Compaction Research: Frequency, Amplitude and Speed QEDQ9874

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Testing was done on five different layers. Therewere four layer thicknesses, ranging from 100 mm(4'') down to 25 mm (1''). Two mix designs withdifferent aggregate sizes were used.One of the most important factors to considerwhen trying to understand compaction issues isthe thickness to aggregate size ratio. In this case,we tested this ratio from about 5:1 all the waydown to 2:1.When the ratio is high, like 5:1, it is usuallypossible to use high force associated with highamplitude and not be too concerned aboutdamaging aggregates. When the ratio is low, like2:1, normally high amplitude is not usable.Thinner lifts with lower thickness to aggregatesize ratios are very challenging, often almostuncompactable.The controlled compaction testing was done in aCaterpillar Dealer’s yard. A parking lot, severallayers thick, was constructed. Each layer includedseveral test “cells”, each cell with a different set ofcontrolled test conditions.The markings on the mat indicate where nucleardensity measurements were made. Each one ofthese indicates a different test cell.The site was constructed using a high traffic volumehighway mix even though it was a parking lot.6
The test was devised to simulate highway pavingconditions.The trucks delivered only enough material to buildone or two cells at a time. The mix temperatureand laydown procedures were the same for eachtest cell to minimize the variables that affectdensity.As each test cell was paved, the compactorsoperated side-by-side to the same position behindthe paver. The compactors were timed so they wereoperating just as they would on a highway job.This bar chart shows the results of all amplitudetesting. The tested amplitudes, expressed in inches,are shown on the bottom and range from the loweston the left end of the chart up to the highestamplitude on the right end. The bars show theaverage density and maximum density reading,expressed in pounds per cubic foot (pcf), for eachamplitude.The unmistakable trend in this chart is higherdensities result from higher amplitudes. Whetherlooking at average density for each amplitude ormaximum density achieved by any machine at agiven amplitude, the general result is the same.Density increases with amplitude.7
Page 1: Compaction Research:Frequency, Ampl
Page 4 and 5: One on-the-job research project too
Page 8 and 9: The next on-the-job research projec
Page 10 and 11: Four models were tested, resulting
Page 12 and 13: This turned out to be “one of tho
Page 14 and 15: When the data are arranged in a bar
Page 16 and 17: In conclusion, the research project
Page 18 and 19: Notes18
Page 20: QEDQ9874 (07/01)© 2001 Caterpillar

Compaction Research: Frequency, Amplitude and Speed QEDQ9874

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