Materials Technology

Yvonne Dean

• Publisher: Routledge
• Year: 2016
• eBook ISBN:
  9781315504278
• Topic: Architecture
• Subtopic: Architecture Methods & Materials

Materials Technology clearly identifies materials and technology as the fundamental generators of buildings and examines how they determine the structure, overall form and quality. It examines the issues that determine the choice of materials, and argues that the decision-making of architects, engineers and designers should take account of the environmental impact of sourcing the basic materials, and of the energy implications of their processing and use in manufacturing.

Materials Technology is an essential resource for Materials Technology units in building, architecture and surveying degree and postgraduate courses; and students of BTEC HNC/D building and surveying. It will also be a useful reference tool for Advanced GNVQ Construction and the Built Environment courses and Built Environment NVQs at levels 3 and 4.

I INTRODUCTION

1 Developing an attitude toward materials

Materials are the fundamental generators of buildings. They determine structure, overall form and quality. In the design process, the choice of materials at the earliest stage is critical and the most successful buildings are always constructed with an attitude to materials that uses knowledge to understand the full possibilities and appropriateness of choice. There are often conflicting attitudes within the building industry dependent on the role of the different professionals and their own criteria for determining choice. An engineer will have an overall ambition for an efficiency of use, and that the materials chosen will perform adequately over a period of time, which is usually the lifespan of the building. In addition, the materials chosen will often have to combine several properties to fulfil function and durability. Expectations about the longevity of the building may also relate not to the overall fabric but to how the internal fabric can cope with changing use. Buildings that are flexible have a longer life potential than those with highly specific use or users, and these expectations of use change with the economic climate and the large scale planning of buildings in cities. For example, the current economic recession in the 1990s has rapidly changed the expectations of use in building, and those buildings built in the 1960s for commercial use are seen as being viable for conversion into housing stock in a way which is far more difficult with the highly-serviced buildings of the 1970s and 1980s. Such radical change is difficult to anticipate and in future, short term solutions will be outweighed by longer term views on the equity of building stock.

There are also significant cultural attitudes which determine choice and there may be expectations as to what may be the most relevant choice. These expectations may be founded in the kind of architecture provided, its function or its permanence. There may be limitations in the availability of materials, the economics of choice or decisions which consciously use local resources. All of these initial strategies may be tempered by regional technologies in the processing of materials, their crafting, assembly or transportation.

Local expectations may be over-ridden by cross cultural solutions which take experience from other regions, whether national or international, and learning from other cultures may optimize structural efficiency or other techniques in building. The transfer of technology should always be measured carefully against the real needs of the local region, whether it is appropriate in terms of climate or regional need.

In our own late twentieth-century industrialized society we are used to thinking of buildings in terms of component technology, sometimes ignoring possible solutions that could be more traditional and labour intensive, but which could be as economic. For example, the recently completed Leicester Engineering School by Alan Short and Brian Ford (1993) is not only an energy-efficient, naturally ventilated building, but was also consciously designed to be labour intensive through its traditional masonry construction and detailing, thereby benefitting the local economy in the creation of extra job opportunities. This is in sharp contrast to the Leicester Engineering Building by Stirling and Gowan (1959) seen as pioneering engineering-led solutions using specialist skills and technologies that were current and pointed the way towards high technology solutions in building.

The economics of building decisions can then have a broader impact on decision making in materials quite apart from the longer-term traditional cost benefit analysis, which would look at facilities management, maintenance and long term equity values.

In the late twentieth century many buildings are conceived in terms of component technology, the availabilty of products and inevitably most buildings must therefore become assemblages, indicative of a production-orientated economy with an efficient manufacturing base. However, some current technologies can be as limited as traditional methods. Some highly-engineered buildings have details and components that signify mass production methods which are illusory. The individual parts, far from showing the innovative use of standard components, display a high degree of individual craftsmanship in the making of a small number of parts, and, although the technologies available are used to their full extent, the advantage in terms of economy through mass production is lost. The use of current manufacturing technologies enables the production of these components, but they become symbols of what has been called Neo-productivism¹ and display the means of production rather than the ethos of the production system and its unspoken justification, which is the production of mass components. At worst this reduces a machine age aesthetic to the level of pure decoration, using non-standard components that are inappropriately engineered.

Figure 1.1 Engineering School, Leicester.

This fundamentally changes the nature of a machine age aesthetic and limits the real possibilities. The means of production now has implications in decision making through a desire to minimize energy wastage. Consequently the secondary production costs for materials as well as their primary processing energy costs become relevant.

Architecture is fundamentally a spatial discipline and the synthesis of built form relies on an awareness of choice, a sensibility to the materials used as a major determinant of structural form and as a response to local conditions and climate. There should also be a consistency about the handling of large-scale structural form as well as the resolution of detail. Within the building industry the range of understanding degrees of knowledge and practical application are wide-ranging, but for professionals to work together well and successfully there has to be a shared knowledge base, a recognition of the overall ambition of the project and an appreciation of how the work can be organized.

1.1 Engineering categorization of materials

In this text all materials are grouped according to their molecular structure and consequent behaviour. This gives a scientific categorization related to engineering use. Materials are put into groups with similar properties and behaviour instead of earlier systems which examined materials individually in turn and continued a Victorian system of classification which became product based. As the range of materials extends in the building industry, small individual knowledge bases on each material become too cumbersome and the scientific categorization gives the student and practitioner a better understanding of behaviour and deterioration across a broad range of similar materials rather than looking for specific failure mechanisms on individual products. This helps to predict performance and aids the appreciation of the main principles that inform behaviour and choice. This strategy is also followed in MBS: Finishes, where the categories are explained and the actual materials are listed under applications. There is a need for practitioners in the building industry to develop a good general knowledge of materials in these categories so that initially the right choices can be made. Often this knowledge is gained by experience, especially experience of failure as a determinant in choice, which will effect careful specification. This is why there is a wide range of practical examples given in this book and illustrated photographically.

There is also a much wider range of issues which now impinge on decision making in the built environment. Knowledge of these issues brings a professional approach to the choice of materials at every level so that considerable thought goes into their selection, which can be conveyed to client and building user.

As emphasis changes in the way that architects design buildings, there are perceptible shifts in how buildings are seen and put together. Although architecture is an exercise in spatial quality, facilitated by an appropriate structure and enhanced and rooted in the materials used, the study of construction can also be too focussed on the individual elements thus reinforcing the component ideology.

Buildings may be justified on purely economic grounds but they then become mere enclosures for use rather than having any architectural or ideological significance. If that is the case they are then impoverished solutions to problems. Enclosures may not work as comfortable solutions if the feeling of enclosure is unrelated to the apparent thickness of wall. Here the material used to construct the wall will then have a quality, which relates to the overall idea of the space and its purpose rather than being thought of as an applied finish, and monolithic solutions may be appropriate.

There can be equally conflicting and ideological dilemmas in determining structure and approach. In structural engineering, loads can be distributed throughout a network of small components, which can each take individual stress, and failure of one of these components will not mean a catastrophic failure of the whole structure. In a monolithic building, construction (paralleled by monocoque structures in marine, aeronautical and automobile engineering) failure in one part can be catastrophic as stress will be passed directly through shells, domes and walls to affect the whole. Here ideology can be in conflict with structurally sensible solutions. Also, depending on the connections and fixings made in architecture, however many components are used, their effective connection may well make the building into a total composite that will again have to resist the stresses imposed as if the whole building were of a monolithic construction.

There are also problems in the transfer of technology and materials to situations that are inappropriate. The wide-spread devastation and loss of life (some 50,000 people) in the 1990 Iran earthquake is thought largely to have been due to changing systems of construction that are more westernized, and therefore inappropriate for earthquake regions. Larger-scale buildings were built in brick with discontinuity in the structure. Instead of frames, brick jack arches between steel beams were built and then infilled to give heavy floor systems which collapsed under the vibrations from earth tremors. This example illustrates the thought that is needed before making decisions that for reasons of climate or geography may be wrong. It is easy to become so comfortable with building in a particular way, using the same materials or construction, that the same methodology can be liberally and yet wrongly applied to a whole range of problems.

There is always a tendency to build and to use materials as economically as possible. Catering for unusual or extreme climatic or ground conditions means evaluating the risk of a particular event happening. The occurrence may be in cycles of 12, 50 or 100 years, but risk assessment should be used more often to establish the likely events so that provision can be made for them. The problem of building with life expectancy cycles of only 30 years means that major events can often miss a generation who will then not make provison for worst case scenarios, and this can lead to loss of life.

Examples of the usage of materials are taken from around the world. They not only show good practice and possible failure, but also emphasize state-of-the-art practice. Buildings have been chosen that are consciously well designed through the architect’s or designer’s own attitude to materials. The illustrations shown might seem unusual but they are intended to change the normal perspective with regard to the use of materials. As far as possible, buildings or artefacts have been chosen that show invention and also a sensible use of materials in given situations, as well as clear failure that can be an even greater learning tool.

The emphasis of this book is on the thinking of materials as a resource, with an indicator of the energy required in their processing. There is also great interest at present in the biology of building materials, particularly in terms of the careful choice of materials for the interiors of buildings that are healthy for users.

The description of each material looked at begins with its basic engineering classification, and works through the details of its microstructure and its behaviour at that scale, to our understanding of it at the macrostructural level. The study of the microstructure of materials gives clues as to the nature and origin of its strengths and weaknesses and its chemical behaviour, particularly in reactions with water and adjacent materials.

There has been an increase in the number of building failures and consequently litigation due to a poor application of knowledge about materials, their misuse in design and detailing, specification and workmanship. There is a need for designers and professionals to be more rigorous about their understanding, and this broader approach in the book gives an appreciation of the technical issues involved.

1.2 Detailed choice of materials

Architects are faced with decisions as to a choice of the materials they use which in turn are determined by environmental constraints. Buildings have to provide a separation between inside and outside to maintain levels of comfort, and they must be structurally sound to support their own basic self-weight and applied loadings.

In addition, there are other applied stresses in the environment which affect the durability of materials chosen which can be physical, in terms of increased wind loadings, chemical in terms of polluted environments, and there are now more complex parameters, such as electromagnetic radiation, which are not so apparent but are becoming increasingly important. Architects are major energy users through the specification of materials and components. They are now having to make choices that show they are sensible decision makers in terms of limiting the total energy demand for a building, not only by its performance but also by understanding the energy needed in the processing and transportation of materials. The knowledge base for architects to make these decisions is currently limited although there is a great deal of information now in the public domain. However, there is a lack of data that can be used as a basis for comparative evaluation and decision making.

Issues that determine choice

There is a wide range of issues that now inform decision making in the building industry and the most important ones that affect choice and building practice are outlined here. A strategy is difficult to propose as the following issues are interdependent, but awareness of these issues is the key to determining new parameters in decision making and they should include:

Storms and global warming

Electromagnetic radiation

Radon

Acid rain

Recycling and energy usage

Pollutants

Health

However, it is possible to develop a checklist which should be used as a basis for evaluating materials and...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Acknowledgements
• Part I Introduction
• Part II Ceramics
• Part III Metals
• Part IV Polymers
• Part V Composites
• Index