Waterproofing treatment of expansion joint

What is an expansion joint?

Joint provided to accommodate the expansion of adjacent building parts(long span buildings).All building materials expand or contract with change in temperature and variation of moisture content. The magnitude of these changes varies with the type of materials used. Most building materials expand when wetted and shrink while drying. RCC slab is part of the building which is most affected by temperature variation.

        In a tropical country like India, the occurrence of large variations in the atmospheric temperature and humidity are to be expected. In summer temperature goes to 45 degrees, while in winter it may come down to 4 to 5 degrees. This type of wide range variation in temperature creates lots of expansion and contraction in RCC slabs and other parts of a building. So, expansion joint must be given to bear those changes in length and avoid any structural failure.

        Expansion joints essentially provide a space between the parts and may sometimes be provided with the load transmitting flexible material between the parts and generally filled with expansion joint filler(like expansion board) which is compressible enough to accommodate the expansion of adjacent parts.

                                                    If you have big building like this

It is sure that the expansion joints are present there somewhere as per the design

These are some pics of expansion joints

                                        Expansion joints are generally 40 mm to 50 mm wide

                   Now, the technical issue comes along with an expansion joint is, It                                  facilitates water ingress to inside of the building and results to leakage & 

                                                  seepage inside the building.
      
                                             so, we have to do its waterproofing treatment

For treatment of expansion joint, most important thing one should keep in mind is, any material to be used for this purpose must be flexible enough to withstand the expansion & contraction of two parts of a building. 
   
       Various methods are there by which it can be done.Some of them I am going to discuss here.

By Acrylic based highly flexible strip

     In this method, a strip is used to stick on the surface on both sides of concrete slab with the help of adhesive. Some load-transmitting material like expansion board should me placed between the gap.

                                                       That flexible strip looks like this
    

    It is recommended that double layer system should be used on the expansion joint present on the top most slab (exposed to the open sky, in direct contact with rainwater). First layer strip of width about 6" and a second layer of about 10" to 12"(as per the site situation).

                                        

                                This is a sectional drawing of application methodology