Cold in Place Rock Crushing and Stabilization of Northern Low ...

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 73 TEST SECTION DESIGN, LAYOUT, AND CONSTRUCTIONThe test sections constructed on SDHT Hwy 918-01were designed and constructed around the objective toevaluate the effectiveness of crushing protruding boulders in-place, and stabilizing the in situ gravel road sand subgrade.The stabilizers considered in this study included low plastic clay, calcium chloride, DL10 Special asphalt emulsion, andSS-1 asphalt emulsion. The in-place rock crushing and stabilization test sections constructed as part of the Highway918-01 test site include:a) In-place rock crushing, reshaping, and recompaction with no stabilization (control section).b) In-place rock crushing, reshaping, recompaction and surface modification with low plastic clay.c) In-place rock crushing, reshaping, recompaction and stabilization/modification with calcium chloride.d) In-place rock crushing, reshaping, recompaction and stabilization/modification with low plastic clay andcalcium chloride.e) In-place rock crushing, reshaping, recompaction and stabilization with DL-10 asphalt emulsion.f) In-place rock crushing, reshaping, recompaction and stabilization with SS-1 asphalt emulsion.Stabilizer concentrations and layer thicknesses were based on the characterization results of the subgrade andthe properties of the alternative stabilizers/modifiers considered in this study. The stabilized test sections aresummarized in Table 2. As seen in Table 2, the asphalt emulsion stabilized test sections considered in this studyincluded the addition of DL10 Special and SS-1 at concentrations of 2.5, 4.5 and 6.5 percent. Given a residual asphaltcement content of approximately 60 percent, the residual asphalt cement content in the field was 1.5, 2.7 and 3.9 percentby dry weight of soil respectively. Table 3 summarizes and Figure 6 illustrates the Marshall stability after a seven-daycure and the retained Marshall stability after a seven-day cure and a 48 hour soak of each SDHT Hwy 918-01 stabilizedmaterial system. Marshall stability was chosen as the relative measure of stability because it is commonly understoodand well referenced. As also seen in Table 3 and Figure 6, the Marshall stability of the Highway 918 subgrade soil wassignificantly improved with the addition of asphalt emulsion whereas the addition of the calcium chloride and clay onlymarginally increased Marshall stability. When soaked for 48 hours, the retained stability of the unmodified Highway918 subgrade and that of the Highway 918 subgrade with clay and/or calcium chloride modification was negligible.However, the retained stability of the Highway 918 subgrade modified with asphalt emulsion was found to be onlyslightly less than that observed from the unsoaked samples, illustrating the moisture resistance of the asphalt emulsionstabilized soil.