Conbextra HES: Technical Details, Specifications, Features, and Applications

Product Overview

Conbextra HES is a high early strength, rapid-setting, flowable cementitious precision grout supplied as a ready-to-use powder. It is manufactured by Fosroc and engineered for applications requiring rapid strength gain and free-flow grouting capabilities. The product is designed to facilitate rapid installation and operation of plant equipment within hours of application.

Key Characteristics and Advantages

Conbextra HES offers several distinctive advantages that make it suitable for demanding grouting applications:

• Rapid Strength Gain: Facilitates rapid installation and operation of plant within a matter of hours, even at low temperatures
• Excellent Initial Flow: Demonstrates excellent initial flow and flow retention characteristics
• Shrinkage Compensation: Unique system compensates for shrinkage in the hardened state through controlled expansion (Class C)
• Durability: High ultimate strength and low permeability ensure long-term durability of the hardened grout
• Chloride-Free: Formulated to be chloride-free, ensuring enhanced durability and corrosion resistance
• Wide Temperature Range: Suitable for application across a wide range of temperatures and consistencies
• RCS Hazard-Free: Classified as non-hazardous for Respirable Crystalline Silica (RCS) in accordance with Australian Inventory of Industrial Chemicals; contains <0.1% RCS
• Non-Shrink: Complies with ASTM C1107:2020 specification for non-shrink grout
• Pumping Capability: Suitable for pumping or pouring across various application conditions

Product Composition

Conbextra HES is a blend of cements, graded aggregates, and additives that impart controlled expansion in the hardened state. This cementitious blend is carefully formulated to:

• Minimize segregation and bleeding across a wide range of application consistencies
• Provide controlled expansion (Class C) to compensate for shrinkage
• Achieve low water requirements for high early strength
• Ensure long-term durability

The maximum aggregate size is 5.0mm.

Technical Properties and Test Results

Australian Standards Testing (AS 1478.2:2005)

Test Method	Consistency	2 Hours	4 Hours	8 Hours	24 Hours	28 Days
Compressive Strength (MPa)	Plastic	30	35	40	42	58
Compressive Strength (MPa)	Flowable	25	30	35	37	50

ASTM Specification C1107:2020 Test Results

Test Method	Standard	Result
Flow Consistency	ASTM C839:2016a	121%
Setting Time - Initial	ASTM C953:2017	30 minutes
Setting Time - Final	ASTM C953:2017	45 minutes
Change in Height at Early Age	ASTM C827:2016	+0.30%
Height Change - Hardened Grout (Moist Cure)	ASTM C1090:2015	1 day: +0.14%, 3 days: +0.18%, 14 days: +0.17%, 28 days: +0.18%
Compressive Strength - 1 Day	ASTM C109:2020b	45.6 N/mm²
Compressive Strength - 3 Days	ASTM C109:2020b	48.3 N/mm²
Compressive Strength - 7 Days	ASTM C109:2020b	58.1 N/mm²
Compressive Strength - 28 Days	ASTM C109:2020b	71.6 N/mm²

Additional Mechanical Properties (AS Standards)

Property	Standard	Result
Modulus of Elasticity	AS 1012.17:2000	23.4 GPa (at 3 hours)
Flexural Strength	AS 1012.11:2000	1 Day: 3.0 MPa, 7 Days: 4.5 MPa, 28 Days: 6.5 MPa
Indirect Tensile Strength	AS 1012.10:2000	1 Day: 1.5 MPa, 7 Days: 2.5 MPa, 28 Days: 3.0 MPa
Fresh Wet Density	ASTM C185:2020	2250 kg/m³ (depending on consistency used)
Alkali Reactive Particles	Rapid Mortar Bar Test (RTA T363)	Non-reactive
Flow Characteristics	AS 1478.2:2005	350mm (Flow Trough)

Application Range

• Minimum Thickness: 15mm
• Maximum Thickness: 150mm (single pour)
• Gap Thicknesses: 15mm to 150mm

Mixing Specifications

Mixing Procedure

A forced-action mixer is essential. The mixing process requires:

1. Mix for 3 to 5 minutes at a slow speed (400/500 rpm) in a suitably sized drum
2. Use appropriate equipment such as a 140mm helical mixing paddle fitted to a heavy-duty 1600W mixer
3. Measure the selected water content accurately into the mixing bucket
4. While mixing, slowly add the total contents of the Conbextra HES bag
5. Mix continuously for 3 to 5 minutes, ensuring a smooth, even consistency is obtained
6. Always add the powder to the water (not the reverse)

Water Requirements and Yield

Required Consistency	Litres of Water per 20kg Bag	Yield (litres of mixed material)
Plastic	2.0 - 2.3	10.0
Flowable	2.3 - 2.6	10.2

Note: The 28-day compressive strength of 50 MPa for flowable consistency was obtained at a water addition of 2.3 litres per 20kg bag.

Larger Volume Mixing

For larger quantities, a high shear vane mixer is required. Do not use a colloidal impeller mixer. Machine mixing capacity and labor availability must be adequate to enable continuous grouting operations. A holding tank with provision for gentle agitation may be necessary to maintain fluidity.

Placing Instructions

• Placement Time Window: Place the grout within 10 minutes of mixing
• Maximum Single Pour Thickness: Up to 150mm when used as an underplate grout
• For Deeper Pours: Where grouting gaps exceed 150mm up to 500mm, either use Conbextra Deep Pour or bulk out with Conbextra Grout Aggregate (not exceeding a 2:1 grout to aggregate ratio by weight)
• Continuous Flow: Continuous grout flow is essential
• Pouring Method: The mixed grout should be poured from one side of the void only to eliminate entrapment of air or surplus pre-soaking water. Pour across the shortest distance of travel while maintaining continuous grout head

Packaging and Supply

Conbextra HES is supplied in 20kg moisture-resistant plastic bags.

Product	Product Code
Conbextra HES 20kg	FC501060-20KG

Shelf Life and Storage

Conbextra HES has a shelf life of 18 months from the date of manufacture when stored in original, unopened bags. Do not use if:

• There are lumps in the product
• A loss of workability is experienced (requiring more water to be added)

Temperature Considerations

Low Temperature Working

• When air or contact surface temperatures are 15°C or below on a falling thermometer, warm water (30°C) is recommended to accelerate strength development
• For ambient temperatures below 15°C, the grout consistency should be flowable and formwork must be maintained in place for a minimum of 24 hours
• Normal precautions for winter working with cementitious materials should be adopted

High Temperature Working

• Conbextra HES should not be used at ambient temperatures above 35°C, as premature setting of the grout may occur, making handling and placement very difficult

Curing Requirements

On completion of the grouting operation, exposed areas should be thoroughly cured using:

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

Cleaning

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

Standards Compliance

Conbextra HES complies with ASTM C1107:2020 specification for non-shrink cementitious grout, ensuring it meets rigorous international standards for quality and performance.

Important Safety and Documentation

A Safety Data Sheet (SDS) is available from the Fosroc website and must be read carefully prior to use, as application or performance data may change from time to time.

References

• [1] Fosroc_Conbextra_HS_TDS.pdf
• [2] Fosroc_Conbextra_HES_TDS.pdf