ENCI 5791 Compaction In-situ soils used as: –Bases for the construction of highway pavements –embankments or leveling material for construction projects Compacted to improve their density: M/V –improves the soil’s strength –lowers it’s permeability –reduces future settlement

ENCI 5792 Compaction Evaluation of density as a result of compactive efforts with rollers and other equipment –common quality control measurement on soils at construction sites –density of a compacted soil is measured and compared to a density goal previously determined in laboratory tests

ENCI 5793 Compaction Maximum Dry Density Maximum dry density must be established for each soil type –clay soil after compactive effort 2000 Kg/m3 –granular soil with no compactive effort may be well above this Dry density of a soil fn (water content)

ENCI 5794 Compaction Maximum Dry Density

ENCI 5795 Compaction Maximum Dry Density Compaction Control Determine the maximum dry density for a particular soil under a certain compactive effort and the water content at which this density is reached. M D /V

ENCI 5796 Compaction Maximum Dry Density

ENCI 5797 Compaction Maximum Dry Density Compaction Test –Moisture density test –Proctor test soil is compacted into 10 cm diameter mold for material passes 4.75 mm sieve (15 cm mold for coarser material) soil is placed in 3 layers each layer compacted 25 blows with a 2.5 Kg hammer dropping 30 cm ( 56 blows)

ENCI 5798 Compaction Maximum Dry Density 25 blow/56 blow compactive efforts are the same and represent the compactive efforts of 1930 construction rollers Compaction Test –sample of soil is mixed with water mass of compacted sample is measured water content determined –sample of soil is mixed with more water –repeated until density decreases

ENCI 5799 Compaction Maximum Dry Density Modified Compaction Test –Modified Moisture Density Test –Modified Proctor Test Increased loading on our pavements Increased compactive effort of equipment Revised test of higher compactive effort is now often used –4.5 Kg hammer, 45 cm drop, 5 layers –higher maximum dry density/lower w/c

ENCI Compaction Maximum Dry Density *Volume of standard mold is cm3 **Dry density = density/(1+w)

ENCI Compaction Maximum Dry Density Zero Air Voids (ZAV) Curve “the maximum theoretical density of a soil at various water contents” with no air left in the soil water mixture ZAV  D =  W 1/RD + W

ENCI 57912

ENCI Compaction Maximum Dry Density Maximum Dry Density of a soil is used in quality control Specification requires a certain % of maximum dry density at optimum water content found by the compaction test for that particular soil –Ensures density –Reduces the compactive effort

ENCI Compaction Maximum Dry Density

ENCI Compaction Maximum Dry Density

ENCI Compaction Maximum Dry Density Note: If the soil was below optimum water content it may be necessary to add water by spraying The most important factor required for successful compaction is having the correct water content

ENCI Compaction Field Density Tests Sampling Methods –sample of compacted material taken –dry mass of the soil taken is determined –volume originally occupied by the sample is measured –field dry density = dry mass/volume of sample Two sampling methods –balloon densometer –sand cone apparatus

ENCI Compaction Field Density Tests Balloon densometer –Dry mass of the soil is determined –Volume of the sample hole is found by forcing a liquid filled balloon into the test hole –A rubber membrane allows the fluid to fill all the cavities of the hole –The volume of fluid required is measured –density calculated –water content determined

ENCI Compaction Field Density Tests Sand Cone Apparatus –Dry mass of the soil is determined –Volume of the test hole is obtained from the mass of loose sand required to fill the hole –Sand is a uniform medium sand with a constant loose density – Volume=mass of sand / loose density of sand –density is calculated –water content determined

ENCI Compaction Maximum Dry Density Example 3-4 Sand-Cone Apparatus: A sand cone holds g. The loose density of the sand is g/cm 3 Field Test Results: Total weight of the soil639.5 g Dry weight of the soil547.9 g Initial weight of the sand-cone apparatus4527.8g final weight of the sand-cone apparatus g

ENCI Compaction Maximum Dry Density Calculations: Mass of the sand used4527.8g g = g Mass in test hole1303.9g-851.0g = g Volume of test hole g = cm g/cm 3 Field dry density 547.9g/316.7 cm 3 = g/ cm 3 Field water content = 16.7% 547.9

ENCI Compaction Field Density Tests Nuclear Moisture-Density Gauge –Results are available within minutes Increases equipment efficiency Know that your construction methods are correct –Gamma rays are emitted into the soil absorbed by the soil according to it’s density rays that pass through the soil are measured by a detector density is then calculated

ENCI Compaction Field Density Tests Nuclear Moisture-Density Gauge –Neutron radiation emitted into the soil neutrons loose energy when they collide with hydrogen atoms in the soil water detector measures the amount of moderated neutrons water content can be calculated –Direct transmission mode –Backscatter mode

ENCI Compaction Field Density Tests

ENCI Compaction Maximum Dry Density Corrected Maximum Dry Density –compaction test is usually done on materials finer than 4.75 mm –sample contains coarse grained sized particles gravel in a soil composed mainly of fine grains can be compacted to 90% of their theoretical maximum density assuming gravel RD=2.65

ENCI Compaction Maximum Dry Density Example Laboratory maximum density of a soil is 1900 kg/m 3. Specifications require 95% compaction. In the filed, dry density of the soil is found to be 1810kg/m 3. A visual check of the soil in the field indicates that it contains about 20% gravel sizes. (Scales can be used for a more accurate determination of the percentage of gravel.) Check for compaction.

ENCI Compaction Maximum Dry Density Corrected maximum dry density is: 0.80 x 1900kg/m x (90% x 2.65 x 1000kg/m 3 = 1520 kg/m kg/m 3 = 1997kg/m 3 Percent compaction is 1810/1997 = 90.6% and is not acceptable

ENCI Compaction Operation and Quality Control Highway components that require compaction: –Subgrade (15-30cm) in depth, provides the foundation for the pavement structure –Fill material used to bring the soil surface up to the subgrade level (15-30 cm compacted lifts) –Backfill material –Layers in granular material used in pavement –Asphalt layers at the surface

ENCI Compaction Compaction Equipment Compaction Equipment –Consists of various types of rollers and tamping equipment –self propelled –compacting wheels equipped to vibrate cycles/minute for most soils and granular materials –smooth steel drums –drums with pads or “feet” –rubber tires

ENCI Compaction Compaction Equipment Vibratory Smooth Drum Rollers –one steel drum and rubber tired drive wheels –two steel drums one of which is the driver –effective for gravel, sand, silt soils –granular base courses and asphalt mixtures – mass of the drum is between 2-15 tonnes –utilized in layers from meters in depth –usually require 3-5 passes to produce specified density

ENCI Compaction Compaction Equipment Vibratory Smooth Drum Rollers

ENCI Compaction Compaction Equipment Padded Wheel or “Sheep’s Foot” Rollers –pads on the rotating drum and may vibrate – effective in clay and silty clay soils –punching action breaks the clay’s bonds which resist rearrangement of the grain structure –pressure exerted by the pad kpa depending on the size of the roller –utilized in layers of cm in depth –usually require 3-5 passes to achieve density

ENCI Compaction Compaction Equipment Padded Wheel or “Sheep’s Foot” Rollers

ENCI Compaction Compaction Equipment Pneumatic Tire Rollers –2-12 rubber tires on each axle –individual tires wobble or weave or move lower than adjacent tires to improve the kneading action –effective in clay and granular soils and asphalt mixtures can be kneaded and compacted –effective depths for soils or base courses is up to 15 cm (larger units of tonnes 30 cm)

ENCI Compaction Compaction Equipment Pneumatic Tire Rollers

ENCI Compaction Compaction Equipment Smooth Drum Non-vibratory Rollers –used for finishing or sealing passes on soils and granular layers –final leveling passes on asphalt layers Vibrating Plates or Tampers –used for trench backfills –around structures where larger equipment can’t operate –larger tamping equipment is usually attached to excavators or other equipment

ENCI Compaction Quality Control Determine which materials are to be sampled and tested Frequency of the testing and type of tests to be performed on the material Transportation authorities usually have specifications outlining these criteria –Moisture Density 1/ soil type (or 5000 m subgrade) –Field Compaction 4/500 m of each layer Method Specification vs EPS Specifications