Joint Sealants Research Articles

Development of a Non-Destructive Evaluation Practice of Installed Weatherproofing Sealant Joints Using a Rolling Device—An Introduction to ASTM C 1736

Abstract This paper provides an overview of the development of standardized methodology to evaluate joint seal continuity, encompassed in the newly published ASTM C 1736-11, “Standard Practice for Non-Destructive Evaluation of Adhesion of Installed Weatherproofing Sealant Joints Using a Rolling Device.” This standard practice was created under the jurisdiction of ASTM Committee C 24 on Building Seals and Sealants and is the direct responsibility of Subcommittee 30 on Adhesion; it was approved July 1, 2011. Fundamental details contributing to the successful usage of this practice are examined by answering the following questions: Where exactly do the stresses produced by this procedure have an effect upon the sealant-to-substrate bond-line? How does joint geometry impact this bond-line stress? What level of stress on a bond-line provides usable information without damaging the seal?

Seismic Racking Test Evaluation of Silicone Used in a Four-Sided Structural Sealant Glazed Curtain Wall System

AbstractThis paper presents the results of a study in which four-sided structural sealant glazing (SSG) insulating glass curtain wall units were subjected to cyclic racking test methods in accordance with AAMA 501.6 testing protocols. The test configuration included three side-by-side primary units and a corner unit. High-resolution cameras were utilized to capture instantaneous images during the racking test so that the displacement within the sealant joint could be captured and isolated from the displacement of the entire glazed unit. Drift capacity of the system in terms of glass attachment and sealant performance is reported in detail for different levels of racking displacements and boundary conditions. The overall behavior of the system is characterized, and specifically the sealant performance at a corner condition during racking drift is discussed. Additionally, expected strains in the sealant were calculated using a linear-elastic finite element model and were then compared with the strains the actual structural sealant joint underwent during system testing. Silicone sealant damage was evaluated using visual observation before and after cyclic racking. The paper discusses proposed acceptable sealant stress levels for seismic design and the durability of silicone used in the SSG system as compared to dry-glazed systems based on glass performance.

A Test Method for Monitoring Modulus Changes during Durability Tests on Building Joint Sealants

Abstract The durability of building joint sealants is generally assessed using a descriptive methodology involving visual inspection of exposed specimens for defects. It is widely known that this methodology has inherent limitations, including that the results are qualitative. A new test method is proposed that provides more fundamental and quantitative information about changes occurring in a sealant during durability testing. This test method utilizes a stress relaxation experiment to evaluate the non-linear viscoelastic behavior of sealants. In particular, changes in the time dependence of the apparent modulus can be observed and related to molecular changes in the sealant. Such changes often precede the formation of cracks and theultimate failure of the sealant. This paper compares results obtained from the new test method and the currently used descriptive methodology.

Experimental and Finite Element Modeling of Friction Stir Seal Welding of Tube-Tubesheet Joint

Tube-tubesheet joints are critical in some applications, where contact between shell and tube side fluids is not tolerable. To ensure joint tightness, standards (ASME and TEMA) recommend performing a combination of rolling-or expansion of tube-tubesheet and seal welding. Available techniques for seal welding are based on fusion welding that sometimes results in a number of defects such as cracking and porosity formation, and such defects may take a newly fabricated heat exchanger out of service. In this work, friction stir welding (FSW) was used for tube-tubesheet seal joint and simulated using a 3D thermo-mechanical finite element model (FEM). The model was analyzed using a commercial finite element (FE) package. The model included the thermal effect of the tool workpiece interaction along with axial load, ignoring the metal flow around the tool. The material model took into account temperature dependency of thermal and mechanical properties. The model objectives were to evaluate the temperature distribution and residual stress in the workpiece resulting from the thermal cycle and axial load during welding for various process parameters, and to study how residual stresses in adjacent roller expanded tubes are affected during welding. The FE results show that the maximum temperature at the welding zone does not exceed the solidus temperature (except at high tool rotational speeds); the process can thus be classified as cold working. Moreover, adjacent tubes temperature does not exceed the annealing temperature. An experimental setup was designed and manufactured to show the feasibility of the process in this constrained size joints and to validate the numerical results. A test cell and a special FSW tool were designed and manufactured for this purpose. Many tests were performed with welding quality depending on process parameters.

Assessment of Tire Noise on Concrete Pavement in California Highways

A 2-year initial study, recently completed in California, measured and compared tire–pavement noise levels with the onboard sound intensity method on existing concrete pavements. The study included 120 pavement subsections at 47 sites; most sections were measured twice in the 2 years. The surfaces encountered were classified into five texture categories: burlap drag, diamond ground, diamond grooved, longitudinally broomed, and longitudinally tined. The experiment was not balanced for age, traffic level, or climate region. The surfaces were further categorized as having new, aged, or worn-out texture. The differences within and between surface types were assessed for spectral content and overall sound intensity. The results revealed a large overlap in the onboard sound intensity levels between texture types. The quietest sections overall were measured on diamond ground surfaces. However, on the basis of the average noise level of the evaluated sections of each texture type, the longitudinally broomed surfaces as a group were the quietest, although they were represented by a small sample in the experiment. The study indicated that the sound intensity of concrete pavements in California ranged from about 99 to about 107 dB(A). The measured onboard sound intensity levels included the effects of joint slap, faulting, and sealant, if present, in addition to the texture.

Development of a Novel Test Rig for the Evaluation of Aircraft Fuel Tank Sealant

Abstract A key concept for the future evaluation of sealant materials for commercial aircraft is to expose realistic sealed joint systems to typical dynamic and environmental parameters representative of actual flight conditions. The development of a mechanism to undertake the full range of test parameters for the evaluation of sealants for current and future aircraft is described in this paper. This mechanism, or model sealed system (MSS), consists of an axial stress machine into which vibrational fatigue, high and low temperatures and pressures can be programmed for automatic operation. The test coupons, within the MSS, can be stressed to simulate flight conditions along with the flight pressures and temperatures. The MSS is described and the results of sealant evaluation to date are presented.

Experimental and Finite Element Modeling of Friction Stir Seal Welding of Tube-Tubesheet Joint

Tube-tubesheet joints are critical in some applications, where contact between shell and tube side fluids is not tolerable. To ensure joint tightness, standards (ASME and TEMA) recommend performing a combination of rolling-or expansion of tube-tubesheet and seal welding. Available techniques for seal welding are based on fusion welding that sometimes results in a number of defects such as cracking and porosity formation, and such defects may take a newly fabricated heat exchanger out of service. In this work, friction stir welding (FSW) was used for tube-tubesheet seal joint and simulated using a 3D thermo-mechanical finite element model (FEM). The model was analyzed using a commercial finite element (FE) package. The model included the thermal effect of the tool workpiece interaction along with axial load, ignoring the metal flow around the tool. The material model took into account temperature dependency of thermal and mechanical properties. The model objectives were to evaluate the temperature distribution and residual stress in the workpiece resulting from the thermal cycle and axial load during welding for various process parameters, and to study how residual stresses in adjacent roller expanded tubes are affected during welding. The FE results show that the maximum temperature at the welding zone does not exceed the solidus temperature (except at high tool rotational speeds); the process can thus be classified as cold working. Moreover, adjacent tubes temperature does not exceed the annealing temperature. An experimental setup was designed and manufactured to show the feasibility of the process in this constrained size joints and to validate the numerical results. A test cell and a special FSW tool were designed and manufactured for this purpose. Many tests were performed with welding quality depending on process parameters.

Evaluation of Sealed Joint Performance for the Selection of Sealants Suitable for Use in Autoclaved Lightweight Concrete Panels

Abstract The strength of autoclaved lightweight concrete (ALC) is evidently lower than that of normal concrete. Therefore, when movement occurs at a sealed joint between ALC panels, the sealant is required to deform and remain intact without damaging the ALC substrate. However, there is currently not sufficient information to permit evaluation of the expected performance of sealants applied to ALC substrates. In this study, static and dynamic tests were carried out in order to obtain an index that could be used to select the modulus of a sealant that can be expected to provide long-term performance when applied to an ALC substrate. To develop this index, an initial study was carried out in order to clarify actual joint movement between ALC panels of buildings; the expansion and contraction at the joint were measured, and shear joint movement was calculated based on the expected story-to-story drift of an external wall due to earthquake loads. Thereafter, in a subsequent stage of the study, five types of two-component polyurethane sealant products, of different elastic modulus, were subjected to tensile and shear tests from which the relationship between stress and the type of joint fracture was determined. The results from these tests revealed that when the stress is greater than 0.6 to 0.7 N/mm2, the ALC substrate is more easily fractured than the sealant. In a final stage of the study, the cyclic fatigue resistance of the same two-component sealants was evaluated using tensile and shear fatigue tests. Results from the fatigue tests indicated that the high modulus sealants lost adhesion from the ALC substrate at an early stage in the test. As well, the fatigue resistance of test specimens with joints having three-sided adhesion was lower than that of specimens having normally configured joints with adhesion on two sides of the sealant. Therefore, on the basis of results derived from all the studies, it was determined that a suitable sealant for use on ALC substrates is a sealant having a low modulus that is applied in the normal fashion as a two-sided joint.

Durability of Acrylic Sealants Applied to Joints of Autoclaved Lightweight Concrete Walls: Evaluation of Exposure Testing

Abstract In Japan acrylic sealants are traditionally the sealant products of choice when specified for use between autoclaved lightweight concrete (ALC) panels. Although, in general terms, the mechanisms of the deterioration of acrylic sealants are well known its long-term durability to outdoor exposure has not, however, been fully investigated. The research described in this paper focuses on the change in the properties and deterioration of acrylic sealant products when exposed to outdoor testing. The two stage project consisted of (i) on-site investigations of deteriorated acrylic sealants that had been placed in external joints of ALC-clad buildings; and (ii) outdoor exposure testing of different types of acrylic sealant in three climate regions located in Japan. The results of the work from the first stage of the study revealed the following. Two-sided adhesion joint configurations installed in deep panel ALC cladding were more reliable than three-sided adhesion joints used for thin panel ALC cladding from the viewpoint of the durability of the sealed joint installed in actual buildings. Most fractures of the sealed joint could be characterized as failure in peel (or thin layer cohesive failures), in which the sealant ruptured at the interface with the ALC substrate to which it was applied. Additionally, in 47 of 62 locations surveyed, surface cracks were apparent on the coating that had been applied to protect the sealant. The second stage of the project focused on the degree of deterioration of coated and non-coated acrylic sealants subjected to outdoor exposure testing in a cold, a warm, and a subtropical climate. Results from this stage showed that aging of the sealant, as determined by the degree of surface cracking, expectedly depended on the local temperature and the respective degree of exposure to solar radiation. It was determined that the longer the exposure period, the lower the tensile performance of the acrylic sealants. The elongation of three-sided adhesive joint configurations after 5 years exposure testing decreased remarkably and their maximum elongation was less than 50 %. A significant number of sealed joints after 5 years ofexposure had ALC substrate failure.

Development of reliable low temperature wafer level hermetic bonding using composite seal joint

A reliable composite metal seal comprising both intermetallic compounds (IMC) and solder joints, which are formed by transient liquid phase bonding and soldering respectively, is proposed and demonstrated in wafer level bonding experiments. Hermetic sealing is demonstrated on 8-in. wafers using low volume Cu/Sn materials at process temperatures as low as 280°C. It is shown that the composite seal is stable when subjected to temperatures of 250°C, and that it provides better hermeticity and reliability than an IMC seal alone.

Detachable sealed joint having two successively placed sealing elements

In this article, an analysis has been made of the force characteristics of a detachable sealed joint having two successively placed gaskets that hermetically separate two chambers in an apparatus where the pressures of the working media are different. The joints were analyzed by using their electrical analog circuits. The analysis helped derive expressions for determining the load on the successively arranged sealing elements and fastening (securing) parts (bolts or pins) under the operating conditions (with due regard for the pressure in each sealed chamber of the apparatus) and the force of preloading of each group of fastening parts. A procedure is proposed for calculating (designing) joints having two successively placed sealing elements. It can also be used for joints having a large number of serially placed sealing elements.

Laboratory evaluation of a silicone foam sealant bonded to various header materials used in bridge expansion joints

A silicone foam sealant was developed to provide an easy-to-use and economical joint sealant for small-movement bridge expansion joints. In studies reported previously, various laboratory tests were conducted to evaluate the performance of the sealant using concrete as the bonding substrate. In the present study, laboratory tests on the sealant were conducted using other substrates found in practice, including steel, asphalt, and polymer concrete. Some of the tests conducted included a tension test, repair test, oven-aged bonding test, salt water immersion test, and a cure (modulus over time) test that evaluated the mechanical properties of the sealant as it developed its final state of cure. Through the laboratory tests, it has been observed that the silicone foam has the ability to bond to various substrate materials and can easily accommodate deformation typical of small-movement expansion joints in bridges.

Studies on synthesis and properties of novel polyurethane pavement joint sealant modified with polydimethysiloxane

The development of a general use pavement joint sealant is described in this paper. A novel two-component polyurethane (PU) modified with hydroxyl terminated polydimethysiloxane joint sealant was developed for the needs of inland Chinese cement concrete pavement joint sealant production and applications. The performances of these sealants after hot pressing and hard drawing were also investigated. The cohesional strength of this new joint sealant material maintained 93·20% after hot pressing and hard drawing and was much higher than conventional PU and tar based PU joint sealants. This new sealant has superior tensile strength, cohesional strength, fatigue and aging resistance compared with currently used sealants.

Design, fabrication, and implementation of thermally driven outdoor testing devices for building joint sealants

The paper describes the development, implementation, and testing of two thermally driven outdoor exposure instruments. These devices are unique in their ability to impose field generated thermally induced strain on sealant specimens while monitoring their resulting load and displacement. The instruments combine a fixed wood and steel supporting frame with a moving polyvinyl chloride frame, and employ differences in the coefficients of thermal expansion between the supporting frame and moving frame to induce strain on the sealant specimens. Two different kinds of instruments have been fabricated, "winter/tension" and "winter/compression" designs. In the winter/tension design, the thermally induced dimensional change is directly transferred to the specimens; while in the winter/compression design, the samples are loaded in an opposite direction with the dimensional change. Both designs are instrumented to monitor load and displacement and are built so that the strain on the specimen does not exceed ±25% over the range of temperatures expected in Gaithersburg, MD. Additionally, a weather station is colocated with the device to record environmental conditions in 1 min intervals. This combination of weather information with mechanical property data enables a direct link between environmental conditions and the corresponding sealant response. The reliability and effectiveness of these instruments are demonstrated with a typical sealant material. The results show that the instruments work according to the design criteria and provide a meaningful quantitative platform to monitor the mechanical response of sealant exposed to outdoor weathering.

Aging management program of the reactor building concrete at Point Lepreau Generating Station

In order for New Brunswick Power Nuclear (NBPN) to control the risks of degradation of the concrete reactor building at the Point Lepreau Generating Station (PLGS) the development of an aging management plan (AMP) was initiated. The intention of this plan was to determine the requirements for specific structural components of concrete of the reactor building that require regular inspection and maintenance to ensure the safe and reliable operation of the plant. The document is currently in draft form and presents an integrated methodology for the application of an AMP for the concrete of the reactor building. The current AMP addresses the reactor building structure and various components, such as joint sealant and liners that are integral to the structure. It does not include internal components housed within the structure. This paper provides background information regarding the document developed and the strategy developed to manage potential degradation of the concrete of the reactor building, as well as specific programs and preventive and corrective maintenance activities initiated.

Strength and Deformation Characteristics of Cement-Treated Reclaimed Pavement with a Chip Seal

The objective of this research was to analyze the strength and deformation characteristics of a cement-treated base (CTB) constructed with full-depth reclamation, microcracked, and then surfaced with a single chip seal. In this field study, strength characteristics of the CTB layer were determined at the time of construction, and both strength and deformation characteristics were evaluated after 9 months of low-volume, heavy truck traffic. Observed distresses at 9 months included transverse cracking, rutting, and chip seal joint failure. The loss of the chip seal was caused by poor chip seal construction practices and not a deficiency in the CTB layer. The average ride qualities in and out of the wheelpath were in the fair ride category; the roughness was not likely caused by trafficking but probably resulted from construction or climatic factors. Structural testing performed after 9 months of service indicated that CTB stiffness and modulus were greater than the values measured after microcracking at the time of construction, indicating continued strength gain. However, trafficking over the 9 months had caused significantly lower stiffness in the wheelpaths than between the wheelpaths. The average unconfined compressive strength (UCS) of the cores tested at 9 months did not differ significantly from the average UCS of the field-compacted specimens tested at 6 weeks. Recommendations for improved CTB performance include the use of a thicker, stiffer, or both, CTB layer to ensure a smooth CTB surface during construction and application of a double chip seal or equivalent.

A performance evaluation method of preformed joint sealant: Slip-down failure

Various preformed joint sealants (PJS) can be used for joint concrete pavement (JCP) to prevent the JCP from distresses such as pumping and faulting. Even though PJS have an important role in concrete pavement structures, most of the test methods that assess PJS focus on evaluating their basic mechanical and chemical properties rather than performance-related properties. In this study, a tester for PJS is developed and utilized to determine the resistant stiffness, which is considered to be a performance-related parameter, of PJS in transverse joints. The resistant stiffness is determined by dividing the peak force by the displacement; and the normalized value, which is used to simplify the relationship between the joint width and the sealant width, is determined by dividing the joint width by the sealant width. From laboratory tests performed on the developed tester, it is found that the resistant stiffness and normalized value are representative parameters that can be used to recommend the proper width of the joint, regardless of the joint width and joint type. Also, the relationship between the slip-down distress and the joint width, which is obtained from field survey results, can be utilized to recommend a minimum width for PJS.

Fatigue behaviour of double lap riveted joints assembled with and without interfay sealant

Fatigue tests on ‘double shear’ riveted specimens were carried out. Material was aluminium alloy, 7075-T73, thickness 3 mm. Specimen surfaces were protected by chromic acid anodization and epoxy primer. The mating surfaces of some specimens were sealed by a two-component manganese-dioxide cured, polysulfide compound. Specimens were pre-assembled by inserting a temporary spring fastener in a pilot hole. The holes were reamed to the final diameter after sealant curing; then the Hi-Loks were installed. Comparative fatigue tests were carried out on dry assembled specimens. Quite surprisingly, the fatigue resistance of sealed specimens was very low when compared with the results of dry assembled specimens. Hysteresis cycles measured in sealed and un-sealed specimens clearly indicated a lubricant effect of the sealing layer, which justified the results obtained. Additional tests were performed on specimens assembled by applying different clamping force during the sealant curing time. The results obtained indicated an independence of the fatigue resistance on this parameter. Different failure modes were observed in sealed and un-sealed specimens: fatigue cracks nucleated outside the hole at a location in the shadow of the rivet in the un-sealed joints, while fatigue cracks nucleated at both sides of the holes in sealed joints. Finite element calculations carried out under different values of the friction coefficient between the mating surfaces confirmed the different location of the fatigue critical areas in sealed and un-sealed specimens.

Photoelectrical setup for electrical power supply of seismological objects

A new preengineered construction and technology of construction of a 280-W photoelectrical station and sealing of silicon solar cells using silicon joint sealants available in the Uzbekistan are described. Methods for assembling accumulators of progressive switching of cells with a capacity of 200 A h and manufacturing a battery charge controller using microprocessors are specified. This photoelectric setup supplies electrical power for the places far from centralized power supplies, among them seismic stations.

Zagospodarowanie odpadow tworzyw termoplastycznych w srodowisku bitumow naftowych

New polymer-bitumen compositions based on thermoplastic polymers and heavy fractions from crude-oil processing have been developed. The parameters for the preparation of homogeneous and stable composites (Table 3) containing particular types of thermoplastic wastes of PE, PP, PS, PC (Table 1) and secondary bitumen oils such as clarified, pirolytic, used engine oils or furfurol extract (Table 2) have also been established. The obtained dual-content compositions underwent comprehensive thermomechanical and Theological tests in order to determine their applicability as binding agents in consumer products (Table 4, Figs. 1, 2). A preparation method developed for application of the new consumer materials for use as the joint sealants, seal mastics, asphalt primer solutions and asphalt-polymer adhesives was established and a full range of tests performed in accordance with current regulations (Tables 5-9, Figs. 3,4) performed on them. The possibility of utilizing the waste polymers in the secondary bitumen environment in extreme conditions (Table 10, Fig. 5) was evaluated. The obtained thermolysis products can be used in the bri-quetting of solid fuels, modification of the poperties of petroleum asphalt and the preparation of sealing components for the construction industry.