Expansion joints foaming

There is a great difference between a compressible expansion joint material and a deformable joint material. A true compressible material is one that can be squeezed together without extruding from the joint. The majority of the useful compressible joint fillers are closed-cell sponges or foams of the type best suited for the environment in which they will be employed. (They are required in totally enclosed joints where materials may not be extruded without disrupting the masonry.) They are installed by compressing them about 25% of their volume and then sliding them into the joint. 

In 20 ft. trenches, with squared ends, it is often possible to eliminate intermediate expansion joints by the use of end pads of closed-cell foam rubber as shown in Drawing 8. This, in effect, "floats" the brick lining between the two foam pads, absorbing its expansion in both directions. The thickness of the two pads must be calculated to accept the maximum movement anticipated in one-half the thickness to be employed in the end pads. 

Li, G. and Xu, T. (2011) Thermomechanical characterization of shape memory polymer based self-healing syntactic foam sealant for expansion joint. ASCE Journal of Transportation Engineering, 137, 805-814. 

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