Postgraduate textbook. Учебное пособие

instance, in a related line of research, Buyukozturk is looking into volcanic ash as a cement additive or substitute. To see whether volcanic ash would improve cement paste's properties, engineers, following the group's framework, would first use existing experimental techniques, such as nuclear magnetic resonance, scanning electron microscopy, and X-ray diffraction to characterize volcanic ash's solid and pore configurations over time.

Researchers could then plug these measurements into models that simulate concrete's long-term evolution, to identify mesoscale relationships between, say, the properties of volcanic ash and the material's contribution to the strength and durability of an ashcontaining concrete bridge. These simulations can then be validated with conventional compression and nanoindentation experiments, to test actual samples of volcanic ash-based concrete. Ultimately, the researchers hope the framework will help engineers identify ingredients that are structured and evolve in a way, similar to biomaterials, that may improve concrete's performance and longevity.

«Hopefully this will lead us to some sort of recipe for more sustainable concrete», Buyukozturk says. «Typically, buildings and bridges are given a certain design life. Can we extend that design life maybe twice or three times? That's what we aim for. Our framework puts it all on paper, in a very concrete way, for engineers to use».

This research was supported in part by the Kuwait Foundation for the Advancement of Sciences through the Kuwait-MIT Center for Natural Resources and the Environment, the National Institute of Standards and Technology, and Argonne National Laboratory.

71

Text 7. BUILDING MATERIALS

Aggregates for the simple definition from the dictionary «aggregates are the materials, such as sand and small stones, that are mixed with cement to form concrete». In other words aggregates (or cushioning materials) can be defined as a mass of practically inert mineral materials, which, when surrounded and bonded together by an active binder, form the rock. This rock is denoted by the general term concrete.

Aggregates have three principal functions in the concrete: they provide a relatively cheap filler for the concreting material, or binder; they provide a mass of particles which are suitable for resisting the action of applied loads, of abrasion, of percolation of moisture through the mass, and of climate factors; they reduce volume changes resulting from the action of the setting and hardening of the concrete mass.

All aggregates, both natural and artificial, which have sufficient strength and resistance to weathering, and which do not contain harmful impurities may be used for making concrete.

As aggregates such natural materials as sand, pebbles, broken brick, gravel, slag, cinder, pumice and other can be used.

Prestressed concrete is not a new material. Its successful use has been developed rapidly during the last two decades, chiefly because steel of a more suitable character has been produced. Concrete is strong in compression but weak when used for tensile stresses.

If, therefore, we consider a beam made of plain concrete, and spanning a certain distance, it will at once be realized that the beam’s own weight will cause the beam to «sag» or bend. This sagging at once puts the lower edge of the beam of tension, and if the crosssectional area is small, causes it to break, especially if the span is relatively large.

If, on the other hand, we use a beam of similar cross-section, but incorporate steel bars in the lower portion, the steel will resist the tensile stress derived from the sag of the beam, and thus assist in preventing it from breaking.

In prestressed concrete steel is not used as reinforcement, but as a means of producing a suitable compressive stress in the con-

72

crete. Any beam made of prestressed concrete is permanently under compression, and is consequently devoid of crack under normal loading, or so long as the «elastic limit» is not exceeded. Prestressed concrete is not only used for beams but is employed extensively for columns, pipes, cylindrical water towers, storage tanks, etc.

Read and summarize the information below

Plastics are man-made materials that can be shaped into any form. They are one of the most useful materials ever created. Engineers have developed plastics that are as rigid as steel or as soft as cotton. They can make plastics that are any color of the rainbow.

Plastics can be rubbery or rigid, and they can be shaped into an endless variety of objects. Plastic products often have a useful life of many years. But why are the chemists so enthusiastic about plastics? Plastics are rapidly becoming important synthetic materials because of their great variety, strength, durability and lightness.

A synthetic product must necessarily be both better and cheaper in order to justify its manufacture. This is essentially true of the various plastics when compared to the material they are to replace. Since plastics combine all the fine characteristics of a building material together with good insulating properties, and are fireproof as well, it is no wonder that the architects and engineers have turned to them to add color and attractiveness to modern homes and offices.

Engineers have created hundreds of different plastics, each with its own properties. They have developed plastics that can replace metals, natural fibers, paper, wood and stone, and glass and ceramics. For example, plastic siding does not dent as easily as that made of aluminum. Plastic pipes are lightweight and easy to cut and join. Moreover, they do not corrode like metal pipes. Plastic wall tiles, bathtubs, and sinks are less fragile, cheaper and easier to install than ceramic ones. Plastics are also used to make insulating foam. Foamed plastics have very low compressive and tensile strength. They can be used between two layers of a hard surface material, such as a metal or plywood, to create a laminated sandwich panel with high stiffness. Laminated panels are used as floors, partitions and exterior walls in building. Nowadays, builders are using plastics in almost any part of a building from the foundation to the final coat of paint.

73

Text 8. ARCHITECTURE

What Is Meant by «Bioclimatic Architecture»

Bioclimatic architecture is a way of designing buildings and manipulating the environment within building by working with natural forces around the building rather than against them. Thus it concerns itself with climate as a major contextual generator, and with benign environments using minimal energy as its target. Bioclimatic architecture aims to protect and enhance the environment and life. It is developing on many different levels from rethinking basic concepts about our need for shelter and the function of the «city» in our lives to developing recycled or sustainable building materials.

The impact of traditional building on the environment and natural resources is enormous. However, the ideal of designing and building structures that are environmentally friendly has become widespread throughout the community of architects and builders in developed nations.

In many areas there is the necessity of complying with new regulations and standards aimed at protecting the environment. In addition, there are an increasing number of incentives for putting up buildings with more efficient energy consumption and reduced negative impacts on natural resources by using recycled or sustainable materials. While these vary around the world, there is awareness that our need for shelter must not jeopardize the environment.

Green Buildings

The definition of green building. Green building is a holistic concept that starts with the understanding that the built environment can have profound effects, both positive and negative, on the natural environment, as well as the people who inhabit buildings every day. Green building is an effort to amplify the positive and mitigate the negative of these effects throughout the entire life cycle of a building.

While there are many different definitions of green building out there, it is generally accepted as the planning, design, construction, and operations of buildings with several central, foremost considera-

74

tions: energy use, water use, indoor environmental quality, material section and the building's effects on its site.

Well designed green buildings will save money, increase comfort and create healthier environments for people to live and work, using improved indoor air quality, natural daylight, and thermal comfort.

Energy use by depleting natural resources as well as CO2 emissions is one of our most important environmental impacts. Volatile energy markets, rising energy costs and increasing environmental awareness about issues such as global warming make energy efficiency and conservation a high priority. Build Green's focus is on reducing building energy usage and increasing occupant comfort.

Environmental Sustainability. In 1987, the World Commission on Environment and Development defined sustainability as: «Meeting the needs of the present without compromising the ability of future generations to meet their own needs». This definition was endorsed at the United Nations Conference on Environment and Development in Rio de Janiero in 1992. In 2003, the Organization for Economic Co-operation and Development (OECD) stated: «The building sector has major impacts not only on economic and social life, but also on the natural and built environment. Various building activities, such as the design, construction, use, refurbishment and demolition of buildings, directly and indirectly affect the environmental performance of the sector».

Against this background, the concept of «sustainable building» – reducing the harmful effect on the environment of buildings and construction activities – has been attracting the attention of stakeholders in OECD countries. This can range from using recycled materials carried by low-polluting forms of transport in construction to maximising energy efficiency in a finished building through improved insulation and solar-powered energy.

A recent OECD report describes the environmental and economic impacts of the building sector and the current situation in regard to environmental policies and makes recommendations for de-

75

signing and implementing policies to encourage environmentally sustainable buildings.

Environmental Benefits of Green Buildings:

1.Emissions Reduction. Pollutants released by fossil fuel fired electricity contribute to global climate change, cause air quality issues such as acid rain and smog, and pose risks to human health. Green building techniques like solar powering, daylighting, and facilitation of public transport increase energy efficiency and reduce harmful emissions.

2.Stormwater Management. Stormwater runoff can cause waterway erosion, flooding, and carry pollutants into water sources. Harvesting and redirecting stormwater, building surfaces with permeable materials, and using green roofs can control and utilize overflow.

3.Temperature Moderation. The heat retention properties of tall buildings and urban materials such as concrete and asphalt are the primary causes of urban heat island effect. These conditions may be offset by conscientious building design and site selection, as well as planting trees to accompany new developments.

4. Waste Reduction. Construction and demolition generates a huge portion of solid waste in the United States. Building deconstruction as an alternative to full-scale demolition results in massive decreases of waste production.

5. Water Conservation. Recycling rainwater and grey water for purposes like urinal flow and irrigation can preserve potable water and yield significant water savings.

Economic Benefits of Green Buildings:

A common impression about green building is that the green premium is too expensive to be considered economically feasible. However, studies have shown that the costs of green buildings are not substantially higher than regular development projects. Higher construction costs can generally be avoided by the inclusion of green design from the outset of the project. Additionally, green buildings provide an assortment of economic advantages.

76

1.Energy and Water Savings. The resource efficiency provided by green design and technology leads to drastic reductions in operation costs that quickly recoup any additional project costs and continue to offer dramatic long-term savings (see statistics). Money previously directed toward utility costs may be used for other purposes.

2.Increased Property Values. With energy costs on the rise, the low operating costs and easy maintenance of green buildings make for lower vacancy rates and higher property values.

3.Decreased Infrastructure Strain. Efficient buildings exert less demand on the local power grid and water supply, stretching the capacity of local infrastructure.

4.Improved Employee Attendance. Green design emphasizes increased natural lighting and control of ventilation and temperatureattributes that improve employee health and prevent absences. The U.S. Environmental Protection Agency reports major reductions in health care costs and work losses resulting from commonly recommended improvements to indoor environments.

5.Increased Employee Productivity. Employee productivity has been positively correlated to indoor environmental conditions, and shows improvements where green principles have been applied.

6.Sales Improvements. Studies show better sales in stores that utilize natural light. Retailers are increasingly using daylighting in an effort to harvest the associated sales benefits.

7.Development of Local Talent Pool. With increased attention being paid to global climate change and the need for renewable energy sources, the field of building design and construction is moving toward sustainability as a permanent objective. As of July 2007, 23 states and more than 80 cities have legislated green standards for municipal buildings. Building green in Bloomington is an investment in the local economy, helping to foster a local talent pool: designers and builders experienced with green projects able to accommodate the growing market demand for sustainable development.

77

Social Benefits of Green Buildings:

1.Improved Health. Poor indoor environmental quality (IEQ) resulting from insufficient air circulation, poor lighting, mold build up, temperature variances, carpeting and furniture materials, pesticides, toxic adhesives and paints, and high concentration of pollutants (typically 10 to 100 times higher than outdoors) contribute widely to respiratory problems, allergies, nausea, headaches, and skin rashes. Green building emphasizes ventilation and non-toxic, low emitting materials that create healthier and more comfortable living and working environments.

2.Improved Schools. An estimated 40 % of schools in the United States are subject to poor environmental conditions that compromise the health and learning of students. The healthier environment and atmosphere in school buildings utilizing green design and construction principles is shown to lead to significant reductions in student absenteeism and improvements in test scores.

3.Healthier Lifestyles and Recreation. A key element of sustainable design is the preservation of natural environments, which afford a variety of recreation and exercise opportunities. Green buildings also seek to facilitate alternatives to driving, such as bicycling and public transport, which eases local traffic while encouraging personal health and fitness.

78

Text 9. WATER SUPPLY

Municipal Water Supply Considerations

There are two fundamental considerations for both designing and evaluating municipal water supply systems. The first and most important is the quality of the water for human consumption – drinking water. The second is the quantity of water required.

In recent years the standards for water quality have been transferred from State health control agencies to the Federal government through two organizations: 1) The United Sates Public Health Service. 2) The EPA.

The quality of water provided by a municipal water system is based on three distinct characteristics, each of which may independently govern the desirable portability of the water. These characteristics are:

1) Physical quality of water. The physical quality of water is the appearance of the water to the consumer. Physical quality includes the clearness of the water, taste, odor, and temperature. For water to be of attractive physical quality, it must be clear in appearance, or have low turbidity (less than 5.0 units of turbidity). The color of the water must be low in concentration so as not to distract the consumer’s attention. Color should be less than 15.0 units of color.

The water should be free of substances that may produce taste and odors upon the addition of chlorine, or upon use of water for cooking purposes. It also should be free of trouble-producing organisms such as aromatic oils of algae or higher bacteria. The temperature of the water will affect the attractiveness to the extent that use by consumers will decrease if the water is of extremely high temperature. Ground water temperatures vary slightly from around 40 to 55 °F (4 to 13 °C). Such temperature changes are dependent upon well depth and aboveground storage facilities. Surface water temperatures vary with seasonal change from around 40 to 80 °F (4 to 27 °C) with even higher temperatures in the deep South and Southwest.

79

2)Bacterial quality of water. The most important quality of water is that of bacteria content. In the early 20th century, disease outbreaks from water and food-borne bacteria were common throughout the world. Progress in bacteriology and water treatment engineering has all but eliminated outbreaks of water-borne communicable diseases in the United States.

3)Water chemistry. Water is an excellent solvent, so it is not surprising that it picks up other chemicals. During this cycle of water movement, water picks up many solid and gaseous components. As the raindrops fall to the earth, they absorb gases. Most gases within the atmosphere are carbon, sulphur, and nitrogen compounds. The raindrops may also pick up particulate materials in the atmosphere.

Many of the particulates are soluble in water and will dissolve within the raindrop. Other constituents are added to the water cycle from surface or ground water flow. Many and varied constituents are added to the water from dissolution of rocks and minerals which come in contact with the water and its movement.

Of particular importance to the water supplier are the following constituents: ~ acidity and alkalinity; ~ calcium; ~ carbon compounds; ~ chlorides; ~ fluorides; ~ iron; ~ magnesium; ~ manganese;

~nitrogen compounds; ~ silica; and ~ sulphur compounds. All of the above and others dissolved in water, determine the chemical quality of the water. Each of these constituents has threshold limits that are governed by the EPA.

80