3 high pressure pup joint rack drawings free sample

The standard detail drawings below apply to all Site Permit Review (formerly Concurrent Review). They are intended to be used as a guide in the preparation and submittal of plans for private development and city contract projects within the City of Raleigh and the city"s extra-territorial jurisdiction.

All construction shall conform to either these City of Raleigh specifications or to the latest edition of the NCDOT Standard Specifications for Road and Structures. If a required detail is not included on this web page, the North Carolina Department of Transportation (NCDOT) Roadway Standard Drawings shall apply. Any questions regarding the NCDOT Standard Drawings should be directed to the NCDOT, Design Services Unit at 919-250-4128.

The following information on joint sealants has been designed as a supplement to existing joint sealant standards for North America. The approach is to provide high level information on joint sealants and a supportive narrative on seals and brief mentions of alternate technologies like pressure sensitive adhesives (PSAs) in bonding structural glazing. The intent is to provide the reader with design and selection considerations and lead the reader to existing standards that provide the comprehensive information and performance criteria for joint sealants.

Materials used for sealing have evolved over thousands of years from relatively low performing (mortar and tar or pitch as a sealant) to high—performance sealants. Naturally occurring bitumen and asphalt containing materials have been widely accepted as sealants for many centuries. Prior to the 1900"s most sealants evolved from vegetable, animal, or mineral substances. The development of modern polymeric sealants coincided with the development of the polymer industry itself, starting in the early 1930"s.

Joint sealants are used to seal joints and openings (gaps) between two or more substrates and are a critical component for building design and construction. The main purpose of sealants is to prevent air, water, and other environmental elements from entering or exiting a structure while permitting limited movement of the substrates. Specialty sealants are used in special applications, such as for fire stops, electrical or thermal insulation, and aircraft applications.

It is important for anyone specifying sealants to understand the particular set of conditions to which the sealant will be exposed. This includes at a minimum, the amount of joint movement, temperature extremes, substrate types and whether the sealant will be subject to immersion in water, and UV exposure. Failure to understand these basics could lead to the wrong sealant selection and ultimately failure of the sealant in use.

The proper application of a sealant involves not only choosing a material with appropriate physical and chemical properties, but also having a good understanding of joint design, substrates to be sealed, performance needed, and the economic costs involved in the installation and maintenance of a joint sealant.

Joint Design: The specifics of a joint design must match up with a sealant"s movement capabilities for the installed conditions. The practicality of installation of the sealant and other joint elements and the desired aesthetic appearance also need to be considered.

Physical and Chemical Properties: Properties of the sealant such as, modulus of elasticity, its stress/strain recovery characteristics, tear strength, and fatigue resistance are all factors that influence sealant performance in a joint. The chemical makeup of the polymer used to prepare the sealant along with additives such as fillers and plasticizers will affect the performance of the product.

Adhesion: The ability of the sealant to stick to the various substrates is critical to the performance. This is especially true in moving joints where an early adhesion failure can lead to loss in performance of the sealant. In certain situations, a primer can be recommended to improve this critical property.

Durability Properties: The preservation of a sealant"s performance to a specific substrate(s) over the design life of the sealant. The sealant durability relates to sealant"s resistance to environmental strains among others ultra-violet radiation, moisture, temperature, cyclic joint movement, movement during curing, and biodegradation which can profoundly influence the service life of the installed sealant.

Application/Installation Properties: Important considerations include the consistency of the sealant (pourable or gunnable), pot life, and skin over time (tooling time), tack free time, application temperature range, and low temperature "gun ability" (i.e., ability to be dispensed easily by sealant gun). Sealants used for interior applications, even in high-rise or light commercial structures, will have properties and needs different from those used in other applications, such as structural sealant glazing or exterior building facade seals.

Compatibility with other Materials: The sealant must be able to be applied in contact or near another construction material without compromising the sealant"s cure profile, its ultimate performance, or the other materials" (substrate) performance. Negative performance indicators can include color change, swelling, hardening, staining, gloss change, softening, and cracking.

Joint sealants are available in two forms: Liquid-Applied and Pre-Formed. The following references to Class indicate movement potential (e.g., Class 25 indicates ± 25% movement). The following table lists the main types of liquid applied sealants followed by a brief description.

Polyisobutylene (PIB) is a fully saturated, aliphatic polymer of high commercial importance due to its gas barrier properties and can be formulated with high chemical/oxidative stability

Cellular non-silicone products meet (ASTM C864), For dense products most meet (ASTM C509), silicone products meet (ASTM C1115) and thermoplastics meet (ASTM E2203)

After removal from the packaging and insertion in the joint opening the foam expands to be compressed in the joint. The silicone rubber face is sealed to the substrates. Products are available to provide water or water and fire resistance.

Weatherproofing is intended to keep rain and other environmental elements from entering a building. To achieve successful weatherproofing sealant joints at least the following parameters must be considered, and where applicable, designed for:

"Joint Movement"—Occurs as a result of changes in material temperature, seismic movement, elastic frame shortening, creep, live load, concrete shrinkage, moisture-induced material movement, and inadequate joint design. Joint movements must be evaluated, designed for, and accommodated.

"Movement Capability"—The ± percent value that indicates the amount of movement the sealant can take in extension (+) and compression (-) from its original cured joint width. Movement capability and expected joint movement must be coordinated.

"Installation Tolerances"—Depending on the substrate materials the joint opening will have a ± tolerance for its designed width which must be considered when establishing width (e.g., for a joint width of 1/2 inch (13 mm) in a brick masonry wall the tolerance for its width could be ±1/8 inch (3 mm) or more)

Moving Joints experience cyclic movement. They are joints where the shape and size of the sealant joint changes significantly when movement occurs, for example, at control, expansion, and isolation joints. There are three types of moving construction joints.

Control joint: A formed, sawed, tooled, or assembled joint acting to regulate the location and degree of cracking and separation resulting from the dimensional change of different elements of a structure. DISCUSSION—The joint is usually installed in concrete and concrete masonry construction to induce controlled cracking at preselected locations or where a concentration of stresses is expected.

Expansion Joint: A formed or assembled joint at a predetermined location, which prevent the transfer of forces across the joint as a result of movement or dimensional change of different elements of a structure or building.

Isolation joint: A formed or assembled joint specifically intended to separate and prevent the bonding of one element of a structure to another and having little or no transference of movement or vibration across the joint.

Sealants, when applied to these joints, typically provide protection from air, water, and other environmental contaminates. Weatherproofing the joint is an application used to integrate sealants, backing materials, and joint substrates to support resistance to weathering.

There are several factors to be evaluated when establishing the required width of sealant joint. Paramount among them is designing the sealant joint for the anticipated movement, construction tolerances, and other effects known to influence the movement capability of a particular application.

Under no circumstances should sealant be applied in a joint opening that is less than 6 mm (0.25 in.) wide. It is very difficult and impracticable to install sealant effectively in such a small width and is generally not recommended by most sealant manufacturers. Generally, for a joint width over 50 mm (2 in.) a liquid-applied sealant in a vertical joint may sag before curing.

Butt joint: A joint where sealant is applied within the joint between approximately parallel substrate surfaces that are face-to-edge or edge-to edge.

Sealants are often the least thought about and contribute the lowest percentage to a project"s overall cost (less than 1%); however, they can become a serious or, for hidden or concealed joints, impossible problem to correct when a sealed joint fails.

There is both a science (joint design, adhesion, and compatibility testing) and an art (sealant and joint components installation) to successful completion of a functional sealant joint.

At the butt joints of exposed aggregate precast concrete panels the aggregate must be deleted and a smooth concrete surface provided for sealant adhesion

For Weatherproofing, a minimum depth of 1/4 inch (6 mm) for the sealant to substrate bond. A minimum width of 1/4 inch (6 mm) opening is necessary to ensure that sealant applied from a caulking gun will flow into the sealant joint properly.

Use joints greater than the minimum of 1/4 inch (6 mm width), since wider joints can accommodate more movement than narrow joints and can also result in a greater joint spacing.

Tape the outside edge of joints if necessary to prevent overlapping sealant application or to keep crisp lines and insure no sealant smears on the substrate.

For movement joints only use a sealant that has a current Validation Certificate from the SWR Institute (Sealants, Waterproofing and Restoration Institute Product Validation). This program provides a listing and certificates for all validated products.

Will the selected sealant accommodate the anticipated joint movement requirements? This can be determined from the ASTM C920 Class that a sealant has achieved. Class 12.5 means the sealant can provide ±12.5% joint movement. Class 25 means ±25% joint movement, etc. Please make sure that the joint movement needed and the Class of joint movement for the sealant match. ASTM C719

Will the sealant adhere to the substrate(s) properly? This is probably the most critical element in the selection process. This can be determined from ASTM C920 and ASTM C794 where adhesions to common substrates (Aluminum, glass or mortar) are listed in the certification for the sealant. In all cases where there is any doubt about adhesion a determination by the manufacturer in addition to a field test ASTM C1521 preferred or mock-up of the actual installation is highly recommended to ensure required adhesion is achieved.

Will the sealant have the requisite durability for the anticipated movement and environmental exposure? Sealant durability depends on many factors. Proper joint design for the anticipated movement, correct surface preparation, correct installation, and adequate adhesion to the substrates, are all required for a sealant joint to perform. Once these factors have been satisfied then the durability of the sealant depends on its ability to survive in the environmental conditions of the application. That is heat, moisture, UV, and joint movement, all of these factors will influence the durability of the sealant. The best source of information on durability must be the sealant manufacturer. There are several practices to understand this performance but this information is not available for every sealant. Sealant suppliers can also provide case studies that can be used to predict if sealant will perform correctly under a similar set of conditions. Finally, there is warranty information that can be considered.

Does the joint opening width allow for sufficient placement of sealant and other joint components? This question is first about access for the installer. In addition, the conditions at the time of installation have an impact. It is not appropriate to install a sealant when the joint is at the extremes of its movement! Ideally the sealant should be installed at the midpoint of the design range of the sealant. For commercial construction (thermally driven movement) the installation should not occur at an extreme temperature where the properly designed joint is not too narrow or wide for proper installation. If the joint as installed is too small to handle the expected movement or is in a place where sealant placement or joint cleaning would be difficult at best, consider using a pre-cured sealant strip that is adhered to the face of the substrate and bridges the gap. This is especially useful when the joint has aluminum or glass substrates that can"t be cut out to make a larger joint.

Has the sealant manufacturer verified by laboratory testing that the selected sealant is compatible with adjacent substrates? For Structural Glazing applications use ASTM C1087. For other applications see the section on compatibility below to determine if adequate adhesion to those substrates has been completed. ASTM C719 (1,2) & ASTM C1635. If aesthetics is a concern that it will not stain adjacent porous surfaces ASTM C1248. Compatibility issues should be resolved in pre-job communications with all relevant parties involved.

With few exceptions, if any, primers should be used for horizontal and submerged joints. This includes traffic joints, and all horizontal joints open to the elements.

Ideal in flat or horizontal joint applications. Fenestration perimeter seal backer, Expansion joints, Log Construction, Pre-Cast, Pavement Joints, Partitions, Pavement applications, repairs

For joints susceptible to the presence of moisture prior to joint sealing such as horizontal joints. Backer rod should be installed carefully because if it is punctured and then sealant installed directly over top a void is created. That void, filled with air, will then compress and expel air as it is heated through typical day to day temperatures and sunlight causing unsightly bubbles. This is commonly referred to as outgassing.

May not be ideal for sealants that have potential to bubble if air escaping the backer material. Ideal for applications where a large amount of movement is expected or compression will be necessary. More airflow allows it to dry smoothly from both sides and can substantially reduce curing times. Open cell backer rod should not be used in flat or horizontal joints that can have water ponding on them as they can wick moisture to the underside of the sealant.

Irregular joints, horizontal or flat work, expansion and contraction joints, window glazing, curtain wall construction partitions, parking decks, bridge construction, modular home gasketing, and log home chinking

This is suited for specialty applications where standard backer rods are not appropriate and is ideal in irregular joint applications where self-leveling, flowable sealants are employed.

Closed cell sealant backing must be no more than 25 to 33% larger than joint width so it remains in compression and in place during sealant installation.

Open cell and bicellular sealant backing must be at least 25% larger than joint width so it remains in compression and in place during sealant installation.

Compatibility of a sealant with the different materials to which it will come into contact is a critical topic for the long-term success of the sealant joint. There are really three issues when thinking about compatibility:

An example of the first type would be a material that when curing generates an alcohol. The alcohol would interfere with the cure of a polyurethane. Therefore, if any of the materials of construction in a joint where a polyurethane sealant is placed generate alcohol during cure, then the cure of that material must be completed before the polyurethane sealant is placed. There are many examples of these types of interferences and the manufacturer of the sealant should be able to supply the types of materials to avoid.

AAMA/FGIA 713 Voluntary Test Method to Determine Chemical Compatibility of Sealants and Self-Adhered Flexible Flashings is one where fresh sealant is placed in contact with self-adhered building flashing materials and then the assembly is placed in an oven for 14 days and the assembly is examined for discoloration, slump, degradation and liquefaction.

For large complex projects, a preconstruction meeting is required. In these meetings there should be a review of the details of the sealant installation, including primer application. The drawings need to be reviewed and especially important is clarity around the transition points as these are often the areas where failures occur.

"Thickness"—defined as the minimum structural sealant dimension between structurally bonded substrates (the panel and frame) to facilitate the installation of a sealant and to reduce stress on the structural sealant joint that results from differential thermal movement.

"Deadload"—the weight that a panel places on a structural sealant joint when, for certain applications, no setting blocks are used to support a panel"s weight

Make sure that the joints have been properly cleaned. In a repair situation make sure that all of the old sealant has been properly removed. If new construction, make sure that the materials of construction are as indicated on the drawings.

The primary use of sealants in vertical walls is for every place there is a break in the wall continuity. That is, all expansion joints, all control joints, joints around windows, joints around doors, and any place the weather could run in. These are the normal weather protecting sealants. In addition to those are joints inside the wall, as in flame and fire control joints. These use specially formulated sealants that retard flame and fire egress from floor to floor. Part of those sealant joints is a non-flammable backing material. Then there are the joints in the windows themselves, the sealants used in the IG units.

There are other considerations when looking at the sealant for special applications. There might be some high temperature lines coming out of a building and those would need special high temperature sealants. There are sealants for the joints in decks and porches on the sides of buildings and they might also need some degree of scuff resistance or special joint designs to keep the foot traffic off the sealant.

The water runs down the walls and if the pressure on the inside of the building is less than the pressure on the outside, that negative gradient will be the vacuum that will pull the water in the building, if there are any holes or voids in the wall. The pressure equalized wall is one that has a façade wall that is not perfectly sealed and a void space behind the outside surface and a second seal deeper into the interior of the wall.

The easiest way to visualize this is to name the outside wall—wall #1 and the inside wall #2. When talking about a two wall system we can have face #1 (outside surface); face #2 inside surface of #1 wall; face #3 (outside surface of #2 wall) and face #4 (inside surface of #2 wall).

The wind can blow in a rain storm and present a higher pressure outside than is had inside the structure. If there is a cavity between wall #1 and wall #2 and vent (weeps) in wall #1, the pressure between the walls will be the same as on the outside. Rain hitting the outside surface will rundown the façade and not be sucked into the structure. If some water does enter and get to the cavity, it runs down face #2 and is leaked through weeps to the outside. Surface #3 is a sealed surface and keeps the air out (and water if water makes it through). Surface #3 typically has a membrane covering either an adhered sheet or a liquid applied coating. Sealants are rarely used on the #3 surface. Sealants are almost always used on the #1 surface as a way of minimizing water infiltration. The sealant bead on the #1 surface has weep holes to let the water out and the pressure to equalize. The sealant on the #1 surface is installed with all the instructions and precautions as any sealant bead in any wall structure.

There is a second type of pressure equalization used when only one wall is used. Conventional thinking has a curtain wall and the sealant at the #1 surface is made as continuous as possible and void free as possible to keep out water and air. The pressure equalized single wall has a bead of sealant installed as close to the #2 surface as possible. Typically, it has a backer rod going out to the #2 surface. The sealant is installed with a deep nozzle to get to the backer and to give a sealant bead that keeps water and air from passing through (as much as possible). There is a void between that deep bead and a bead of sealant on surface #1. A backer is installed just below the #1 surface and a sealant applied to it. It is done carefully, as if it were a single seal, so as to make the wall waterproof from this surface seal, except there are vents and weeps holes in this bead to allow pressure equalization and again not allowing a pressure differential from pulling the water into the building. It is a dual seal within a single wall. The outside joint has a vented space behind it and the inside bead is as continuous and water and air tight as possible. The inner seal, because of the location next to the building, will experience a lower UV exposure. Because of these different exposure conditions, different sealants may be employed for the inner and outer seal. It is important during installation to not cross contaminate either seal.

What is the overall impact of the products being used in the building on the environment? This is measured by preparing an Environmental Product Declaration, EPD, for the sealant being used on the building. Information on EPDs can be found in ISO 21930, Sustainability In Buildings And Civil Engineering Works—Core Rules for Environmental Product Declarations Of Construction Products And Services. To complete an EDP there needs to be a Product Category Rule, PCR, for the product being evaluated. A PCR was prepared and then published in 2016 by the Adhesive and Sealant Council (ASC) (product-category-rule-(pcr)-for-sealants). A PCR sets the rules for the Life Cycle Assessment (LCA) that will be completed to generate the data set for the EPD.

State regulatory agencies and Non-Governmental Organizations (NGOs) have been encouraging the sealant industry to reduce the use of VOCs in sealants. VOCs tend to have an odor, are flammable, and contribute to smog, and if in high enough concentrations can have negative health effects. South Coast Air Quality Management District in California (SCAQMD) has set the most stringent VOC levels for sealants and sealant primers these can be found in Rule 1168, SCAQMD (Rule 1168 for Adhesives and Sealants). Most manufactures of sealants and sealant primers sell products that comply with these stringent requirements. Some of the sustainable building programs above require that the sealant and sealant primer meet the SCAQMD Rule 1168 requirements. In addition for those materials used inside the building they require that the sealant and sealant primer to pass the CDPH Standard Method v1.2, (Emissions Testing 01350) . Whereas Rule 1168 sets a concentration limit for VOC content in a product, the CDPH Standard Method v 1.2 sets a limit for VOC emitted by the material inside a chamber that mimics a standard room, office or classroom.

The temperature the sealant will see in use and how long will it endure the high heat needs to be known. It is not uncommon to see temperatures on surfaces on the sunny side of buildings in the heat of summer hit 70°C (158°F) or even 80°C (176°F) or in some applications and climates 90°C (194°F). Sealants around hot pipes can see these high temperatures or even higher. Often a sealant specifier, architect or contractor will have to contact the manufacturer to get the performance endurance at higher temperatures. Often manufacturers may not have this data publicly available but might supply it upon request.

The movement, or change in gap width, expected for the application is a key value. Later there will be comments on calculating joint movement but simply stated it is a function of the nature of the material times the length of the panel and times the expected temperature change. Please note that thermal expansion coefficient for commercial buildings, other materials might change dimensions might change with other environmental factors, such as wood with moisture. The expected temperature range experienced by the actual materials on/in the application is fundamental. Once the movement is known, and the desired joint size is selected, a sealant must be chosen with the movement ability to satisfy the chosen joint size and movement expected. That is one of the most difficult data points. Most, if not all sealant data sheets indicate the movement ability as tested by ASTM C719. However, this is data from a sealant that is only 6 weeks or less in the sealant test joint. All that being said, looking at ASTM C719 data, validated by the SWR Institute (SWR Institute Product Validation Program), is the only quality data readily available when making a sealant selection decision. Other data if often needed, that that has typically obtained from the sealant manufacturer.

The longevity. The building owner, architect, specifier, and applicator need to know how long the sealant will maintain the properties needed to successfully seal the building. Presently there are only a few ways to predict the longevity of a sealant in a given application. One is to look at similar jobs, with similar joints, in a similar climate with the given sealant. This is a difficult to achieve fact base. There is also ASTM C1589 10B and 10C which are outdoor studies with movement while the sealants are weathering. Section 10B has the joints in a continuous movement and 10C has the joints opened or closed manually each season. Many architects, engineers, suppliers, contractors have equatorial facing outdoor racks and move the joints periodically. They have the most pertinent data on long term durability. It can be assumed that many sealant manufacturers also have these kinds of test racks. An additional consideration is that the sealant must have adequate adhesion to the substrates.

Sunlight resistance is included in the total outdoor study mentioned above. However, there are many manufacturers who have data with their sealant in UV exposure, even in artificial weathering machines including water and heat with the UV exposure. However, data from the artificial weathering with no stress induced while weathering is distinctly different from similar data done with stress during the artificial weathering. A sealant that looks like it could last many years in outdoor exposure on a test rack, might fail in less than 2 years in outdoor exposure with movement, or after a few months in artificial weathering with induced movement. Thus, the indicator is to look at the weathering data, obtained with stress and strain induced while weathering. Realize the difference between the usual weathering tests and these new data points from sealants that had strain while weathering.

Tolerance to heat, light, water, and movement for the most common type joints noted above is fundamental to looking for durable products. The specification for sealants in weatherproofing applications is ASTM C920 and it is considered one of the most difficult sealant specifications in the world, however it does not consider in-service performance. It is very important to realize that there is no compulsory sealant testing and certification of sealant performance in the U.S. The closest there is to verified performance, even if it is just short-term data, is validation of an ASTM test. ASTM C719 Durability of Adhesion and Cohesion to cyclic movement in Elastomeric Sealants (the most difficult test in specification ASTM C920) by the SWR Institute.

A second aspect of the 5,000 hours of testing in ASTM C1184 is that if a sealant manufacturer wants to suggest a sealant is appropriate for SSG applications, because of the possible high liability in case of sealant failure, these sealants need at least 20,000 or 30,000 hours of accelerated testing. In this case, look for changes in the sealant performance as well as its adhesion. A specifier of a non-silicone for structural glazing needs to get data from the sealant manufacturer that gives indication of an expected 20 or 30 years of acceptable performance in such an application where many times the sealant bond to the glass will see full sunlight. Making a small transition from normal joints to structural glazing in this introduction makes it logical to provide some notes about Insulated Glass here as well.

Temperature inside IG units can be quite high, sometimes in the 70°C (158°F) and 80°C (176°F) range. Thus, the sealant used in all applications in IG units needs to have data on heat stability testing to be sure it is stable at the expected temperature in those units. However, when the IGU is used in a SSG application, the IG secondary sealant is a structural glazing sealant and needs to be tested as one.

Fundamental to all discussions on sealants is the physical properties of the sealant relative to the physical properties needed in the application. This correctly implies that the person designating the sealant for a job should have some knowledge of what properties the sealant needs to have. It also correctly implies that the sealant manufacturer needs to know the properties of the product they produced and made available for sale. There are many uses for sealants in buildings and thus there are many types of sealants to be considered. Consider first what many consider the most demanding application for sealants in most buildings, the outside, moving joints in the equatorial direction (South facing in northern hemisphere, North facing in the southern hemisphere, this effect is a strong function of latitude as well) of the building. In the equatorial direction, the sealant will get the maximum heat, which also translates to maximum movement and it will see the maximum sunlight (UV radiation). Being outside it will see water from rain, dew, snow, fog, and sometimes sea spray.

A comprehensive general statement on critical sealant performance is in the FGIA/AAMA JS-91 Aluminum Curtain Wall Series on Joint Sealants, which has been replaced with FGIA/AAMA 851-20 Fenestration Sealants Guide for Windows, Window Walls and Curtain Walls. Under the title Critical Sealant Properties, it says "Sealants, like other building materials, have specific physical characteristics which determine how they will react under conditions of use. The design of joint systems must take into account such factors.

The properties of many sealant materials vary with temperature. The temperature range occurring on the surface of a building is sufficient to cause changes in the properties of some types of sealant—changes sufficient to cause failure in some cases. It is essential, too, that the basic properties of the sealant do not change significantly with age. Should such changes occur, the assumptions regarding their behavior which originally governed the joint design are no longer valid.

Is it important that the critical properties—adhesion strength, cohesive strength, and modulus—be kept in proper balance in conjunction with the proper joint design and sealant configuration. If the modulus is high and the adhesive strength is low then adhesive failure will occur. If the modulus is high and the adhesive strength is high, substrate failure may occur. If the modulus is low and the adhesive strength is high, then cohesive failure may occur. Some low modulus sealants will fail in working joints.

This means that there must be some way of testing for the sealant"s ability to handle the joint movement, under field conditions, and not experience adhesive or cohesive failure for some acceptable time. There must be tests and specifications for building sealants.

The most rigorous specification for such a sealant (in the US) is ASTM C920 Standard Specification for Elastomeric Joint Sealants. This specification and the tests with in it are often used in many other countries of the world. Within that specification are different types (single component (ready to use) or multicomponent (mix on site)); different grades as P = pourable or self-leveling and NS = gunnable, non-sag; and different movement classes. The movement classes range from +100% / -50%, ±50%, ±35%, ±25%, ±12½%. The movement is tested by ASTM C719. This is often considered the principal test method in the specification. Before going into the details of the specification, it is instructive to study the C719 test method.

Miniature test joints (triplicates are made). The joints are held, without movement for 21 days while they cure. They then go into water for 7 days, taken out and flexed. This is sometimes a tough step since sometimes this water interferes with adhesion but sometimes this step is beneficial since it allows more cure time and enhanced performance. In any case the joint is then hand flexed to approximately 60o and examined for adhesive and cohesive flaws. The joints are then compressed to the maximum compression being tested and put into a 70°C (158°F) for a week. During this period there are a number of possible changes that may be occurring to the sealant including changes to the cross-link density, slow curing, solvent loss, or viscous flow. These changes in compression make the subsequent expansion back to the original dimension and then to the extended state much more difficult. If the sealant is stable before it is taken into compression, it is still a difficult stage since the forces on the sealant and the bond in compression are higher than those created by a similar percent movement in extension. However, the damage is never seen when the joint is compressed and only noted when it is extended and an adhesion loss is seen or a tear is started (cohesive failure started).

Next, the sealant joint is put through continuous extension to compression and back and forth for 10 cycles. They are examined for adhesive and/or cohesive failure.

Next, they are compressed again to the maximum compression being tested and put into an oven for 16 to 20 hours at 70°C (158°F), taken out, allowed to cool then put into the extension machine that is now in a freezer at -26°C (-15°F) where it is moved at 1/8 inch (3mm) per hour until it reaches its maximum planned extension. Block the joint at this extension, take it out of the freezer and examine it for adhesive and cohesive failures (note any other flaws as well). Repeat this hot and cold cycling 10 times.

This is considered the most rigorous test for sealant durability in the specification and probably one of the most rigorous standard tests in the sealant industry. However, note that the joint cures while sitting still for 21 days and in the field. On the job, the joint will move from the moment it is installed. Movement during curing always decreases sealant performance in either adhesion or cohesion and often in both. Note also that this test is done as soon as the sealant is cured. This sealant has not seen weathering with movement, as is seen in the field. This combination of weathering with movement always decreases a sealant"s performance relative to what is seen if the sealant is not moved while weathering. There is a synergism between the deterioration factors movement, heat, light and water. However, it is difficult to combine all of these into a reasonably fast test and this has not yet been done commercially in a nationally recognized specification.

An important consideration is the passing criteria from a sealant tested to ASTM C719 for the ASTM C920 specification is 75% of the joint has not failed. Thus, it allows as passing up to 25% joint failure from any combination of adhesive and cohesive failure. Some consider this very liberal pass/fail criteria, and yet it is the most difficult and rigorous standard specification for construction sealants.

The important message here is that if the sealant cannot pass C719 test method to the specified movement being tested, it will almost surely not be able to handle that degree of movement in the field. An equally or more important message is that since the sealant in the joint in this test method had no accelerated weathering there is no indication of how long it will continue to perform in the field application. The specifier or user must contact the sealant manufacturer and ask for data to predict useful life in a given climate and application.

There are some test procedures that give some indication of the ability to handle joint movement while weathering and handle the conditions for extended times. Look to ASTM C1589/C1589M and in there look to Section 10.2 Procedure B—Outdoor Weathering of Building Joint Sealants With Continuous Movement and/or Section 10.3 Procedure C—Outdoor Weathering of Building Joint Sealants with Periodic Manual Extension and Compression. These are not accelerated tests but attempts to simulate the conditions seen and damage done in various climates. Consider these tests as buildings where the movement is precisely measured (in procedure B) and the joint movement is precisely controlled (in procedure C).

Figure 27: One of The Durability Lab"s sealant test racks (ASTM C1589 Procedure C). See also: Durability of Elastomeric Sealants by Beth Anne Feero and David Nicastro.

The joints used are similar to those in ASTM C719 (or modified to match joint configurations used on jobs (hourglass as opposed to square cross-sections). The joints are put on racks and the racks put out in various climates in the US, and other places, and the sealants are studied for adhesive and cohesive failures along with cracking and crazing and dirt pickup and any other anomalies seen. It is probable that this test procedure will never be in a specification since it takes a very long time (not an accelerated test) and the damage will vary from location to location. It is a test procedure (see ASTM C1589) that many engineering firms, contractors, distributors, and sealant applicators are conducting this procedure to help select which sealants they want to specify for given applications in various climates. It can be assumed that many manufacturers are also doing outdoor weathering, with movement using one or both of the procedures mentioned. For a more nuanced discussion see the durability section.

Looking further in Specification ASTM C920 is the use designations—uses T1, T2. T1 indicates if the sealant is harder, generally desired for traffic areas, especially pedestrian traffic however there are many exceptions to this and often traffic areas need a lower modulus sealant and in that case a T2 sealant is used. NT is a softer, lower modulus sealant most often used in general sealant applications. Again, there are exceptions that are job specific and one most look the specific application and then determine if, for that specific job, do they want a harder or softer sealant (determined by Shore A hardness testing) but truly it is the modulus of elasticity that is most critical and that is tested by ASTM C1735, ASTM 1135 devices and not part of the C920 specification.

Use I (immersion) is of special interest referring to applications that see continuous submergence. Note carefully that one has to go to the test method ASTM C1247 and be aware of how it is tested and see if that is satisfactory to indicate a utility in a specific application. This Use I has Class 1 which is held at 50°C (122°F) for 6 weeks immersion before testing and Class 2 which is held in immersion for 10 weeks before testing. If the application will have continuous immersion for more than 10 weeks the only acceleration of deterioration is a temperature increase. However, it is reasonable to assume that for each 10°C (18°F) increase in temperature, the rate of failure will double (a maximum approximation). Thus, if the application will see immersion at near ambient (77°F, 25°C) the acceleration of this test at best near 5 times. Thus, 10 weeks in tests is at best a year in service, if the sealant is continuously immersed. Note as well, the sealant is held in a neutral position while immersed. After immersion the sealant is moved in extension and compression cycles as in ASTM C719. If the sealant will see movement while immersed the test might not be as difficult as the actual application. That being noted, it is a good test for a sealant"s ability to handle immersion conditions. Note that anyone can modify the test to more closely match their job conditions or modify it to run at higher temperatures to further accelerate the damage, but care must be taken in doing that so the temperature is not so high as to produce a degradation mechanism that would not be seen in actual use.

Note well that the specifications, if passed, means that the sealant passed the minimum condition to be used in conventional glazing, but not in structural glazing. The 200 hours of UV exposure (artificial weathering) represents no more than 6 weeks to 12 weeks of continuous sunlight and does not come near to predicting what happens to the bond after 20 years or 30 years of direct sunlight in a South facing, structurally glazed window.

A consideration with the specification is that the specification of a specific minimum adhesive value of 22.2 Newtons does not consider the stiffness value of the product. The stiffness of the product will dictate what the adhesive strength has to be to handle the forces produced by a given movement (strain). The 22.2 N is probably adequate for a lower modulus sealant but not for a higher modulus sealant. Thus, the test, as used in the specification C920 has some subtleties not well understood by the general user but is part of the required properties to pass C920 and be qualified for use on most major projects.

Inspecting the C794 test, 22.2 N is too low an adhesive value for a higher modulus, stiffer sealant but okay for the lower modulus, softer products. Now imagine a company with a medium modulus sealant which pulls a very high value of 35 N, however, at the high adhesive value, it fails more than 25% in adhesion. A perfectly good sealant cannot pass the important C920 specification because even though the sealant adhered to a very high force on the bond line, its final failure is in the wrong mode. A sealant must have or exceed a specific adhesion value and then the mode of failure is irrelevant. If a manufacturer can produce test data showing excellent adhesion in this test, the product could be accepted for a given application, in spite of having more than 25% adhesive failure. Note there is no adhesion value that can be stated as sufficient in this test even though the specification calls for 22.2 N minimum. The proper adhesion force is a function of the modulus and not a fixed value. A stiff, high modulus sealant will need a much higher adhesion value then a lower modulus, softer product. The sealant manufacturer should have data to give to the customer as to the minimum value to achieve with their product.

With the above commentary about ASTM C794 it must be noted that it (or a modified version of it) is probably the most often used test in the manufacturer"s labs. It is used as the screening test for adhesion since the strip of sealant can be easily adhered to most job site substrates. It is common practice (especially for major jobs) to send in job type substrates to the manufacturer to determine if adhesion can be obtained and if a primer is needed. Most of the time this is the method that is used sometimes ASTM C1135 is used to determine adhesion in a joint). Above it was noted that appropriate values for adhesion are modulus dependent. It is important to note that the most reliable test for actual modulus is ASTM C1735 Standard Test Method for Measuring Time Dependent Modulus of Sealants Using Stress Relaxation.

The ASTM C1246 is part of the C920 specification. It keeps a sealant for 3 weeks in a forced air oven at 70°C (158°F) and then it is examined for cracking and chalking and weighed for weight loss. Few of the sealants that qualify for C920 specification have trouble with this test, however, the test is worth mentioning since the method is sometimes used for other sealants like hot melts and PIB sealants used in insulated glass applications. Sometimes done at 70°C (158°F) and sometimes at 80°C (176°F) if that is a temperature that can be expected in the IG units at a specific location (other temperatures are sometimes used). The test lab looks for slumping and/or change in viscosity. Other applications might also use this test or modifications of it. Most manufacturers run some sort of heat stability testing to be able to tell the highest stable temperature for use of their product. Most often look at a hardness change or plasticity change as function of temperature with time and that is not in an ASTM test or sealant specification but is quite fundamental information in determining the suitability of a product in high temperature applications.

There is ASTM C639 to determine the amount of slump or sag. The C920 specification puts limits on the amount of sag a sealant can have in a joint, so the sealant doesn"t sag out of the joint when it is still in the paste form as it is installed. It also dictates the conditions for a sagging or self-leveling sealant (for some horizontal joints).

There is also ASTM C1183/C1183M-13(2018). This test has limits in the C920 specification that requires a sealant be soft and pliable enough to extrude nicely in a caulking gun. It also is a shelf-life determinant with mix-on-site sealants. The sealant is putting into a standard caulking gun with a fixed pressure (40 psi) and the rate of sealant extruded in a minute is noted and a minimum value needs to be met or exceeded.

SWR Institute (SWR Institute Product Validation Program)—One more critical comment in properties before we go further into this section. The manufacturer"s data sheets are the most convenient way to see some of the key performance properties of a specific sealant. The SWR Institute (a contractor driven organization) has a validation program where they looked at the tests for sealants and decided that the ASTM C719 Standard Test Method for Adhesion and Cohesion of Elastomeric Joint Sealants Under Cyclic Movement is the key short term test of a sealants ability and thus have their program (voluntary), and if a manufacturer wants to have the data from a C719 test verified and published for all to see that is a true, they can have an independent test lab purchase the product, and test it according to ASTM C719, and the independent lab send the properties to the SWR Institute for publication. Many manufacturers have done this with their architectural sealants, and anyone can call the SWR Institute office and ask about a specific product as to what class of movement did it pass and on what substrates was it tested and if a primer was used in the test. It is a unique source of validated properties.

The discussion above was based on typical joint sealants, of toothpaste-like consistency and applied to a joint where they cure in place. There are some sealants called "pre-cured sealants". Imagine a band-aid that is typical in shape but not one inch or a half inch wide but many feet wide. They are thin strips of cured rubber (sealant) that are put on top of joints that would be difficult or impossible to clean or seal by conventional techniques. These are shown very well in the pictures in ASTM C1518. This specification exemplifies the comment at that start of this section Specifications show the "Necessary but not sufficient properties a product must have". Note that this specification is for materials that are often only 2 mm or 3 mm thick. The title indicates that it is for silicone materials only. By stating that in the title it doesn"t have to include the several months of accelerated, artificial weathering testing since silicones have almost no detrimental effects from sunlight. If other materials are used in this application then one would need to see extensive aging in weathering conditions. However, it does include a minimum of 2500 hours in an accelerated weathering machine because adhesion can be greatly influenced by heat and water (and sometimes light if the silicone formula is such that is allows light to transfer through the sealant to the bond to the substrate) or if the sealant sees a continuance of cure and become a bit harder with time. Fundamentals here are the tests for adhesion and for tears and cracks since the rubber sheet put over the joint is very thin (so as not to be visually obtrusive). The test methods are defined in ASTM C1523.

In all cases, the specifier has to look at the specific joint sealing situation, the conditions that will be encountered, determine the joint configuration and sealant that will tolerate the expected environment. There are guides to this and some are: ASTM C1850, Table 1; Klosowski,J.M. and Wolf, A.T. "Sealants in Construction—Second Edition" CRC Press—Taylor Francis Group, pg 14 fig 2.1; BelCher, W.E., "Installation of Joint Sealants & Guides" Pg 11–12, www.uniproseal.com. The ASTM C1193 in Section 5 General Considerations has comments on a large selection of properties needed in sealant applications.

ASTM C1481 talks of the uniqueness of this application and gives insight as to the properties, especially adhesion and the special considerations needed since the substrate is relatively week. The properties needed for EIFS applications are determined by some of the standard tests mentioned earlier C719 and C794 but because of the unique composite structure of EIFS the test method ASTM C1382 is used and exclusively used for EIFS systems. The methods for conditioning of the sealants before stressing are unique and after the heating and freezing steps and accelerated weathering, the test pieces are strained in a tensometer as in ASTM C1135 (Standard Test Method for Determining Tensile Adhesion Properties of Structural Sealants), but here the tensile strength is measured at 10%, 25%, 50% and 100% (a chart of the secant modulus is prepared). Note as well that low and very low modulus sealants are often preferred in this application because of the weakness of the EIFS composite (although the EIFS manufacturer generally direct the sealant be adhered to the base coat instead of the finish coat, and most often a primer is requested).

There are special tests and specifications generally used with solvent diluted sealants like butyls and the acrylics and similar typically low movement sealants. However, there are some sealants in these classes that are considered for the higher performance architectural applications and in these cases they are required to be able to conform to the ASTM C920 specifications and all the test methods therein.

There is a specification for latex sealants. Latex as defined in ASTM C717 is an aqueous dispersion of polymers that can be solidified into rubber. A water-based sealant can be based on a variety of different base chemistries including but not limited to: acrylic (most common), urethane, or silicone. The specification for such sealants is ASTM C834. The ASTM C920 is a specification for sealants intended for difficult situations (like exterior moving joints) and the material formula is irrelevant. The specification ASTM C834 calls out test methods and values that are not designed for exterior moving joints. Latex sealants intended for the exterior moving joints have to pass ASTM C920. The majority of the applications for sealants that are tested to the qualifications called out in ASTM C834 are indoor (less exposure and less movement).

ASTM C732. A channel is made of wood on one side, aluminum on the other and polyethylene in the bottom. A latex sealant is put in the channel, allowed to cure (and the water evaporate) for a week. This channel is then put in an artificial weathering machine for 500 hours (sometimes considered equivalent to one year outdoors in some climates) and then examined visually for cracking, slump, washout, discoloration and adhesion loss (caused primarily or exclusively) from shrink forces. Visually determined twenty five percent bond loss or less is still a pass.

ASTM C734. Here the sealant is put onto a thin aluminum panel and cured, put into an artificial weathering machine for 500 hours, then put into a freezer and cooled to 0°F (-17°C) or 32°F (0°C). While cold, the panel with the sealant attached is quickly bent over a 1–inch (25.4 mm) diameter mandrel. The difference in the cold temperature of the bend makes for 2 classes. The sealant is then examined for cracking through to sealant to the bottom substrate and for adhesive failure. The pass criteria is no failure.

ASTM C736. Note this does not test for joint movement having extension and compression cycles but only has a single extension movement. The test consists of making a joint, curing it then extending the width to +25% holding it there for 5 minutes, releasing the strain and then watching it recover. Examine the sealant for adhesive failure and the % of recovery. The specification allows for 25% adhesion loss and it must have 75% or more recovery. It is a performance test but with milder conditions for sealants to be used in applications that are less demanding.

Another important test in the ASTM C834 specification is the test method ASTM C1241. Many latex sealants have significant water in them, and its evaporation gives significant shrink. There is a class OP (Opaque) that allows up to 30% volume shrinkage and a class C (Clear or Translucent) that allows up to 50% shrinkage. Shrinkage is a key since it can produce internal stresses and/or stresses on the bond line. The shrinkage also causes joint deformation which might or might not be a problem. The other tests in the specification are ASTM D2202 for slump, ASTM D2203, ASTM D2377 and ASTM C1183 for Extrudability. These are to make sure the sealant comes out of the tube without significant force, doesn"t slip out of the joint as it is being installed and cures in a reasonable time.

Latex sealants are generally paintable, and with the lesser joint movement the paint tends to adhere. Thus the latex sealants that qualify by this specification are sometimes called "painter"s caulk" and similar names that describe their principal use.

There are some latex sealants that pass the ASTM C920 specification based on the 28–day post cure weight loss test method ASTM C1246 referenced in ASTM C920 at 7%). Manufacturers who want to have their product used in demanding outdoor applications will often indicate their sealant passes ASTM C920 class 25. Some applications for these high-end latex sealants are in housing, DIY markets and more demanding applications. The attraction there is the paint ability, the ease of use and ease of clean-up while still getting a durable seal. The difficulty is in determining which latex sealants are truly high-end in performance and have durable adhesion. It is also of interest that a sealant might be paintable, and the paint has durable adhesion if there is minimal joint movement but some of the durability of the adhesion of the paint to the sealant is lost when the sealant has significant, repeated movement. It is appropriate to contact the manufacturer of such sealants and receive a written indicating the appropriateness of use in a given application.

As discussed above and also below one component sealants cure by different mechanisms. Some are reactive, where moisture in the air reacts with a component of a sealant completing the cure; others cure by releasing solvent or water. Most of the water containing sealants also cure through coalescence of the latex polymers contained in the sealant as the water is diffusing out of the sealant. The movement of moisture into a sealant bead and the movement of water and solvent out of a sealant bead is diffusion controlled. This means the process of loss of solvent and or water or moisture cure takes time for the moisture to migrate into the sealant bead or for the solvent and water to migrate out of the sealant bead. The larger the bead the longer this process will take before all of the solvent or water has migrated in the desired direction. Therefore, the larger the bead the slower the cure. Historically, ASTM C920 contained a weight loss specification, based on ASTM C792 that was a maximum of 7%. Current ASTM C920 uses ASTM C1246 as the standard for weight loss, with the same specification of 7%. ASTM C792 and ASTM C1246 differ in some significant ways. ASTM C792 requires curing of the adhesive for 7 days at standard conditions prior to over aging for 21 days at 70°C (158°F) to determine the weight loss. ASTM C1246 allows a 28–day cure before the 21 days in the 70°C (158°F) oven. In addition, the thickness of the bead in ASTM C792 is 6.4 mm whereas the thickness of the bead in ASTM C1246 is 3.2 mm. Based on these curing conditions ASTM C792 would give a higher percent weight loss than ASTM C1246. Some companies also report percent solids for their one component sealant. The percent solids are not measured by ASTM C792 or ASTM C1246. It is either determined by a loss in weight test in an oven or IR balance or is calculated based on the formulation.

The percent solids can also be misleading as some sealants contain small molecules that react into the polymer that would be lost in a percent solids test but would actually be incorporated into the final cured sealant. The reason why weight loss is important for a high-performance sealant is to reduce the stresses that could build up in the cured sealant. As the sealant loses weight it would start to shrink, minor shrinkage might not be negative as it could produce a more hourglass profile of the sealant, however, major shrinkage could induce significant tensile loads on the adhesion of the sealant to the substrate. These tensile loads would become higher as the joint opens. If the tensile load exceeds the adhesive strength of the sealant to the substrate then a loss in adhesion would occur or if the tensile load exceeds the tensile strength of the sealant there could be a cohesive break in the sealant. It is for this reason that high performance sealants that need to achieve high joint movement need to have low weight loss to keep the internal stress as low as possible. It is important for the specifier and architect to understand the nature of the sealant being specified and to work with the supplier to ensure that the sealant being specified is suitable for the application.

There is a family of sealants used in both interior and exterior applications that are generally called "Solvent Release Sealants". These are formulated sealants based on elastomeric polymers that "cure" by evaporation of the solvent. There is no chemical reaction taking place after the application of these types of sealants. These sealants are designed for applications in static joints where there is only a limited amount of joint movement, generally less than 7.5%. These types of sealants are covered by ASTM C1311.

ASTM C1311 has a set of performance criteria that a sealant of this type must meet. See Table 1 below taken from the standard. As with all ASTM performance standards, the criteria are minimum performance that a sealant needs to meet. These criteria are not necessarily the performance that is required in a specific application. It is incumbent on the specifier to be aware of the demands of the application and to make sure that the sealant selected has the required performance. The following is a brief discussion of four of the tests included in ASTM C1311, Bubbling ASTM C712, Adhesions and Cohesive loss, ASTM C1216, ASTM D2203, Accelerated weathering, ASTM C1257.

Note the accelerated aging referenced in Table 1 calls out 10,000 hours of exposure. However, in the body of ASTM C1311 the actual test duration is 1000 hours.

Adhesion and Cohesion loss, ASTM C1216, is an adhesion test that uses a modification of cyclic movement. The sealant is first applied in a joint configuration to various substrates, glass, aluminum, and a concrete mortar, allowed to cure. Once cured the sealant is subjected to expansion at low temperature, -12°C (10°F) and compression in an oven, 50°C (122°F). During the low-temperature cycle, the sealant is expanded at a rate of 3.8 mm (1/8 inch) per hour to +12.5% of the initial joint opening. In the high-temperature cycle, the sealant is compressed to -12.5% of the initial joint opening. The sealant assembly is subjected to 5 cycles and then the loss in adhesion or cohesive failure is evaluated. The test requires the amount of loss in either adhesion or cohesive failure to be less than 9 cm² on any set of three substrates used in the test. That is roughly 47% loss in adhesion or cohesive failure will still pass this performance criterion.

Accelerated Weathering, ASTM C1257, exposes the sealant to 1000 hours of UV exposure. The sealant is applied into aluminum channels, of the following dimensions 76 mm in length by 19 mm wide by 9.5 mm deep (3 inches x 3/4 inches x 3/8 inches), where the sealant has been applied to completely fill the channel. After 1000 hours the sealant is visually evaluated and compared to standard pictures to rate the amount of failure, see below for Edge cracking rating pictures. 1000 hours is not a very long amount of UV exposure, especially for a sealant that will be in direct sunlight. However, in the UV exposure chambers, the temperature is usually in the 50°C to 60°C (120°F to 140°F), range. At this temperature range for 1000 hours, about 42 days, most of the solvent would have evaporated from the sealant. So, while this test is not an extreme UV test it is a good test for issues due to shrinking of the sealant due to solvent evaporation. The maximum allowed rating is a 3 which does allow some Edge Cracking and Loss in Adhesion.

Figure 31: Edge cracking from ASTM C1257. At the end of the accelerated exposure period the specimens are examined for chalking, color change, center cracking, edge cracking and loss of adhesion versus the unexposed file specimen. Ratings range from zero for no damage to 5 for severe damage.

Bubbling, ASTM C712 looks at the potential for these types of sealants to bubble or blister on application. In the test method, a 25 mm wide x 95 mm long x 3.2 mm tall (1–inch x 3.75 inches x 1/8 inch) thick bead of sealant is applied to the various substrates. Aluminum and concrete mortar is standard substrates in this test method but others can be used. Three replicates are applied for each substrate. Once the sealant is applied it is allowed to cure for 48 hours at standard conditions then it is placed in a 50°C (122°F) oven for 72 hours. Aft