Representative image of highway in Spain (Image Credits: Pexels)
For the laboratory mix, the researchers determined that the stabilized soil should contain 5% WPFA and 8.2% water, while the reference mixture contained 3% CEM IV/B (Q) 32.5N cement and 7% water. Laboratory specimens made from the WPFA mixture reached an average 1.8 MPa against the minimum requirement of 1.5 MPa and met the Spanish requirement for seven-day unconfined compressive strength. The stiffness of the completed layer was assessed through load-plate tests and in 14 days the WPFA section recorded an average Ev2 above 334 MPa. The Spanish regulations required thresholds of more than 60 MPa for E1, more than 120 MPa for E2 and more than 300 MPa for E3, according to the study.
The measured value therefore placed the WPFA-stabilized roadbed in the E3 category. The work was part of the EU-funded Paper Chain project, which examined whether WPFA could work as a hydraulic binder, replacing conventional cement work for stabilizing soils used beneath road pavements. it was used by agricultural vehicles and trucks travelling to a local service area Although the road section didn’t carry high intensity of traffic. The WPFA solution replaced a cement-stabilized soil classified as S-EST3 under Spanish road regulations, with a double bituminous treatment over the improved subgrade. Researchers also sampled the construction materials, surrounding soils, vegetation, groundwater and nearby surface waters before and after construction. The monitoring plan examined potential pathways for WPFA particles and focused on airborne dispersion during spreading and water transport via runoff. The concentrations of trace elements found in soils and dust collected from vegetation were similar before and after construction and no conclusive evidence was gathered by the researchers pertaining to the dispersal of WPFA through the identified construction pathways. Furthermore, all measured concentration remained below the threshold limits established for urban use soils in Aragon.
Having previously investigated WPFA at laboratory scale and in other field trials, the researchers, however, focused on the construction and monitoring of one Spanish pilot.
