EFFECT OF ELAPSED TIME AFTER MIXING ON THE PROPERTIES OF LIME – IRON ORE TAILINGS STABILIZED BLACK COTTON SOIL
No Thumbnail Available
Date
2021-08-06
Journal Title
Journal ISSN
Volume Title
Publisher
Ahmadu Bello University Zaria
Abstract
The black cotton soil (BCS) used in the study was classified as A-7- 6(14) soil group of the American Association State Highways Transportation Officials (AASHTO) soil classification system and CH soil group in the Unified Soil Classification System (USCS). The study focused on the effect of elapsed time (i.e., 0, 1, 2 and 3 hours) after mixing on the properties of black cotton soil (BCS) treated with lime and iron ore tailings (IOT) in stepped concentration of 0, 2, 4, 6 and 8 % as well as 0, 2, 4, 6, 8 and 10 % by dry weight of soil, respectively. Tests were carried out on the natural and treated soil to determine index properties, compaction characteristics, unconfined compressive strength
(UCS) and durability as well as California bearing ratio (CBR). Specimens were prepared
using three (3) compactive efforts (i.e., British Standard light, BSL, West African Standard, WAS or „Intermediate‟ and British Standard heavy, BSH).The results obtained show that the maximum dry density (MDD) of the BCS increased from 1.47, 1.55 and 1.63Mg/m3 for the natural soil to 1.60, 1.67 and 1.79 Mg/m3 at 6 % lime / 10 % IOT
treatment for BSL, WAS and BSH compaction, respectively. The corresponding optimum moisture content (OMC) values decreasedwith higher compactive effort and IOT content from 25.6, 20.3 and 19.0 % to 15.2, 15.8 and 16.8 % at 4 and 8 % lime / 10% IOT treatment for BSL, WAS and BSH compaction, respectively.Peak UCS values of 2,696.51, 3,628.88 and 3,888.93 kN/m2were obtained at 8 % lime/ 8 % IOT treatment within 0 -2 hours elapsed time after mixing for BSL, WAS and BSH compaction, respectively. Thereafter,the UCS values decreased with higher elapsed time after mixing
for the lime and IOT contents considered. Peak CBR values of 147.5 %, 172.21 % and 229.31 % were obtained at 8 % lime / 8 % IOT treatment within 0 - 2 hours elapsed time after mixing for BSL, WAS and BSH compaction. However, CBR (un-soaked and soaked conditions) values decreased with higher elapsed time after mixing for the lime and IOT contents considered. The resistance to loss in strength increased with elapsed time. Durability value of 98.2 % was obtained at 3 hours elapsed time for BSL compaction from 96.1 % at 1 hour elapsed time after mixing.Micro analysis of specimens
showed that the crystalline hydration products contributed to the strength of the treated soil. Statistical two - way analysis of variance (ANOVA) ofthe tests results show that effects of lime and IOT on the properties of BCS were significant. It is recommended thatBCS treated with 8 % lime / 8 % IOT when compacted with WAS and BSH energy and maximum 2 hours elapsed time after mixing be used as sub base and base material in the construction of low-volume roads.