Technical Bulletin on Design and Construction of Crack Attenuating Mixes (CAM)

The crack attenuating mix (CAM) is proposed as a thin, long-lasting, cost effective surface mix for pavement maintenance and preservation. Developed under Texas Department of Transportation (TxDOT) research study 0-5598, this very fine mix is designed to pass both the current Hamburg wheel test (HWTT) to ensure moisture susceptibility and good rut resistance and strict overlay tester (OT) requirements to ensure good crack resistance. It is typically placed as a 1-inch thick mat. This mix has been evaluated in several districts around Texas, and the performance to date has been very good. A new statewide specification is under preparation and will be available in 2009. This comprehensive specification includes all aspects of material selection, mix design, and construction. The design of the mix relies on the traditional volumetric approach. In this report a new mix design procedure is proposed that builds on the fact that in the CAM design the aggregates and asphalt are paid for separately. The proposed procedure attempts to define a window of asphalt contents where both cracking and rutting requirements are satisfied. The optimal asphalt content (OAC) is defined as the middle of the acceptable range. The volumetrics are then checked after the performance tests are satisfied. This procedure has several advantages. It will rapidly identify aggregate/asphalt combinations that will not work so that costly re-runs of the volumetric designs will be avoided. This new procedure can save money by identifying a window of asphalt content that will provide satisfactory performance.


  • English

Media Info

  • Media Type: Web
  • Edition: Technical Bulletin
  • Features: Figures; Photos; Tables;
  • Pagination: 20p

Subject/Index Terms

Filing Info

  • Accession Number: 01154198
  • Record Type: Publication
  • Report/Paper Numbers: Report 0-5598-P1
  • Contract Numbers: Project 0-5598
  • Created Date: Apr 8 2010 3:47PM