AT System: SERVITITE® AT 200/SERVISEAL® AT 240

Description

AT System waterstops have been specially developed for water excluding and retaining structures such as basements, reservoirs, sewage treatment works, etc. The AT System is an important advance in concrete joint protection which combines Active Technology with the conventional mechanical properties of PVC waterstops.

Conventional PVC waterstops work by the normal action of the concrete shrinking away from the joint and against one face of the ribs or bulbs of the waterstop. This creates positive pressure on the rib or bulb causing a “valve action” to resist water ingress. However, this shrinkage movement also forms an inevitable void on the opposite face of the rib or bulb which can allow water under high pressure to track along the waterstop searching for a path to bypass the waterstop. Subsequent cyclical movement of the joint can compound the problem resulting in further leakage.

AT System waterstops mechanical properties prevent water ingress by the same valve action but also actively seal the void around the rib or bulb to stop water bypassing or migrating. The hollow core of the bulb deforms to control the expansive forces to prevent damage to the concrete.

Advantages

• Increased security – combines advantages of PVC waterstop with active hydrophilic elements to provide maximum resistance to water pressure
• Continuously active sealing – hydrophilic elements swell in contact with water to plug voids formed by normal concrete shrinkage
• Prevents water tracking – location of active element is designed to prevent lateral migration of water along waterstop bulb
• Engineered profile – for construction and expansion joints
• Co-extruded section – integral active elements cannot be displaced during concreting
• Protective coating – prevents premature swelling of hydrophilic element whilst exposed and for 12 to 18 days after casting to avoid spalling of fresh concrete
• Simple installation – fix and heat weld as conventional waterstops
• Comprehensive system – internal and externally placed sections complete with a range of factory fabricated junction pieces

Effect on SERVITITE® AT 200 after concrete cures and comes into contact with water

Conventional Waterstop

AT System with Active Element

^{Details shown are typical illustrations only and not working drawings. For assistance with working drawings and additional technical advice please contact GCP Technical Services.}

Construction/Expansion/Movement Joints

SERVITITE® AT 200

SERVISEAL® AT 240

Performance

Property	Typical Values
Tensile Strength	> 14 N/mm2
Elongation at break	> 250%
Shore A Hardness	80 ± 4
Specific Gravity	1.4

Applications

SERVITITE® AT 200 is an internally placed waterstop; which is cast centrally in the concrete to resist internal and external water pressure. SERVISEAL® AT 240 is cast on the external face for water excluding structures, such as basements and sub structures or ground bearing slabs only of water retaining structures. The two profiles can be combined, using factory produced transition junctions where SERVISEAL® AT 240 is used on the base slab and SERVITITE® AT 200 is used within walls.

SERVITITE® AT 200 and SERVISEAL® AT 240 can be supplied in rolls with standard or special junction pieces, or alternatively formed in fabrications to minimise site jointing. Butt jointing is achieved by heat fused welds similar to that for traditional PVC waterstops.

Installation

A continuous waterstop network should be used at all joints to prevent the ingress of moisture using only factory produced fabrications for changes of direction or profile with site jointing limited to simple butted welds. Before concreting, waterstops must be clean and free from concrete laitance, oil, grease or any other contamination that might prevent a good waterstop to concrete bond.

SERVISEAL® AT 240 Slab Joints

The SERVISEAL® AT 240 waterstop should be loose laid directly on the blinding concrete or securely fixed into vertical shutters using nails bent over to prevent displacement during stripping of shutter.

SERVITITE® AT 200 Elevated Slab Joints

The SERVITITE® AT 200 waterstop should be supported in specially prepared split stop-end formwork which holds the waterstop in the horizontal plane to prevent displacement and folding. Care must be taken to ensure that the waterstop is retained in the horizontal plane and that adequate compaction of concrete takes place below the web of the waterstop in order to avoid “honeycombing”. Lifting the waterstop during compaction to release entrapped air will assist in forming good dense concrete free from voids.

After stripping the formwork, the second half can be cast into the adjoining slab with similar precautions taken with regard to “honeycombing”.

Wall Joints

The SERVITITE® AT 200 waterstop must be supported in split-end formwork as described for slab joints, with great care taken to ensure that the waterstop does not fold over under the weight of poured concrete. The waterstop should be securely wired to the reinforcing steel using Large Secura Clips fastened over the end bulbs. Swelling commences 12 to 18 days after being embedded in concrete.

Factory made junctions and fabrications

Available in shapes and configurations to suit site requirements. Coils and fabrications supplied in polyethylene wrapping to protect against the elements.

Storage

Under cover protected from water and temperatures exceeding +40°C.

Ancillary Products

Small (20 mm) Secura Clips - to tie SERVITITE® AT 200 reinforcement

Equipment by GCP

Jointing Jigs

Jig AT System (AT 200/AT 240)

Welding Knife

Electric Knife Large (110v and 220v)

Equipment by Others:

Fine tooth saw, wire brush, Stanley knife, 110v or 220v power source

Limitations

Store covered with a waterproof sheet. Maximum exposure period before concrete encapsulation, 7 days.

Health and Safety

For SERVITITE® AT 200 & SERVISEAL® AT 240 read the Safety Data Sheet (SDS) before use. Irritating fumes (Hydrogen Chloride) will be liberated when the product is heat welded. Ensure adequate ventilation. There is no legal requirement for a SDS for Secura clips. SDS’s can be obtained from GCP Applied Technologies or from our web site at gcpat.com.

NBS Specification Clause

Refer to Clause E40 310.