Investigation of Accelerated Curing of Soil-Lime and Lime-Fly Ash-Aggregate Mixtures.

The objectives of this investigation were to examine current mix design procedures for soil-lime and lime-fly ash-aggregate mixtures and to develop accelerated curing test procedures for estimating long-term field strengths. Unconfined compression tests were conducted on Vicksburg silt ML plus 3 and 5 percent lime, Vicksburg buckshot clay CH plus 5 and 8 percent lime, and 90 percent clay gravel and 90 percent sandy gravel plus 3 or 6 percent fly ash, respectively. Representative groups of specimens were normally cured at 50 F and 72 F each for 7, 28, and 56 days, while other groups were accelerated cured 1, 3, and 5 days at 90 F, 105 F, and 120 F each. The soil-lime mixtures could be judged to be reactive or nonreactive. Accelerated curing times equivalent to 28-day normal-cure strengths depended upon curing temperature, soil type, and to a lesser extent on lime content or lime fly ash ratio. Hence, no universally applicable equivalent 28-day curing time exists for accelerated-cured soil-lime or lime-fly ash-aggregate mixtures. Because none of the existing maturity rules for concrete were found to be applicable to soil-lime mixtures, a method was developed based upon normal-cure 7-day and accelerated-cured 105 F strengths for estimating 28-day strengths. Procedures for mix design evaluation of soil-lime and lime-fly ash-aggregate mixtures are presented.