Tyler District, Recycled RAP

The Texas Department of Transportation have accumulated significant quantities of RAP (Recycled Asphalt Pavement), most of which is stockpiled at various locations adjacent to public roads. Recognizing the value of these RAP stockpiles as a source of high quality material, the Tyler DoT District office contacted Wirtgen to discuss the use of the KMA 150 Cold mix plant to recycle the RAP into a usable base material.

Following a site inspection by the engineers of Loudon International, the stockpile adjacent to Road 69 was identified as a suitable candidate to implement a trial section to create the BSM material by using the KMA 150 Cold mix plant from Wirtgen.

Samples were taken form the stockpile area to do detailed laboratory investigation and mix design using a Wirtgen WLB10 foam bitumen mobile laboratory. Other test performed on this material included grading analysis, moisture/density relationships test and optimum binding agent determination. Two grades of bitumen, 64-22 and 150/160 penetration, were used during the design process with different foam water percentages. The 150/160 penetration grade bitumen with 3% foam water was found to be the optimum combination in terms of expansion and half-life.

Full mix designs were then done on material samples taken from the RAP stockpiles using a Wirtgen WLB10 foam bitumen mobile laboratory. The mix design was determined to be to addition of 2% of foamed bitumen and 1.5% cement.

Having determined a suitable mix design, it was agreed to carry out a trial section in the form of an overlay on Road FM724. The material was paved with a Vogële paver to a thickness of 100mm followed by a single surfacing seal. Although space was extremely limited at the RAP site it was still possible to position the Wirtgen KMA 150 in an adequate position to allow for the loading of RAP material to the rear hoppers and for the discharging of recycled RAP material into receiving trucks.