Environmentally Sensitive Maintenance for Dirt & Gravel trails TRAIL MIX. TRAIL MIX: aggregate for trails

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1 TRAIL MIX: aggregate for trails Environmentally Sensitive Maintenance for Dirt & Gravel trails Penn State University: Center for Dirt and Gravel Road Studies Dave Shearer TRAIL MIX TRAIL AGGREGATE Penn State s Center for Dirt and Gravel Roads has developed a mixture of aggregate specifically designed for surfacing trails. Driving Surface Aggregate TRAIL MIX stems from the Center s development of DSA in the late 1990 s to address Municipal concerns with existing aggregates. TRAIL MIX How is Trail Mix different? Material Gradation 98% stone (no soil or clay added) Specification Other Considerations: Moisture ph Hardness Original Trail Mix Specification Was difficult for quarries to produce f Old Trail Mix -To much large stone -To difficult for quarries to produce Passing Sieve Lower % Higher % 1 inch By weight: 65% #67aggregate 35% #10 aggregate 3 /4 inch 3 /8 inch #4 #8 # #

2 Re-designing trail mix Class Project by PSU engineering students to come up with a RECIPE for trail mix. - Use readily available stone specifications. - Achieve maximum compacted density. Re-designing trail mix Class Project by PSU engineering students to come up with a RECIPE for trail mix. - Use readily available stone specifications. - Achieve maximum compacted density. Instructions: Add water and mix well 4 parts unwashed AASHTO #10 (or B3 sand) 4 parts AASHTO # 8 1 part -#200 fines (collector fines) Re-designing trail mix Lab Testing d f Old Trail Mix New Trail Mix Rock FINES are the glue that holds it together! 98% of the Fines in DSA must be crushed rock! Crushed rock fines from other sources that meet standards can be added. Limestone fines can be added to sandstone aggregate (and reverse). Fines can be made up of Lime/Cement Kiln Dust. 2

3 Re-designing trail mix Trail Mix RECIPE 1 part -#200 fines (collector fines) Instructions: Add water and mix well 4 parts unwashed AASHTO #10 (or B3 sand) 4 parts AASHTO # 8 1 part - #200 fines (collector fines) 4 parts AASHTO #10 (or B3 sand) 4 parts AASHTO # 8 Instructions: Add water and mix well 4 parts unwashed AASHTO #10 (or B3 sand) 4 parts AASHTO # 8 1 part -#200 fines (collector fines) TRAIL MIX other considerations Hardness LA abrasion of less than 40% LA abrasion test -Aggregate is placed in steel drum with steel spheres and rotated a set number of times. - results are expressed as % loss, Lower meaning less aggregate was crushed 3

4 TRAIL MIX other considerations OPTIMUM MOISTURE Trail mix is to be delivered and placed at optimum moisture Optimum Moisture is essential for: - Reducing segregation by size - Proper compaction Optimum moisture percentage should be defined by the supplier in purchasing documents. Get a proctor analysis. compaction 0 TOO DRY JUST RIGHT moisture TOO WET TRAIL MIX other considerations OPTIMUM MOISTURE Trail mix is to be delivered and placed at optimum moisture TRAIL MIX - placement PLACEMENT - Prepare base: shape of base will be reflected on surface - Allow for crown or side slope IN BASE TRAIL MIX - placement PLACEMENT - Prepare base: shape of base will be reflected on surface - Allow for crown or side slope IN BASE - Place aggregate with paver (or box spreader) - Place in one layer 3-4 thick TRAIL MIX - placement - Place aggregate with paver when possible - Place in one layer 3-4 thick TRAIL MIX - placement PLACEMENT - Prepare base: shape of base will be reflected on surface - Allow for crown or side slope IN BASE - Place aggregate with paver - Place in one layer 3-4 thick - Compact with roller 4

5 TRAIL MIX - placement - Compact with minimum 4 ton vibratory roller Aggregate Gradation Proctor Analysis Aggregate Delivered Max Dry Density lbs/sqft Optimum Moisture 7.7% 5

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7 Density Testing Density Testing Max Dry Density lbs/sqft Optimum Moisture 7.7% Max Dry Density lbs/sqft Optimum Moisture 7.7% 7

8 2) 3) In On 4x4 s surface 8

9 resources - dsa TRAIL MIX: aggregate for trails Introduction Base & Drainage TRAIL MIX Development Gradation Other Considerations TRAIL MIX: aggregate for trails Environmentally Sensitive Maintenance for Dirt & Gravel trails Penn State University: Center for Dirt and Gravel Road Studies Dave Shearer drs32@psu.edu 9