Category Adhesives: 4th Volume

Overview

Introduction

The Fourth ASTM International Symposium on Durability of Building and Construction Sealants and Adhesives (2011-DBCSA) was held on June 16­17, 2011 in Anaheim, California. It was sponsored by the ASTM Internation­al Committee C24 on Building Seals and Sealants in cooperation with the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM). The symposium was held in conjunction with the standardization meetings of the C24 Committee. With presenta­tions from authors representing nine countries in North and South America, Europe, Asia, and Australia, the symposium was a truly international event.

As in the previous events of this symposium series, the 2011 symposium brought together architects, engineers, scientists – researchers and practi­tioners. One of the stated goals of the symposium was to transfer new ideas, gained from laboratory research and field work, to the study of sealant and adhesive durability and the development of new products and test meth­ods. The symposium provided an excellent forum for international experts to share and compare their experiences, network with their peers, and exchange best practices with regard to the durability testing and assessment of build­ing and construction sealants and adhesives. It also provided a platform for an expert panel discussion. The panel discussion was originally conceived as a discussion on sealant warranty issues, but became a spirited conversa­tion regarding the impact of the newly developed ASTM C1736 Standard Practice with participation by the panelists, ASTM C24 members, as well as presenters and participants of the international symposium. Perhaps the greatest value of this series of symposia lies in the discussions occurring during these events and in the utilization of the resulting information.

The current series of ASTM symposia on Durability of Building and Con­struction Sealants and Adhesives is a continuation of tri-annual symposia which were inaugurated by the RILEM Technical Committee 139-DBS Durability of Building Sealants in 1994. Today, this continuing series of symposia provides the best scientific forum globally in the building and con­struction industry for peer-reviewed papers on all aspects of sealant and adhesive durability. Furthermore, data presented at those symposia over the past 17 years have been the single most important factor influencing ASTM International and ISO standards as well as RILEM technical recommenda­tions related to construction sealant durability.

In several languages, such as Dutch, Finnish, Romanian or French, sustainable is translated as durable. This synonymous use of durable and sustainable is not surprising, as durability plays a key role in achieving

sustainable construction, because “one way of extending resource productiv­ity is by extending the useful life of products” (DeSimone & Poppof, 1998). The increased utilization of sustainable construction practice, i. e., design­ing for durability by utilizing building science and life cycle analysis as its foundation, as well as mandatory government regulations, such as the Euro­pean Construction Products Directive, have elevated the importance of the durability and service life performance of building and construction seal­ants and adhesives. All products, not just those involved in safety-critical applications, must demonstrate durability as part of their fitness for purpose assessment. Life cycle costing considerations increasingly drive investment decisions towards products and systems with longer service life cycles and lower maintenance costs.

Against a background of national and international efforts to harmonize testing and approval of building materials and structures, ASTM Interna­tional and RILEM have been looking for ways of bringing together the expe­rience of international experts active in the application and testing of build­ing and construction sealants and adhesives.

As with most scientific disciplines, substantial advances often occur through a series of incremental steps, each contributing pieces of the puzzle, rather than in giant leaps. This is also the case for the papers presented at the Fourth International Symposium on Durability of Building and Con­struction Sealants and Adhesives (2011-DBCSA). Many of the papers reflect progress reports on on-going research. At the 2011-DBCSA symposium, we saw several examples of the steady progress being made by leveraging these scientific advances into a new generation of test methods as well as assess­ment practices.

This book contains twenty-three of the twenty-seven papers presented at the symposium as well as two papers submitted only for publication in the proceedings. It also contains an editorial summary of the panel discussion. The contributions condensed in this STP volume represent state-of-the-art research into sealant and adhesive durability and reflect the varying back­ground, experience, profession, and geographic location of the authors. The following major themes are evident in this collection:

• Laboratory Testing and Specialized Outdoor Exposure Testing

• Factors Influencing the Durability of Sealed Joints and Adhesive Fixing

• Development of New Test Methods and Performance-Based Specifica­tions

• Field Experience with Sealed Joints and Adhesive Fixing

• Performance under Seismic Loads

Choosing Wisdom over Intelligence

Energy effectiveness also requires ‘Intelligent Design’ – meant here as a con­sideration of all interactions at the highest system level and anticipating unexpected side-effects. For instance, some poor designs meant to improve energy efficiency of buildings have led to major problems in terms of comfort and health for the building occupants. As mentioned earlier, reducing air leakage from the building envelope and ductwork is typically among the most substantial improvements that can be made to reduce operational en­ergy use. Sealing the building envelope leads to a reduction in the air ex­changes previously achieved by ‘natural ventilation’. The desired effect is a reduction in the HVAC operational energy. However, when poorly designed, the undesired side-effect is an increase in potentially harmful volatile or­ganics, radon, moisture and mold growth, with negative impact on the com­fort and health of the building occupants. On the other hand, when prop­erly planned by combining air tight envelopes with mechanical ventilation

systems having integrated heat exchangers, very low operational energy consumption can be achieved, down to the level of ‘passive house’ standard, while at the same time providing good air quality to the building occupants.

The challenges both designers and businesses face when moving from tra­ditional design and production methods to ones that promote a sustainable future are huge. For the designer, it is important to appreciate, what build­ing owners really want: Sustainability, but not at the expense of perform­ance and aesthetics! Designers who balance and optimize the technical and aesthetic life-span requirements for a building product or component with the environmentally related characteristics and performance attributes can reduce the energy and materials dedicated to these requirements.

The adhesives and sealants industry as well as academia will choose wisely if they seek out the environmental attributes that can be delivered by their products with the key aim of lowering the operational energy consump­tion and the life-cycle costs of the building. Enhancing a product’s function and life span with the added benefit of improving its environmental profile and impact should be a key focus in future research and development efforts. More effort can be put into the design phase of building materials, such as adhesives and sealants, building components, building systems, and finally the whole building to truly achieve improved sustainability. As highlighted a number of times in this preface, durability and sustainability are related in different ways and at different levels. As an industry, will we choose wisely? Will we see more papers and presentations on this topic at one of the future Durability of Building and Construction Sealants and Adhesives symposia?

Maybe ‘Intelligent Design’ is not an adequate term anyway. Intelligence predicts the success of individuals without regard to the consequences of their success to others. Wisdom, however, reflects the ability to make adap­tive decisions in a social context. It requires altruism, balanced judgment, competent reality testing, and a consistent view of the big picture. This is why wisdom, not intelligence, applies to the survival of species[21].

What we must strive to achieve is sustainability, supporting the long­term ecological balance, certain in the knowledge that “the most sustainable energy is the energy saved”. ‘Wise Design’ takes this fundamental truth into account, and has the potential of truly living up to the expectations of Caro­lus Linnaeus, the father of modern biological classification (taxonomy), who in 1758 applied the name Homo sapiens (Wise Man) to our species.

Andreas T. Wolf Wiesbaden, Germany

Choosing Energy Effectiveness Rather than Efficiency

In order to be energy effective, it is important to look at the Life-Cycle Analysis (LCA) to see what lifecycle stage (material production, manu­facturing, use, end-of-life) has the greatest environmental impact. It is important to focus efforts first on this stage before dedicating time to the others. Operational energy reduction is a key priority, since the most sus­tainable energy is energy saved. Energy itself is not of particular interest, but rather is a means towards desired ends. Clients desire the services that energy can deliver, for instance, comfort, illumination, power, trans­portation – not energy by itself. Hence, maximum energy efficiency with minimal environmental impact is the architectural challenge that ulti­mately allows us to “have our cake and eat it too”. In this context, mate­rial choices that impact operational energy are important, while they are less significant for the energy spent in manufacturing, construction and demolition of the building.

Therefore, two of the key objectives in designing sustainable buildings are to lower the operational energy consumption and the life-cycle costs of the building. This should be achieved by:

• First, focusing on improving the performance of the building envelope in order to lower the energy demand, as the life span of the envelope is between 50 and 100 years. Commonsense already tells us to focus on things such as air tightness of the building envelope, the quality of the insulation and especially of the windows, and to avoid thermal bridges.

• The second priority then should be to avoid energy use, for instance, by using efficient appliances and through the increased use and conver­sion of energy embedded in natural day-lighting (the ultraviolet and infra-red fractions).

• Once this has been accomplished, the focus should shift towards the generation of energy from ‘renewable’ source, as the life span of these systems is in the 10-25 years range. This approach is also dictated by simple economic considerations, as more capital is needed for an over­sized renewable energy system to compensate for a poorly designed building envelope or for inefficient appliances.

In building, the most technically appropriate materials will lower opera­tional energy costs over the life cycle of a building and demonstrate excel­lent durability. For example, composite materials involving carbon fibers or ceramic compounds may have a relatively high embodied energy, but when they are used appropriately, they can save energy in a building’s use-phase due to their advanced physical properties, e. g., insulation, strength, stiff­ness, heat or wear resistance.

Design Choices Involving Sealants and Adhesives in Building Construction and Their Impact on our Environmental Footprint

Whether sealants and adhesives will be seen from an ecological point of view as being part of the solution or part of the problem – especially when one considers recycling of materials and components at the renovation or demo­lition stage – depends largely on decisions made during the design phase.

First, it should be recognized that, even if the design process itself had only a minor contribution to the cost of building, a considerable portion of the cost (as well as material and energy use) associated with later life cycle phases is committed at the design stage. It has been estimated that more than 80 percent of a product’s environmental impact is determined during its design phase[15] [16] [17], and it is likely that the same holds true for buildings. Therefore, it is essential to consider environmental aspects of the whole buildings as well as of the components and materials used from the first stages of design and de­velopment. Such an approach is generally termed ‘Eco-innovation’ or ‘Design for Environment (DfE)’. The purpose of Design for Environment then is to design a building in such a way as to minimize (or even eliminate!) the envi­ronmental impacts associated with its life cycle. Design for Environment, as applied to buildings, typically focuses on energy efficiency and effectiveness, materials innovation, and recycling. While energy efficiency often is under­stood as addressing energy savings at the sub-system level, for instance in terms of the heating, ventilation and cooling (HVAC) system, energy effec­tiveness may be defined as producing the best overall results with the least amount of energy. Materials innovation addresses the need to develop new materials that allow construction of low embodied energy, light weight, and durable components which also meet the need for improved recyclability (which often is a challenge with composites) and have less environmental impact. Recyclability finally is considered at the design stage by ‘Design for Deconstruction (DfD)’. Design for Deconstruction is an emerging concept that borrows from the fields of design for disassembly, reuse, remanufac­turing and recycling in the consumer products industries1617. According to the ISO 14021:1999 standard “Environmental labels and declarations – Self­declared environmental claims (Type II environmental labeling)”, the use of the term ‘design to disassemble’ refers to the design of a product that can be separated at the end of its life-time, in such a way its components and parts are reused, recycled, recovered as energy form, or in some other way sepa­rated from the remainders flow. The overall goal of Design for Deconstruc­tion is to reduce pollution impacts and increase resource and economic ef­ficiency in the adaptation and eventual removal of buildings, and recovery of components and materials for reuse, re-manufacturing and recycling. From

an environmental point of view, building adhesives and sealants often face two contradicting requirements: On the one hand, these materials should be durable and resist the environmental stressors, such as sunlight, water, and heat; on the other hand, there is the need to easily separate substrates for recycling or repair. Recently, there has been increased interest in ‘Debonding on Demand’, which refers to the process of easily separating two adhered surfaces. Heat and light switchable adhesives have been developed, as well as primers that can act as a separation layer when activated by infrared or microwave radiation181920. Surely novel methods for Debonding on Demand will be developed in the near future and it will be interesting to see what the environmental durability of these sealants and adhesives will be.

Returning to the topic of dematerialization, it should be noted that less material use does not automatically imply less environmental impact. If the dematerialized product or component is inferior in quality and has a shorter usable life, then more replacements will be needed during the over­all life of the building, and the net result likely will be a greater amount of waste in both production and use. Design for Dematerialization, therefore, must always be accompanied by Design for Reliability and Durability, i. e., designing a product or component to perform its task in a reliable, consist­ent manner, and ensuring that it will also have a long life span. From an environmental viewpoint, therefore, dematerialization should perhaps be better defined as the reduction in the amount of waste generated per unit of building product.

When considering Design for Durability, a fair question to ask is: What should be the design life of a building or a material or component used in the building? Clearly, there is a trade-off between the embodied energy in the building and its energy efficiency and effectiveness. Building components that are still far from being fully optimized in terms of their impact on ener­gy efficiency should not last forever; rather they should be easily replaceable with new, more efficient components and easily recycled at the end of their life. Obviously, the corollary to this statement is that the higher the energy efficiency associated with a building component is, the higher its expected service life should be. The same holds true from an economic point of view: The higher the investment cost, the longer it takes to recover the invest – [18] [19] [20]

ment, the higher the durability of the component should be. Consequently, recyclability is more important for short-lived products and components than for more durable ones.

Another, very effective approach to dematerialization is moving from a product to a service orientation, i. e., using less material to deliver the same level of functionality to the building owner. After all, building own­ers and users are more interested in the value a product provides than in its physical presence. For example, the newly published ASTM Stand­ard C 1736-11 “Practice for Non-Destructive Evaluation of Adhesion of Installed Weatherproofing Sealant Joints Using a Rolling Device” offers the sealant applicator an opportunity to move from installation contracts to product-oriented service contracts. Probably most applicators will ini­tially view the concept of inspecting the quality of installed joint seals as challenging their reputation, possibly resulting in increased liability for them. However, when this inspection is offered as part of a periodic maintenance contract, sealant failures can be repaired locally and without replacing the entire installation. Such maintenance results in material savings as well as satisfied building owners (and facility managers), as the functionality of the seals is ensured and maintained at a high level, and, ultimately, also results in better and more stable relationships between sealant applicators and their clients due to the more frequent contacts and the higher value provided. Similarly, sealant manufacturers initially will be concerned that such service contracts will lead to decreasing seal­ant product sales. However, revenue models could be developed that allow extension of sealed joint warranties based on certification fees associated with the inspection of the building.

21st Century Potential for Positive Change – Contributions by Sealants and Adhesives

What do the previous comments have to do with a book focused on the dura­bility of building and construction sealants and adhesives?

Sealants and adhesives are at the interface between building materials and/or components and provide important functions, such as sealing, bond­ing, strengthening, movement accommodation, shock protection, fire reten­tion, thermal or electrical insulation, and many others. These functions pro­vide added value to the building and can enable a reduction in the building’s ecological footprint. Below are just a few examples of the contributions that sealants and adhesives can make to the reduction of operational energy as­sociated with a building:

• Energy-efficient ventilation achieved via controlled air and moisture flows (elimination of both ‘infiltration’ and ‘exfiltration’, the uninten­tional and uncontrollable flow of air through cracks and leaks in the building envelope).

• Improved thermal insulation of windows achieved by replacement of existing glazing by durable, sealed high performance insulating glass units.

• Renewable energy generation: Use of sealants and adhesives in the assembly and sealing of photovoltaic (PV) solar modules as well as dur­ing installation of building integrated photovoltaic solar panels (BIPV) in the building envelope.

The use of a structural sealant or adhesive may also allow redesign of a building component such that the dematerialization results in a reduction of the associated embodied energy of the component.

One example is the elimination of steel reinforcement bars in uPVC win­dows by bonding the glass panes to the uPVC frame as an alternative rein­forcement measure. Experience gained with silicones in structural glazing and protective glazing systems and with polyurethanes in automotive direct glazing led to the development of these structurally bonded window sys­tems. Obviously, the strength of the window then depends on the structural strength of the glass unit. However, glass has a good load bearing capability (stiffness) and can contribute considerably to the overall strength of the sys­tem. In addition to their environmental benefit (smaller carbon footprint), these constructions also offer functional benefits, such as leaner and more slender frame designs (the larger vision area results in increased light trans­mission via the window opening and provides improved natural lighting) as well as improved protective glazing properties (resistance to burglars, bomb blasts, hurricanes, earthquakes, avalanches, etc.)[13]. In this example, dema­terialization is achieved by satisfying several product functions through one component (sealant) of the overall product (window).

A second example is the replacement of concrete beams by hybrid compos­ite beams. These composite beams are one-tenth the weight of concrete, one – third the weight of steel, yet they are strong enough to replace structural concrete beams. Manufactured by filling fiberglass composite boxes with a concrete and steel arch, covered by composite tops secured using a two-part methacrylate adhesive, they show excellent environmental durability and are expected to have a useful life of at least 100 years, during which they need less maintenance than existing materials. Furthermore, due to their resilient, energy absorbing, construction, they provide seismic shock resist – ance[14]. The ‘dematerialized’ components mentioned here in the two examples can lower the carbon footprint of construction projects due to the reduction in their materials’ embodied energy, and the lower fuel usage needed to ship these lighter weight components.

Impact of Buildings on the Environment and the Way Forward

One of the principal needs essential for the human race to survive is subsist­ence, which relies on an unconditional availability of food and shelter. The services involved in the operation of ‘modern shelters’, i. e., residential and commercial buildings — lighting, heating in the winter, cooling in the sum­mer, water heating, electronic entertainment, computing, refrigeration, and cooking — require a staggering amount of energy. The energy required for the operation of buildings in the U. S.[5] [6] [7] alone corresponds to 42 EJ (1 Exa- joule = 1018 Joule) or about 1 Giga-ton-oil-equivalent (1 toe = 41.87 GJ). This accounts for almost 40 percent of the total U. S. energy use. This amount is equivalent to the energy released by about 670,000 atomic bombs of the ‘Little Boy’ type dropped over Hiroshima on August 6, 1945, a bomb that exploded with an energy of about 15 kilotons of TNT (63 TJ).

In addition to the operational energy employed during use, buildings embody the energy used in the mining, extraction, harvesting, processing, manufacturing and transport of building materials as well as the energy used in the construction and decommissioning of buildings. This embodied energy, along with a building’s operational energy, constitutes the building’s life-cycle energy and carbon dioxide (CO2) emissions footprint.

Energy efficiency of buildings has been on the agenda of many govern­ments during the past 20 years. However, in order to effectively shrink the ecological footprint of our buildings, we must seek ways to ‘decarbonize’ our energy sources, i. e., we have to shift from the burning of fossil fuels to energy sources that do not release additional CO2 to the atmosphere. Renewable en­ergy sources, such as wind, hydro, tide and wave, geothermal, photovoltaic and thermal solar, biomass fuels, as well as synthetic fuels produced, for in­stance, by genetically modified algae or bacteria or by the Fischer-Tropsch process from existing atmospheric CO2 are likely to play an increasingly im­portant role in the future energy mix6,7. However, this shift towards more benign and renewable energies does not imply that energy efficiency is off the agenda. On the contrary, we have to strengthen our efforts directed at making our buildings more energy efficient. Finally, we have to consider ways of de – materializing as well as rematerializing our buildings. Dematerialization is a

reduction in the bulk (mass) of hardware and the associated embodied energy used in the construction of buildings (“doing more with less”), while remate­rialization is the reuse or recycling of building materials at the demolition stage. Both dematerialization and rematerialization recognize that there are finite limits to the amount of materials we can extract from our planet.

The amount of carbon dioxide emissions that construction can influence is substantial. A British report, published in autumn 2010, estimates that construction-related CO2 emissions account for almost 47 percent of total carbon dioxide emissions of the United Kingdom[8]. The previously cited U. S. EPA report estimates that buildings in the United States contribute 38.9 percent of the nation’s total carbon dioxide emissions. Due to the energy inef­ficiency of the existing housing stock, CO2 emissions generated during use of buildings in the U. K. account for over 80 percent of total CO2 emissions. Pre­vious life-cycle energy analyses have repeatedly found that the energy used in the operation and maintenance of buildings dwarf the energy embodied in building materials. For example, Cole and Kernan[9], in 1996, as well as Reepe and Blanchard[10] [11], in 1998, found that the energy of operation was between 83 to 94 percent of the 50-year life cycle energy use. Even for new, highly efficient office buildings located in China, where currently considerably less energy is being consumed by the operation of buildings when compared to the U. S.A. or Western Europe, operational energy accounts for 56 percent of the total life cycle energy11.

Building construction and demolition are major contributors to the waste we generate. In a report issued in April 2009, the U. S. EPA estimates that 160 million tons of building-related construction and demolition (C&D) de­bris is generated in the U. S.A. annually, of which 8 percent is generated during new construction, 48 percent is demolition debris, and 44 percent is

renovation waste. An estimated 20 to 30 percent of building-related C&D de­bris is recovered for processing and recycling. The materials most frequently recovered and recycled were concrete, asphalt, metals, and wood[12].

Regardless of one’s personal opinion about the consequences of the above facts and statistics for the future of humanity, any rational thinker among us must appreciate the serious cost overhead associated with all this waste. In monetary terms, can the waste laden expenditures of the past continue to be expanded and sustained by humankind in the 21st Century?

Preface

What Impact Do Design Choices in the Building Industry Have on Our Destiny?

The global population of Homo sapiens reached four billion in 1974, five bil­lion in 1987, six billion in 1999, and seven billion by the end of October 2011. It continues to soar at a rate of 1.1 percent per year and is expected to reach eight billion sometime within the time frame of 2025-2027, and nine billion around mid-century1.

Whilst the population has increased by a factor of about 2.7 during the past 60 years, the global annual primary energy consumption has grown by a factor of 4.5, a trend bearing the signs of a typical runaway process. A worry compounding this symptom is that only a small share of the global population, some 1.2 billion people (approximately 15 percent of the total population) located in the OECD countries, accounts for the lion’s share (47 percent) in global energy consumption23. The developing countries are now eagerly adopting this historically ‘proven formula’ for success.

The biosphere, and hence the environment, of planet Earth is self-regu­lating. If humankind is not capable of simultaneously halting or reversing population growth whilst drastically reducing its average footprint of energy consumption per capita, this runaway process will result in an environmen­tal implosion, which will be aided by increasing demand for water, produc­tive land (food) as well as waste generation[1] [2] [3] [4]. The ensuing starvation and environmental disasters will drastically decimate our population to a level that again can be sustained by Earth’s fragile (and then damaged) environ­ment. Assuming that we are able to quickly and effectively minimize our impact on the environment, we are still facing an environmental bottleneck in this century.