Many public works departments and utility companies have discovered that flowable fill offers many advantages over aggregate-based backfills. The City of Tulsa public works department, Oklahoma, however, has discovered something even better--a quick-setting flowable fill that offers all the advantages of regular flowable fill and none of the disadvantages. The successful performance of the quick-set fill has made it increasingly popular as a back-fill material for street repair work.
In 1989, the Tulsa public works department and local utilities adopted, as standard, the use of regular flowable fill as backfill for utility trenches. Despite its advantages, however, Tulsa experienced some problems with the material. The cement and fly ash in the fill would migrate to the top of the backfill and form a hard crust that was not diggable using conventional tools. Another problem was the fill's tendency to shrink or consolidate during the curing process, resulting in the need to delay paving over the material until curing was complete.
In 1990, Tulsa developed specifications for a quick-setting flowable fill that overcomes the problems of standard fill. Currently, two mix designs are routinely specified--one uses a quick-set cement instead of type I portland cement and another uses a nonchloride accelerator and Type I cement. Unlike regular flowable fill, neither material contains fly ash or an air entraining admixture.