Abstract:
Adherence to the Contiguous Aggregate Packing (CAP) principle on a granular material
aggregate grading curve allows for the calculation of Rational Bailey Ratios (RBRs). RBRs
enable calculation of porosity of such contiguous aggregate or fraction ranges along the
grading curve. Previous work with asphalt aggregate packing showed RBRs can be
related and correlated to porosity, density (through compaction indices), and permeability
of asphalt mixes. Untreated granular materials (UGMs) also have grading curves, even
though for lower quality UGMs, grading is not necessarily specified. Previous work done
by Semmelink (1991) on developing a scientific basis for compaction determination of
UGMs was revisited and the data base reworked. Semmelink (1991) succeeded in
correlating Atterberg indicators, other material indicators such as loose bulk density and
Optimum Moisture Content (OMC), with various methods and calculations of density. The
original work by Semmelink had limited success in incorporating grading curve information
in wide ranging correlation study with various methods of density determination and
calculation. Acceptable correlation was also achieved with the universal material strength
indicator, California Bearing Ratio (CBR), but was correctly criticised as an empirical
strength indicator with significant variation.The Semmelink data set was reworked to
“unpack” the wealth of “inherent properties” in the grading curve by calculating the RBRs.
This was done through application of the CAP principle using RBRs of the obtained
grading curves with the available Atterberg indicators and OMC for a variety of UGM
quality materials. Very good correlations were obtained via these reworked correlation
studies proving that the CAP principle and use of RBRs can also be used to improve
prediction of density and strength of UGMs.
