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The objective of this project was to characterize the freeze-thaw properties of recycled concrete(RCA)and asphalt(RAP)as unbound base and to assess how they behaved in the field for nearly 8 years.This paper includes an examination of existing information,laboratory studies of freeze-thaw behavior,and evaluation of data from Mn ROAD field-test sections in a seasonally cold region,i.e.,in Minnesota,USA.Test sections were constructed using recycled materials in the granular base layers at the Mn ROAD test facility.One test section included 100%RAP,another 100%RCA,a third one a 50/50blend of RCA/natural aggregate,and a fourth one only natural aggregate(Class 5)as a control.The stiffness(i.e.,elastic modulus)was monitored during construction and throughout the pavement life by the Minnesota Department of Transportation,along with the variation of temperatures and moisture regimes in the pavement to determine their effects on pavement performance.The resilient modulus of each material was determined by bench-scale testing in accordance with NCHRP 1-28a,as well as by field-scale tests incorporating a falling-weight deflectometer.Specimens were subjected to as many as 20 cycles of freeze-thaw in the laboratory,and the change in their resilient modulus was measured.In the field-test sections constructed with the same materials as the base course,temperature,moisture,and field modulus(from fallingweight deflectometer tests)were monitored seasonally for nearly 8 years.From the temperatures in the base course layer,the number of freeze-thaw cycles experienced in the field was determined for each test section.Inferences were made relative to modulus change versus freeze-thaw cycles.Conclusions were drawn for long-term field performances of the recycled base(RAB)in comparison to natural aggregate.
The objective of this project was to characterize the freeze-thaw properties of recycled concrete (RCA) and asphalt (RAP) as unbound base and to assess how they behaved in the field for nearly 8 years. This paper includes an examination of existing information, laboratory studies of freeze-thaw behavior, and evaluation of data from Mn ROAD field-test sections in a seasonally cold region, ie, in Minnesota, USA. Test sections were constructed using recycled materials in the granular base layers at the Mn ROAD test facility .One test section included 100% RAP, another 100% RCA, a third one a 50 / 50blend of RCA / natural aggregate, and a fourth one only natural aggregate (Class 5) as a control. The stiffness (ie, elastic modulus) was monitored during construction and throughout the pavement life by the Minnesota Department of Transportation, along with the variation of temperatures and moisture regimes in the pavement to determine their effects on pavement performance. resilient modulus of each material was d etermined by bench-scale testing in accordance with NCHRP 1-28a, as well as by field-scale tests incorporating a falling-weight deflectometer. Specimens were subjected to as many as 20 cycles of freeze-thaw in the laboratory, and the change in their resilient modulus was measured in the field-test sections constructed with the same materials as the base course, temperature, moisture, and field modulus (from falling weight deflectometer tests) were monitored seasonally for nearly 8 years. layers, the number of freeze-thaw cycles experienced in the field was determined for each test section.Inferences were made relative to modulus change versus freeze-thaw cycles. Conclusions were drawn for long-term field performances of the recycled base (RAB) in comparison to natural aggregate.