Unprocessed Rice Husk Ash as a Partial Replacement of Cement for Low-Cost Concrete by Dorothy Kamilah Brown B.S., Massachusetts Institute of Technology (2010) Submitted to the Department of Civil and Environmental Engineering In partial fulfillment of the requirements for the degree of Master of Science in Civil and Environmental Engineering at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2012 @ 2012 Massachusetts Institute of Technology All rights reserved Signature of Author......................../ . ........... ......... .............. Department of Civil and Environmental Engineering August 10, 201 Certified by ........................................................ -- John A. Ochse~dorf Associate Professor of Building Technology and Civil and Environmental Engineering Thesis Supervisor A Read by........................................................................ Linn W. Hobbs Professor of Material Science and Nuclear Science and Engineering 1A hesis Reader A cce pte d by . ..... ....................... ........ ................... .... .. .. CaHeidi M. Nepf Chair, Departmental Committee for Graduate Students Unprocessed Rice Husk Ash as a Partial Replacement of Cement for Low-Cost Concrete by Dorothy Kamilah Brown Submitted to the Department of Civil and Environmental Engineering on August 10, 2012, in partial fulfillment of the requirements for the degree of Master of Science in Civil and Environmental Engineering Abstract Cement is a very valuable commodity as it can be used to construct structurally sound buildings and infrastructure. However, in many developing countries cement is expensive due to the unavailability of local resources to produce enough cement in-country to meet the demand for this material, and therefore it has to be imported. In rice-producing countries rice husk ash-a material naturally high in silica-can be used as a supplementary cementitious material and can substitute a portion of Portland cement in concrete without sacrificing the compressive strength. This study investigates the use of Cambodian rice husk ash in 10, 20 and 30% replacements of Portland cement by mass in mortar, without optimization of the ash by controlled burning. Five ashes collected from different sources in Cambodia were assessed for their suitability for use in rural Cambodian construction via compression strength testing of 2" (50 mm) mortar cubes. A 20% replacement of unprocessed Cambodian rice husk ash was deemed appropriate for use in small-scale, rural structural applications. Low-tech methods of grinding the ash were also investigated and were found to drastically increase the compressive strength of RHA-cement mortars in comparison to mortars made with unground RHA. Thesis Supervisor: John A. Ochsendorf Title: Associate Professor of Building Technology and Civil and Environmental Engineering Thesis Reader: Linn W. Hobbs Title: Professor of Material Science and Engineering, Professor of Nuclear Science and Engineering Acknowledgements There are several people who have all played a part in making this thesis possible. I would like to thank Professor John Ochsendorf, my advisor, for his guidance throughout the duration of my Master's Program and without whose help this project would never have been realized. I am also grateful for the countless hours Professor Linn Hobbs spent helping me understand the material science involved in concrete and assisting with characterizing the physical and chemical properties of the materials used in this study. This thesis would not have been possible without funding from the Public Service Center and D-Lab: Schools, in addition to the instruction and guidance of Steve Ray in the development of the original Cambodia project out of which this research project grew. I would like to thank Steven Rudolph, Scott Speakman and David Bono for their assistance with using laboratory equipment at MIT and I owe my deepest gratitude to James Lee at Wentworth Institute of Technology, Chris Swan and Stephen Fratto at Tufts University, and John Flynn at W.R. Grace for providing equipment essential for making this research project possible. Additionally I am grateful for the support I have received from several people and groups during my time at MIT. The MIT Concrete Sustainability Hub and Office of the Dean of Graduate Education were pivotal in providing financial support for my Master's Program. Devan Tisdale provided the inspiration for part of this project and I am very thankful to him as well. I would like to thank my family and friends-my brother David, and my friends, Yotam, Maria, Nancy, Polina, Claudia and Interphase EDGE 2012-who always believed in me even when I had trouble believing in myself. Lastly, I would like to thank my mother, Olevia Brown, for her many sacrifices and constant encouragement over the years and for always making me feel like I can accomplish anything. This work made use of the MRSEC Shared Experimental Facilities at MIT, supported by the National Science Foundation under award number DM R-08-19762. Table of Contents List of Figures.....................................................................................................................................9 List of Tables....................................................................................................................................11 1 Introduction ............................................................................................................................. 12 1.1 Background/ Context .................................................................................................................. 12 1.1.1 Rice Husk Ash ...................................................................................................................... 13 1.2 Potential for use of Rice Husk Ash in Cambodia ...................................................................... 14 1.2.1 Rice and Cement Production .......................................................................................... 15 1.3 Research Objective ..................................................................................................................... 17 1.4 Outline of Thesis ......................................................................................................................... 20 1.5 Chapter Sum mary ....................................................................................................................... 21 2 Literature Review ..................................................................................................................... 23 2 .1 In tro d u ctio n ................................................................................................................................ 2 3 2.2 Studies with partially ground RHA .......................................................................................... 24 2.3 Studies with M ortars...................................................................................................................26 2.4 Studies without Superplasticizer ............................................................................................ 27 2.5 Chapter Sum mary ....................................................................................................................... 28 3 M aterials and M ethods.............................................................................................................29 3.1 Introduction ................................................................................................................................ 29 3.2 M aterial Sourcing ........................................................................................................................ 29 3.2.1 Cement................................................................................................................................ 29 3 .2 .2 Sa n d..................................................................................................................................... 30 3.2.3 Rice Husk Ash ...................................................................................................................... 30 3.3 M aterial Characterization Procedures .................................................................................... 34 3 .3 .1 De n sity ................................................................................................................................ 34 3.3.2 Particle Size Distribution ................................................................................................. 35 3.3.3 Chem ical Analysis................................................................................................................ 36 3.3.4 Am orphous Silica Content............................................................................................... 39 3.4 Bending Tests in the Field ...................................................................................................... 42 3.5 Com pression Tests in the Laboratory ...................................................................................... 47 7 3.5.1 M ix proportions and curing ........................................................................................... 47 3.6 Chapter Sum mary ....................................................................................................................... 51 4 Results ..................................................................................................................................... 52 4.1 Introduction