Madrid Engineering Group (MEG) is pleased to announce the acquisition of equipment for and expansion of test methods into the realm of Hot Mix Asphalt testing. The new equipment includes an NCAT Oven, Orbital Shaker, and a Bulk Density/Specific Gravity station. The acquisition allows MEG to perform Specific Gravity/Bulk Density measurements and to determine Asphaltic Content and Gradation of Hot Mix Asphalt (HMA) samples.

The purpose of the NCAT Oven is to burn away the asphalt or other binder in a paving mix to leave only the aggregate behind. The weights before and after the burn allow one to calculate the asphaltic content.

The NCAT oven is a highly specialized furnace designed by the National Center for Asphalt Technology. It was developed to automate the process of determining asphaltic or other binder content in HMA samples. The benefits of automation are reduction in error due to human factors, and relieving the lab technician from a tedious test method for production elsewhere. Samples are collected either from the asphalt plant at the time of mix design, or samples from the construction site at the time of asphalt paving. The oven includes a pyrometer and thermostat to control furnace temperature, an internal scale that constantly monitors the weight of the sample being burned, a fan and exhaust system, and a paper receipt-type report that prints out in real time. The oven operates at a temperature in the range of 450 to 650 degrees Celsius (842 to 1202 degrees Fahrenheit). The oven truly is a furnace in that it incorporates forced air to ensure complete combustion of asphaltic contents. The fan’s exhaust is piped outside to maintain a pleasant working environment for the lab technician. The oven is typically set to maintain a temperature at the low end of the scale, but will get much hotter when the asphalt binder ignites. The oven will stay busy tracking weight and maintaining at least the minimum temperature until the unit determines there is no further appreciable change in sample weight over time.

The material left over after the burn is all aggregate material, usually a combination of sand and gravel. The aggregate can be run through a set of nested sieves to determine the relative amounts of different size particles, or gradation. Together with the Specific Gravity, the Asphaltic Content and Gradation will tell one if their HMA is up to snuff.