Excessively Wet Subgrade Improvement with 100 Industry By-products for Heavy Traffic Pavement II.Mechanical Behavior and Durability of Stabilized Soils

摘要

The workability of excessively wet subgrade can be effectively improved by using a "green materials" based entirely on industry byproduct of combination of fly ash (FA) with carbide lime (CL) and flue gas desulfurization gypsum (FGDG).This paper presents the results of a further systematic investigation on the mechanical behavior and durability of FA/CL/FGDG treated silt from Dezhou in Shandong province.FA,CL and FGDG were added at 3 levels in percentages of 8%-24%,2%-6% and l%-3% by dry weight of the soils,respectively.The unconfined compressive strength as well as splitting tensile strength (STS),volumetric expansion (VE),California bearing ratio (CBR),dry-wet cycles test and freeze-thaw cycles test were performed.The best strength of 0.802MPa was achieved for 24%FA/6%CL/1%FGDG treated soil,while the 16%FA/6%CL/1%FGDG treated soil also produce good strengths of 0.742MPa,after 7 days curing.STS keeps increasing with curing period in the first 8 weeks throughout the investigation.According to the VE test,a mellowing period may help prevent swelling from ettringite precipitation by letting these minerals form and hydrate before compaction.The FA/CL/FGDG treated soil has a better durability with strength loss ratio less than 15% after 10 wet-dry cycles,and the maximum weight loss around 25% after 10 freeze-thaw cycles.CBR decreases with decrease of compaction degree,but the values are still around 70 even in a poor compaction degree of 93%,meeting the general requirements of subgrade.So,if the silt subgrade is in excessively wet state and could not be compacted to the required density,the modified subgrade would still serve as a strong platform and could provide necessary support for pavement.