Expansion Joint Materials

Perimeter slab/wall crack and expansion joints (tool crack or use zip -off expansion joint material. 

Make a slab edge joint that is easy to seal (tooled joint or zip-off expansion joint material). 

There are many expansion joint materials. The general practice is to leave the mortar out of the joint. Then partially fill with a vinyl sponge rod as a back-up. 

The designer should note that if this type of rigid membrane is used, it will be because no flexible membrane can accept the exposure to the anticipated chemical environment. Therefore, there is no flexible expansion joint material that can accept this exposure either. Consequently, any vessel that must be lined with such a membrane should be so designed that no expansion joints are required. For such design, see the section on design elsewhere in this volume. 

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. 

Verify that all expansion joint materials brought to the site meet the specifications. Observe the installation and if there is any deviation from the manufacturer s instructions or the specifications, stop the work at once and remove all material that has been installed which does not meet the exact standards and specifications. 

In the manufacture of rubber expansion joints, material selection and formulation should be considered against the constructional characteristics required in the product. Rubbers, compounds, adhesives and solvents are all thoroughly checked for quality, to avoid possible layer separation or delamination of the layers while the joints are being built. 

For a high-temperature system, a separate subheader may be run up to the point where the temperature drops down to the allowable limit of a less expensive material. It may then be connected to the main flare header (either low pressure or high pressure).To properly evaluate this a heat loss calculation is needed. As a rule of thumb a heat loss of 10 BTU/hr/ft may be assumed for a quick estimate for bare pipe. Consideration should also be given to the need for expansion joints. Main flare headers may be as large as 36 to 42 inches in diameter for a large-capacity plant. Expansion joints of such magnitudes may be so expensive as to call for a separate small header for the hot flare system. 

The coefficient of hnear expansion of this alloy in the temperature range of 21 to 100°C (70 to 212°F) is 12.2 x l(r /°C (6.8 x 10- /°F), which is slightly above that of cast iron (National Bureau of Standards). Since this material has practically no elasticity, the need for expansion joints should be considered. Connections for flanged pipe, fittings, valves, and pumps are made to ASME B16.1, Class 125. 

A sealant is a material that is installed into a gap or joint to prevent water, wind, dirt, or other contaminants from passing through the joint or gap. This joint or gap may be a fixed joint, but is often an expansion joint which may also be called a working joint. Sealants, which can also be defined by how they are tested, are rated by their ability to stretch, twist, bend, and be compressed while maintaining their bulk properties so that they do not tear apart under stress. A most important rating of a sealant in many applications is the movement ability of the sealant. The adhesion required of a sealant is simply the strength to hold the sealant in position as it is stressed and strained. 

When selecting a bellows valve, it is important to pay some special attention that the material selection is in accordance with the process conditions. Some SRV manufacturers use as standard bellow material INCONEL alloy 625LCF-UNS N06625 (ASME SB0443). This material is not perfect either but, compared to simple stainless steel, has an enhanced resistance to mechanical fatigue and sour gases it is commonly used in refinery FCC systems for expansion joints. 

These polytetrafulorothylene (PTFE) pumps along with the associated plastic expansion joints were installed, because the sponsors were blinded by the advantages. No one took the time to question their suitability in handling flammable liquids. The plastic pumps are just not fire-safe. They are frail in a fierce hydrocarbon fire. The presence of a containment material, such as plastic, can jeopardize the built-in mechanical integrity of the surrounding equipment. 

Figure 6.2 Joint types (a) butt joint (b) expansion joint (c) (i) glass-to-glass lap joint, (ii) concrete-to-concrete lap joint (d) triangular joint (e.g. sanitary seals and glazing seals). H = sealant S = backing material [part (c)]...

Fiorillo, A.R. (1994) Case-histories of successfully sealed expansion joints with polysulfide sealants, in Proceedings of Third Symposium on Science and Technology of Building Seals and Sealants, FL, USA, ASTM special technical publication 1254, part 3, American Society of Testing and Materials, Philadelphia, PA. 

All of these materials-brick, mortars and membranes-will be fully discussed in later chapters along with (1) Castables, grouts, and polymer concretes (2) Monolithics (troweled, sprayed and gunned linings) and (3) Expansion joint compounds, plus rigid plastic fabrications such as polyethylene, polypropylene and PVC. These components made from a whole host of materials are effectively used in a wide variety of industrial applications requiring superior chemical and thermal resistance. 

If there is no membrane under the joint, as in an expansion joint in a tile floor laid directly over a crack in the concrete slab, the deformable sealant will adhere to the bottom as well as the sides of the joint. If this happens, the deformable material will not function properly. The joint cannot open without pulling the filler off the sides of the joint at the bottom, or close without tearing it loose at the bottom and top of the joint. 

The designer should make clear on his drawings that the expansion joint must extend all the way down to the membrane (through the bed) and may contain absolutely no hard or rigid material-only the specified expansion joint filler. 

Locations of expansion joints in trenches must be planned, not only to accommodate thermal expansion and brick growth, but to protect brick at outside corners from being pushed off the membrane by back pressure from deformable elastomeric material in the expansion joints. In trenches, therefore, in addition to the normal spacing of expansion joints and the placing of expansion joints around fixed objects and over all points of movement and cold seams and control joints in the substrate, at not more than 20 ft. intervals (or evenly spaced apart at lesser distances if the length does not divide evenly into such intervals) they should be placed in both directions at not more than 3 ft. or less than 2 ft. from all changes in direction and intercepts, and before all step changes in depth in trenches. 

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