FLY ASH AS FILL AND BASE MATERIAL IN ARKANSAS HIGHWAYS

Fly ash, similar to that to be produced in Arkansas, reacts chemically like quick lime, generating heat and possessing self hardening characteristics. Reactivity of the ash may be due to the relatively high CaO content of 20%. Two Arkansas soils, an organic clay and a sand (classified OH and SP-SM by the Unified system) were stabilized with the fly ash. Addition of 20% fly ash to the clay reduced the fraction of less than 2 micron particles from 58% to 8%. Twenty percent fly ash increased modified compaction density by 0.96 g/cc (6 pcf) in the clay and .32 g/cc (10 pcf) in the sand. Unconfined compressive strengths with 20% fly ash increased by 15.5 Kg/sq. cm (220 psi) in clay and 51 Kg/sq. cm (720 psi) in sand when compacted immediately and cured 7 days. Unconfined compressive strengths were improved with lime and cement admixtures. A delay in compaction causes large decreases in strength and density of sand-fly ash mixtures. After a one hour delay, only 18% of the initial strength and 83% of initial dry density are retained. Delays of 4 hours produced strengths and densities at the same level as 1 hour delays. Addition of salt retards the sand-fly ash reaction. After a one hour delay with 2% salt added, 66% of initial strength and 98% of initial dry density are retained. After 4 hours delay in compaction, however, only 22% of the initial strength and 86% of initial dry density are retained. /FHWA/

Media Info

  • Pagination: 107 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00130691
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: Final Rpt., FCP 44C2-132
  • Files: TRIS, USDOT
  • Created Date: Mar 29 1976 12:00AM