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(Appendix E to ASR Transition Plan)
A Table of Contents has been provided for your convenience. You can directly access the chapter of interest by clicking on the subject below. The original text is supplemented to reflect recent findings and conclusions developed by the AASHTO ASR Lead State Team Members since this document was printed in 1994. For reference, all text that has been added or modified from the original document appears in Italics. 1. The Nature of Alkali-Silica Reactivity (ASR) 4. Identification of ASR gel in Field Structures Alkali-Silica Reactivity (ASR) is a major cause of the deterioration of highway structures and pavements in the United States. The Strategic Highway Research Program (SHRP) has addressed this problem through its Project C-202, Eliminating or Minimizing Alkali-Silica Reactivity. One task of this research was to find means to mitigate damage caused by ASR in existing concrete structures and pavements. The first steps toward achieving this goal are to detect ASR and to distinguish it from other types of damage, particulalry in its early stages. This handbook is intended to serve this purpose. It uses color photographs of actual examples to illustrate the ASR damage in a number of field structures. It then describes a simple and rapid chemical test for ASR detection. An early diagnosis of the problem should greatly help in the timely and economical repair or rehabilitation of the affected concrete structure. Inam Jawed This handbook provides guidance for the field identification of Alkali-Silica Reactivity (ASR) in portland cement concrete structures such as highway pavements and bridges. ASR development is assessed on two bases : 1) the occurrence and disposition of cracking and displacement of concrete, and 2) the presence of reaction products from ASR. Descriptions and color photographs provide detailed information. Other causes of cracking or volume changes, such as freezing and thawing, corrosion of reinforced steel, superimposed loading, or plastic shrinkage, may have occurred in the structure under inspection. Distress similar to that resulting from ASR but not caused by ASR is also identified. The reader should keep in mind that distress to concrete can be very complicated, and that it is not uncommon for secondary distress mechanisms such as freezing and thawing and corrosion of reinforced steel to be accelerated once the integrity of concrete is affected by ASR-induced cracking. This handbook, therefore, is meant to act as a guide for an initial assessment of potential ASR distress in the field, not for definitive assessment of distress mechanisms. Any field observations should be confirmed in the laboratory by an experienced petrographer before making definitive conclusions. The descriptions and photographs of evidence of ASR presented in this handbook are based on almost 30 years of field and laboratory investigations of a wide variety of concrete structures. Most of the information presented was obtained under SHRP Project C-202, "Eliminating or Minimizing Alkali-Silica Reactivity." The uranyl acetate procedure for identifying ASR gel reaction products was developed by Drs. K. Hover and K. Natesaiyer of Cornell University. (1, 2) The ASRDetect procedure was developed by Bill Carey and George Guthrie at the DOE Los Alamos National Laboratories. 1. NATESAIYER, K. and Hover, K.C., "Insitu Identification of ASR products in Concrete", Cement and Concrete Research, Vol. 18, May 1988, pp. 455-463.
This handbook is divided into four sections. Color photographs are used thoughout the handbook to aid in accurate identification. Section 1 describes the nature of ASR and its causes and effects. Section 2 deals with the manifestations of ASR-related volume changes in highway pavement. Section 3 covers ASR in bridge structures. Section 4 describes a rapid field procedure to identify the presence of ASR reaction products in concrete. The presence of the reaction products is indisputable evidence of ASR, but it does not necessarily reflect development or severity of distress. Thus, assessment of associated distress together with identification of reaction products provides the greatest assurance whether expansive ASR has developed in the concrete structure. Confirmation of ASR by petrographic analysis is recommended to reach reliable conclusions that the distress is indeed due to ASR expansion. |
The following provides the full text with pictures of SHRP C-315, one of the key products of the Strategic Highway Research Program, Contract C-202, ASR project developed by the National Research Council, 2101 Constitution Avenue N.W., Washington, DC 20418. Author of the original manuscript is David Stark, Construction Technologies Laboratories, Inc., Skokie, IL, USA.See also the web site for the AASHTO Technology Implementation Group