg and 25kg:

• 20kg bags yield approximately 9.5 litres of grout
• 25kg bags yield approximately 12.0 litres of grout

Key Specifications

Water Requirements

Conbextra BB92 requires water for preparation with a recommended mixing ratio:

• 2.2 to 2.4 litres of water per 20kg bag
• 2.5 to 3.0 litres per 25kg bag

Gap Depth Capability

• Suitable for gap depths in the range of 10 to 150mm (for standard placement)
• Can be placed in thicknesses up to 200mm in a single pour for large volumes

Compressive Strength

Conbextra BB92 achieves specified compressive strength values under laboratory testing conditions:

• 1 Day: >60 N/mm² (Flowable consistency at 0.12 w/p ratio)
• 7 Days: >80 N/mm²
• 28 Days: >90 N/mm²

At lower water-to-powder ratios (pumpable 0.10 w/p ratio):

• 1 Day: >70 N/mm²
• 7 Days: >90 N/mm²
• 28 Days: >100 N/mm²

Flexural and Tensile Strength

• Flexural Strength: >7.5 N/mm² @ 1 day; >11 N/mm² @ 7 days; >13 N/mm² @ 28 days
• Indirect Tensile Strength: 4.8 MPa (AS1012.10)

Flow Characteristics

• Initial Flow @ 20°C (EN 1015-3 cone): 290 - 315 mm
• Brass cone flow: 240 - 280mm
• Final set: <5 hours (AS1012.18)

Physical Properties

• Wet density: 2.29 kg/litre
• Granulometry: 0 - 2mm
• Expansion: 0-1%
• Fresh mixture density: 2.25 - 2.35 kg/m³

Performance Advantages

Conbextra BB92 offers several key performance characteristics:

• High Fatigue Resistance - Designed to withstand repetitive and dynamic loading typical of wind turbine operations
• Non-shrink - Compensates for shrinkage and settlement in the plastic state
• No Segregation or Bleeding - Ensures consistent final physical performance and prevents pump blockages
• High Early Strength - Enables quick return to service and removal of temporary supports
• Made in Australia - Locally manufactured product
• Suitable for Pumping or Pouring - Versatile application methods across large range of applications

Storage and Shelf Life

Conbextra BB92 has a shelf life of 12 months from date of manufacture if kept in dry store in the original, unopened bags.

Storage Conditions

• Store in dry conditions in the original, unopened packaging
• If stored at high temperatures and/or high humidity conditions, the shelf life may be reduced
• Do not use if there are lumps in the product, or if a loss of workability (requiring more water to be added) is experienced

Standards Compliance

Conbextra BB92 complies with EN 1504-6:2006 for anchoring and grouting products, meeting requirements for:

• Pull-off strength: displacement ≤ 0.6 mm for a 75 KN load
• Chloride ion content: ≤ 0.05%
• Reaction to fire: Class A1
• Dangerous substances: Complies with 5.3

Application Instructions

Foundation Surface Preparation

The substrate surface must be free from oil, grease or any loosely adherent material. If the concrete surface is defective or has laitance, it must be cut back to a sound base. Bolt holes or fixing pockets must be blown clean of any dirt or debris.

Base Plate Requirements

It is essential that the base plate is clean and free from oil, grease or scale before Conbextra BB92 application.

Pre-soaking

The formed grouting area should be pre-soaked with clean water for a minimum of 2 to 3 hours (or several hours prior to grouting). Immediately before grouting, any free water should be removed by draining or vacuum. Particular care should be taken to blow out any bolt holes and pockets.

Mixing Process

The mixing process involves:

• Adding Conbextra BB92 powder to water and mixing continuously for 5 minutes
• Use of a mechanically powered grout mixer for best results
• For quantities up to 50kg, a slow speed mixer fitted with a high shear paddle is suitable
• Larger quantities require a high shear vane mixer
• Note that during the first 2-3 minutes consistency will appear dry—do not add additional water unless expressly instructed

Placing

• Placing should only commence once flow properties are confirmed using the specified flow test (EN 1015-3 flow cone)
• For large volumes, Conbextra BB92 shall be pumped with the stinger at the bottom of the trench
• The mixed grout should be poured only from one side of the void to eliminate entrapment of air or residual water
• Continuous grout flow is essential
• The grout head must be maintained at all times to achieve a continuous grout front
• In windy conditions, freshly installed grout should be protected by draping dampened hessian

Curing

On completion of the grouting operation:

• Exposed areas should be thoroughly cured using Fosroc Concure A99 curing membrane
• Wrap with wet hessian/polyethylene
• Curing compound should also be applied to the exposed edge of the grout after formwork is removed
• Formwork must remain in place for a minimum of 24 hours to allow adequate initial set and curing

Formwork Requirements

• Formwork should be constructed to be leakproof as Conbextra BB92 is a free flowing grout
• All joints must be well sealed
• Steel angle is suitable for making reusable forms
• The unrestrained surface area must be kept to a minimum
• Generally, gap width between perimeter formwork and plate edge should not exceed 100mm on the pouring side and 70mm on the opposite side
• No gap at the flank sides

Temperature Limitations

Conbextra BB92 has specific temperature application requirements:

• Minimum: 5°C and rising; substrate must be free of ice
• Maximum: 35°C (at higher temperatures, store mixed grout in shade and use cool water below 20°C for mixing)
• When air or contact surface temperatures are around 5°C, it is recommended to warm-condition the product and mixing water
• Grout should not be exposed to moving water or rainfall during application and prior to final set
• When grouting at temperatures below 5°C or above 35°C, contact Fosroc for advice

Health and Safety

Conbextra BB92 is alkaline and should not come in contact with skin and eyes:

• Avoid inhalation of dust during mixing
• Gloves, goggles and dust mask should be worn
• If contact with skin occurs, wash with water
• Splashes to eyes should be washed immediately with plenty of clean water and medical advice sought
• In emergency, contact any Poisons Information Centre (phone 13 11 26 within Australia) or a doctor for advice

Cleaning

Conbextra BB92 should be removed from tools and equipment with clean water immediately after use. Cured material can be removed mechanically.

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References

• [1] Fosroc_Conbextra_BB92_TDS.pdf
• [2] Fosroc_Conbextra_BB92_(AU)_TDS.pdf