AGGREGATE GRADING AND THE INTERNAL STRUCTURE OF CONCRETE

It is shown that there are many gradings for concrete aggregate that can be considered as optimum for one purpose or another. In addition to the behavior of the concrete in the frash as well as in the hardened state, visual inspection of the internal structure of concrete reveals whether the grading used is close enough to the desired optimum. A method, adopted from a procedure used in petrography, is presented for such evaluation of the structure of concrete. This is based on the measurement of the intercepts of mortar layers among coarse aggregate particles in the finished concrete. Various kinds of concretes are analyzed by this method. The results indicate that there exists a needed minimum value for the average mortar layer intercept below which the workability of the concrete is inadequate; this needed minimum mortar intercept is dependent on several factors such as the method of compaction and the grading of the sand; and the minimum value seems to be independent of the particle shape of the coarse aggregate. The effect of the particle shape of coarse aggregate on the grading optimum is also discussed. Based on this, two methods for measuring the angularity of the particles are recommended. Finally, internal structures of concretes made with continuous gradings and comparable gap gradings are contrasted.

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 56-64
  • Monograph Title: Grading of concrete aggregates
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00159547
  • Record Type: Publication
  • ISBN: 0309021723
  • Files: TRIS, TRB
  • Created Date: Sep 20 1977 12:00AM