Sealant joint design

Certain specifications and standards provide excellent tutorials on adhesives and sealants. For example, MIL-HDBK-691 offers a complete handbook on adhesive bonding, and MIL-HDBK-725 provides a guide to the properties and uses of adhesives. ASTM C 962 provides an excellent source of information regarding sealant joint design and the types of sealants that are appropriate for various substrates. Although this specification is primarily for construction sealants, much of the information that it contains is generally useful for other sealant applications. 

The term primer is used to describe any liquid preparation used to modify the surface of an adherend. While there are some primerless systems, the sealants used in construction often require primers as the surface condition may be extremely variable (See Sealant joint design, Seaiants in doubie giazing and Selection of joint sealants). 

Performance of primers has been studied both in general construction and water-retaining structures.Further information may be found in articles on Selection of joint sealants. Sealant joint design, Paint primers and Primers for adhesive bonding. 

This is made primarily on the basis of the intended joint movement (see Sealant joint design), though other criteria are important such as compatibility with joint surface materials. To achieve a satisfactory bond to certain surfaces under the prevailing site conditions, it may be essential to employ an appropriate primer (see Primers for sealants). Table 1 summarizes the types of sealants available commercially and indicates their performance characteristics. 

Sealant joint design J C BEECH Design of butt and lap joints... 

Sealant joint design J C BEECH Design of butt and lap joints Sealants in double glazing G B LOWE Types of materials, durability Silicones properties B PARBHOO Range of properties... 

Adhesive joint designers will take maximum advantage of this second effect by designing the joint configuration for protection or by specifying a protective coating and/or sealant around the exposed edges of the adhesive. 

Polysulphide sealants fulfil the requirements of expansion joints in concrete structures such as bridges, subways and high-rise buildings where a high level of joint movements occur. They are suitable for compression movement, extension movement and shear movement in butt joints as well as overlap joints. The only joint in which a sealant can accommodate more than +50% movement is in lateral shear in an overlap joint. In all other joint designs the sealant cannot take more than 25% move-... 

A preliminary article indicates the scope and types of Sealants. In designing a sealant joint, it is essential to select a snitable sealant with adequate capability to withstand the expected movement at the joint... 

The choice of joint design should also take account of the fact that the lifetime of the chosen sealant may well be less than that of the building and that at some future date the sealant will have to be replaced. If such an operation is likely, a design of joint must be used that allows defective sealant to be removed and the joint surfaces cleaned and prepared before reapplication of fresh sealant. Because this procedure is fairly straightforward in the butt joint, this is the solution most frequently adopted by designers. In the discussion of some other aspects of joint design that follows, it is assumed that the butt joint is the option chosen. 

When calculating the design width of joints in a building, it is essential to take account of the tolerances on the relevant dimensions of the components and the accuracy in placing them that is likely to be achieved on site. For these reasons, there may, in practice, be considerable variation in the widths of a number of ostensibly identical joints. The joint width for the design must ensure that in no joint will the sealant be subjected to a level of compression or extension that, when expressed as a proportion of the achieved joint width, exceeds its movement capability. (See the Selection of joint sealants, where Table 1 gives maximum movement permitted for each major type of sealant.) However, considerable variation in formulation and properties may occur between different brands of the same chemical type, which may affect this value. The maximum tolerable joint movement quoted by the manufacturer should be used in joint design calculations. 

Amstock, J. S. 2000. Handbook of Adhesives and Sealants in Construction. New York McGraw-Hill. Chapters on the various sealant materials are followed by discussions of specifications, joint design, and performance and repair. 

General design, specification and application procedures for sealant joints on Exterior Insulation and Finish Systems are discussed with specific recommendations for avoiding sealant joint failure due to finish coat delamination. 

The following is a description of the selection of the appropriate sealant, then proper joint design and installation for construction sealant/ caulk applications. 

Sealant joints cannot be designed until a decision is made as to what sealant we desire to utilize. Its ability to expand and contract remains the most important factor in that decision. Major manufacturers indicate the movement capacity of a sealant as plus or minus a certain percentage of its designated width. 

Abstract This chapter describes the many factors that go into the design of reliable sealant joints. Common causes of sealant joint failure are addressed. The various joint types are discussed and illustrated, and their critical dimensions and materials are described. Sealant properties critical to joint assembly, cure, function, reliability, and aging are discussed. These include chemical, physical, mechanical, and adhesion properties. Proper measurement of these properties is also presented. Finally, calculation of the differential movement of the substrates in a sealant joint, the accommodation of which is the primary mechanical requirement of a sealant joint, is discussed. 

Proper design of sealant joints is critical to the reliability of the joints. The general types of sealant joints and the critical geometric parameters that must be considered in joint design will be discussed in detail. Because the proper selection of materials is absolutely critical to the reliability of sealant joints, the critical sealant properties will also be discussed. 

In addition to this text, there are several other references dealing with the design of sealant joints (Amstock 1973 Prane 1977 Panek and Cook 1984 Petrie 2007). Also, ASTM International has a written standard on the use of sealants in joints, standard C-1193. 

There are many sealant properties that are critical to the design and assembly of reliable sealant joints. These critical properties include chemical, physical, and mechanical aspects of the sealant material. 

Thompson JE (1990) Design considerations unique to sealants. In Postal CA (ed) Engineering materials handbook adhesive and sealants, vol 3, 3rd edn. ASM International, Materials Park Wolf AT (2009) Sealant durability and service life of sealant joints. In Mittal KL, Pizzi A (eds) Handbook of sealant technology. CRC Press, Boca Raton, pp 143-190... 

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