Special Issue "Engineering Sustainable Building Materials: Advancing the Structural Performance of Earth-based Technologies"

Type of Paper: Article
Title: A Research and Development Roadmap for Advancing the Structural Use of Earth-Based Bricks: Key Findings from the NSF US -Tanzania 2009 Workshop
Authors: Esther Obonyo ¹, Derrick Tate ² and Mang Tia ³
Affiliation: ¹Rinker School of Building Construction, University of Florida, PO Box 115703, Gainesville, Fl 32611, USA; E-Mail: obonyo@ufl.edu
² Mechanical Engineering Department, Texas Tech University, 7th and Boston, Lubbock, TX 79409, USA.
³ Civil and Coastal Engineering, University of Florida, PO Box 116580, Gainesville, Fl 32611, USA
Abstract: A two-day NSF supported workshop was held in Tanzania in July 2009. It provided a forum for sharing best practices in earth-based technologies and developing a research and development roadmap. The priority research areas were broadly classified as characterizing the physio-mechanical properties of earth as a building material and managing socio-cultural impediments. Durability issues emerged as a key impediment to the use of earth-based technologies. There is a need for models for predicting how long a brick house or building would last under different environmental conditions. The group specifically identified the hygrothermal performance of bricks as a subject that is not well understood. Given the significant amount of time required for monitoring the building units in the field, researchers should leverage on facilities such as the Ridge National Laboratory that rapidly characterize the hygrothermal performance of building materials. Several small-scale testing can also be done in University laboratories using modified experimental procedures. It was also noted that as earth-based bricks can absorb bullets and withstand explosion, there is an opportunity for interfacing with efforts directed at countering terrorism through collaboration with agencies such as the DTRA (Defense Threat Reduction Agency). For the socio-cultural challenges, there appears to be a widespread misconception that earth-based technologies constitute cheap strategies for poor people. This problem can addressed through education and public awareness campaigns. Finally, as mismanagement of resources in the production of fired bricks triggered opposition from the environmental community, the use of soil in earth-based technologies must be coupled with a well defined resource management strategy.
Keywords: earth-based bricks; physio-mechanical properties; sustainability

Type of Paper: Article
Title: Strategies for Mainstreaming Earth-Based Building Envelopes in Developed Countries through Use of Large-Scale Compressed Earth Blocks
Authors: Derrick Tate, Kuhn Park, William Lawson and Larry Williamson
Affiliation: Texas Tech University: 1Mechanical Engineering, 2Architecture, 3Civil Engineering, 4EarthCo Building Systems, Inc. Lubbock, Texas 79409, USA; E-Mails: d.tate@ttu.edu (D.T.); kuhn.park@ttu.edu (K.P.); william.d.lawson@ttu.edu (W.L); larry.earthco@gmail.com (L.W.)
Abstract: This paper considers strategies for integrating earth blocks as a sustainable material with mainstream building practices for developed countries. The Architecture / Engineering / Construction industry should approach energy, economic, and environmental considerations in a holistic manner in order to meet the global challenge of dramatically decreasing energy consumption and material resource use. On-going collaboration between the Texas Tech University Whitacre College of Engineering, TTU College of Architecture, and EarthCo Building Systems has resulted in a holistic strategy for producing building envelopes with large-scale compressed earth blocks. By scaling up the production and placement of CEBs, manual labor and production time can be minimized, and CEB technology can be made cost competitive with traditional building technologies. The strategies for mainstreaming adoption of earthen building envelopes in developed countries include 1. achieving a better understanding the properties of earth blocks relative to strength, durability, thermal conductivity, construction techniques, and architectural adaptability, 2. reducing the cost of production, and 3. designing an integrated earthen building envelope that affects the envelope, structure, mechanical, and interior systems. Case studies are presented of recent construction using large-scale CEBs in west Texas.

Type of Paper: Article
Title: Cob Construction in Italy: Some Lessons from the Past
Authors: Enrico Quagliarini ¹, Alessandro Stazi ¹, Erio Pasqualini ², Evelina Fratalocchi ²
Affiliations: ¹ Department of Architecture, Building and Structures, Polytechnic University of Marche, via Brecce Bianche, 60131, Ancona, Italy; E-Mail: e.quagliarini@univpm.it
² Department of Physics, Materials and Soil Engineering, Polytechnic University of Marche, via Brecce Bianche, 60131, Ancona, Italy
Abstract: Raw earth is a construction material unknown for most people. Anyway nowadays there is a growing interest both for rescuing the heritage and both for a rediscovered environmentally friendly building material. In these areas, we find the problems of a lack of skilled people at all levels, from designer to masons, because it is a forgotten technique, as well as how to carry out compatible conservation works on earthen heritage. This paper tries to fill the gap for a peculiar historic earthen building technology, namely cob (or bauge), that is relevantly present at Macerata in the centre of Italy, regaining possession of the material and constructional aspects and their initial structural resources, and giving guidelines to improve the technology for its new reuse and to accurately work on it for its compatible and sustainable conservation.
Keywords: raw-earth architecture; cob; bauge; earthen building technology; initial mechanical properties; reuse; conservation; workmanlike

Type of Paper: Article
Title: Flooding Effect on Earth Walls
Author: Gabriela M. Medero ¹, Justin H. Kennedy ¹, Peter K. Woodward ¹ and Meysam Banimahd ²
Affiliation: ¹ School of the Built Environment, Heriot-Watt University, EH14 4AS, Edinburgh, UK; E-Mails: G.Medero@hw.ac.uk (G.M.M.); jhk5@hw.ac.uk (J.H.K.); P.K.Woodward@sbe.hw.ac.uk (P.K.W.)
² Technip, Westhill Industrial Estate, Westhill, Aberdeenshire, AB32 6TQ, UK; E-Mail: mbanimahd@yahoo.com (M.B.)
Abstract: Earth building is a sustainable, environmental friendly and economical method of construction that has been use worldwide for many centuries. Since the past three decades, earth as a building material has seen a revival as modern construction method due to its benefits in terms of low carbon content, low cost and energy involved during construction as well as the fact that it is a sustainable technology of building. Climate change is changing the precipitation levels and patterns around the world and as consequence flood risk is increasing rapidly. When flooding occurs, earth buildings are exposed to water by submersion, causing an increase of the degree of saturation of the earth structures and therefore a decrease of the suction between particles. This study investigated the effect of cycles of flooding (consecutive events of flooding followed by dry periods) on earth walls. A series of characterization tests were carried out to obtain the physical and mechanical properties of the studied earth material. In a second stage, Flooding Simulation Tests (FST) were performed to explore the earth walls response to repeatable events of flooding. The obtained results of the tested earth wall/samples with reinforced material (straw) revealed hydraulic hysteresis when subject to cycles of wetting and drying.
Keywords: flooding; earth walls; laboratory testing