Mix-Design with Low Bearing Capacity Materials

The roadway construction requirements for soils are generally fixed by Standards. The most common constraints involving materials are optimum moisture content (OMC), maximum dry density (MDD) and bearing capacity predictable by using Proctor test and California bearing ratio (CBR) test. These traditional tests can be combined with other simple field tests to gain the maximum density. However, the use of low bearing materials such as clay and silt, and local resources is an important means of simplifying and economizing the road-building still further. The main purpose of this experimental analysis is a procedure to characterize some road materials by its bearing capacity (CBR and MDD) from two simple standard tests (Sieve Analysis and Atterberg Limits), and then a method to employ silt and/or clay in road mixture. The planned method suggests the minimal volume of high quality material in the roadway mixture added to silt and clay, that must be available in the analyzed location, obtaining an ideal bearing capacity. Different soil-types from various quarries and digs located in Southern Italy were used. The classic laboratory tests to assess the soil properties of all amassed study-soils were carried out, i.e., the Atterberg limits and grain-size distribution (GSD). Correlations based on linear regression were then performed to determine the optimal combination of the properties measured with dependent CBR variables and maximum dry density (MDD) to be predicted for low-volume roads. These equations were then validated by using four material-types from outside the calibration sample.