Conbextra C: Dual Shrinkage Compensated Cementitious Grout

Product Overview

Conbextra C is a high-flow, dual shrinkage compensated, precision cementitious grout supplied as a ready-to-use dry powder. It is specifically designed for general-purpose grouting applications where high flow and dual shrinkage compensation are required. The product is manufactured and sold under license from Fosroc International Limited by Parchem Construction Supplies Pty Ltd.

Key Features and Advantages

Conbextra C offers several distinctive characteristics that make it suitable for demanding grouting applications:

• Dual Expansion System: Compensates for shrinkage in both plastic and hardened states, providing superior dimensional stability
• Non-Shrink Compliance: Meets ASTM C1107:2020 standards for non-shrink properties
• High Ultimate Strength: Ensures durability and longevity of hardened grout with low permeability
• Versatile Application Methods: Can be dry packed/rammed, trowelled, flowed, and pumped
• Hydrogen-Free Gas Expansion: Non-metallic iron content prevents rusting
• RCS Hazard Free: Classified as not hazardous for Respirable Crystalline Silica (RCS), containing less than 0.1% RCS
• Pre-packaged Material: Overcomes potential on-site mixing variations
• Prepackaged material provides consistent quality across applications

Product Composition

Conbextra C is a blend of Portland cement, specially graded fillers, and chemical additives that work together to provide:

• Controlled expansion in both plastic and hardened states
• Minimized water demand ensuring high early strength
• Uniform mixing characteristics through graded filler design
• Consistent, flowable grout production
• Maximum aggregate size of 0.3mm for pumping applications

Application Range

Conbextra C is designed for gap thicknesses ranging from 10mm to 100mm. Typical applications include:

• Baseplates and soleplates of machines
• Structural steel column baseplates
• Voids between precast concrete and infilling blockwork

Compressive Strength Properties

Conbextra C demonstrates progressive strength development across multiple time intervals and consistency levels:

Consistency	1 Day (MPa)	7 Days (MPa)	28 Days (MPa)
Stiff	45	60	70
Plastic	35	50	60
Flowable	25	45	55

Additional Strength Properties

• Flexural Strength (Modulus of Rupture): 5.0 MPa (1 day), 9.5 MPa (7 days), 9.6 MPa (28 days)
• Indirect Tensile Strength: 2.7 MPa (1 day), 4.4 MPa (7 days), 4.8 MPa (28 days)
• Fresh Wet Density: 2100 kg/m³ (depending on consistency used)

ASTM C1107:2020 Test Results

Conbextra C meets rigorous international standards with the following performance characteristics:

Test Method	Standard	Result
Flow Consistency	ASTM C939:2016a	>145%
Setting Time (Initial:Final)	ASTM C953:2017	300 mins : 360 mins
Volume Change at Early Age	ASTM C827:2016	+0.40%
Volume Change of Hardened Grout (moist cured)	ASTM C1090:2015	+0.01% to +0.03% (1-28 days)
Compressive Strength	ASTM C109:2020b	23.3 N/mm² (1 day) to 56.2 N/mm² (28 days)

Thickness Specifications

• Minimum Thickness: 10mm
• Maximum Thickness: 100mm (single pour application)

Mixing Requirements

Water Addition Rates

The water content directly affects the consistency and yield of the mixed grout:

Required Consistency	Litres of Water per 20kg Bag	Yield (Litres of Mixed Material)
Stiff	2.6 - 3.4	10.4
Plastic	3.4 - 3.6	10.7
Flowable	3.6 - 3.9	10.8

Mixing Equipment and Procedure

• Mixer Type: Forced-action mixer operating at 400-500 rpm (slow speed)
• Mixing Duration: 3 to 5 minutes
• Equipment: 140mm helical mixing paddle fitted to a heavy-duty 1600W mixer
• Procedure: Add powder to water (not water to powder) while continuously mixing to ensure smooth, consistent mixture
• Large Volumes: High shear vane mixer recommended (do not use colloidal impeller mixer)

Placement and Curing

Preparation Requirements

• Foundation Surface: Must be free from oil, grease, and loosely adherent material; defective surfaces should be cut back to sound base; mechanical abrasion recommended
• Base Plate: Clean and free from oil, grease, scale, paint, or coatings; air pressure relief holes required
• Pre-soaking: Grouting area should be filled with clean water for minimum 2 hours before application; free water must be removed by draining or vacuum before grouting

Application Timing and Flow

• Placement Window: Within 20 minutes of mixing at 23°C to gain full benefit of expansion process
• Continuous Flow: Essential to prevent air entrapment and ensure complete void filling
• Flow Characteristics: 400-600mm (Flow Trough) as measured by AS 1478.2:2005

Curing Methods

Exposed areas should be thoroughly cured using:

• Concure curing membrane, or
• Continuous application of water and/or wet hessian

Cleaning

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

Environmental and Temperature Considerations

Low Temperature Working

• Below 5°C: Grouting should be postponed when air or contact surface temperatures are 5°C or below on a falling thermometer
• Below 10°C: Formwork should be maintained in place for at least 36 hours
• Standard precautions for winter working with cementitious materials should be adopted

High Temperature Working

• Above 35°C: Cool water (below 20°C) should be used for mixing to maintain proper grout properties

Supply and Storage

Packaging

Conbextra C is supplied in 20kg moisture-resistant plastic bags with product code FC501040-20KG.

Shelf Life and Storage Conditions

• Shelf Life: 36 months from date of manufacture
• Storage Requirements: Keep in original, unopened bags in dry conditions
• Quality Check: Do not use if lumps are present or if loss of workability is experienced (requiring excess water addition)

Standards Compliance

Conbextra C meets the following standards:

• AS 1478.2-2005 Appendix E: Early Volume Change test
• AS 1478.2-2005 Table 4.1.2.2: Consistency test
• ASTM C1107:2020: Non-shrink cementitious grout specification
• AS 1012.11-2000: Flexural strength testing
• AS 1012.10-2000: Indirect tensile strength testing

Alternative Products and Recommendations

For applications requiring maximum flow properties and extended flow retention times, Conbextra HF should be considered as an alternative. For grouting gaps exceeding the maximum thickness of 100mm up to 500mm, Conbextra Deep Pour is available as a specialized solution.

Safety and Technical Documentation

A Safety Data Sheet (SDS) is available from the Fosroc website and must be read carefully prior to use. In emergency situations, contact any Poisons Information Centre (phone 13 11 26 within Australia) or a doctor for advice. The Technical Data Sheet should be reviewed as application or performance data may be updated periodically.

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References

• [1] Fosroc_Conbextra_C_TDS.pdf
• [2] Fosroc_Conbextra_Deep_Pour_TDS.pdf
• [4] Fosroc_Conbextra_HF_TDS.pdf