Quantifying the benefits of improved rolling of chip seals : final report - Page 117 |
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106 3.8 2.6 2.4 2.1 3.4 0.0 1.0 2.0 3.0 4.0 5.0 Aggregate Loss (%) Delayed Rolling Time ( min.) 2.0 3.5 5.0 7.5 10.0 Figure 7- 11 Aggregate loss results as a function of delayed rolling time using dry aggregate ( 0% water content) The percentage of aggregate loss using unwashed dry aggregate represented in Figure 7- 11 is calculated using the weight of the aggregate and using Equation ( 2). The large empty circle symbols indicate the average aggregate loss of the three replicates for each delayed rolling time. The MMLS3 test results in Figure 7- 11 show a significant trend in the amount of aggregate loss according to the five delayed rolling times ( 2.0, 3.5, 5.0, 7.5, and 10 min.). Contrary to normal expectations, the worst aggregate retention performance among the various delayed rolling times occurred when the compaction was conducted with a 2 min. delayed rolling time after the aggregate was spread. This result may be due to the water in the emulsion that is comprised of binder and water. The aggregate in the emulsion is wet with water from the emulsion because water is more forcefully attracted to aggregate when the aggregate is spread on the emulsion film. This water between the aggregate and binder eventually evaporates, but nonetheless leaves a weaker zone at the interface. If the newly constructed chip seal pavement is subjected to rolling too early, a greater surface area of aggregate is exposed to water and, therefore, the chip seal contains a greater area of weak interface due to poor adhesion between aggregate and binder. On the other hand, if the initial rolling is delayed too much, the emulsion
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Title | Quantifying the benefits of improved rolling of chip seals : final report - Page 117 |
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Full Text | 106 3.8 2.6 2.4 2.1 3.4 0.0 1.0 2.0 3.0 4.0 5.0 Aggregate Loss (%) Delayed Rolling Time ( min.) 2.0 3.5 5.0 7.5 10.0 Figure 7- 11 Aggregate loss results as a function of delayed rolling time using dry aggregate ( 0% water content) The percentage of aggregate loss using unwashed dry aggregate represented in Figure 7- 11 is calculated using the weight of the aggregate and using Equation ( 2). The large empty circle symbols indicate the average aggregate loss of the three replicates for each delayed rolling time. The MMLS3 test results in Figure 7- 11 show a significant trend in the amount of aggregate loss according to the five delayed rolling times ( 2.0, 3.5, 5.0, 7.5, and 10 min.). Contrary to normal expectations, the worst aggregate retention performance among the various delayed rolling times occurred when the compaction was conducted with a 2 min. delayed rolling time after the aggregate was spread. This result may be due to the water in the emulsion that is comprised of binder and water. The aggregate in the emulsion is wet with water from the emulsion because water is more forcefully attracted to aggregate when the aggregate is spread on the emulsion film. This water between the aggregate and binder eventually evaporates, but nonetheless leaves a weaker zone at the interface. If the newly constructed chip seal pavement is subjected to rolling too early, a greater surface area of aggregate is exposed to water and, therefore, the chip seal contains a greater area of weak interface due to poor adhesion between aggregate and binder. On the other hand, if the initial rolling is delayed too much, the emulsion |