Application of the contiguous aggregate packing principle to predict density potential,CBR and resilient modulus of untreated granular materials

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.