Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. FHWA/TX-05/7-4920-2 4. Title and Subtitle 5. Report Date SELECTING OPTIMUM CEMENT CONTENTS FOR September 2001 STABILIZING AGGREGATE BASE MATERIALS Resubmitted: February 2002 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. W. Spencer Guthrie, Stephen Sebesta, and Tom Scullion Report 7-4920-2 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Texas Transportation Institute The Texas A&M University System 11. Contract or Grant No. College Station, Texas 77843-3135 Project 7-4920 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Texas Department of Transportation Technical Report: Research and Technology Implementation Office September 1998−August 2001 P. O. Box 5080 14. Sponsoring Agency Code Austin Texas 78763-5080 15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration. Project Title: Improving Long-Term Flexible Pavement Performance URL:http://ttitamu.edu/documents/7-4920-2.pdf 16. Abstract Researchers designed a laboratory test sequence to identify the optimum amount of portland type I cement for stabilizing two aggregates, limestone and recycled concrete, typically used in the Houston District. Smectitic compositions identified through mineralogical investigations corresponded with the poor performance of the untreated aggregates in preliminary testing and substantiated the need for stabilization. Samples were subsequently treated with 1.5, 3.0, and 4.5 percent cement and tested for strength, shrinkage, durability, and moisture susceptibility in the laboratory. Strength was determined with the Soil Cement Compressive Strength Test (TxDOT Test Method Tex-120-E), and a linear shrinkage test was developed to assess shrinkage characteristics. Durability was evaluated with the South African Wheel Tracker Erosion Test (SAWTET), and moisture susceptibility was assessed with the Tube Suction Test (TST). The limestone aggregate was also subjected to modulus testing. Based on these parameters, stabilized samples exhibited markedly improved performance with minimum additions of cement. Based on the results of the laboratory testing, the recommendation of this report is 3.0 percent cement for the limestone and 1.5 percent cement for the recycled concrete. For future testing of aggregate base materials to determine optimum cement contents, the joint utilization of the strength test and the TST is recommended. Sufficient quantities of cement should be added to tested samples to obtain minimum unconfined compressive strengths of 300 psi in the former and maximum average surface dielectric values of 10 in the latter. The minimum amount of cement necessary to satisfy both criteria should be recommended for pavement construction. In addition to these tentative specifications, a provisional pre-cracking procedure is also suggested in this report for further evaluation. 17. Key Words 18. Distribution Statement Aggregate Base Materials, Cement Stabilization, No restrictions. This document is available to the Durability, Moisture Susceptibility, Pre-cracking, public through NTIS: Shrinkage Cracking, Tube Suction Test National Technical Information Service Springfield, Virginia 22161 http://www.ntis.gov 19. Security Classif.(of this report) 20. Security Classif.(of this page) 21. No. of Pages 22. Price Unclassified Unclassified 64 Form DOT F 1700.7 (8-72) Reproduction of completed page authorized SELECTING OPTIMUM CEMENT CONTENTS FOR STABILIZING AGGREGATE BASE MATERIALS by W. Spencer Guthrie, E.I.T. Graduate Research Assistant Texas Transportation Institute Stephen Sebesta Assistant Transportation Researcher Texas Transportation Institute and Tom Scullion, P.E. Research Engineer Texas Transportation Institute Report 7-4920-2 Project 7-4920 Project Title: Improving Long-Term Flexible Pavement Performance Performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration September 2001 Resubmitted: February 2002 TEXAS TRANSPORTATION INSTITUTE The Texas A&M University System College Station, TX 77843-3135 DISCLAIMER The contents of this report reflect the views of the authors, who are responsible for the opinions, findings, and conclusions presented herein. The contents do not necessarily reflect the official views or policies of the Texas Transportation Institute (TTI) or the Texas Department of Transportation (TxDOT). This report does not constitute a standard, specification, or regulation, nor is it intended for construction, bidding, or permit purposes. Trade names were used solely for information and not for product endorsement. The engineer in charge of the project was Tom Scullion, P.E. #62683. v ACKNOWLEDGMENTS The authors wish to acknowledge Mr. Pat Henry, P.E., of the Houston District for arranging this project and serving as project director. His support and flexibility are appreciated. While Mr. Henry provided the recycled concrete evaluated in this project, Mr. Paul Waites, supervisor of the Melendy Plant of the Martin Marietta Company in Jersey Village, donated the limestone aggregate. Mr. Lee Gustavus of TTI was instrumental in obtaining the aggregate samples and facilitating laboratory needs. Mr. Seungwook Lim and Mr. Imran Syed, graduate students in the Department of Civil Engineering at Texas A&M University, assisted with the literature review provided in this report. With assistance from Dr. Pat Harris of TTI, Mr. Syed also performed the mineralogical evaluation of the recycled concrete aggregate. The mineralogical investigation of the limestone aggregate was accomplished with support from Dr. Joe Dixon and Dr. Norman White of the Department of Soil and Crop Sciences at Texas A&M University. Dr. White provided the scanning electron microscopy images (SEM) included in this report. Uniaxial resilient modulus tests were performed by Mr. Gene Schlieker of TTI. vi TABLE OF CONTENTS Page LIST OF FIGURES ........................................................................................................ix LIST OF TABLES...........................................................................................................x CHAPTER 1 INTRODUCTION ...................................................................................1 General.....................................................................................................1 CHAPTER 2 BACKGROUND .....................................................................................3 Design Considerations.............................................................................3 Mineralogy...............................................................................................3 Strength....................................................................................................4 Shrinkage .................................................................................................5 Durability .................................................................................................6 Moisture Susceptibility............................................................................7 Modulus ...................................................................................................9 CHAPTER 3 TEST PROCEDURES...........................................................................11 Aggregate Characterization Tests..........................................................11 Mineralogy Tests...................................................................................12 Strength Test..........................................................................................15 Shrinkage Test .......................................................................................15 Durability Test .......................................................................................17 Moisture Susceptibility Test..................................................................19 Modulus Test.........................................................................................20 CHAPTER 4 TEST RESULTS....................................................................................23 Aggregate Characterization Test Results...............................................23 Mineralogy Test Results........................................................................24 Strength Test Results .............................................................................31 Shrinkage Test Results...........................................................................33 Durability Test Results ..........................................................................34 Moisture Susceptibility Test Results .....................................................35 Modulus Test Results.............................................................................36 vii TABLE OF CONTENTS (CONTINUED) Page CHAPTER 5 CONCLUSION......................................................................................39 Summary................................................................................................39 Findings..................................................................................................40 Recommendations..................................................................................41 REFERENCES ..............................................................................................................43