Synthetic Lightweight Aggregate for Highway Construction

The objective of this study was to develop a new product, Synthetic Lightweight Aggregate (SLA), from two materials, waste plastics and fly ash. SLA is being developed and evaluated for use in construction applications such as geotechnical lightweight fill, concrete masonry blocks, and lightweight concrete structures. SLA is produced by melt compounding high concentrations of fly ash from coal with various thermoplastics. In this study, a series of lightweight aggregate samples were produced using several different thermoplastics as binders at several fly ash-to-binder ratios. The SLA samples were produced using flexible thermoplastics, rigid thermoplastics, and mixed thermoplastics as binder. The fly ash used as filler contained various levels of carbon content ranging from less than 4% to more than 30%. The physical properties of the melt-compounded materials such as Izod impact, hardness, flexural, and flammability, were evaluated to determine the relationship between variables such as the binder stiffness and the SLA stiffness as well as the filler concentration and the SLA physical properties. The results of the study show that the SLA properties are influenced by both the fly ash concentration and the thermoplastic binder composition. However, as the fly ash concentration increases, the physical properties of the SLA become less dependent on the thermoplastic binder’s properties. At fly ash concentrations of 80%, the physical properties of the SLA are fairly insensitive to the composition of the thermoplastic binder. Samples of SLA were tested for their properties as a geotechnical fill and as a concrete aggregate. An expanded clay lightweight aggregate and a normal weight aggregate were used for comparison. For geotechnical applications, the SLAs were tested for gradation, specific gravity, bulk density, absorption, 1-D compression (consolidation), and triaxial compression properties. The SLA exhibited a very high friction angle, high compressive strength, and a higher compressibility than normal fill. Concrete made with SLA exhibited a lower compressive strength as compared with the control material. As fly ash contents of the SLA increased, all properties of the SLA concrete were improved. SLA concrete can satisfy the minimum strength of 170 kPa (2500 psi) required for structural lightweight concrete and non load-bearing concrete masonry units. The SLA concrete samples tested for compressive strength exhibited a low elastic modulus and a unique post cracking ductile behavior. The concrete samples made with the SLA that contained the maximum amount of fly ash (80%) showed an excellent freeze-thaw salt scaling resistance, surpassing concrete made with both natural and lightweight aggregate.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 92p

Subject/Index Terms

Filing Info

  • Accession Number: 01531740
  • Record Type: Publication
  • Files: TRIS, ATRI, USDOT
  • Created Date: Jul 18 2014 2:08PM