Nov 28, 2022
Set Constant Temperatures for Paving QC/QA
There are some temperatures you will want to attain, and some you will want to avoid, to get a bonus-worthy mat. Of course, each temperature you consider depends on a host of variables. In the old days, contractors were advised to lay asphalt when ambient temperatures were 48 degrees F and rising. With the advent of warm-mix asphalt (WMA) designs, cooler ambient temperatures are not as detrimental to success as they once were. Let’s look at the constants.
When you heat the screed at the beginning of the shift, you typically want it to reach 300 degrees F to match the arriving mix temperature. Use a temperature gun to check at least three points across the full width of the screed plates so you know the screed is heating evenly and none of the elements are malfunctioning.
Here’s a moving constant for you. The temperature of the mix coming from the plant should not vary more than 20 or 25 degrees from truck to truck. Use a stick thermometer to determine exact temperature of the delivered mix. The best hole in the truck bed to use for this is the one that is two-thirds of the way from the back because it will measure the temperature from the second drop during loadout. (Here’s an article about the three-drop method.)
If the second truck to the job measures 260 degrees F, then you want to see each truckload after that measuring no less than 235 degrees F. (Remember that the first truck on the job is probably delivering mix that was waiting in the silo cone, and it may be 10 to 20 degrees lower than the temperatures you’ll expect from the subsequent trucks.)
If there’s a sudden difference beyond 20 to 25 degrees, find out what that specific truck driver did differently during his route. If the truth is “nothing different,” then call the plant operator to find out what’s going on.
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