Every sizeable concrete retaining wall, basement slab, reservoir tank, length of tunnel must have joints. These may be a mixture of construction or expansion joints but all such joints in direct contact with water need the protection of a water stop. The water stop can be hydrophilic or impervious PVC strips which are cast into the concrete at the joints to prevent the passage of water.
To cater for every application, Fosroc have a portfolio of Supercast PVC and Swellable waterstops which have been successfully installed all over the world for many decades.
As their name implies, these joints are used to simplify construction; they are not intended to accommodate movement. Nevertheless, cracks tend to develop at breaks in construction whether wanted or not, so construction joints have to be designed with cracking in mind; for example a PVC water stop placed over the blinding and cast into a basement floor
These create a gap in the structure to allow for both expansion and contraction caused by thermal and moisture movements. These joints are usually formed by installing a compressible filler board between sections. ” Settlement” joints are included under this heading – or any joint designed to take up such movement. Locating expansion joints demands careful thought, considering not only the spacing needed to avoid cracking but also a pleasing appearance and access for subsequent maintenance.
These are for relieving shrinkage stresses induced in concrete as it sets; stresses that would otherwise cause random cracking. A contraction joint may be designed as a complete break in the structure, each cast butting against the previous one. If more structural stability is needed between sections the reinforcement may be continued across the joint to restrict its opening. Forming grooves in the concrete surface – top, bottom or both – makes another kind of contraction joint to induce cracks to form along predetermined planes of weakness. A water stop may be incorporated into such joints.