The effect of compaction on the design life of rehabilitated insitu cement powder stabilised pavements

Abstract

[Abstract]: This project involves conducting visual inspections and Falling Weight Deflectometer (FWD) tests on a number of road pavements which have been reconstructed over the last eighteen months by cement powder insitu stabilisation. The roads are within the area serviced by the Mackay District of the Department of Main Roads, Queensland. The results of these tests are compared with the compaction dry density test results, taken for quality control purposes at the time of construction, to ascertain whether there is a correlation between the two values and whether failure to meet the specified requirement of 100 percent standard compaction affects the “cured” pavement strength. The results indicate that there is no correlation between the field dry density and the modulus of the pavement found by the FWD tests. While plots of modulus and Relative Dry Density (RDD) suggest a similarity where the higher field density results often correspond to high modulus values, many of the comparisons exhibit the opposite behaviour. The investigation identifies that the modulus valves used in the design of pavements often appear to be relatively conservative with some of the tests achieving modulus values up to twenty times the targeted value. Of the 21 lots investigated only 2 lots passed the requirement of 100% standard compaction, however, using the same statistical analysis method on the moduli values, 19 of the 21 lots passed. Failure to meet the specified 100% RDD requirement does not mean that the required strength has not been obtained. It is concluded that the current processes for the design and construction of cement powder insitu-stabilisation are providing satisfactory results, however there appears to be a need for more controlled investigations into obtaining the design data and forecasting the resulting modulus of the stabilised layer after treatment.