Improved methods for selection of k value for concrete pavement design

Kathleen T. Hall, Michael I. Darter, Chen-Ming Kuo

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


The results of research conducted to improve guidelines for k-value selection for concrete pavement design are summarized in this paper. The research included a review of the evolution of k-value concepts and methods, a review of k-value results from several field studies, an examination of the AASHTO Guide's k-value methods, and proposed new guidelines for selection of design k values by a variety of methods. The k value was originally considered a useful and simple parameter for characterizing slab support provided by natural soils of fairly low shear strength. Recognizing that real soils are not true dense liquids, early researchers developed standardized test methods which provided k values in good agreement with full-size slab deflections. Later, substantially higher k values were attributed to granular and stabilized base layers, based on plate tests on top of bases, although slab tests had shown that such bases did not increase k values. Based on the historical review, review of results from several field studies, and a thorough examination of the k-value methods introduced in the 1986 AASHTO Guide, it is recommended that k values be selected for natural soil materials, and that base layers be considered in concrete pavement design in terms of their effect on the slab response, rather than their supposed effect on k value. Improved guidelines were developed for determining k value from a variety of methods, including correlations with soil type, soil properties, and other tests; backcalculation methods; and plate-bearing test methods. Guidelines for seasonal adjustment to k, and adjustments for embankments and shallow rigid layers were also developed.

Original languageEnglish
Pages (from-to)128-136
Number of pages9
JournalTransportation Research Record
Issue number1505
Publication statusPublished - 1995 Jul 1

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Mechanical Engineering


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