Hand Mix Demonstration

#Paragon Technical Services Hand Mix Demonstration March 27, 2017 Paragon Technical Services is a state-of-the-art laboratory that provides product development, testing and mix design services for #Ergon Asphalt & Emulsions and third parties. ### The following are tools you will need to conduct a hand mix test: a scale, spatula and mixing bowl, cement and water, emulsion, felt paper or paper towels, a timer and a worksheet to record your mixture composition. Recording your mixture composition is important to the next steps in the hand mix process and ultimately to achieving consistency in your mix. Step 1: Determine the moisture content of your aggregate. All determinations made are based on dry aggregate. Knowing the moisture content of the initial batch of aggregate is important because it will help you determine how much extra aggregate is needed in order to account for that moisture. The goal is to have 100% dry aggregate. In order to determine moisture content, you must first record the initial waiting grams of your aggregate. Then, refer to the AASHTO T225 test method for calculating moisture content and record your calculation. Step two: Add aggregate. Aggregate is added to account for moisture content. Again, the goal is to have 100% dry aggregate. Once you have the moisture content percentage, use the following formula to determine the amount of aggregate to add into the mix. (Initial weight in grams/100) – (moisture content % number) / 100. Step 3: Add Portland cement. Refer to your mixed design for the proper amount of cement to add to your mix. For example, when the cement content is one percent, it means that for every 100 grams of aggregate you would add one gram of cement. Make sure the cement is mixed in and evenly distributed. Step 4: Add water. When adding water to achieve optimum water content, you want to take into account the initial moisture that was already in the aggregate. Note: Optimum water content of the mix includes both the initial moisture content of the aggregate and the added water. Refer to your mixed design for the proper amount of water to add to the mix. As you are mixing, the wet aggregate should start to stick to the sides of the mixing container. Step 5: Add emulsion and start your timer. The proper amount of emulsion to add into the mix is outlined in your mix design. Note: the amount will always stay the same and is not subject to change like the moisture content. Start your timer immediately after adding the emulsion and begin mixing. Mix for 30 seconds until uniform and pour a small sample onto felt paper, about half of the mixture. This will be used to determine how much time the contractor will have to work with the emulsion. When mixing you should achieve a consistency similar to a good brownie mix. Just remember don't eat it. As you are mixing, you are looking to record three specific times: mix time, break time and work time. Mix time is how long it takes the mix to break and start to clump up and stack onto more mix without going back to a uniform state. Once mixed time is achieved, record time and continue mixing. Break time is the time it takes before the mix begins to come apart or crumble. Record time if you reach 300 seconds; you may also stop mixing and note the time as 300 plus. Work time is how much time the contractor has to work with the emulsion before it begins to break. Recording work time is highly important for projects where contractors have to repair drag marks and move material around. Work time is determined using the sample previously poured onto felt paper. Make a line through the mix sample and repair it, repeating this step every 15 to 20 seconds until it can no longer be repaired without damage. Once the mix starts to get gravelly on top, you are at the end of your work time. Record time. Always make sure mix time, break time and work time fall within the proper ranges of the established guidelines.