Article 1 — Description
Compact embankment, subgrade, base, surface treatments, broken concrete pavement, or asphalt pavement using rollers. Break up asphalt mats, pit run material, or base materials.
Article 2 — Equipment
Use any type of roller to meet the production rates and quality requirements of the Contract unless otherwise shown on the plans or directed. Use equipment that meets the requirements of this Item when specific types of equipment are required. The Engineer may allow the use of rollers that operate in one direction only when turning does not affect the quality of work or encroach on traffic. Table 1 Roller Requirements1 Roller Type Materials to be Compacted Load (ton) Contact Pressure Roller Speed (mph) Steel wheel Embankment, subgrade, base, asphalt concrete ≥10 ≥325 lb. per inch of wheel width 2–3 Tamping Embankment, subgrade – 125–550 psi per tamping foot 2–3 Heavy tamping Embankment, subgrade – ≥550 psi per tamping foot 2–3 Vibratory Embankment, subgrade, base, asphalt concrete Type A < 6 Type B > 6 Type C as shown on the plans Per equipment specification and as approved As approved Light pneumatic Embankment, subgrade, surface treatment 4.5–9.0 ≥45 psi 2–6 Asphalt c oncrete 4–12 Medium pneumatic Embankment, subgrade, base, surface treatment 12–25 ≥80 psi, as directed 2–6 Asphalt c oncrete 4–12 Heavy pneumatic Embankment, subgrade, base, previously broken concrete pavement, other pavements ≥25 ≤150 psi 2–6 Grid Embankment, breaking up existing asphalt mats or base 5–13 – 2–3 1. Unless otherwise specified in the Contract.
2.1 Static Steel Wheel Rollers. Furnish single, double, or triple steel wheel, self -propelled power rollers
weighing at least 10 ton capable of operating in a forward and backward motion. Ensure all wheels are flat. The Contractor may use vibratory rollers in the static mode when static steel wheel rollers are required. 161 For single st eel wheel rollers, pneumatic rear wheels are allowed for embankment, subgrade, and base. Provide rear wheels for triple steel wheel rollers with a minimum diameter of 48 in., a minimum width of 20 in., and a minimum compression of 325 lb. per inch of wheel width.
2.2 Tamping Rollers . Furnish self -propelled rollers with at least one self -cleaning metal tamping drum capable
of operating in a forward or backward motion with a minimum effective rolling width of 5 ft. Mount drums in a frame so that each drum moves i ndependently of the other for rollers with more than one drum. Operate rollers in static or vibratory mode.
2.2.1 Tamping Roller (Minimum Requirement) . Provide tamping feet that exert a static load of 125– 550 psi and
project at least 3 in. from the surface of the drum for all tamping rollers except for heavy tamping rollers.
2.2.2 Heavy Tamping Roller . Provide tamping rollers that have:
two metal tamping drums, rolls, or shells, each with a 60- in. minimum diameter and a 5- ft. minimum width ; or one rear and two forward drums, each with a 60- in. minimum diameter. Arrange drums so that the rear drum compacts the space between the two forward drums and the minimum overall rolling width is 10 ft. Equip drums with tamping feet that: project at least 7 in. from the drum surfac e, have an area of 7– 21 sq. in., are self -cleaning, exert a static load of at least 550 psi, and are spaced at 1 tamping foot per 0.65– 0.70 sq. ft. of drum area.
2.3 Vibratory Rollers . Furnish self -propelled rollers with at least one drum equipped to vibrate. Select and
maintain amplitude and frequency settings per manufacturer’s specifications to deliver maximum compaction without material displacement or shoving, as approved. Furnish the equipment manufacturer’s specifications concerning settings and controls for amplitude and frequency. Operate rollers at speeds that will produce at least 10 blows per foot unless otherwise shown on the plans or approved. Pneumatic rear wheels are allowed for embankment, subgrade, and base. Equip each vibrating drum with: separate frequency and amplitude controls, controls to manually start and stop vibration, and a mechanism to continuously clean the face of the drum. For asphalt -stabilized base and asphalt concrete pavement, furnish a roller that also can : automatically reverse the direction of the rotating eccentric weight, stop vibration before the motion of the roller stops, and thoroughly moisten the drum with water or approved asphalt release agent.
2.3.1 Drum (Type A). Furnish a roller with a static weight less than 6 ton and a vibratory drum.
2.3.2 Drum (Type B). Furnish a roller with a minimum static weight of 6 ton and a vibratory drum.
2.3.3 Drum (Type C). Furnish a roller as s hown on the plans.
2.4 Pneumatic Tire Rollers. Pneumatic tire rollers consist of rubber tire wheels on axles mounted in a frame
with either a loading platform or body suitable for ballast loading. Arrange the rear tires to cover the gaps between adjacent tires of the forward group. Furnish rollers capable of forward and backward motion. Compact asphalt pavements and surface treatments using a roller equipped with smooth- tread tires. Compact without damaging the surface. Moisten the wheels with water or an approved asphalt release agent when necessary. 162 Select and maintain the operating load and tire air pressure within the range of the manufacturer’s charts or tabulations to attain maximum compaction throughout the lift, as approved. Furnish the manufacturer’s chart or tabulations showing the contact areas and contact pressures for the full range of tire inflation pressures and for the full range of loadings for the tires furnished. Maintain individual tire inflation pressures within 5 psi of each other. Provide uniform compression under all tires.
2.4.1 Light Pneumatic Tire . Furnish a unit:
with at least nine pneumatic tires, with an effective rolling width of approximately 5 ft., capable of providing a total uniform load of 4.5–9 ton, and with tires capable of maintaining a minimum ground contact pressure of 45 psi.
2.4.2 Medium Pneumatic Tire . Furnish a unit:
with at least seven pneumatic tires, with an effective rolling width of approximately 7 ft., capable of providing a total uniform load of 12– 25 ton, and with tires capable of maintaining a minimum ground contact pressure of 80 psi or 90 psi as directed.
2.4.3 Heavy Pneumatic Tire. Furnish a unit:
with at least four pneumatic -tired wheels mounted on axles carrying no more than two wheels, with wheels arranged to carry approximately equal loads on uneven surfaces, with a width between 8 and 10 ft. that can turn 180 ° in the crown width, capable of providing a total uniform load of at least 25 ton, with tires capable of maintaining a maximum ground contact pressure of 150 psi, and with liquid -filled tires inflated to such a level that liquid will flow from the valve stem when the stem is in the uppermost position.
2.5 Grid Rollers . Furnish rollers that have two cylindrical cages with a minimum diameter of 66 in. and a
minimum width of 32 in. Mount cages in a rigid frame with weight boxes. Use a cage surface of cast or welded steel fabric grid with bars 1- 1/2 in. wide, spaced on 5- in. centers in each direction, that undulate approximately 1 in. between the high and low points. Furnish rollers capable of providing a total load of 5– 13 ton and capable of being operated in a forward or backward motion.
2.6 Alternate Equipment . The Contractor may use alternate compaction equipment that produces results
equivalent to the specified equipment as approved. Discontinue the use of the alternate equipment and furnish the specified equipment if the desired results are not achieved.
Article 3 — Construction
Perform this work in conformance with the applicable Items using equipment and roller speeds shown in Table 1. Use only rubber -tired equipment to push or pull compaction equipment on base courses. Use equipment that does not damage material being rolled.
Article 4 — Measurement and Payment
The work performed, materials furnished, equipment, labor, tools, and incidentals will not be measured or paid for directly , but will be subsidiary to pertinent Items.