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

COLD IN PLACE ROCK CRUSHING AND STABILIZATION OFNORTHERN LOW VOLUME ROADS:A CASE STUDY APPLICATION OF GROUND PENETRATINGRADAR FOR COLD-IN-PLACE RECYCLED ROAD SYSTEMSPrepared By:Curtis BerthelotAssistant Professor of Civil EngineeringUniversity of SaskatchewanRon GerbrandtPreservation EngineerSaskatchewan Highways and TransportationLarry SafronetzArea ManagerSaskatchewan Highways and TransportationGordon SparksProfessor of Civil EngineeringUniversity of SaskatchewanPresented at80 th Annual Meeting, Transportation Research BoardWashington D.C.CDROM Proceedings Paper #01-2615January, 2001

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 1ABSTRACTSaskatchewan Department of Highways and Transportation (SDHT) is responsible for maintainingapproximately 6500 kilometers of northern gravel surfaced roads. Many of these northern gravel roads are built onpoorly graded sand subgrades and may contain protruding bedrock and/or large boulders. Because of this,washboarding, protruding rocks, rutting and potholes are common performance problems of many northern gravelroads. Routine blading of these roads is often ineffective because unstable sand does not maintain its shape andcompaction, protruding bedrock and boulders damage motor grader blades, boulders may become dislodged leavingholes in the road, and dislodged boulders are a safety hazard when windrowed along road side-slopes. Clay cappingand base stabilization have been used to provide a stable wearing surface, cover protruding bedrock and largeboulders, and reduce traffic dust. However, the long-term performance of clay capping and base stabilization can behighly variable and the associated costs can make these conventional solutions untenable. As a result, SDHTinvestigated the use of in-place rock crushing and stabilization/modification for northern gravel roads withsignificant proportion of boulders in the grade using a rotomixer/stabilizer. Based on the findings of this study, inplacerock crushing and stabilization/modification is a technically feasible solution for eliminating protrudingbedrock and boulders contained near the surface. However, in-place crushing of boulders with unconfinedcompressive strengths over 50,000 psi resulted in significant damage to the rotomixer mandrel resulting in anapproximate cost of just under $13,684 CDN per kilometer. in situ rock crushing with subgrade stabilization anddouble seal was found to cost approximately $52,017 CDN per kilometer.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 21 INTRODUCTIONSaskatchewan Department of Highways and Transportation (SDHT) is responsible for maintainingapproximately 6500 kilometers of northern gravel roads. Many of these gravel roads are built on poorly graded sandsubgrades and may contain protruding bedrock and/or large boulders. Because of this, these roads may exhibit washboarding, protruding rocks, rutting and potholes which results in decreased service level and potential driving hazards.Routine blading is often ineffective because unstable sand does not maintain its shape and compaction, protrudingbedrock and boulders damage motor grader blades, boulders may become dislodged leaving holes in the road, anddislodged boulders are a safety hazard when windrowed along road side-slopes.In the past, clay capping and base stabilization have been used to provide a stable wearing surface, coverprotruding bedrock and large boulders, and reduce traffic dust (1). However, the long-term performance of clay cappingand base stabilization can be highly variable and the associated costs can make them untenable. As a result, significantbenefits could result from a more effective maintenance and upgrade treatment for northern gravel roads characterized byprotruding boulders and bedrock and/or comprised of unstable sand subgrades. In the search for more appropriatemethods for maintaining northern gravel roads, an in-place rock crushing and stabilization pilot project was undertakenon Highway 918-01 in 1999 between kilometers 12.80 and 21.84.Historic performance problems with Highway 918-01 include rough road surface due to severe potholes,rutting, protruding boulders and washboarding. Routine blading of Highway 918-01 has been relatively ineffective dueto unstable subgrade conditions and protruding boulders. Commercial traffic on Highway 918-01 is limited to suppliesto the Patunak First Nations Reservation, which is comprised of approximately 1500 residents. There is no residential orcommercial development along Highway 918-01.2 PRELIMINARY SITE INVESTIGATIONA preliminary site investigation and visual site survey was performed along Highway 918-01 in early summer1999. Figure 1 and Figure 2 show protruding boulders and unstable sand subgrade conditions common to Highway918-01.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 3FIGURE 1 Highway 918-01 Typical Boulders In Grade and Along Road EdgeFIGURE 2 Highway 918-01 Typical Unstable Sand Subgrade

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 4In situ subgrade soil samples were retrieved from Highway 918-01. The resulting grain size analysis from eachsample is illustrated in Figure 3. As seen in Figure 3, Highway 918-01 subgrade is comprised of uniform sand withapproximately 15 to 20 percent fines. Atterburg limit characterization of the fines portion determined the fines portion tobe non-plastic. AASHTO classification determined the subgrade to be non-plastic fine sand (A-3) and the Unified SoilClassification System determined the subgrade to be poorly graded sand with high non-plastic fines content (SM).Standard Proctor moisture density characterization was performed as per ASTM protocols and is shown in Figure 4. Ascan be seen in Figure 4, the optimum standard proctor density was found to be approximately 2070 kg/m 3 at 7.5 percentmoisture content and the optimum modified proctor density was found to be approximately 2160 kg/m 3 at 6.5 percentmoisture content.100908070% Passing6050403020100.075 .25.15.425.852.04.75 6.3Sieve Size 0.45 (mm)9.512.519.0Kilometer 10 Kilometer 20FIGURE 3 Highway 918-01 in situ Subgrade Grain Size Distribution

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 52180215521302105Dry Density (kg/m 3 )2080205520302005198019551930190518803 4 5 6 7 8 9 10Moisture Content Percent11Modified ProctorStandard ProctorFIGURE 4 Standard and Modified Proctor Moisture-Density of SDHT Highway 918-01 SubgradeIn situ boulders were sampled from Highway 918-01, were identified as to their type, and characterized withrespect to unconfined compressive strength. The rock type identification and unconfined compressive strengthmeasurements are summarized in Table 1 and illustrated in Figure 5. As seen in Table 1 and Figure 5, the in situboulders exhibited mean unconfined compressive strengths ranging from 121.1 MPa (24.0 ksi) for weathered granitoidto 358.1 MPa (51.9 ksi) for fine-grained metamorphic basalt.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 6TABLE 1 Highway 918-01 in situ Rock Unconfined Compressive Strength MeasurementsRock TypeSampleLength(mm)SampleWidth(mm)SampleL/DRatioLoad(KN)UCS(ksi)UCS(MPa)Fine Grained Metamorphic A 80.7 38.5 2.10 431 53.8 370.7Fine Grained Metamorphic B 84.3 38.5 2.37 402 50.1 345.5Granite A 82.1 38.5 2.13 318 39.7 273.7Granite B 80.7 38.6 2.09 316 39.2 269.8Pegamite A 74.9 38.5 1.95 281 35.0 241.4Pegamite B 80.7 38.5 2.10 243 30.3 208.9Pink Granitoid A 82.8 38.6 2.15 185 23.0 158.6Pink Granitoid B 82.5 38.6 2.14 241 29.8 205.6Weathered Granitoid A 76.7 38.6 1.99 185 22.9 157.8Weathered Granitoid B 80.6 38.6 2.09 214 26.5 182.5Weathered Granitoid A* 82.5 38.5 2.14 82 10.2 70.1Weathered Granitoid B 84.9 38.5 2.21 200 25.0 172.0Grey Granitoid A 81.1 38.6 2.10 160 19.9 136.9Grey Granitoid B 81.2 38.6 2.10 234 29.0 199.8* Sample contained internal fracture plane.MeanUCS(MPa)358.1271.8225.1182.1170.2121.1168.4400350358Mean UCS (MPa)300250200150100271225182170168121500Fine Grained MetamorphicGranitePegamitePink GranitoidWeathered GranitoidGrey GranitoidWeathered Granitoid FracturedFIGURE 5 SDHT Hwy 918-01 in situ Rock Unconfined Compressive Strength Measurements

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.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 8ChainageStart (km)ChainageEnd (km)TABLE 2 Highway 918-01 Test SectionsSectionLength(m)Stabilizer Type and AmountSurfacingGravel(Tonnes)SurfacingDoubleSeal (m)12.80 13.44 640 none 100 013.44 13.94 500 20% clay (150 tonnes) 100 013.94 14.44 500 20% clay (150 tonnes) 100 014.44 15.44 1000 15% clay (200 tonnes) 100 015.44 15.90 460 15% clay (100 tonnes) 100 015.90 16.40 500 10% clay (75 tonnes)100 016.40 16.60 200210% clay (25 tonnes) 1 l/m 2 25 016.60 16.80 200 10% clay (25 tonnes) 2 l/m 2 25 016.80 17.00 200 10% clay (25 tonnes) 3 l/m 2 25 017.00 17.20 200 3 l/m 2 CaCl 25 017.20 17.40 200 2 l/m 2 CaCl 25 017.40 17.60 200 1 l/m 2 CaCl 25 15017.60 17.75 150 None 0 15017.75 18.55 800 None 150 020.34 20.49 150 2.5% DL10 Special 0 020.49 20.64 150 6.5% DL10 Special 0 020.64 20.72 80 4.5% DL10 Special 0 7520.72 20.87 150 2.5% SS-1 0 15020.87 21.02 150 6.5% SS-1 0 15021.02 21.18 160 4.5% SS-1 0 15021.18 21.84 660 none 108 0Totals 7250 1008 825TABLE 3 Highway 918-01 Subgrade Marshall Stability Across Stabilizer Types and ConcentrationsStabilizer Type andConcentration7-Day CuredMarshall Stability(KN)7-Day Cured and 48-Hour Soak MarshallStabilityUnmodified 1.9 010% Clay 3.1 015% Clay 82.1 020% Clay 3.7 010% Clay 11/m 2 CaCl 3.6 010% Clay 21/m 2 CaCl 3.4 010% Clay 31/m 2 CaCl 3.0 01 1/m 2 CaCl 2.4 02 1/m 2 CaCl 2.0 03 1/m 2 CaCl 1.8 02.5% DL10 Special 18.6 9.84.5% DL10 Special 14.3 12.56.5% DL10 Special 9.2 10.32.5% SS-1 19.1 19.14.5% SS-1 28.4 23.46.5% SS-1 25.2 17.2

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 9Mean Marshall Stability (KN)302520151050Unmodified10% Clay15% Clay20% Clay10% Clay 11/m2 CaCl10% Clay 21/m2 CaCl10% Clay 31/m2 CaCl1 1/m2 CaCl2 1/m2 CaCl3 1/m2 CaCl2.5% DL10 Special4.5% DL10 Special6.5% DL10 Special2.5% SS-14.5% SS-16.5% SS-17-Day Cure7Day Cure-48 Hour SoakFIGURE 6 Marshall Stability of SDHT Highway 918-01 Stabilized SystemsFigure 7 through Figure 14 show the process used to construct the Highway 918-01 test sections. The processincludes primary in-place rock crushing with a rotomixer/stabilizer CMI650 with mandrel cutting down (Figure 7).Although the CMI R/S 650 did crush almost all in situ boulders, it provided on average a 200 mm minus crush, whichrequired raking with a motor grader to remove the larger pieces of crushed rock out of the grade to achieve effectiveshaping and compaction (Figure 8). Following the in-place rock crushing process; primary shaping and compaction ofsubgrade (Figure 9); secondary in-place rock crushing and injection of stabilizers using the CMI R/S 650 with mandrelcutting up (Figure 10); final shaping and compaction (Figures 11 and 12); and application of surface coarse traffic gravelor double seal (Figures 13 and 14) was performed.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 10FIGURE 7 Primary Rock CrushingFIGURE 8 Windrowing and Separating Crushed Rocks

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 11FIGURE 9 Clay ModificationFIGURE 10 Asphalt Emulsion Stabilization

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 12FIGURE 11 Final Shaping and Compaction of GradeFIGURE 12 Typical Compacted Final Grade

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 13FIGURE 13 Typical Gravel Wearing CoarseFIGURE 14 Typical Asphalt Emulsion Stabilized Wearing Coarse

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 144 CONSTRUCTION COST EVALUATIONThe total construction cost for each test section was equilibrated to a per kilometer basis segmented with respectto labor; equipment; gravel; stabilizer/modifier; miscellaneous costs including fuel, teeth, and housing for the crew; anddouble seal surfacing as summarized in Table 4 and illustrated in Figure 15. As seen in Table 4 and Figure 15, asignificant portion of the cost to crush boulders in-place was equipment costs. Because the CMI R/S 650 employed inthis project is designed to rotomix asphalt concrete with an unconfined compressive strength of one to five MPa at roomtemperature, boulder unconfined compressive strengths as 358 MPa inflicted severe mandrel damage when highconcentrations of boulders were encountered. During the 7.25 kilometers of rotomixed road, $13,222 of mandrel teethwas consumed. However, this pilot was intended to be a “worst case scenario” and therefore, sections of Highway 918-01 with high concentrations of boulders were selected in order to provide an extensive field evaluation of the in-placerock crushing process. It is believed that redesigned mandrel will improve efficiency, reduce teeth costs, and result infewer equipment breakdowns. Figure 16 illustrates the mean total construction cost by test section type. As seen inFigure 16, the mean construction cost per kilometer ranged from $13,684 for in-place rock crushing and a gravel wearingcoarse to $52,017 for in-place rock crushing, asphalt emulsion stabilization and a double seal wearing coarse.TABLE 4 Highway 918-01 Test Section Construction Cost Per Kilometer by Cost TypeTestSection(m)GravelCost($/Km)Stab.Cost($/Km)SealCost($/Km)Misc.Cost($/Km)TotalCost($/Km)Labor EquipTest SectionCost CostNo Stabilization 640 3,127 11,931 1,844 0 0 3,220 20,12220% Clay 500 3,104 11,407 2,185 0 0 3,022 21,29620% Clay 500 3,353 12,320 2,360 0 0 3,264 21,29615% Clay 1000 1,617 7,542 2,360 0 0 3,263 14,78215% Clay 460 3,515 16,613 2,565 0 0 3,263 25,95610%Clay-2/3l/m 2 CaCl 500 2,453 10,122 2,360 5,409 0 2,596 22,94010%Clay-1l/m 2 CaCl 200 6,133 25,304 1,475 2,823 0 2,595 38,33510%Clay-2l/m 2 CaCl 200 6,133 25,304 1,475 4,397 0 2,595 39,90510%Clay-3l/m 2 CaCl 200 4,662 20,128 1,475 5,971 0 2,595 34,8303l/m 2 CaCl 200 4,662 20,128 1,475 5,971 0 2,595 34,8302l/m 2 CaCl 200 4,662 20,128 1,475 4,397 0 2,595 33,2601l/m 2 CaCl & Seal 200 4,662 20,128 1,475 2,823 6,719 2,595 38,405No Stabilization & Seal 150 0 7,206 0 0 8,959 2,593 18,760No Stabilization 800 954 4,286 1,967 0 0 2,769 9,3522.5% DL10 Special 150 6,410 21,874 0 6,456 0 2,593 37,3336.5% DL10 Special 150 6,410 21,874 0 19,369 0 2,593 50,2474.5% DL10 & Seal 80 7,125 22,888 0 12,106 6,463 2,600 51,1812.5% SS-1 & Seal 150 7,117 22,894 0 6,706 6,467 2,593 45,7806.5% SS-1 & Seal 150 7,117 22,894 0 16,766 6,467 2,593 55,8404.5% SS-1 & Seal 160 6,672 21,464 0 10,365 6,063 10,706 55,269No Stabilization 660 1,457 4,971 1,931 0 0 2,595 10,954

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 1560,000Construction Costs ($/Km)50,00040,00030,00020,00010,0000No Stab (control)20% Clay20% Clay15% Clay15% Clay10% Clay-2-3l CaCl10% Clay-1l CaCl10% Clay-2l CaCl3l CaCl10% Clay-3l CaCl2l CaCl1l CaCl SealNo Stab & SealNo Stab (control)2.5% DL10SLabor Equipment Gravel Stabilizer Misc.6.5% DL10S4.5% DL10S Seal2.5% SS1 SealSeal Coat6.5% SS1 Seal4.5% SS1 SealNo Stab (control)FIGURE 15 Highway 918-01 Test Section Construction Cost per Kilometer by Cost Type$60,000Construction Cost ($/Km)$50,000$40,000$30,000$20,000$10,000$13,684$18,759$24,448$34,002$35,497$38,403$43,790$52,017$0GravelGravel w/ SealClay StabilizedClay/CaCl ModifiedCaCl ModifiedCaCl Modified w/ SealAsphalt Emulsion StabilizedAsphalt Emulsion Stabilized w/ SealFIGURE 16 Mean Total Construction Cost per Kilometer Grouped by Test Section Type

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 165 POST CONSTRUCTION PERFORMANCEInspection of the Highway 918-01 test sections was performed immediately after construction and one yearafter construction. For comparative purposes, a control test section comprised of in-place rock crushing with a gravelwearingsurface coarse and no stabilizers added to the subgrade was constructed. After one year of performance, theclay modified test sections were determined to exhibit improved stability of the subgrade, assisted in maintainingmoisture after rainfalls, and assisted in retaining gravel into the wearing coarse. However, the clay modified test sectionsproduced increased traffic dust in dry weather conditions and became slippery in wet weather conditions when comparedto other test sections.Calcium chloride modified test sections were constructed at concentrations of one liter/m 2 , two liter/m 2 andthree liter/m 2 to a depth of 150 mm. To evaluate the relative influence that clay has on the retention and performance ofcalcium chloride modification, test sections with and without ten percent clay by dry weight of subgrade soil wereconstructed. It was determined that calcium chloride provided improved compaction properties of the sand subgrade,assisted in moisture retention within the grade, and assisted in embedding gravel into the wearing coarse. The calciumchloride modified test sections significantly reduced dust in dry weather conditions when compared to other test sections.Clay modification of the calcium chloride treated subgrade increased the amount and duration of moisture retention. Itwas concluded that with ten percent clay added to the subgrade, one liter/m 2 of calcium chloride provided the optimalbalance of moisture retention and stability. Calcium chloride concentrations of two liters/m 2 and three liters/m 2 with tenpercent clay resulted in surface ponding, potholes, rutting, and slippery driving surface after rainfalls. It was alsodetermined that the calcium chloride without clay was less sensitive to rainfall and only exhibited minor surface pondingand potholes after rainfall up to concentrations of three liters/m 2 .SS-1 and DL10 Special asphalt emulsion was used to stabilize test sections at respective concentrations of 2.5,4.5 and 6.5 percent by dry weight of soil to a design depth of 150 mm. SS-1 is a slow set anionic asphalt emulsion thatemploys medium residual penetration asphalt designed to increase the stability and strength of granular materials. DL10Special is an anionic soft pen residual asphalt emulsion designed to provide added stability, improved environmentaldurability and surface workability in hot weather.Based on the observations of the SS-1 and DL10 Special asphalt emulsion stabilized test sections immediatelyafter construction, the test sections with increasing concentrations of asphalt emulsion increased the sand subgradestability, provided a tighter surface wearing coarse and reduced dust as would be expected. It was found that the asphalt

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 17emulsion stabilized test sections required minor shaping for a period of approximately two weeks after placement untilthe emulsion fully cured. Minor wheel path abrasion was also observed two months after placement with no wearingsurface coarse placed on the stabilized sand subgrade after construction. To minimize wheel path abrasion, it isrecommended that a thin layer of crushed rock or traffic gravel be embedded into the wearing surface immediately afterplacement and prior to the asphalt emulsion curing. In addition, a residual pen asphalt emulsion and/or faster settingemulsion may help reduce wheel path rutting and abrasion and eliminate the need for blading during curing. Double sealwearing coarse was also placed on select portions of the asphalt emulsion stabilized test sections, one-year afterconstruction the sealed test sections constructed on the asphalt emulsion stabilized subgrade was found to be performingwell with only minor edge breaks present.6 SUMMARY, CONCLUSIONS AND FUTURE RECOMMENDATIONSSDHT is responsible for maintaining approximately 6500 kilometers of northern gravel roads. Many of thesegravel roads are built on poorly graded sand subgrades and may contain protruding bedrock and/or large boulders.Furthermore, many of these roads exhibit washboarding, protruding rocks, rutting and potholes, which result in severeroad roughness and a potential driving hazard. Routine blading is often ineffective because unstable sand does notmaintain shape and compaction, protruding bedrock and boulders damage motor grader blades, boulders may becomedislodged leaving holes in the road, and dislodged boulders are a safety hazard when windrowed along road side-slopes.SDHT undertook an in-place rock crushing and subgrade stabilization pilot project on sections of Highway918-01. The objective of this project was to evaluate cold in-place rock crushing to reduce protruding boulders and toevaluate the feasibility of in-place modification/stabilization to stabilize sand subgrades. The construction of theHighway 918-01 test sections determined that in-place rock crushing with the CMI R/S 650 is technically feasible andprovides a workable surface free of large boulders. The addition of clay and calcium chloride and asphalt emulsion tothe uniform sand subgrade resulted in increased stability and reduce traffic dust. The construction costs for this pilotproject ranged from $13,684 for in-place rock crushing and a gravel wearing coarse to $52,017 for in-place rockcrushing, asphalt emulsion stabilization and a double seal wearing coarse.Based on the results of this study, further investigation of in-place rock crushing and sand stabilization shouldconsider:a) A roto mixer mandrel specifically designed for in-place rock crushing.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 18b) Stabilization designs should be based on fundamental subgrade soil behavior including physical andmechanical properties of alternative stabilization systems to quantify the performance related behavior ofthese systems.REFERENCES1. Safronetz, J., Berthelot, C., Sparks, G., and Gerbrandt, R. Alternative Maintenance Treatments forNorthern Saskatchewan Gravel Roads. Proc., Canadian Society of Civil Engineers, pp. 449-458, Regina,June 1999.

Berthelot, Gerbrandt, Safronetz, and Sparks. Page: 19LIST OF FIGURESFIGURE 1 Highway 918-01 Typical Boulders In Grade and Along Road EdgeFIGURE 2 Highway 918-01 Typical Unstable Sand SubgradeFIGURE 3 Highway 918-01 in situ Subgrade Grain Size DistributionFIGURE 4 Standard and Modified Proctor Moisture-Density of SDHT Highway 918-01 SubgradeFIGURE 5 SDHT Hwy 918-01 in situ Rock Unconfined Compressive Strength MeasurementsFIGURE 6 Marshall Stability of SDHT Highway 918-01 Stabilized SystemsFIGURE 7 Primary Rock CrushingFIGURE 8 Windrowing and Separating Crushed RocksFIGURE 9 Clay ModificationFIGURE 10 Asphalt Emulsion StabilizationFIGURE 11 Final Shaping and Compaction of GradeFIGURE 12 Typical Final GradeFIGURE 13 Typical Gravel Wearing CoarseFIGURE 14 Typical Asphalt Emulsion Stabilized Wearing CoarseFIGURE 15 Highway 918-01 Test Section Construction Cost per Kilometer by Cost TypeFIGURE 16 Mean Total Construction Cost per Kilometer Grouped by Test Section TypeLIST OF TABLESTABLE 1 Highway 918-01 in situ Rock Unconfined Compressive Strength MeasurementsTABLE 2 Highway 918-01 Test SectionsTABLE 3 Highway 918-01 Subgrade Marshall Stability Across Stabilizer Types and ConcentrationsTABLE 4 Highway 918-01 Test Section Construction Cost Per Kilometer by Cost Type