Understanding IC | Intelligent Compaction Improves Efficiencies
Intelligent compaction has been used in Europe for more than 20 years. Now, IC rollers are finally being used more widely in the United States. Interestingly, it’s not contractors but state regulators that are driving the increased use of IC. About half the states now spec IC machines for soil and/or asphalt projects. Those who want to bid have to acquire the machines.
Specifications can vary widely from state to state, in terms of detail. But they usually require at least that:
- Rollers have capability to monitor and assess compaction in real time.
- A satellite-based positioning system is incorporated to show mapping of pass counts and compaction levels. For asphalt work, temperature must be mapped, too.
- The operator be able to see data on a color-coded monitor while working.
- Data be retained for use in reporting and analysis.
For work in areas where satellite reception is a challenge – cities with tall buildings, for instance – some IC rollers are equipped with total-station positioning that enables the technology to work.
Does intelligent compaction really improve efficiencies?
Consider the results of this trial:
- An experienced operator was asked to use an IC-outfitted machine on a highway paving project. The IC monitor was covered so the operator couldn’t see it. He covered 316,000 square feet in over 21 hours, making between 2 and 13 passes over each area.
- Then the monitor was uncovered, and the operator went back to work. He covered 380,000 square feet in just 18 hours. The paver stopped once for the roller to catch up, whereas it had to go through this process four times when the monitor wasn’t visible.
So why the big differences? The operator could more accurately gauge his progress using the monitor. He could pre-set the optimum number of passes for each area, and when he reached that number he could move on. This system promotes more consistent compaction of both asphalt and soil using continuous quality control. That eliminates the need for periodic nuclear-gauge readings or taking asphalt cores and then using that data to extrapolate across the entire area. Less time, no guesswork.
You can also use the system to proof-roll base materials. Finding and fixing weak spots before you start paving eliminates the need for rework, which wastes time and money.
What is intelligent compaction technology?
It runs the gamut, from basic meters with LED lights that show the degree of compaction to sophisticated integrated systems that recommend roller settings based on pre-set parameters. Some systems automatically adjust drum force, too, again based on pre-set targets.
Experts note there is a difference between intelligent compaction measurement value (ICMV) and density. ICMV measures load-bearing capacity – the material’s ability to resist deformation under load. Density measures the volume of air voids – the fewer, the better, because air pockets reduce uniformity. Density is often used by departments of transportation to assess job quality.
One downside to using ICMV as a job assessment tool on asphalt projects is that conditions must remain constant. ICMV for a specific job is determined by compacting (and validating) a test area that meets the target density for that project. The IC roller is run over that compacted area to produce the ICMV number. The ICMV is then correlated as well as possible with the density target for the project so that the operator can use the ICMV as a benchmark instead of density.
Problems arise if conditions during paving differ from conditions at the time of the test. Temperature, material lift thickness and the underlying base all have to be consistent to produce the desired, uniform result.
Looking into the future
IC-capable machines cost more, of course. Most manufacturers say they expect customers to keep a watchful eye on the development of intelligent technology to decide if the benefits outweigh the costs for their firms. Meanwhile the number of states incorporating intelligent compaction into their specs is likely to grow, so demand is likely to follow.