Conbextra HS: Ultra High-Strength Flowable Grout

Overview

Conbextra HS is a dual shrinkage compensated, ultra high-strength cementitious grout specifically designed for heavy-duty precision grouting applications. It is supplied as a ready-to-use dry powder that produces a free-flowing precision grout when mixed with controlled amounts of clean water.

Product Description

Conbextra HS is formulated as a blend of portland cements, graded fillers, and chemical additives that impart controlled expansion in both the plastic and hardened states. The filler grading is engineered to minimize segregation and bleeding across a wide range of application consistencies, ensuring consistent performance regardless of placement conditions.

The low water requirement of the product ensures high early strength and long-term durability, making it suitable for demanding construction environments. The maximum aggregate size for pumping applications is 1.0mm.

Key Features and Advantages

• Dual Shrinkage Compensation: Non-metallic dual expansion system (Class A & Class C) compensates for shrinkage in both plastic and hardened states
• Non-Shrink Certification: Complies with ASTM C1107:2020 non-shrink specification
• Excellent Flow: Excellent initial flow and flow retention suitable for both large and small grout pours
• Rapid Strength Gain: Facilitates efficient installation and operation of plant equipment
• High Durability: High ultimate strength and low permeability ensure durability of hardened grout
• Hydrogen-Free Expansion: Non-metallic gaseous expansion system
• Chloride-Free Formulation: Safe for use in chloride-sensitive environments
• Versatile Application: Suitable for pumping or pouring over a large range of application consistencies and temperatures
• Health and Safety: RCS (Respirable Crystalline Silica) Hazard Free (contains <0.1% RCS)

Application Range

Conbextra HS is designed for gap thicknesses ranging from 10mm to 125mm. Primary applications include:

• Baseplates and soleplates of large machines subject to moderate dynamic loads
• Crane rail soleplates, beams, columns, and structural building members
• Heavy-duty precision grouting where high flow and high ultimate strength are required

Technical Specifications

Compressive Strength (MPa)

The compressive strength of Conbextra HS varies based on consistency and temperature conditions:

At 23°C (Flowable Consistency):

• 8 hours: 5 MPa
• 12 hours: 20 MPa
• 1 day: 55 MPa
• 7 days: 80 MPa
• 28 days: 100 MPa
• 56 days: 105 MPa

At 30°C (Flowable Consistency):

• 8 hours: 26 MPa
• 12 hours: 40 MPa
• 1 day: 60 MPa
• 7 days: 90 MPa
• 28 days: 100 MPa
• 56 days: 105 MPa

Fluid Consistency (23°C):

• 1 day: 40 MPa
• 7 days: 70 MPa
• 28 days: 85 MPa
• 56 days: 90 MPa

Flexural Strength

• 1 day: 5.8 MPa
• 7 days: 11.4 MPa
• 28 days: 13.7 MPa

Flow Characteristics

Flow distances are provided as guidelines and vary based on gap depth and hydrostatic head:

Flowable Consistency (100mm Head):

• 10mm gap: 300mm
• 20mm gap: 760mm
• 30mm gap: 1200mm
• 40mm gap: 1760mm
• 50mm gap: 2400mm

Flowable Consistency (250mm Head):

• 10mm gap: 960mm
• 20mm gap: 2080mm
• 30mm gap: 2400mm
• 40mm gap: 2400mm+
• 50mm gap: 2400mm+

Fluid Consistency (23°C):

• 10mm gap: 900mm (100mm head), 2500mm (250mm head)
• 20mm gap: 1900mm (100mm head), 3000mm (250mm head)
• 30mm gap: 3000mm (100mm head), 3000mm+ (250mm head)

Fresh Material Properties

• Fresh Wet Density: 2200 kg/m³ (flowable consistency)
• Setting Time:
  • Initial set: 240 minutes
  • Final set: 295 minutes

Consistency Options and Water Requirements

Flowable Consistency:

• Water required: 2.7 litres per 20kg bag
• Yield: 9.8 litres of mixed material

Fluid Consistency:

• Water required: 3.0 litres per 20kg bag
• Yield: 10.1 litres of mixed material

Standards Compliance

Conbextra HS meets the following standards:

• AS 1478.2:2005: Australian standard for grout testing
• ASTM C1107:2020: Non-shrink grout specification
• AS 1530.3-1999: Fire testing specification
• EN 12190: European standard for grout
• ASTM C939:2016a: Flow consistency testing (>104%)
• ASTM C953:2017: Setting time testing
• ASTM C827:2016: Early age expansion testing
• ASTM C1090:2015: Hardened grout height change testing
• ASTM C109:2020b: Compressive strength testing

Fire Classification

• Ignitability Index: 0
• Spread of Flame Index: 0
• Heat Evolved Index: 0
• Smoke Developed Index: 0-1

Packaging and Storage

Supply:

• Conbextra HS 20kg: FC502000-20KG

Shelf Life:

• 36 months from date of manufacture when kept in original, unopened bags

Storage Conditions:

• Store in dry conditions in original, unopened moisture-resistant plastic bags
• Do not use if lumps are present or loss of workability is experienced

Preparation and Application Requirements

Foundation Surface Preparation

The substrate surface must be free from oil, grease, or loosely adherent material. If concrete surfaces are defective or have laitance, they must be cut back to sound base. For maximum bond, surfaces should be abraded or roughened using mechanical means such as needle gun, grit blasting, or grinding. Bolt holes and fixing pockets must be blown clean of dirt and debris.

Formwork Requirements

Formwork must be constructed to be leakproof as Conbextra HS is a free-flowing grout. This can be achieved using foam rubber strip or construction silicone sealant beneath the formwork and between joints. The formwork should include outlets for draining pre-soaking water, and the unrestrained surface area should be kept to a minimum.

Mixing Procedure

A forced-action mixer operating at 400-500 rpm is essential. Mix for 3 to 5 minutes at slow speed in a suitably sized drum. Always add the powder to water, not vice versa. For larger volumes, a high shear vane mixer is required.

Placement

Place grout within 15 minutes of mixing to gain full benefit of the expansion process. Conbextra HS can be placed in thicknesses up to 125mm in a single pour. Continuous grout flow is essential, and the grout must be poured from one side of the void to eliminate air entrapment.

Temperature Limitations

• Low Temperature: When air or contact surface temperatures are 5°C or below, warm water (30-40°C) is recommended. For temperatures below 10°C, flowable consistency should be used and formwork maintained for at least 36 hours.
• High Temperature: At temperatures above 35°C, store mixed grout in shade and use cool water (below 20°C) for mixing.

Health and Safety

Conbextra HS is alkaline and should not contact skin and eyes. Appropriate personal protective equipment including gloves, goggles, and dust masks should be worn during mixing. A Safety Data Sheet (SDS) is available from the Fosroc website and should be read prior to use. In emergencies, contact the Poisons Information Centre at 13 11 26 (within Australia).

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References

• [1] Fosroc_Conbextra_HS_TDS.pdf
• [2] Fosroc_Conbextra_HF_TDS.pdf
• [6] Fosroc_Conbextra_Deep_Pour_TDS.pdf