bluuebunny/crossref_metadata_2025 huggingface dataset:
Adiabatic Compression of Oxygen: Real Fluid Temperatures
Authors: Barragan M , Wilson DB , Stoltzfus JM
Published: April 2008

The adiabatic compression of oxygen has been identified as an ignition source for systems operating in enriched oxygen atmospheres. Current practice is to evaluate the temperature rise on compression by treating oxygen as an ideal gas with constant heat capacity. This paper establishes the appropriate thermodynamic analysis for the common occurrence of adiabatic compression of oxygen and in the process defines a satisfactory equation of state (EOS) for oxygen. It uses the EOS to model adiabatic compression as isentropic compression and calculates final temperatures for this system using current approaches for comparison.
Modeling the NASA/ASTM Flammability Test for Metallic Materials Burning in Reduced Gravity
Authors: Steinberg TA , Wilson DB
Published: April 2008

Flammability tests of iron using the Lewis Research Center's (LeRC) 2.2 s drop tower are modeled. Under the conditions of the test, after ignition, about 2.0 s of burning in reduced gravity (0.01-0.001 g) occurs. Observations (film and video) show the accumulating product mass to be well-mixed; therefore the system is modeled as a semi-batch reactor, that is, reactants continuously fed with the product accumulating in the reactor. The regression of the melting sample is considered steady-state. Real-time temperature and pressure measurements of the chamber gas provide measurements for model validation. The model consists of a set of 22, non-linear, first-order differential equations which are solved using MATLAB®. The model predicts, for 0.32-cm-diameter iron rods burning at 4300 kPa, an average reaction temperature of 3600 K and a molten oxide temperature of 3400 K. The system experimental parameters are the thermal conductivity of the molten liquid, kFe(ℓ), the thermal conductivity of the molten iron oxide mixture, kFeO(ℓ), and the heat transfer coefficient, h, between the molten oxide and the oxygen in the chamber and chamber itself. These model parameter values are: kFe(ℓ)=1.4 J/s cm K, 1.8 ⩽ kFeO(ℓ) ⩽ 35.0 J/s cm K, and 0.24 ⩽ h ⩽ 2.24 J/s cm2 K. It is suggested that the internal circulation within the molten ball formed during burning decreases as the ball grows. More work is necessary to understand the chemical nature of the reacting oxygen and determine the species formed during burning.
Failure Analysis of Aluminum-Bodied Medical Regulators
Authors: Newton BE , Hull WC , Stradling JS
Published: April 2008

Over the past 5 years 16 fires have been reported to the FDA involving aluminum-bodied medical regulators. These incidents are reported to have caused severe burns to 11 health care workers and patients. Many of the incidents have occurred during emergency medical use or during routine equipment checkouts. This paper summarizes the investigation and failure analysis of several of these fires and provides the cause and origin analysis for each. Ignition with catastrophic burnout of the regulator has been observed in each of these cases. The active ignition mechanisms are felt to have included particle impact in some cases, contaminant promoted ignition in other cases, and adiabatic compression in at least one other. Several of the fires are believed to have been caused by paniculate debris entrained in the oxygen flow stream from aluminum high-pressure cylinders. The regulator design, pertaining to the exposure of aluminum to active ignition mechanisms, and the use of aluminum cylinders with aluminum regulators are discussed.
Emergency Oxygen in the United States, Canada, and France: Assuring Proper Training
Authors: Starr LM , Derossi A
Published: April 2008

While the Food and Drug Administration (FDA) in the United States requires that users of medical oxygen be properly trained, the agency has not defined training content. ASTM STP 1267 suggested seven essential training content criteria, and evaluated the degree to which four national oxygen administration programs in the U.S. met them. ASTM 1319 examined the degree to which the criteria were met by a new national workplace oxygen administration curriculum. The present paper extends the evaluation to additional U.S. oxygen training programs, as well as to those in Canada and France. It also identifies the FDA's new “general guidelines” for oxygen safe handling and use. Recommendations for standardizing and assuring quality oxygen training programs are provided.
Evaluation of Contaminant-Promoted Ignition in Scuba Equipment and Breathing-Gas Delivery Systems
Authors: Forsyth ET , Durkin RJ , Beeson HD
Published: April 2008

As the underwater diving industry continues to use greater concentrations of oxygen in its scuba systems, contaminant ignition becomes of greater concern. In this study, several scuba component assemblies from the Neutral Buoyancy Lab at NASA Johnson Space Center were tested after 1 year of use. They were pneumatically impacted with 50 percent nitrox gas at 20.7 MPa (3000 psi) to evaluate their ignition resistance then disassembled to assess their cleanliness. A follow-up study was then conducted on the ignition thresholds of hydrocarbon-based oil films in oxygen and nitrox environments to characterize the cleaning requirements for these systems. Stainless steel tubes were contaminated to known levels and tested by pneumatic impact. Ignition was determinedwith a photocell connected to the end of the contaminated tube. The results of the scuba component tests, cleanliness evaluation, and contaminant ignition study are discussed and compared for 50 percent nitrox and 100 percent oxygen environments.
Flame Spreading and Violent Energy Release (VER) Processes of Aluminum Tubing in Liquid and Gaseous Oxygen Environments
Authors: Mench MM , Kuo KK , Sturges JH , Hansel JG , Houghton P
Published: April 2008

This work is motivated by the need for a fundamental understanding of the unintentional combustion of aluminum heat exchange equipment used in liquid oxygen (LOX) service; in which combustion can be quite energetic and cause severe damage. The promoted ignition, flame spreading, and combustion phenomena of aluminum tubing filled with LOX, surrounded by a shell of gaseous oxygen (GOX), were systematically observed and recorded. Parameters studied include the tube- and shell-side pressures, GOX and LOX flow rates, and GOX quality (the mass fraction of GOX in the two-phase flow inside the tube sample). Results from high-speed movie films indicate that under certain operating conditions, a transition from a “normal” (much slower) burning mode to an extremely rapid and violent burning mode occurs. This transition was shown to occur in some cases after a period of delay and in other cases immediately after the onset of ignition. The “Violent Energy Release,” or VER burning mode, is characterized by an extremely high flame spreading rate (1-2 orders of magnitude higher than the flame propagation rate in a purely GOX environment), a high luminosity flame-zone, and a very rapid rate of heat release. Within the range of initial conditions tested, the major parameters that tend to enhance the degree of violence of aluminum combustion in a LOX/GOX environment include increasing initial pressure and decreasing GOX quality (higher LOX fraction). A burning regime map showing the threshold boundaries between conditions of no self-sustained flame propagation, “normal” burning, and VER burning mode is presented. It was found that the threshold boundaries between the different regimes of burning are essentially determined by the tube-side conditions. In addition a detailed insight into the controlling mechanisms of the VER reaction has been obtained, and a physical description of the transition mechanism is presented.
A Promoted Ignition Combustion Test Apparatus for Evaluating the Flammability of Metallic Materials
Authors: Chou TC , Lemcoff NO , Henningson RL
Published: April 2008

To sustain the ever-increasing demands of material development for various oxygen applications, a promoted combustion test system was established at the BOC Group for evaluating the flammability of metallic materials in oxygen-enriched atmospheres. The system was designed with the following key features: (1) a cylindrical, vertically oriented, high-pressure vessel with two observation ports; (2) a diaphragm-type oxygen compressor; (3) a dynamic flow regulating device for constant flow rate and pressure controls; (4) two water-cooled, tube heat exchangers; (5) a temperature probing device with 3 thermocouples; and (6) a strip-chart data recording system with digital displays of test pressure and temperature. The pressure vessel, with an internal gas volume of about 5.7 liters, was designed to be operated at maximum working pressure 55.17 MPa (8000 psig) and at maximum temperature 650°F. It is capable of performing a promoted combustion experiment under either static or dynamic flow conditions. Details are presented in this paper to describe the system layout, materials of construction, and system operation as well as performance characteristics. Based on a flow simulation study, the distribution of gas velocity in the vicinity of a rod-shaped test specimen was profiled at selected combinations of gas pressure and flow rate under dynamic flow conditions. As a baseline calibration study, threshold pressures and self-extinguishing pressures were determined for metallic materials including Al 6061 alloy, 316 SS and 304 SS in pure oxygen (at least 99.6% purity). The test results are compared with those that were generated from NASA White Sands Test Facility and other industrial laboratories.
Determination of Oxidizing Ability of Gases and Gas Mixtures
Authors: Schroeder V , Mackrodt B , Dietlen S
Published: April 2008

According to a number of international and European regulations a gas, or mixture of gases, is classified as an oxidizing substance if it is more oxidizing than air. For classification it is necessary to have a method to determine reliable and comparable numerical data for the oxidizing ability of gases and a reliable calculation method for mixtures of gases. In ISO 10156 “Gases and gas mixtures — Determination of fire potential and oxidizing ability for the selection of cylinder valve outlets” a test method is given using pieces of plastic as combustible reference material. This method was tested in the past by Hoechst AG, Germany, and BAM and failed in the case of oxidizing gases other than air and oxygen. Therefore BAM developed a new test method in cooperation with ISO subcommittee ISO/TC58/SC2. The new procedure is based on the same apparatus and criteria applied for determination of flammability in ISO 10156. The reference combustible is the gas “Ethane”. This paper describes the new test procedure and gives “coefficients of oxygen equivalency (Ci)” for the oxidizing gases air, nitrous oxide, nitric oxide, chlorine, fluorine and nitrogen trifluoride. In the case of nitrous oxide, oxygen, air and nitrogen, a calculation method for gas mixtures was checked.
An Analysis of Autoignition Temperature Round Robin Test Data
Authors: Hirsch D , Bryan C , Barthélémy H , Chou T , Binder C
Published: April 2008

Autoignition temperature (AIT) round robin tests were conducted by seven laboratories on eight polymeric materials. A statistical analysis was conducted that focused on investigating data variability both within and between test methods. With some exceptions, the methods ranked the materials consistently and as expected from their chemical makeup. There was no consistent difference between AIT values determined at 6.9 and 10.3 MPa. BAM and ASTM G72 consistently provided lower, more conservative AITs at both 6.9 and 10.3 MPa. Within an estimated accuracy obtained from all methods from this round robin, data from the following methods appeared to be more accurate than the rest: NF E 29763/88 and Parr Bomb at 6.9 MPa; automated ASTM G72 at 10.3 MPa. The following methods provided lower within-method variability than the average for all methods: BS 3N 100 and ASTM G72 at 6.9 and 10.3 MPa; Parr Bomb at 6.9 MPa. At 6.9 MPa the BAM method provided data with greater within-method variability than the average for all methods. For most materials, the automated ASTM G72 method at 10.3 MPa provided data with greater within-method variability than the average for all methods. Two data points for this method, Zytel®6 and Teflon®6 FEP, exceeded critical k. At 6.9 MPa, the largest within-method variability resulted from NF E 29763/88 on Zytel, the only data that exceeded critical k. Two extreme results were caused by significant effects of method-specific test parameters: BAM on Zytel at 6.9 MPa and BS 3N 100 on Viton®6 at 10.3 MPa. Statistically these results had a probability of less than 5 percent of occurring by chance.
Predictability of Gaseous Impact Ignition Sensitivity from Autoignition Temperature Data
Authors: Hirsch D , Skarsgard E , Beeson H , Bryan C
Published: April 2008

An analysis of cumulative binomial probabilities for a quantal test like ASTM G 74 indicates that for a probability of reaction in a single trial of 0.05, the probability of obtaining zero reactions in 20 trials is approximately 36 percent. Since the lack of precision of the ASTM G 74 test logic could be potentially misleading, an investigation was conducted to determine if pneumatic impact sensitivity could be predicted more reliably from other, more precise test methods. Pneumatic impact sensitivity testing was conducted following ASTM G 74 but using a rigorous test logic; autoignition temperature (AIT) testing was conducted per ASTM G 72. Polyethylene, polyoxymethylene, polytetrafluoroethylene (PTFE), polyamide, hexafluoropropylene/vinylidene fluoride copolymer, and silicone were the polymers used. After a fixed number of pneumatic impact tests was performed at set pressures, a plot of reaction frequency over a 3.4 to 24.1 MPa impact pressure range indicated that PTFE, hexafluoropropylene/vinylidene fluoride copolymer, and silicone would outperform the other polymers tested. The 50 percent pneumatic impact reactivity level was determined with the Bruceton test method. The data obtained resulted in a strong correlation between the 50 percent reactivity level and the AIT of polymers, indicating similar ignition mechanisms.
Repeatability of the Resilient Modulus Test Procedure
Authors: Boudreau RL
Published: April 2008

Through the work of the Strategic Highway Research Program (SHRP, 1987–1992) and the Federal Highway Administration (FHWA, 1992-present), the government has provided financial and technical assistance to develop and improve a laboratory test method to determine the resilient modulus properties of unbound materials. Although the work — part of the Long Term Pavement Performance (LTPP) study — has led towards the adoption of test procedure T307-99 in the current release of the American Association of State Highway and Transportation Officials (AASHTO) Tests, many skeptics insist that the method does not lend itself towards repeatable, reproducible test results.

This paper acknowledges that the work conducted by SHRP and FHWA focused rimarily upon developing a test method that would be relatively simple and highly productive with less variability inherent in the previous, existing test procedure. Variables not investigated included compaction methodology, instrumentation location and sensitivities to other influencing factors such as precision of confining pressure, waveform control, membrane thickness and porous stone properties. Additionally, the testing program did not successfully establish a precision and bias statement for the test method utilized.

The repeatability of the test is examined by utilizing eight replicated test specimen ub sampled from a homogenous Alabama soil and nineteen replicated test specimen sub sampled from a homogenous Georgia soil. Each test specimen was prepared using the five-lift static compaction method. All specimens were tested within the range of ±1 pound per cubic foot density and ±0.4 percent moisture content, thus minimizing variations of results due to material variation. Averages, standard deviations, and coefficients of variation (c.v.) were determined for resilient modulus values calculated at each load sequence, resulting in c.v.s of below 4.5%. The resilient modulus values were calculated using the constitutive model: Mr = K1(Sc)K2 (S3)K5 in order to normalize the data for comparative purposes.

The test method can promote repeatable test results, although much more testing is recommended to produce precision and bias statements within and between laboratories.
Resilient Modulus Variations with Water Content
Authors: Li J , Qubain BS
Published: April 2008

Resilient modulus (MR) variations with water content were carefully examined for three subgrade soils—lean clay, clayey sand, and clayey gravel. For each soil type, four MR tests were performed at the following water contents: 2 to 3% dry of optimum, at optimum; 2 to 3% wet of optimum; and at full backpressure saturation. The backpressure-saturated samples were molded at optimum and gained up to 6% moisture during saturation. The MR testing of the non-saturated specimens was conducted according to ASSHTO T307-99 and specific testing adjustments were developed for the backpressure-saturated ones. After achieving saturation, the specimens were consolidated at a confining pressure equivalent to the stress level of pavement surcharge and then subjected to five levels of deviator stresses under undrained conditions. The test results were utilized together with in situ stresses to develop design curves for resilient modulus versus water content.
Effect of Moisture Content and Pore Water Pressure Buildup on Resilient Modulus of Cohesive Soils in Ohio
Authors: Butalia TS , Huang J , Kim DG , Croft F
Published: April 2008

High positive pore pressures in subgrade soils can be expected to contribute to reduction in soil strength and stiffness. Measurement of elevated pore water pressures in the subgrades of instrumented sections of Specific Pavement Studies conducted in Ohio over the past several years have raised concerns about the long-term stability of these test sections. The objective of this study was to identify the effects of moisture content and pore water pressure on the resilient modulus (Mr) of unsaturated and saturated cohesive soils. Test results conducted on unsaturated cohesive soils at three different moisture contents (optimum, 2 to 4% dry of optimum, and 1 1/2 to 3% wet of optimum) showed that the resilient modulus and the effect of confining stress decreased with increasing moisture content. Laboratory tests on fully saturated cohesive soils showed that the resilient modulus of saturated soils decreased to less than half that of soil specimens tested at optimum moisture content. Residual pore water pressure increased with an increase in the deviator stress, and a decrease in the loading period. The time to dissipate residual pore water pressure, which was large in comparison to the load rate, increased with increasing deviator stress. The resilient modulus of fully saturated cohesive soil was much less under faster (1 second per cycle) cyclic loading than slower (8 seconds per cycle) cyclic loading.
Design Subgrade Resilient Modulus for Florida Subgrade Soils
Authors: Bandara N , Rowe GM
Published: April 2008

Many agencies still use empirical correlations developed to determine design subgrade resilient modulus based on California Bearing Ratio (CBR), R-Value or Soil Support Value (SSV) for pavement design projects. These relationships do not consider the stress dependency of the laboratory determined resilient modulus value. Backcalculated subgrade modulus values from Falling Weight Deflectometer (FWD) tests are also used for this purpose. This study was conducted to determine the relationships between laboratory determined subgrade resilient modulus and the results of Lime Rock Bearing Ratio (LBR) and FWD tests for certain Florida subgrade soils. Laboratory resilient modulus values were determined using subgrade soil samples collected from nine pavement sections. The resilient modulus values were computed by considering stress levels under a standard dual wheel in three typical pavement sections. The roadway sections were selected from various locations in Polk County, Florida. FWD tests were conducted along the selected roadways and LBR tests were conducted on bulk subgrade soil samples. Preliminary relationships to determine design subgrade resilient modulus equivalent to AASHTO Road Test subgrade from FWD and LBR tests were developed for considered typical pavement sections.
A Low-Cost High-Performance Alternative for Controlling a Servo-Hydraulic System for Triaxial Resilient Modulus Apparatus
Authors: Bejarano MO , Heath AC , Harvey JT
Published: April 2008

A triaxial test apparatus for the characterization of pavement materials was designed and built at the Pavement Research Center (PRC) at the University of California, Berkeley (UCB). The system was designed for high quality testing of unbound, stabilized, and asphaltic materials. The design process included the design of the hardware and the servo-controlling systems. An important step in the design of the system was the design of the controller for the servo-hydraulic system. Alternatives for controllers of servo-hydraulic systems for waveform generation included the use of the data acquisition system along with proportional, integral, and derivative (PID) algorithms for setting the minimum and maximum loads/displacement. Software programming for these solutions was very complex with limited satisfactory consistency. Commercial ready-to-use controllers are expensive and limited to the specifications of the manufacturer. Therefore, a commercially available programmable motion controller PIC card was implemented for controlling the servo-hydraulic system. The motion controller required only one PID controller to generate repeated waveforms or monotonic loading. An available commercial test solution software compatible with the motion controller card was used to program the motion controller and data acquisition system. This capability was preferable to provide flexibility in modifying the system based on research needs. Software programming was simple. In addition, the cost of the new system was reduced by about 80 percent with respect to the ready-to-use motion controllers.

The paper describes the implementation of the motion controller, the philosophy of the software program, and the success obtained with the new system. The system meets all the quality control provision of the LTTP Protocol P-46. Currently the triaxial apparatus is being use to investigate the resilient response and permanent deformation performance of typical California aggregate base and subbases.
Water-Based Acrylic Concrete Seals
Authors: Tysak T
Published: April 2008

Stringent environmental regulations have forced the concrete finishing market to reduce volatile organic compounds (VOCs). Formulators use water based polymers to reduce these emissions. In this paper, the chemical composition of commercial aqueous acrylic latex concrete seals, and their performance is presented. A discussion of efflorescence and its prevention, as well as concrete sealer application and maintenance procedures are also presented.
Polish Maintenance for Fun and Profit
Authors: Tysak T
Published: April 2008

The cost of polish maintenance is many times greater than the cost of the chemicals and their application. The physics and chemistry of the various procedures and processes in polish maintenance are discussed, with an emphasis on high speed burnishing.
The Effect of Polish Maintenance on Static Coefficient of Friction
Authors: Owens JM
Published: April 2008

The static coefficient of friction (μs) of polishes, measured by the James machine and ASTM D2047, provides a measure of the inherent slip resistance of the polish film. When in use, polish films are invariably modified by traffic and routine maintenance procedures that could, theoretically, change the inherent slip resistance of the film. Portable tribometers are not appropriate for measuring μs of polishes in traffic because they have not yet demonstrated a correlation with the James machine, so they provide no criterion for determining whether the surface is slip resistant.

A protocol was developed using the James machine and a modification of ASTM D2047 to measure μs of polish films after pedestrian traffic and routine maintenance had been performed. The maintenance procedures included high speed burnishing, high speed spray buffing, low speed spray buffing, damp mopping, autoscrubbing, deep cleaning (partial stripping), dust mopping, and dry sweeping.

The protocol was extended to test the effect of traffic and maintenance on μs. This paper also reports the μs changes observed with three compositionally different but commercially typical floor finishes and two widely used commercial polishes of unknown composition.
Managing Slips and Falls: A Legal Perspective
Authors: Balek WC
Published: April 2008

Annually, slip and fall incidents exact a substantial toll in terms of death, personal injury, personal suffering, workers compensation, loss in productivity and civil liability. The cause of slip and fall incidents and resultant damages are multiple and include unclean/unsafe floors, physiological characteristics of individuals, lack of training, inappropriate footwear and even fraud. A clear understanding of the underlying causes of slip and falls provides us with the framework for identifying those factors we can control and thus minimize and otherwise reduce one's potential liability.

Numerous parties may be responsible and therefore potentially liable for a slip and fall incident depending on the particular circumstances of a given situation. Parties that may be liable in a slip and fall incident include owners or operators of retail and other commercial facilities, and distributors and manufacturers of floor care products, flooring and footwear.

This paper outlines various proactive measures that individuals and companies can implement and which will help to eliminate or substantially reduce the incidence of slip and fall injuries, and any potential liability.
Secondary Drainage System for Architectural Panel Systems
Authors: Carbary LD , Ryan MW
Published: April 2008

In conjunction with the exterior cladding system, field applied architectural sealant joints are the primary source of resistance against air and water intrusion on most high-rise residential and nonresidential commercial structures. Jobsite practices and quality in workmanship will dictate deficiencies in application of the high performance sealants specified for this purpose. When these deficiencies allow water and air to enter the structure, or when water condenses and collects behind the walls, damage caused by water is detrimental to the structure. The condition known as percolation, where outside positive pressures associated with Heating Ventilation and Air Conditioning (HVAC) systems in combination with wind driven rains literally vacuum water into the building, further amplifies this problem. The damages attributed to water and air infiltration can be corrosion of structural anchors, reduction in insulation efficiency, damage to interior walls, damage to floor coverings and mold growth.

This paper reports on the design, development and testing of a state of the art secondary drainage system that is used behind prefabricated panelized Glass Fiber Reinforced Concrete (OFRC), Architectural Precast Concrete (APC), Composite Architectural Precast (CAP), and natural stone on truss systems.

This system consists of silicone extrusions, tubes and joint protection collection reservoirs with one way valves (JPCROV) that are attached to the back of the concrete or stone panels using adhesive attachments, which are compatible and marry intimately into the exterior architectural sealant joints. Unique designs of gutters that are resistant to jobsite debris that can clog drains and render them inadequate are presented along with the JPCROV that prevents percolation and allows water to weep out of the system These additional materials within the wall cavity also must have benign fire properties due to the concern for toxic gasses and smoke in the event of a fire.

The technology of the silicone extruded gutters, tubes and percolation boxes is most suitable for the alkaline variable temperature and humidity environment found in these wall cavities. Silicone adhesive technology of one-part neutral cure RTV silicone sealant is used to mount the secondary drainage system within the wall to provide a long-term performing solution. Durability data is presented on the bonds between the silicone extrusions and concrete substrates for this application. Modified ASTM Standard Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading (Metal-to-Metal) (D1002-99) data after room temperature cure, water immersion, and both elevated temperature and high humidity is presented as data simulating the actual application. System design capacities and proper installation for maximum coverage are also presented.
Lock-Strip Gasket System Retrofit: A Case History
Authors: Schmidt MK
Published: April 2008

The facade of the subject 20-year-old, three-story building is comprised of insulating glass units in vision areas and single monolithic glass sheets in spandrel areas. Both products have a reflective metallic coating on the exterior surface and are completely captured by a perimeter lock-strip (zipper) gasket system. The zipper gasket intersections are butted, not vulcanized, causing numerous Oavenues for water penetration. Attempts to seal some of these gaps with sealant had been made in the past, yet active leaks still existed. Furthermore, there was a concern regarding the premature failure of the insulating glass units within the inadequately drained glazing pockets of the zipper gasket system.

In order to address these gasket conditions properly and to protect the insulating glass units for the long-term, custom designed repairs consisting of overlapping preformed silicone shapes and extrusions were utilized to create a watertight barrier. Unique elements of this application include accommodation of undulating gaskets and misalignment of intersecting gaskets, complete coverage of the previously repaired lock-strip gaskets (believed to be contributing to the glass staining) with the preformed shapes and extrusions, sealant pockets within the extrusion to control bond surface area, and selection of sealant adhesive to mitigate future glass staining. Lessons learned from the application of this barrier system, including issues related to sizing and fabrication of the preformed silicone parts, are presented. The experiences gained via the prolific use of preformed silicone products on this project will be beneficial to all those involved in the maintenance of lock-strip gasket systems and other types of building facades.
Durability by Design: Load Carrying Silicone Bonding, Herz Jesu Church, Munich
Authors: Hagl A
Published: April 2008

The design of conventional glass façades in Germany is typically based on the extensive use of point supports that keep the glass panels in position and which provide the load transfer of the façade. Besides the aesthetic disadvantage of discrete elements being visible in the glass façade, the application of point supports leads to highly concentrated stress regions substantially affecting sizing and durability of the façade components. In order to overcome these limitations, a new approach has been chosen for the design of the glass façade of the Herz Jesu Church, Munich. One peculiarity of the overall glass façade of this box-shaped building consists in horizontal and vertical glass beams used for the support of the façade. Silicone adhesives bond steel stringers along the main edges of the horizontal and vertical glass beams in order to establish load paths between beams and façade. The hereby-realized bonding design offers special features being favorable for the durability of the building. Load carrying capacities have been provided by line-type connections, substantially reducing stress concentrations. Major attention has been given to the geometric layout of the bonding. Thus, detailed finite element (FE) analysis has guided the careful selection of an adequate channel cross section for the stringers. The design philosophy of the bonding is characterized by a small exposed surface of the silicone adhesive, offering only a very small area of attack for environmental degradation. Additionally, the exposed surface is only stressed at a low level avoiding the critical combination of highly loaded areas exposed to aggressive environmental conditions. Furthermore, two principal load paths (tension and shear) are established, leading to a fail-safe design principle of the bonding. These key considerations provide major contributions to the high durability design of the glass façade bonding.
Water Absorption in Cold Liquid-Applied Waterproofing
Authors: Strong JC , Kovach JR
Published: April 2008

Some widely used cold fluid-applied waterproofing materials are prone to failure involving water absorption. These products meet the standards of ASTM Specification for High Solids Content, Cold Liquid-Applied Elastomeric Waterproofing Membrane for Use with Separate Wearing Course (C 836). Experienced investigators of waterproofing systems are familiar with this failure mode; some refer to the convoluted appearance of a membrane after water absorption as “braining.”

Our investigation into this mode of failure examines the properties of waterproofing materials and application methods. This report includes the results of testing with four different application methods, and varying conditioning periods. Testing included immersion in water at 50 °C (122 °F).

Test specimens absorbed more water than allowed by the Canadian General Standards Board's (CGSB) standard Membrane, Elastomeric, Cold-Applied Liquid, for Non-Exposed Use in Roofing and Waterproofing (CAN/CGSB-37-58).
Silyl-Terminated Polyurethanes for Construction Sealants
Authors: O'Connor AE , Kingston T
Published: April 2008

Construction sealants produced through the curing of silyl-terminated oligomers (STO) display properties similar to conventional polyurethanes, but they possess several distinct advantages.This paper provides a state-of-the-art review of silane-functional polymers for sealants in construction. Properties of silyl-terminated polyurethanes (STPU) are compared with traditional polyurethanes as well as silyl-terminated polyether (STPE) sealants. Urethane prepolymers, prepared from the reaction of a diisocyanate and a conventional polyol, are end-capped with an organo-functional silane. As a consequence, there are no free isocyanate molecules in the sealant. These sealants show improved adhesion to glass, UV stability, and weatherability. Sealants based on STPU chemistry are presently in use for industrial and transportation applications, which require medium to high modulus. Current work explores methods to reduce the modulus and increase elongation while retaining good cohesive properties. STPU sealants have been prepared with varying isocyanates, polyols, and silanes. They have been evaluated in accordance with several ASTM tests, including those in the ASTM Standard Specification for Elastomeric Joint Sealants (C920). The glass-transition temperatures and rheological characterizations of STO-based sealants are presented. Correlations are made between these fundamental material properties and the sealant's behavior in use, as measured by ASTM test methods. These measurements could provide a method for identifying candidate formulations that are expected to pass more extensive ASTM testing. These material characterizations as well as the results of mechanical property testing are compared for selected STPU, STPE, polyurethane, and silicone sealants.
Effect of Foam Backer Rod on the Mechanical Performance of Sealed Joints
Authors: Iglauer S , Hutchinson AR , Lee TCP
Published: April 2008

Backing foams are inserted into sealed joints in cladding systems on high-rise buildings. However, limited previous research suggested that backing rods could reduce the performance of sealed joints, in particular if the joints were moved during the early stages of sealant cure. This stimulated a comprehensive investigation of backing foams and how they influence the mechanical performance of sealed joints. Different commercially used backing foams were selected and analysed in terms of their mechanical, structural and surface properties. The influence of the foams on the static tensile and fatigue (at 1 Hz) behaviour of standard tensile adhesion joints, subjected to both static and dynamic curing over a twenty eight day period, was evaluated; this data was compared with peel forces obtained from 180° peel tests of sealant on foam specimens. It was found that the presence of backing foam could significantly reduce the fatigue performance of sealed joints.
Artificial Weathering and Cyclic Movement Test Results Based on the RILEM TC139-DBS Durability Test Method for Construction Sealants
Authors: Miyauchi H , Enomoto N , Sugiyama S , Tanaka K
Published: April 2008

The purpose of this study was to assess the effect of artificial weathering and cyclic movement in a laboratory test based on the RILEM Technical Recommendation (RTR) “Durability Test Method for Curtain Wall Joint Sealants.” Eleven sealants being used in Japan were tested, including two silicones, two silicon-modified polyethers, two polysulfides, two polyurethanes — each as one- and two- part products — one two-part silicon-modified polyisobutylene, one two-part urethane cure acrylic, and one one-part water-borne acrylic. The two-part polyurethane, the two-part urethane-cure acrylic, and the one-part water-borne acrylic were also evaluated with and without painting the sealant surface. Test specimens were prepared using anodized aluminum and mortar as substrate materials; primers were used for all sealant/substrate combinations as recommended by the manufacturers. All sealant specimens were conditioned according to Method A. The durability test, consisting of weathering and thermo-mechanical cycling, was carried out both with and without the influence of fatigue cycling. The durability cycles were repeated three times. Weathering was conducted in a fully automatic weathering machine using a xenon arc light source. Sealants without painting were observed to chalk and craze at an earlier stage in the durability cycles than the ones with painted surfaces, confirming the effectiveness of painting the sealant surface in protecting organic sealants from aging. A substantial difference in the behavior of sealants was observed for exposures with and without fatigue cycling, confirming the importance of fatigue cycling in the degradation of sealants. In order to obtain a good correlation between accelerated weathering and actual service performance, a proper balance of degradation factors is essential.
Effect of Float Glass Surface Composition on Silicone Sealant Adhesion Tested After Simultaneous Exposure to Hot Water and Ultraviolet Light
Authors: Wolf AT , McMillan CS , Stiell W , Lieb K
Published: April 2008

The objective of this study is to evaluate the effect of float glass surface composition on silicone sealant adhesion in a wet environment. Float glass samples obtained from six different European glass manufacturers were characterized analytically (XPS) and tested for their hydrolytic stability (DIN 52296). Fifteen tensile/adhesion joints (H-pieces) were prepared for each float glass sample using a two- part, tin-catalyzed, condensation-cure silicone sealant containing a controlled amount of free aminosilane adhesion promoter. Five H-pieces each were tested after four weeks of ambient cure conditioning (reference specimens) as well as after an additional 500 h and 1000 h immersion in 45°C hot water with simultaneous UV exposure. As expected, all reference specimens failed cohesively in the tensile/adhesion test. All specimens exposed to the additional 500 h of hot water immersion and UV also showed cohesive failure. However, after 1000 h of exposure, differences in adhesion behavior could be observed. while the sealant failed cohesively (all five specimens) on one float glass, partial adhesive failure was observed on the other glass samples. For these glasses, the average extent of adhesive failure varied between 4–19%. Because of the limited amount of float glass samples studied, the experimental results must be interpreted cautiously. No correlation is observed between the hydrolytic stability of float glass samples and sealant adhesion. However, the chemical surface composition of the float glass appears to affect sealant adhesion. Low levels of Na and K (added to the glass composition as alkaline oxides) result in better sealant adhesion. Higher surface concentrations of these ions can be tolerated if the glass surface is also rich in Al ions. Poorer adhesion results, however, when high levels of alkaline Na or K oxides are combined with a low level of Al.
Comparison of Butyl versus Modified Asphalt Window Flashing Adhesives
Authors: Zima AD , Weston TA , Katsaros JD , Hagood R
Published: April 2008

In the last few years, using window flashings to keep moisture out of wall systems has become an increasingly used practice. Builders have identified moisture intrusion as a key reason for callbacks. Window flashing products are expected to keep moisture from entering a wall system, around windows in particular, over the life span of a home. Traditionally, felt splines have been used to flash flanged windows, but now flexible flashings are emerging as the industry standard. Peel-and-stick flexible flashing integrates the window into the wall system by creating a seam between the window flange and wall system. Because the flashing product relies on its adhesive to create and maintain this seam over the life of the home, the durability of the flashing adhesive is very important There does not seem to be a good understanding of the in-use performance aspects of the typical adhesives, butyls and modified asphalts, used in flashing materials. This study characterizes key attributes of these different adhesive systems, which can be related to performance differences between typical butyl and modified asphalt adhesives used in window flashing products.

There are a number of key aspects that are important when considering what adhesive system to choose for a window flashing material. This study targets some of these parameters as ways to compare butyl and modified asphalts. The properties that will be tested are:- long term durability (simulated aging and exposure), - staining tendencies, - peel adhesion over a wide temperature range, and — compatibility to vinyl (a common window material).

Choosing the correct window flashing product is an important decision when it comes to keeping moisture out of wall systems over the life span of a home. The results of this study will help the building science community decide on the best way to protect homes from moisture intrusion.
Durability and Adhesion Rate of One-Part Silicone Sealants to Silicone Rubber Extrusions for New and Remedial Glazing and Weatherproofing Applications
Authors: Carbary LD , Zimmer EA
Published: April 2008

The use of extruded and molded silicone rubber attached with a one-part silicone sealant is becoming a popular method of curtainwall and general building renovation. The use of extrusions provides an aesthetically pleasing restoration method for sealing out water from the outside of the building. The extrusions and molded parts have become popular for restoration because of the ease and speed of installation. An economical fix for leaking walls coupled with the aesthetics has provided building owners a good solution.

As with any restoration solution, the question of durability and speed of adhesion has been asked. This paper presents data on the cure and adhesion rate of the one-part silicone sealants used in the attachment of the extruded and molded parts by reporting data on the strength and modulus with time using a modified ASTM C1135 test method. Also data is presented on the durability of these bonds using this test method and exposing the samples to 2700 hours of QUV accelerated weathering. Test results are reported for samples that are comprised of glass and fluorocarbon painted aluminum substrates. Silicone rubber extrusions with Shore A durometer hardness of 30 and 56 are evaluated. These samples are evaluated at several different cure times (4 hours, 14 hours, 24 hours, 7 days, 3 weeks) and also subjected to various thermal and atmospheric conditions (heat, cold, QUV exposure, and water immersion).

Conclusions are that the silicone adhesive can provide adequate cure and strength in less than 24 hours to withstand typical stresses incurred during the first day's movement. The accelerated weathering shows no effect on the bonds of the silicone adhesive sealant to the extrusions used in this study. Hence, the method of restoration currently used with these parts is expected to perform as a long-term weatherproofing solution similar to the use of silicone sealants as structural glazing and weathersealing applications.
Nondestructive Field Testing of Installed Weatherproofing Sealant Joints
Authors: Huff D
Published: April 2008

A durable building seal requires full and continuous adhesion of the weatherproofing sealant in the joint at all locations. At times, mere nominal adhesion is achieved. Reasons for nominal adhesion will not be discussed here, but they vary widely. This condition is not easily detected, and traditional methods of test verify adhesion to the substrate, not the continuity of the seal itself. The result can be leaky buildings despite successful intermittent field “pull testing”. The challenge becomes finding and repairing sealant beads that may not be visibly failing.

This paper makes a case in support of the recently published “Standard Practice for Evaluating Adhesion of Installed Weatherproofing Sealant Joints” (ASTM C1521-02). The practice describes a nondestructive procedure that places a strain on the sealant and a stress on the adhesive bond. The procedure consists of applying the strain to the sealant bead using a “blunt dowel shaped probe”. Use of this dowel shaped probe is subjective, however, and is wholly dependent on the user to gauge the appropriate strain required to obtain an appropriate elongation.

A device has been created that is able to comply with this non-destructive procedure in a uniform and controlled manner. This paper describes the device and its workings. Additionally, a detailed description of the process by which the device has been calibrated to the properties of a variety of sealants is presented. Finally, reports of the successful field use of the device are given.

In conclusion, this paper asserts that the future of field-testing of sealants will necessarily include non-destructive procedures that have the ability to test 100% of installed sealants. This approach to field-testing will provide all concerned with a new level of confidence that a durable building seal can be achieved.