Frequently Asked Questions

What is the correct width and spacing of expansion joints in a concrete industrial floor slab using Expancell filler?

The width and spacing of expansion joints in a concrete industrial floor slab depend on the slab panel dimensions, the anticipated temperature range at the site, and the structural design of the floor. Standard practice for industrial concrete floor slabs in India is to provide contraction joints (saw-cut) at intervals of approximately 4 to 6 metres in each direction (or as specified by the floor design engineer) and expansion joints at larger intervals — typically 30 to 50 metres or at the perimeter of the building where the floor slab meets the wall structure. Expansion joints are typically 20 to 25 mm wide (using a 20 or 25 mm Expancell filler board) to accommodate the maximum anticipated thermal expansion of the concrete panel. The Expancell filler board is placed full depth of the slab against the boundary form, producing a consistent joint width across the full slab thickness. The top portion of the joint (typically the top 25 to 30 mm of the slab depth) is reserved for filling with a joint sealant (such as Colpor 200PF) to seal the joint against debris ingress and water — a backing rod is placed on top of the Expancell to provide the bond break for the sealant at the correct depth.

Can Expancell be used in vertical expansion joints in concrete retaining walls and basement walls?

Yes. Expancell is suitable for use as the expansion joint filler in vertical expansion joints in concrete retaining walls, basement walls, and other vertical concrete elements. Vertical expansion joints in retaining walls accommodate the thermal movement of the wall panels along their length and any differential settlement movement between the foundation of adjacent wall sections. The Expancell filler board is fixed to the face of the previously cast wall section before the adjacent section is cast, typically using concrete nails, adhesive, or by temporary restraint from the formwork system. The board is trimmed to fit the full height of the joint, including any step or change in cross-section in the wall profile. For basement walls below water table, the expansion joint must be incorporated into the waterproofing system — the Expancell filler board provides the compressible element within the joint, but the waterproofing seal (typically a pre-formed joint seal or hydrophilic waterstop combined with external membrane) must bridge the joint on the water-side face to maintain the waterproof barrier across the movement joint.

Is there a standard for the Expancell filler board material and how does it perform in the long term?

Pre-formed compressible expansion joint filler boards are manufactured to BS 2751 or equivalent standards covering compressibility, water absorption, and material consistency. The standard material types used for Expancell include bitumen-impregnated fibreboard (the traditional material with good compressibility and very low water absorption), and closed-cell polyethylene or polyurethane foam board (which provides better recovery after repeated compression cycles). The long-term performance of the filler board within a concrete expansion joint is generally excellent — the board is permanently encased within the concrete joint and protected from UV, weathering, and most chemical attack. The filler board remains in place and continues to provide the compressible gap as long as the concrete structure is in service. Deterioration of filler boards over the structure design life (50 to 100 years) is uncommon for bitumen-impregnated board in non-aggressive environments — the board retains its compressibility and does not degrade significantly under normal temperature and moisture cycling.