Performance Comparison of Base Materials Under Accelerated Loading

The Louisiana Transportation Research Center (LTRC) recently conducted a research effort using the Accelerated Loading Facility (ALF). Nine test sections were constructed for this research using the same wearing course material but having different thicknesses of crushed stone and soil cement bases and subbases. The soil cement base is the most commonly used base material in Louisiana, and crushed stone is a preferred base material in northern Louisiana. The performance of several configurations of crushed stone and soil cement constructed at the Pavement Research Facility and tested using the ALF machine is compared. The comparisons are based on rutting, roughness, and crack development measured on each lane during ALF loading. From the analysis it was found that the combination of crushed stone base over a soil cement subbase, known as an inverted pavement, provided better performance than the soil cement bases and resisted rutting and retarded the occurrence of reflection cracking. This finding confirmed results from other research conducted previously. On the basis of the analysis, it is recommended that an inverted pavement section definitely be considered for use in Louisiana even in those areas where the subgrade is relatively soft. In addition, soil cement bases of 4 percent cement and mixed in place should be constructed and their performance observed and compared with that of the more standard 10 percent mixed-in-place soil cement bases.