TYPICAL LAYING PROCEDURE
1 Expansion joints are full depth joints provided transversely in concrete pavements and also between structural members of a structure like slabs, beams and columns, etc to allow their expansion and contraction without stressing them. The cross-linked closed cell polymer filler may be used as shuttering on one side of the expansion joint by abutting with the already cast RCC member and fixed in proper position by using double sided adhesive tape or synthetic rubber adhesive as per manufacturer’s recommendations. Both open ends of the polyethylene filler or bituminous boards (already fixed on exposed face of structural member) shall be restrained and kept in position with the normal shuttering materials as per the manufacturer’s recommendations.
2 When forming expansion joint with the polymer based filler or bituminous boards in cast-in-situ concrete, joint sealing slots are to be formed in the following manner:
a) Shape of the field moulded sealant is important as it is subjected to compression and tension during expansion and contraction phases of concrete members. The alants which are solid at service temperatures are likely to change in their shape when subjected to varying temperatures and humidity, but their volume will remain same. The shape of the sealant is important as strains developed in them during expansion and contraction should not exceed the permissible limit recommended by the manufacturers. In all the cases, width and total depth of expansion joint is always known but only depth of the sealant is to be worked out which varies depending on the location and its environmental conditions like temperature and humidity etc, around the place.
b) For cast-in-situ concrete work in respect of concrete pavements as well as structures, the polymer based filler board is used in expansion joint as one side shuttering for the entire depth of concrete. To enable application of sealant in the expansion joint groove, the filler board has to be cut according to requirements and removed upto the sealant depth. In order to achieve this requirement, the filler board or bituminous boards provided for the entire depth, is cut up-to sealant depth ‘D’ for the entire length and further subdivided into two or more lengths as per site requirements and convenience, before concreting of the adjoining panel. This cut top strip is pinned back on to the bottom strip using nails at two inch intervals or as per recommendations of the manufacturers, after ensuring that the slot is clean and dry. Also install a strip of filler material on top of the filler, flush with the finished surface using either a tape/synthetic rubber based adhesive. This top strip shall remain in this position till completion of concreting (including water curing and drying the concrete surface completely) in adjoining panel, before application of sealants in the joint groove. This top strip shall however be removed at the time application of sealants in the expansion joint groove (see Fig.1).
3 The filler material may also be used as shuttering on one side the expansion joint by abutting with the already cast member. To hold the two free sides of shuttering, suitable MS bolts both threaded sides may be used at every regular interval (say 1 m) and secured with concrete using appropriate nuts. These bolts shall be taken out later and the hole grouted with suitable cement mortar (see Fig. 2)