Asphalt quality control

The life of a lab tester is a busy one . My job is to make sure the customer gets what they pay for in the asphalt game.

My morning starts out by testing the recycled asphalt product or (RAP) first I split it into a manageable sample then I let it dry in the oven , drying it will take any residual moisture out of the sample .

After drying the RAP it will be placed in an ignition furnace for the oil to be burned out of it . The difference between the starting weight and the dry weight will determine the oil content contained in the recycled product .

After the burn is completed I will weigh the product and then wash the bottom ends out of it "bottom ends is anything smaller than 80 microns" . After the bottom ends are washed out of the sample then it's time to determine the gradation " gradation is the weigh of every size of aggregate in the sample"

When a new asphalt project is scheduled the government decides how much recycled product can be used in the new "mix" the percentage of recycled product allowed to be used is based on the specifications of the new "mix design" in the case of the calagry ring road that amount has been determined to be 20% recycled asphalt . Here is what some crushed rap looks like .

After the RAP is dried of all all residual moisture it is then placed into a "burn basket" to be placed into the ignition oven mentioned earlier . Here is a picture of said basket .

The rap is then place into the burn basket and sent into the furnace to be burned . The ignition oven is a blistering 560° Celsius. The mix itself will ignite around 480° Celsius. So gloves and a faces held must be used in order to maintain safety standards.
Here is a picture of said ignition furnace.

When testing a sample we must also "pound a marshall" a Marshall is basically puck but quite a bit larger , 1225 grams give of take a few , the hot mix is loaded into a mould and struck a certain amount of times with a "Marshall hammer " the puck is then weighed dry and in water to determine the density of the mix . Here is a picture of a Marshall hammer and a puck .

The Marshall hammer has a specific weight and drop height to make sure the pucks are all hit with the same amount of force .

The Marshall is the true density of the particular sample . Now let's move onto the "MTD" MTD stands for "maximum theoretical density" in this test a loose sample of mix is placed into a bucket of water in which a vacuum pump sucks out all the air from said sample , and is then weighed in water to find the maximum density that can be achieved by the mix .

All of these test combined tell us what the oil content on the mix is , the density of the mix , the maximum density in absence of air , the gradation of the aggregates, and the air voids within the finished product . This senerìo is repeated throughout the building of a road by tonnage , 1 test for every 500 tons of mix laid .

The government really appreciates this process as it tells them if they are getting what they pay for . On the other side of the coin the company I work for really appreciates this process too , because we can then try to use the minimum amount of new oil that goes into the mix , saving the company tons of money .

Thank you for tuning into this post and if you have any questions or comments feel free to ask or post .