Chapter 1. Introduction

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1.1 OVERVIEW

Alkali-silica reaction (ASR) is a major durability problem that has resulted in premature deterioration of various types of concrete structures in the United States and throughout the world. Although the potential for lithium compounds to control ASR-induced expansion has been known for about 50 years, there have been limited field applications with even less comprehensive performance monitoring. In the past 10 years, however, there has been renewed interest in using lithium as either an admixture in new concrete or as a treatment of existing structures. Because of the limited use of lithium compounds in laboratory research and field applications, guidelines have been lacking. This report presents recommendations for practitioners to test, specify, and use lithium compounds in concrete construction and repair applications.

1.2 SUMMARY OF REVISIONS AND MODIFICATIONS TO GUIDELINES

This report replaces the previously published lithium guideline report (Guidelines for the Use of Lithium to Mitigate or Prevent Alkali-Silica Reaction (ASR), Folliard, et al., 2003). Substantial changes have been made, and the recommendations provided within the current document should be considered to be the most relevant and applicable to future applications of lithium. The following highlights some of the key modifications and revisions made to the current guideline document:

• Deleting the prescriptive recommendations for the use of lithium as an admixture in new concrete. The exact relationship between the amount of lithium required and the nature of the reactive aggregate is not clearly understood. As discussed in chapter 3, recent studies have shown that dosages higher than 100 percent of the standard dosage may be needed to suppress expansion for several major aggregate types. Consequently, it is not appropriate to specify a single dose for all reactive aggregates and the dose required has to be determined by testing individual aggregate sources with lithium.
• Deleting the modified accelerated mortar bar test (AMBT) in the performance specification. This test underestimates the amount of lithium required for the control of expansion with a number of reactive aggregate types.
• Updating summary of field studies to include recent applications of lithium.
• Updating literature review to include recent publications.

1.3 ORGANIZATION OF REPORT

This report is organized in seven chapters, including this brief introductory chapter. Major topics are summarized below.

Chapter 2 provides a basic overview of ASR, including information on mechanisms, symptoms of ASR damage in field structures, mitigation approaches, test methods, and specifications. The main objective of this chapter is to provide the reader with sufficient technical background on ASR, which is essential in understanding how lithium compounds affect the process.

Chapter 3 summarizes basic information on lithium compounds, including their production and availability. This chapter presents a comprehensive review of laboratory research on using lithium compounds to control ASR-induced expansion, including discussions on the proposed mechanisms by which lithium additives suppress expansion. It also includes a brief discussion on specifications related to lithium usage as an admixture in new concrete.

Chapter 4 describes several major field applications of lithium compounds aimed to minimize or prevent ASR-induced expansion in new concrete and that treat field structures already showing signs of distress due to ASR. Relevant information on materials, mixture proportions, supporting laboratory data (if applicable), and field performance is provided for the selected case studies.

Chapter 5 presents recommendations for using lithium compounds as an admixture in new concrete and as a method of treating existing structures suffering from ASR-induced damage. The recommendations are aimed at helping practitioners test, specify, and use lithium in concrete construction applications. The guidelines are based on a comprehensive review of laboratory and field applications of lithium compounds and on a survey of relevant specifications.

Chapter 6 discusses the economic considerations of using lithium compounds in new concrete and to treat existing structures. This chapter presents various factors that should be taken into account when considering the use of lithium.

Chapter 7 summarizes some of the major conclusions from this report and identifies some technical and practical issues that should be considered for future laboratory studies and field applications.