To create a road, one needs tons of rock mixed with just the right amount of tar. It's put down and rolled out. Seems simple, right?
The science of making a road and making it last is actually a complicated process.
Two tests on the density of the asphalt are done for every half-mile. One sample is tested before it is put down, and one after it has been compacted.
"They have a specification on the particular asphalt they have designed and you need to be within that range," says Ali Regimand, a nuclear engineer who studied at N.C. State. "If you're outside that range, you might have to make modifications to your material."
Testing the density of the asphalt is so important because if it is not right, it will not be long before tires start to wear ruts in the road or the pavement simply begins to crack.
The problem in testing the asphalt density is not easy, and it is time-consuming.
Regimand invented a way to make the testing easier and more reliable. It is called Corelok.
A vacuum pump takes all the air out of the sample so the weight of the air is not included in the weight of the asphalt. The machine makes the test more accurate.
"The more involvement an operator has in a test, the bigger the error," Regimand says. "This takes some of the error away."
The real breakthrough with Regimand's machine is how much time it saves. A test that once took 2-1/2 hours in a lab now takes less than five minutes. Crews can work faster, and the asphalt will last longer, saving money down the road.
"I think for any engineer that goes to school, the goal is what can you do to pay back what you've learned," Regimand says. "I think this is a great thing for me to see that they're using the device, and the device is helping them get the results that they want."
Ali Regimand has sold 100 machines to agencies in 15 states at a price of $4,000. North Carolina is still evaluating the machine. Here is the difference in how the asphalt has changed. It used to be smooth but now it's made up of bigger rocks so it can handle the load of more cars and trucks But these bigger pieces make it more difficult to get the air out of the sample because there are more places for the air to hide in the knooks and crannies. Two tests are taken one before the asphalt leaves the truck and then another like this a core sample taken after the rollers have put it down. To get the density, you measure the sample on a scale, then put it in water and get another weight. That's why if you have air in the sample, it will throw the results off. -->