Abstract
The study evaluated the effect of elapsed time after mixing on the strength properties of lime and iron ore tailings (IOT) treated black cotton soil (BCS) (an expansive tropical black clay) as road construction material. BCS was treated with 0, 2, 4, 6, and 8% lime and 0, 2, 4, 6, 8, and 10% IOT content by dry weight of soil. Tests carried out include Atterberg limits, compaction, unconfined compressive strength (UCS), California bearing ratio (CBR) (unsoaked condition), and microstructure of specimens. Statistical analysis was done using MINI-TAB software. Results show that the liquid limit (LL) of BCS–lime–IOT mixtures decreased with increase in lime and IOT content. The LL values of all the treated BCS increased between 0 and 1 h elapsed time after mixing. On the other hand, the plastic limit (PL) of BCS decreased with increase in lime and IOT content while the plasticity index (PI) decreased from 27.7 to 22.9% for 0% lime/0% IOT content and from 30.6 to 26.6% for 0% lime/10% IOT content. Maximum dry density (MDD) of BCS increased while optimum moisture content (OMC) decreased with higher IOT content. The natural BCS recorded OMC value of 25.6% decreased to 15.2% for 8% lime/10% IOT treatment. The strength (i.e., UCS and CBR values) increased with increase in lime/IOT contents between 0 and 2 h elapsed time after mixing. Peak values were recorded for 8% lime/8% IOT treatment for all lime content considered. Regression analysis shows a strong relationship between the strength properties and the soil parameters. An optimal 8% lime/8% IOT treatment of BCS for elapsed time after mixing not exceeding 2 h was established and is recommended as sub-base material for low-trafficked roads.
Highlights
Civil engineering construction works are sometime subjected to construction delays that might be caused by several factors such as human error, machine breakdown, or environmental factors
The variation of maximum dry density (MDD) of black cotton soil (BCS) with elapsed time after mixing for 0% lime–up to 10% iron ore tailing content (IOT) and optimal 88%%lilmime–eu–puptot1o0%10I%OTIOtrTeatmreeantmt iesnsthoiswsnhionwFniguinreF8iag–udr.eG8ean–edr.alGlye, ntheeraMllyD,DthvealMueDinDcrveaasluede ifnorcruepasteod2fhoreulapptsoed2 thimeleapafsteedr mtimixeinagftfeorrmalilxtihneglfiomreaallntdheIOliTmtereaantdmIeOnTtstcroeantsmideenretsdcboenfsoirdeedredcrbeaesfoinrge date3crheaeslianpgseadt t3imheealfatpersemdixtimnge. aAftseirmmilaixritnrgen. dAwsiams rileaprotrrteenddbywAasbdreuplloarhtied[48b]yanAdbdNuwlladhio[g4b8u] [a5n0d]
The early increase in the unconfined compressive strength (UCS) for the first 2 h may be attributed to the fact that, once compaction is delayed, hydration processes that bind particles in their loose state are formed, thereby leading to aggregations of the soil particles and an increase in the density of the soil, which results in incirnecarseeadsesdtrestnrgetnhgt[h4][.4T].hTehdeedcreecarseeasieninUCUSCSafateftrera a3 3hhddeelalayymmaayybbeedduuee ttoo dessttrruuccttiioonn of the cementitious bonds formed during the soil–lime–IOT reaction over the period between mixing and compaction
Summary
Civil engineering construction works are sometime subjected to construction delays that might be caused by several factors such as human error, machine breakdown, or environmental factors. Black cotton soils (BCS) occupy an estimated 104,000 km in the northeast region of Nigeria [7] They are a product of disintegrating shale and argillaceous deposits as well as volcanic rocks. Construction of roads on expansive soil is problematic since there is the possibility of expansion and contraction with adjustment in water, due to the presence of montmorillonite [7,8,9,10] Improvement of such soil is a cheaper alternative to replacing it in the field, the need for the use of various additives such as cement, lime, and industrial and agricultural waste with pozzolanic potential prior to field application. This study was focused on the improvement of BCS with lime using IOTs as admixture for elapsed time after mixing of up to 3 h. The objective was to determine the effect of elapsed time after mixing for an optimal formulation for road construction material (or equivalent)
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