GUIDE to Cement-Stabilized Subgrade Soils
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GUIDE TO Cement-Stabilized Subgrade Soils MAY 2020 About the CP Tech Center About this Guide The mission of the National Concrete Pavement This document, Guide to Cement-Stabilized Subgrade Soils, Technology Center (CP Tech Center) at Iowa State is a product of the CP Tech Center with funding from University is to unite key transportation stakeholders the PCA. It provides guidance for engineers, producers, around the central goal of advancing concrete pavement contractors, and owners to improve soil properties for technology through research, tech transfer, and construction of various types of infrastructure. The focus technology implementation. of this guide is roadway applications. About the PCA Reference Information for this Guide The Portland Cement Association (PCA) is a nonprofit Gross, J. and W. Adaska. 2020. Guide to Cement- organization founded in 1916 that serves America’s Stabilized Subgrade Soils. Portland Cement Association, cement manufacturers through policy, research, education, Washington, DC, and National Concrete Pavement and market intelligence. PCA members represent 91 Technology Center, Iowa State University, Ames, IA. percent of US cement production capacity with facilities in all 50 states. PCA promotes safety, sustainability, © 2020 Portland Cement Association and innovation in all aspects of construction, fosters continuous improvement in cement manufacturing and Front Cover Image Credits distribution, and generally promotes economic growth Jeff Wykoff, California Nevada Cement Association and sound infrastructure investment. For More Information Disclaimers For technical assistance regarding cement-based concrete Neither Iowa State University nor the Portland Cement paving, contact the Portland Cement Association or the Association nor this document’s authors, editors, CP Tech Center: designers, illustrators, distributors, or technical advisors make any representations or warranties, expressed or Wayne Adaska, Director implied, as to the accuracy of information herein and Pavements and Geotechnical Markets disclaim liability for any inaccuracies. Portland Cement Association 200 Massachusetts Avenue NW, Suite 200 This publication is provided solely for the continuing Washington, DC 20001 education of qualified professionals. This publication 847-972-9056 should only be used by qualified professionals who [email protected] possess all required licenses, who are competent www.cement.org to evaluate the significance and limitations of the information provided herein, and who accept total Peter Taylor, Director responsibility for the application of this information. National Concrete Pavement Technology Center Iowa State University Iowa State University does not discriminate on the basis 2711 S. Loop Drive, Suite 4700 of race, color, age, ethnicity, religion, national origin, Ames, IA 50010-8664 pregnancy, sexual orientation, gender identity, genetic 515-294-5798 information, sex, marital status, disability, or status as [email protected] a US Veteran. Inquiries regarding nondiscrimination https://cptechcenter.org policies may be directed to the Office of Equal Opportunity, 3410 Beardshear Hall, 515 Morrill Road, Ames, Iowa 50011, telephone: 515-294-7612, hotline: 515-294-1222, email: [email protected]. Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. PCA Special Report SR1007P 4. Title and Subtitle 5. Report Date Guide to Cement-Stabilized Subgrade Soils May 2020 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Jerod Gross and Wayne Adaska 9. Performing Organization Name and Address 10. Work Unit No. National Concrete Pavement Technology Center Iowa State University 11. Contract or Grant No. 2711 South Loop Drive, Suite 4700 Ames, IA 50010-8664 12. Sponsoring Organization Name and Address 13. Type of Report and Period Covered Portland Cement Association Guide 200 Massachusetts Avenue NW, Suite 200 14. Sponsoring Agency Code Washington, DC 20001 15. Supplementary Notes Visit https://cptechcenter.org for color pdfs of this and other research reports. 16. Abstract The primary purpose of this guide is to describe the characteristics, uses, and benefits of cement-stabilized subgrade (CSS) and present methods for geotechnical evaluation, mix design, construction, and field testing that will produce a satisfactory project. The material in this guide updates and expands on the information presented in the Portland Cement Association’s 2008 publication Guide to Cement-Modified Soil (CMS). To clarify the scope of this guide, CSS is distinguished from CMS as follows. CMS describes otherwise untreated soils, particularly clayey soils, that have been treated with a relatively small proportion of portland cement to provide improved characteristics, including reduced plasticity and volume change potential and increased bearing capacity. CSS not only provides the benefits of CMS but also substantially increases soil stiffness and strength to the point where the treatment can provide structural benefits to pavement and building foundations. Unless stated otherwise, this guide primarily discusses CSS. This guide discusses several critical aspects of CSS. The first two chapters describe the key terminology related to cement-treated soil, the effects of cement on the various material properties of the treated soil, the benefits that CSS provides, and the soil properties and classifications relevant to cement treatment. The third chapter provides a systematic procedure for conducting a geotechnical evaluation and a field sampling and testing program. The fourth chapter outlines a step-by-step mix design process for determining the proper cement content for a desired application and treated soil characteristics. The fifth chapter summarizes construction, field inspection, and testing methods, and the final chapter presents several case studies to illustrate the information provided in the guide. Design engineers, testing laboratory personnel, contractors, and owners will find this document useful for determining whether CSS is appropriate for a particular application and the proper steps to follow to produce a satisfactory project. 17. Key Words 18. Distribution Statement cement-stabilized subgrade soils—cement-modified soil—soil-cement— No restrictions. subgrade stabilization 19. Security Classification 20. Security Classification 21. No. of Pages 22. Price (of this report) (of this page) 59 NA Unclassified. Unclassified. Guide to Cement-Stabilized Subgrade Soils May 2020 Authors Jerod Gross, Snyder & Associates, Inc. Wayne Adaska, Portland Cement Association Contributing Technical Authors James Bertsch, Certified Testing Services Sybil Ferrier, Construction Materials Testing Andrea Marsh, Snyder & Associates, Inc. Technical Contributors Jason Havel, City of Iowa City Dave Panos, City of Iowa City (formerly) Dave Schnickel, Manatt’s, Inc. Technical Editing, Graphics Support, Layout, and Production Pete Hunsinger, Alicia Hoermann, Sue Stokke, and Oksana Gieseman, National Concrete Pavement Technology Center Publications Sponsored by © 2020 Portland Cement Association A guide from National Concrete Pavement Technology Center Iowa State University 2711 South Loop Drive, Suite 4700 Ames, IA 50010-8664 Phone: 515-294-5798 / Fax: 515-294-0467 https://cptechcenter.org Acknowledgments The authors, the National Concrete Pavement Technology Center, and the Portland Cement Association gratefully acknowledge the contributions of the technical contributors and the technical advisory committee (TAC) members, who helped establish the technical direction for the guide and reviewed several drafts. Their feedback and suggestions were invaluable. • Stan Bland, Southeast Cement Promotion Association • Garth Benjamin Reese, Raba Kistner, Inc. • Brendan Daly, LafargeHolcim • Matthew Singel, Cement Council of Texas • Marco Estrada, Pavement Recycling Systems Inc. • Kimbel Stokes, The Miller Group, Inc. • Gregory Halsted, Portland Cement Association • David Stowell, New Field Inc. • Andrew Johnson, Southeast Cement Promotion • Matt Wood, Ash Grove Cement Company (formerly) Association • Blake Wright, Raba Kistner, Inc. • David Meyer, Continental Cement Company • Jeff Wykoff, California Nevada Cement Association • Brady Pryor, Ash Grove Resources • Corey Zollinger, CEMEX • Dane Redinger, Resource International, Inc. iv Guide to Cement-Stabilized Subgrade Soils Contents Acknowledgments iv Resilient Modulus (Mr) 13 Executive Summary ix California Bearing Ratio (CBR) 13 Chapter 1. Introduction 1 Unconfined Compressive Strength (UCS) 14 Terminology 1 Expansive Characteristics 14 Soil-Cement 1 Stability 15 Cement-Modified Soil (CMS) 1 Sulfate Content 15 Cement-Stabilized Subgrade (CSS) 1 Soil pH 15 CSS and CMS 2 Organic Content 16 Cement-Treated Base (CTB) 2 Chapter 3. Geotechnical Evaluation and Field Full-Depth Reclamation (FDR) 2 Sampling 17 Comparison of CMS, CSS, CTB, and FDR 2 Geotechnical Evaluation 17 CSS and CMS 2 Field Sampling 19 CSS and CTB 3 Types of Field Sampling 19 FDR 3 Common Field Sampling and Testing Methods 19 Summary 3 Test Pits 19 Modification Mechanisms 4 Coring and Sampling through Existing Pavement 20 Cation Exchange 4 Auger Sampling 20 Particle Restructuring 5 Tube Sampling 21 Cementitious Hydration 5 Standard Penetration Test (SPT) 21 Pozzolanic Reactions 5 Dynamic Cone Penetrometer (DCP) 21 Benefits of CSS 6 Other Field Testing Methods 22 Time and Cost Savings 6 Falling Weight Deflectometer (FWD) 22 Environmental Benefits 6 Automated