Preface

Traditional earth building materials were the mainstay of a significant proportion of past societies, and today it is estimated that around one-third of the world’s population live in buildings made from unfired earth. Since these materials and techniques are the most prolific, both historically and in modern times, and have one of the greatest proven track records in terms of longevity (some buildings being several hundred years old) it might well seem reasonable to argue that by definition they are the most conventional construction material of all. Ironically, they are commonly referred to with terms such as ‘non-conventional’, ‘alternative’ and ‘low environmental impact’ within the modern construction industries of western society. Whilst the latter point is not intended to be derogatory, it is also implicit in these terms that the material must be at a low level of technological advancement, in-situ performance, and with little capacity for refinement or integration with ‘conventional’ materials and systems of building. However, these conclusions rest on one significant assumption; that earth construction materials are already well-understood and that our rationale for not using them instead of fired brick masonry, concrete, timber or pre-fabricated composites must be based on this knowledge. The main purpose in creating this book is to test this hypothesis and to challenge the assumption on which it is based. The editors assert that modern earth construction represents high-quality materials and finishes, standardised approaches and accurate placement systems, significant flexibility in terms of advanced structural engineering, the ability to passively regulate indoor temperature and humidity, enhance thermal comfort and indoor air quality, and present a viable alternative to load-bearing masonry or in-situ concrete walling with numerous functional advantages. It is hoped that the evidence for these assertions, presented throughout this book, will validate this perspective and encourage others to explore the opportunities that modern earth construction can bring.

Modern earth building could make significant contributions towards the current priorities of the construction materials sector by restoring a carbon neutral and economically sustainable existence. Firstly and most obviously, we know that sustainability is durability and that earth buildings have demonstrated that they can last for hundreds of years and still remain structurally sound, they can be made using less energy than fired materials and require less operational energy during their lifetime to retain comfortable, healthy indoor environments. Secondly, modern earth buildings have the capacity to refresh humanity’s delight in the simple and the modest without compromising comfort, style and desirability. Indeed a properly built modern earth house adds immeasurably to the comfort of inhabitants with less cost to the environment.

Part I: Introduction to modern earth buildings begins with an overview of modern earth building including its definition and global extent as an industry, with discussion relating to the changing demands in terms of aesthetics, economics, sustainability and continually advancing structural solutions (Hall, Lindsay and Krayenhoff). This is complemented by two successive chapters that consider the behaviour and performance of earth structures in terms of building physics fundamentals. The first of these chapters focuses on hygrothermal behaviour (coupled heat and moisture transport/storage), which is central to the way earth walls passively regulate indoor air temperature and relative humidity, as well as controlling mould growth and enhancing air quality. The chapter presents materials data, approaches to modelling hygrothermal behaviour, and occupant thermal comfort and health (Hall and Casey). The next chapter relates to fabric insulation materials (including properties), and also includes a detailed review of thermal bridging phenomena and current approaches to 2D and 3D computer modelling. Within this context, cavity earth wall construction detailing is explained and illustrated along with acoustics performance and isolation (Hopfe and Hall). This is followed by a global review of building codes, standards, regulations and compliance relating to modern earth construction. It also includes details of regional and national level standards and normative documents covering aspects such as material selection, production methods and various material types (Schroeder). The section concludes with a discussion of energy efficient design in buildings with particular emphasis on the applications for highmass construction materials such as earth. This is framed within the context of Passive House design principles as an aspirational standard of operational efficiency for future earth building projects (Rongen).

Part II: Earth materials engineering and earth construction begins with a technical review of soil properties, classification and test methods that can be applied in order to determine suitability for a given application or technique plus details of clay mineralogy, Atterberg limits and compaction (Jain, Reddi and Yun). The next chapter reviews the types, origins and properties of alternative and recycled materials as alternatives to quarried (primary) aggregates for potential use in earth construction. It also includes the relevance of life cycle assessment and future recycling, as well as age-related performance and leaching (Dawson). Strength and mechanical behaviour are dealt with in the next chapter in a review of soil mechanics, which primarily relates to soils without the addition of binders. The topics covered include effective stress, experimental and numerical models for shear stress, and unsaturated behaviour in relation to earth construction materials (Augarde). This is complemented by a detailed technical review of soil stabilisation including lime, cement and pozzolanic reactions, bituminous binders and emulsions, synthetic, polymeric, adhesives and fibre reinforcement including a selection tool for modern earth construction materials (Hall, Najim and Dehdezi). The next chapter explains the state-of-the-art technology in admixtures and surface treatments for modern earth materials. This includes hydrophobic additives with associated test data for durability and moisture transport, stabiliser set enhancers/retarders, workability enhancers and surface coatings (Kebao and Kagi). Weathering and durability of earthen materials and structures is addressed with a technical discussion of current test methodologies along with discussion of the principal erosion mechanisms and case studies of the efficacy of surface coatings/renders (Morel, Bui and Hamard).

Part III: Earth building technologies and earth construction techniques opens with a view to the past covering the historic origins and progression of different earth construction techniques throughout the world dating from ancient times to modern history (Jaquin). The other chapters in Part III review the modern-day forms of these traditional techniques, many of which have become highly commercialised enabling them to compete with conventional materials in the global construction industry. Stabilised compressed earth blocks for structural masonry is a prolific modern earth technology and is given a comprehensive review that includes soil grading/suitability, block production, approaches to stabilisation, physical-mechanical properties and extensive details of results from experimental testing and case studies (Reddy). The following chapter provides detailed and insightful discussion about modern rammed earth construction techniques. Detailed coverage includes material sourcing and proportioning, mixing and formwork technology, along with installation (including compaction) and a forecast of future trends, technological challenges and developments (Easton and Easton). Next is a technical review and summary of pneumatically impacted stabilized earth (PISE); a novel modern earth construction technique that has only recently been developed. Specific details include proportioning, mixing and delivery along with details of formwork and placement methodologies (Easton). Finally, techniques and methodologies for the conservation of historic earth buildings are explained, along with detailed case studies and principles relating to erosion mechanisms and the factors that affect them (Calabrese).

Part IV: Modern earth structural engineering is intended to provide both an understanding and an appreciation of the current capacity for structural engineering and innovation in modern earth construction. It opens with a comprehensive chapter that explains the structural theory behind arches, vaults and domes, with specific examples and case studies relating to both traditional and modern earth buildings, as well as providing a set of design criteria (Dahmen and Oschendorf). In relation to modern-day stabilised rammed earth (SRE) wall construction, the next chapter provides structural design guidelines for the use of steel reinforcement. This includes technical drawings and detailed specifications from a range of real-life examples (Lindsay). Design and construction guidelines for modern earth buildings in seismic regions, as well as regions subject to high wind loading/ tropical storms, flooding, landslides and volcanic activity are reviewed in a comprehensive chapter that also gives details of structural reinforcement and risk mitigation (Morris). Finally, the application of modern earth materials in embankments and earthfill dam structures is reviewed in terms of materials and techniques, design, maintenance and stability assessment tools (Wu, Berhe and Ashour).

Part V: Application of modern earth construction: international case studies provides a series of region-specific reviews demonstrating the current state-of-the-art in contemporary earth materials across the world. It begins with North America (including USA and Canada) including many case studies and the development of stabilised insulated rammed earth (SIRE), design variables to suit the wide range of climatic conditions, seismic design, embodied energy and energy efficiency. It also includes significant development in mixing, formwork and delivery technology as well as admixtures and surface treatments, and several advances in surface details and texturing effects (Krayenhoff). Next, we move over to Australasia where numerous case studies are used to explain the significant developments in material selection and standardisation of formwork technology, along with insulated SRE, design for thermal comfort, costs and business models for the industry, plus a summary of future trends (Lindsay). Since the 1970s modern earth construction in India is prolific, perhaps much more so than any other single country, and is almost exclusively represented by stabilised compressed earth block technology which is already covered in great detail in Part III (Reddy). The next chapter in Part V summarises the current developments and case studies in Europe, which consists of both stabilised and unstabilised rammed earth and compressed earth block, plus non-structural clay-based renders and in-fill materials. It explains how heritage conservation and the revival of traditional techniques has led to modest yet active growth in the application of modern earth materials in many parts of Europe and a high level of innovation and research (Hall and Swaney). Finally, modern rammed earth construction has entered the rapidly expanding nation of China and has already resulted in significant innovation and expansion of this technique as demonstrated by the numerous case studies cited, which look set to expand even further (Wallis).

The main text of the book is supported by two appendices that are intended to provide the reader with supporting information in relation to techno-economic analyses coupled with environmental impact assessment. This has been limited to the two regions of the world (Australasia and North America) where modern earth construction has been developed and proven to the extent that it now forms a part of mainstream construction industry, and represents a viable technology that can be selected or indeed exported to other developed regions of the world where the expertise/industry does not currently exist. Clearly, the techno-economic criteria for these two regions are quite different, and so have been presented as separate appendices for greater clarity whilst incorporating the relevance of environmental impact in each case.

The editors sincerely hope that this book will serve not only to educate and inspire students of this subject around the world, but to provide a useful reference source to professionals including designers, planners and potential end users who may seek to utilise the benefits of modern earth construction materials in their future projects. The editors are also very aware that technological developments and the current state-of-the-art in one region of the world may not be well known in other parts, particularly for diverse fields such as earth construction. Therefore, this book is also intended to provide knowledge, understanding and an appreciation of the global context in terms of achievement and development in this field, whilst giving the relevant technical information needed at local level for all readers.