Hydrocell: Semi-Rigid Polyethylene Joint Filler

Product Overview

Hydrocell is a semi-rigid, UV-resistant, cross-linked, closed-cell polyethylene sheet material designed as a non-absorbent joint filler for construction and sealing applications. Manufactured by Fosroc, it serves as a multi-purpose backing strip and joint filler material for expansion joints in various structural applications.

Key Features and Advantages

Hydrocell offers several distinguishing characteristics that make it suitable for demanding construction environments:

• Non-absorbent: Water absorption is less than 2% after 28 days, ensuring durability in wet conditions
• Non-tainting and rot-proof: Suitable for use with potable water applications and drinking water storage structures
• Semi-rigid composition: Provides continual joint support, distinguishing it from open-cell alternatives
• UV resistant: Enables reliable performance in outdoor and exposed applications
• Bitumen free: Safe for use in diverse environmental conditions
• Heat resistant: Maintains performance in applications up to 80°C

Technical Specifications

Material Properties

Property	Specification
Form	Semi-rigid, closed-cell, polyethylene foam sheet
Density	110 kg ± 5 kg per m³
Water Absorption	Less than 2% after 28 days
Load (50% compression)	420 kPa
Recovery	>90%
Extrusion	0.5 mm (at 50% compression)
Chemical Resistance	Excellent to hydrochloric acid, caustic soda, acetone, motor fuel, and diesel fuel

Standards Compliance

• AS 4020:2018: Suitable for use in drinking water at an exposure level of 15,000mm² per litre (AWQC Report 320286)
• TfNSW Specification 3204: Meets performance requirements for preformed joint fillers for concrete road pavements and structures
• Accelerated Weathering: Excellent performance with no degradation

Primary Applications

Hydrocell is utilized in forming expansion joints across diverse construction applications:

• Brickwork and blockwork construction
• Concrete structures: Roads, bridges, and deck slabs
• Water-retaining structures: Dams, reservoirs, culverts, and irrigation channels
• Water-excluding structures: Basement structures, subways, and sewage treatment works
• Heavy traffic environments: Concrete roads and traffic-bearing floor joints
• Potable water facilities: Raw and potable water reservoirs

Function as Backing Strip and Bond Breaker

Hydrocell serves a critical dual function in joint sealing systems:

Backing Strip Support

As a backing strip material, Hydrocell provides firm, consolidated support for joint sealants, preventing excessive compression and ensuring proper sealant depth maintenance.

Bond Breaker Mechanism

Hydrocell acts as an effective bond breaker in deep joints, preventing sealants (particularly elastomeric sealants) from adhering to the bottom of the joint. This three-sided bonding arrangement is essential for allowing sealants to flex and move appropriately as joints expand and contract, thereby ensuring long-term performance and durability of the sealing system.

Comparison with Alternative Products

vs. Expandafoam Open Cell

Hydrocell is recommended as an alternative to Expandafoam Open Cell for applications requiring continual joint support, particularly in:

• Water-retaining structures
• Floor joints subject to traffic
• Heavy load applications

vs. Hydrocor Corkjoint Type 3 and Type 106

While Hydrocor Corkjoint products provide self-expanding cork alternatives, Hydrocell offers a non-staining polyethylene option, making it particularly suitable for applications where staining concerns exist, especially with light-colored concrete or exposed aggregate finishes.

Application Instructions

Joint Sealing Slots

Hydrocell can be supplied pre-cut with a "zip top" feature, or joint sealing slots can be formed on-site by:

1. Cutting off a strip to the required depth
2. Pinning the strip back onto the main filler using small nails
3. Installing the filler flush with the finished surface
4. Pulling the top strip easily from the joint prior to sealing to provide an uncontaminated sealing slot

Installation Considerations

• In suspended slabs, partly projecting copper nails or daubs of adhesive help prevent displacement
• Elastomeric sealants will not bond to Hydrocell, eliminating the need for additional bond breaker strips
• Proper positioning ensures accommodation of required sealant depth

Supply Specifications

Hydrocell is supplied in sheet sizes of 2.4m long × 1.2m wide with the following thickness options:

• 10mm (FC701000-UNIT)
• 15mm (FC701010-UNIT)
• 20mm (FC701015-UNIT)

The material can be easily cut to required size with a sharp knife or fine saw.

Storage Requirements

Hydrocell should be stored in a clean area and not left exposed for long periods, especially in hot climates, to maintain optimal performance characteristics.

References

• [1] Fosroc_Hydrocell_TDS.pdf
• [2] Fosroc_Expandafoam_Open_Cell_TDS.pdf
• [3] Fosroc_Hydrocor_Corkjoint_Type_106_TDS.pdf