Time-dependent stiffness increase of foamed asphalt stabilized base material

Foamed asphalt stabilized base (FASB) is a cold-recycling process that combines reclaimed asphalt pavement and/or recycled concrete with a small amount of foamed asphalt binder. The combination of water and binder causes a gain in stiffness after placement due to drying effects and the irreversible bonds formed between the binder and aggregate during curing. To investigate this process, a series of experiments was conducted on a 20 cm thick FASB base layer for a lane addition project in Maryland. ln-place overall stiffness of the section was measured over seven consecutive days using a Zorn lightweight deflectometer (LWD) and a Humboldt GeoGauge. The stiffness increase with time was compared to that for a conventional 20 cm thick granular aggregate base (GAB) on top of the same subgrade. The stiffness values measured by each of these in-situ devices were different because of differences in applied stress states and zones of influence and the influence of subgrade stiffness on the overall response. The stiffness increases for both the FASB and GAB layers were corrected based on elastic 2-layer assumptions which revealed that the equivalent stiffness of FASB layer increases by a modulus ratio (FU) of 8.2 while this factor is about 3.9 for the GAB layer. FU was predicted using partially saturated soil mechanics, which affirmed that the stiffness gain in FASB layer is significantly higher than can be explained by mere drying of granular materials. This higher rate of stiffening in FASB layer reveals the effects of curing and the development of adhesive bonds between the binder and coated aggregates. The long-term post-construction stiffness was also measured using a Dynatest falling weight deflectometer (FWD) on the final pavement structure 4 months after construction. Backcalculated layer moduli showed that the final stiffness of the field-cured FASB was about 2524 MPa, 15 times higher than that for the GAB material.

Language

  • English

Media Info

  • Pagination: pp 939-948
  • Monograph Title: Bearing capacity of roads, railways and airfields: proceedings of the ninth International Conference on the Bearing Capacity of Roads, Railways and Airfields: Trondheim, Norway 25-27 June 2013. Vol 1-2

Subject/Index Terms

Filing Info

  • Accession Number: 01596590
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • ISBN: 9788232102853
  • Files: ITRD, VTI
  • Created Date: Apr 21 2016 12:35PM