Development of Cost-Effective Earthen Building Material for Housing Wall Construction: Investigations into the Properties of Compressed Earth Blocks Stabilized with Sisal Vegetable Fibres, Cassava Powder and Cement Compositions. A Doctoral Dissertation, Approved by the Faculty of Environmental Science and Process Engineering of the Brandenburg Technical University Cottbus and Submitted in Fulfilment of the Requirements for the Award of the Degree of Doctor-Ingenieur By Saul Sitati Namango From Bungoma, Kenya Supervision: Prof. Dr.-Ing. Wolfgang Spyra Prof. Dr.-rer. nat., habil. Ing. Reinhard Frey Frau Dr.-Ing. Angelika Mettke Date of the Disputation: 17.07.2006 Entwicklung von preisgüstigen Erdbaustoffen für Wand- konstruktionen: Untersuchung der Eigenschafften von gepressten Erdblöcken stablisiert mit Sisalfasern, Maniokpulver und Zement Von der Fakultät für Umweltwissenschafften und Verfahrenstechnik der Brandenburgischen Technischen Universität Cottbus zur Erlangung des akademischen Grades eines Doktor-Ingenieurs genehmigte Dissertation vorgelegt von Diplom-Ingenieur Saul Sitati Namango aus Bungoma, Kenya Gutachter: Prof. Dr.-Ing. Wolfgang Spyra Gutachter: Prof. Dr.-rer. nat., habil. Ing. Reinhard Frey Frau Dr.-Ing. Angelika Mettke Tag der mündlichen Prüfung: 17.07.2006 Declaration I, Saul Namango, hereby do declare that I have personally written this doctoral dissertation, and that I have done so only with the assistance of the literature sources and other supportive material herein contained and mentioned. Saul Namango March 2006 II Acknowledgements It stirs in me great emotion to offer gratitude and appreciation to the numerous people and institutions that lend me a hand at the time of need. If I was to name all these angels in person, I would probably need an extra chapter. Prof. Dr.-Ing. Wolfgang Spyra and Prof. Dr.-rer. nat., habil. Ing. Reinhard Frey gave great scientific guidance to this project; I wish to express my very sincere gratitude to them. Frau Dr.-Ing. Angelika Mettke constantly directed and supervised my work with great dedication; without her financial involvement, this project would not have taken place. My experimental work was extremely labour intensive; I would never have had enough physical resources to carry it out on my on. With respect to this, a friend – Mr. Raymond Babanawo - taught me what friendship is all about. A friend, it is said, is a second self. No, a friend is more than this. Mr. Werner Kiwit, director “artefact gGmbH Glücksburg”, provided the soil block press at minimum cost, thank you. My very deep appreciation goes to Dr.-Ing. Christian Stollberg from the Chair of Mineral Processing at BTU for constantly being with me at the hour of need, for his academic and financial assistance, throughout the time I researched and wrote this piece of work. I appreciate the kindness of Prof. Dr.-Ing. habil. Peter Ay; he allowed me unlimited access to his laboratories without any financial reciprocation. Dr.-Ing. Normen Langner, Dr.-Ing. Almut Lottmann and Ms. Christina Olschewski were very helpful, for this I say thank you. The FMPA staff assisted in carrying out some experimental tests; for this I feel particularly indebted to Dipl.-Ing. Armin Schwiegk, Ms. Sabine Bergmann, Ms. Sabine Zeidler and Mr. Frank Uhlemann. I wish to also thank, Dr.-Ing. habil. Klaus Hünger and Dr. Ing. Manfred Pettke for the tremendous support. May I too, say thank you, to the staff at the Chair of Chemical Engineering and Hazardous Wastes - Dipl.-Ing. Ricarda Hensel, Dipl.-Ing. Cynthia Thomas, Dipl.-Ing. Sören Heyn and Dipl.-Ing. Jan Czyganowsky - as well as to the staff at the Chair of Mineral Processing for always being available. Last but not least, “Asante Sana” to Mr. Siegfried Müller-Fehn, Mr. Uwe Kränsel, Mr. Marco Baumeier and Ms. Grit Gericke- top technicians and secretary at of the Chair of Mineral Processing – for helping me out with the laboratory tests and related preparations. III Dedication For love, patience and support of Rosemary Nabonwe, Marsha Wabuti, Juanita Namenya, Tim Asomba and Peggy Pendo. To Grace and Isaac Namango for great wisdom and love. In memory of my late loving brothers Gilbert Sianga, Eliud Sikuku, Paddy Maloba and Jacob Waswa I thank God for the strength he gave me so as to go through this very challenging moment of my life. IV Abstract Need to develop affordable housing is necessary because of the numerous homeless people living in the developing countries; the present work is an attempt to alleviate the housing problem facing populations of these countries. In the current investigations, a study programme illustrating the effect of various sisal, cement, cement-sisal and cassava proportions to the compressive strength, flexural strength, dry block density and porosity of compressed earth blocks (CEB) is outlined. A constant volume manual press has been used to fabricate earth blocks, at a fairly uniform pressure. The relationship of strength, block densities and porosity to reinforcement levels has been determined. A considerable increase in strength with increasing sisal fibres, cassava powder, cement as well as cement-fibre content within certain limits is observed. Results show that sisal fibre content outside these stated limits are detrimental to the strength characteristics of compressed soil blocks. The critical sisal fibre volume for soil-sisal mix has been established. Compression and flexural strength at optimal fibre content are comparable to those of soil blocks stabilized by the already well studied conventional binders as cement; besides, these results are not recorded in literature yet. Dry block densities and porosity reflect closely on the fibre, cement, cement-fibre and cassava content. Light optical microscopy (LOM) and scanning electron microscopy (SEM) analysis have been used to verify the block morphology. Compressed earth blocks manufactured from a limited addition of cassava powder to the soil, show improved strength. Indeed the ideal strength is above one recommended by various CEB standards. Past researchers have not documented any research related to cassava as a building material. Water vapour transmission properties of the earth blocks have been determined; values show that the earth blocks may provide better indoor air quality than conventional building materials like concrete. A simple method by which strength of earth blocks could be determined in the absence of laboratory facilities in the rural villages of Kenya and related regions has also been developed. V Use of traditional hydraulic stabilizers like cement can significantly improve the strength of compressed blocks. These additives are, however, costly; a negative factor especially for the poor rural communities of the developing nations. This research has shown that the commercial binders can be replaced by cheap material, thus, sisal vegetable fibres and cassava powder. Besides, a new building material, thus compressed earth blocks stabilised with cassava powder has been developed. It should however, be mentioned that the roof construction should be done in such way that rain does not directly pound the compressed earth blocks when applied for building of walls. Kurzfassung Die Entwicklung bezahlbarer Wohnbauten ist ein wichtiger Aspekt für die Verbesserung der Situation der zahlreichen obdachlosen Menschen, die in den Entwicklungsländern leben. Einen Beitrag zur Lösung dieses Problems stellt daher das Ziel der vorliegenden Dissertation dar. In der vorliegender Forschungsarbeit sollen die Auswirkungen verschiedener Anteile von Sisal, Zement, Zement-Sisal und Cassava auf die Druckfestigkeit, Biegefestigkeit, Trockenblockdichte und Porosität von komprimierten Erdblöcken (KEB) dargestellt werden. Zur Herstellung der Erdblöcke wurde ein Handpresse verwendet, die mit gleich bleibendenm Druck betrieben wurde. An den so hergestellten KEB wurden die Verhältnis von Festigkeit, Blockdichte und Porosität zu den Verstärkungsniveaus ermittelt. Mit steigendem Sisalfaser-, Cassavapulver-, Zement- sowie Zement-Faser-Gehalt wird innerhalb bestimmter Grenzen eine erhebliche Festigkeitserhöhung beobachtet. Die Ergebnisse zeigen, dass ein Faseranteil außerhalb dieser angegebenen Grenzen für die Festigkeitseigenschaften der komprimierten Erdblöcke nachteilig ist. Die kritische Menge an Sisalfasern für die Erd-Sisal-Mischung wurde bestimmt. Druck- und Biegefestigkeit sind bei einem optimalen Faseranteil mit der von Erdblöcken vergleichbar, die mittels der bereits umfassend studierten, herkömmlichen Binder, wie zum Beispiel Zement, stabilisiert wurden; außerdem wurden die vorliegenden VI Ergebnisse bisher noch nicht in der Literatur erfasst. Trockenblockdichte und Porosität spiegeln deutlich den Faser-, Zement-, Zement-Faser- und Cassavagehalt wieder. Es werden Analysen durch lichtoptische Mikroskopie (LOM) und Rasterelektronenmikroskopie (REM) vorgenommen, um die Blockmorphologie zu verifizieren. Komprimierte Erdblöcke, hergestellt mit einem begrenzten Zusatz von Cassavapulver zur Erde, weisen eine verbesserte Festigkeit auf. Die ideale Festigkeit liegt faktisch über den Werten, die in verschiedenen KEB-Standards empfohlen wurden. Bisherige Forscher haben keinerlei Forschungsarbeiten in Bezug auf Cassava als Baumaterial dokumentiert. Die Eigenschaften der Wasserdampfdurchlässigkeit der gefertigten Blöcke wurden bestimmt. Die Werte zeigen, dass die Erdblöcke für eine bessere Innenraumluftqualität sorgen können als herkömmliche Baumaterialien, wie zum Beispiel Beton. Es wurde ebenfalls eine einfache Methode