PCC PAVEMENT DETERIORATION AND EXPANSIVE MINERAL GROWTH

In order to evaluate the importance of newly-formed minerals in the premature deterioration of Iowa highway concrete, a two-phase study was undertaken. In the first phase, the authors performed petrographic and SEM/EDAX analyses to determine chemical and mineralogical changes in the aggregate and cement paste of samples taken from Iowa concrete highways that showed premature deterioration. In the second phase, they experimentally simulated environmental changes occurring in highway concrete after different deicer chemicals were applied, in order to evaluate the role of deicers in premature deterioration. In highways exhibiting premature concrete deterioration, ettringite completely fills many small voids and lines the walls of larger voids. Microscopic ettringite is also commonly disseminated throughout the paste of many samples. Severe cracking of cement paste is usually associated with ettringite locations, and strongly suggests that ettringite contributed to deterioration. Pyrite is present in coarse/fine aggregates in several concretes. Sulfate ions released by its oxidation contribute to ettringite formation. In poorly performing concretes containing reactive dolomite aggregate, brucite resulting from partial dedolomitization of the aggregate, was most common. No cracking was observed to be spatially associated with brucite, but most brucite crystals are microscopic in size and widely disseminated in the cement paste of less durable concretes. Expansion stresses associated with its growth at many microlocations may be relieved by cracking at weaker sites in the concrete. In the experimental phase of the study the authors found that each deicer salt can cause characteristic concrete deterioration by altering dedolomitization rims at the coarse-aggregate paste interface, by altering cement paste, and/or by forming new expansive minerals in the paste. Magnesium in deicer solutions produces the most severe paste deterioration by forming non-cementitious magnesium silicate hydrate and brucite. Chloride in deicer solutions promotes decalcification of paste and alters ettringite to chloroaluminate. Acetate seems to accentuate Mg-induced deterioration. Magnesium chloride, calcium magnesium acetate and magnesium acetate were the most deleterious.

• Record URL:
  • http://www.ctre.iastate.edu/pubs/crossroads/71pcc.pdf
• 
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/096523102X
• Corporate Authors:

  Iowa State University, Ames

  Center for Transportation Research and Education
  2711 South Loop Drive, Suite 4700
  Ames, IA  United States  50010-8664
• Authors:
  • Lee, H
  • Cody, A M
  • Cody, R D
  • Spry, P G
• Conference:
  • Crossroads 2000
  • Location: Ames, Iowa
  • Date: 1998-8-19 to 1998-8-20
• Publication Date: 1998

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 71-75
• Monograph Title: CROSSROADS 2000 PROCEEDINGS

Subject/Index Terms

• TRT Terms: Aggregates; Chlorides; Concrete pavements; Cracking of concrete pavements; Deicing chemicals; Deterioration; Ettringite; Expansion; Highways; Magnesium; Minerals; Portland cement concrete; Pyrite
• Uncontrolled Terms: Brucite
• Subject Areas: Design; Geotechnology; Highways; Pavements; I22: Design of Pavements, Railways and Guideways;

Filing Info

• Accession Number: 00770467
• Record Type: Publication
• ISBN: 096523102X
• Files: TRIS
• Created Date: Oct 11 1999 12:00AM