| 4000 vpm vibratory rollers for Superpave mix!! | |
| Two 4000 vpm double drum vibratory rollers with
67" (1.7m) and 79" (2.0m) wide drums, respectively, have been
developed by SAKAI for Superpave mix. Efficien compaction perfomance will
be achieved before the mix temperature drops below 240°F (115°C)
using these rollers. The high frequency of the vibration raises the
per-hour density of the mix increasing roller productivity through faster
rolling speed and/or the greater number of impacts per foot traveled.
The 4000 vpm roller will finish compaction before the mix drops into the
tender zone, i.e. the temperature range of 200°F–245°F (93°C–118°C).
Sometimes, it may be difficult to achieve density with the high frequency
roller alone since the Superpave mix is complex and its characteristics
may very widely. In another situations, a pneumatic tire roller may be
appropriate,such as described below. Thesting of a 4000 vpm vibratory roller was carried out in Japan bu the SAKAI research team in the summer of 1998. The prototype of a vibratory roller used for this test had a weight of 9.4ton (8.5 metric tons), a drum width of 67" (1.7m) and a diameter of 51" (1.3m). The roller's operating variables, rolling speed, frequency, nominal amplitude of vibration and number of passes were varied to evaluate the mix under various impact spacing.*2 Three test strips were paved and compacted with the roller,each strip being of a different type of mix.The first two strips were Superpave mixes with respective maximum aggregate size of 1/2"and3/4"and the third was SMA(Stone Matrix Asphalt).The resulting physical properties such as density,shear stress,skid resistance and riding quality of each compacted mix were then measured. |
| Frequency of Vibration | Speed of a roller in mph & in (km/h) | |||||||||
| 1.0 (1.6) |
1.5 (2.4) |
2.0 (3.2) |
2.5 (4.0) |
3.0 (4.8) |
3.5 (5.6) |
4.0 (6.4) |
4.5 (7.2) |
5.0 (8.0) |
||
| vpm | Hz | |||||||||
| 4000 | 67 | 45.5 | 30.3 | 22.8 | 18.2 | 15.2 | 13.0 | 11.4 | 10.1 | 9.1 |
| 3200 | 53 | 36.4 | 24.2 | 18.2 | 14.5 | 12.1 | 10.4 | 9.1 | 8.1 | 7.3 |
| 2400 | 40 | 27.2 | 18.2 | 13.6 | 10.9 | 9.1 | 7.8 | 6.8 | 6.1 | 5.4 |
| IMPACT SPACING | |
| The impact spacing,which is one of the indexes for compactive efforts given by the vibratory roller to the mix,is shown in Table 1. It has been suggested recently that impact spacing should exist ideally in the range of 10 to 12 impacts/ft. |
| TEST RESULTS | |
| An example of the relationship between
the degree of compaction (the ratio of the density to the theoretical
density) and inpact spacing is shown is Fig.1. The density increases to
the macimum, then decreases with an increase in impact spacing. The test
results show that the same of similar density was obtained under the same
impact spacing. For more information, please contact SAKAI. |
 |
| ROLLER PATTERN | |
| A suggested roller pattern to cover the lane width by two rollers is shown in Fig.2.Each roller,having a drum width of 67" (1.7m)or 79"(2.0m),makes three passes across the width of a 12 ft.lane in order to cover the lane width.When the first roller starts to roll from the left side of the mat,it goes and returns 2 times.Then it goes and returns once in the middle lane.The roller then returns to the left lane to travel forward.Another roller passes 4 times on the right side,then 2 times in the middle lanes, and returns to the right lane to the travel forward. |  |
| THE ULTIMATE IN ROLLER TRAINS | |||
| Both the SW800(67"-1.7m)and the SW850(79"-2.0m)have the largest drum diameters in their drum width category and they will give the best compaction performance and layer smoothness without shoving or checking. | |||
SW800
|
and/or | SW850
|
x2 UNITS |
| Drum:51" dia. x 67" wide, 4000vpm, (1.3m x 1.7m) |
Drum:55" dia. x 79" wide, 4000vpm, (1.4m x 2.0m) |
||
| ROLLER TRAINS AS ALTERNATIVE COMPACTION1 | ||||
| The following ROLLER TRAINS will help to achieve the required density,if the density is not obtained with the 4000 vpm roller alone.The suggested specifications of a tire roller are;tire pressure should be 80 to 90 psi(5.6–6.3 kg/cm2)or greater,and the wheel load shall be a minimum of 2,800 to 4,500 lbs.(1,270–2,042 kg)*1. Both of these requirements are satisfied by the TZ600.If the tires pick-up asphalt,see the release agent described later.A static steel roller,R2H, with a maximum linear pressure of 355 lbs/inch(63 kg/cm)and diameter of 64"(1.6m)will achieve compaction and layer smoothness without shoving or checking.The R2H is especially effective for pavement temperatures below the tender zone. | ||||
|
SW800 or SW850
 Drum:51"dia. x 67" wide, (1.3m x 1.7m) Drum:55"dia. x 79" wide, (1.4m x 2.0m) |
 |
TZ600
 Tire press.:36 - 85 psi(6kg/cm2) (2.5 - 6.0 kg/cm2) Wheel load.:3,860 - 4,730 lb (1,215 - 2,115 kg) |
|
SW800 or SW850
|
|
SW800 or SW850
Drum:51"dia. x 67" wide, (1.3m x 1.7m) Drum:55"dia. x 79" wide, (1.4m x 2.0m) |
|
TZ600
Tire press.:36 - 85 psi(6kg/cm2) (2.5 - 6.0 kg/cm2) Wheel load.:3,860 - 4,730 lb (1,215 - 2,115 kg) |
|
R2
 Drum:64"dia. x 83" compaction width (1.62m x 2.1m) Linear press:260 - 355 lbs/in. (46 - 63 kg/cm) |
| OUR UNIQUE VIBRATION SYSTEM | |
| Whether the rotation of the eccentric weight should hit the mat in the same direction as the roller travels(Fig.3)has been a controversial issue among roller manufacturers.It could be considered that the resultant vector of the eccentric forces in the two drums takes one circular,doubled path and this periodically gives a circular motion to the machine.This motion may affect the compaction of the mix and the operator's riding comfort. | |
 |
 |
| Our unique vibrating system has been incorporated into a series of double drum vibratory rollers.Each of eccentric weight inside the front and rear drums rotates opposite one another,and the centrifugal forces act on the mat simultaneously.The horizontal components of the forces in the two drums are cancelled as shown in Fig.4.This results in higher compaction performance,the elimination of shoving and checking,and in a reduction of unpleasant noise and harmful vibration to the operator and surrounding area. | |
 |
 |
| THE VERTICAL VIBRATING SYSTEM or VVS is realized more precisely as shown in Fig.5.The synchronized eccentric weights inside the drum rotate in opposite directions,thereby producing the vertical centrifugal force,which acts on the mat. | |
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|
| ASPHALT RELEASE AGENT FOR RUBBER TIRES | |
| With the aid of"NEPPARAN",compaction using tire rollers can be completed on schedule. The roller may pick up asphalt,if the machine begins rolling at a temperature higher than the critical range and/or if modifiers are used in the mix. NEPPARAN will help a rubber-tire roller to roll without waiting for the mix to cool down.There are two options; one is a water dilution(emulsion)type named NEPPARAN-W.Put one 4.7 gallon can of NEPPARAN-W into the water tank of the TZ600(a pneumatic rubber-tire roller),which has a 925 gallon (3,500 litter)capacity.Allow the NEPPARAN-W to mix with the water(dilution ratio,1:200)by forced self- circulation of the water in the tank.Spray it during rolling through the water spray nozzles patented by SAKAI. Another is a non-dilution type named NEPPARAN-S. NEPPARAN-S is easier to use.Fill an extra tank (liquid tank)with it and push the switch marked cLIQUID SPRAYc,as required.This is why both the water and liquid spray systems are equipped for SAKAI TZ600 or TW type combination. NEPPARAN's ingredients do not affect the asphalt mix or the rubber-tires,and are safe for both the operator and the environment. |
| REFERENCES | |
| *1 NAPA,FHWA,Superpave Construction Guidelines,A Report
Developed from NAPA/FHWA Sponsored Colloquium,p.14,1997. *2 US Army Corps of Engineers,HOT/MIX ASPHALT PAVING HAND BOOK,pp.3-80 |
Copyright(c)2000 SAKAI HEAVY INDUSTRIES, LTD.All Rights Reserved.
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