Abstract

Expansive/swell-shrink soils exhibit high plasticity and low strength, which lead to settlement and instability of lightly loaded structures. These problematic soils contain various swelling clay minerals that are unsuitable for engineering requirements. In an attempt to counter the treacherous damage of such soils in modern geotechnical engineering, efforts are underway to utilize environmentally friendly and sustainable waste materials as stabilizers. This study evaluates the strength and consolidation characteristics of expansive soils treated with marble dust (MD) and rice husk ash (RHA) through a multitude of laboratory tests, including consistency limits, compaction, uniaxial compression strength (UCS), and consolidation tests. By using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, the effect of curing on UCS after 3, 7, 14, 28, 56, and 112 days was studied from the standpoint of microstructural changes. Also, the long-term strength development of treated soils was analyzed in terms of the interactive response of impacting factors with the assistance of a series of ANN-based sensitivity analyses. It is found from the results that the addition of MD and RHA lowered down the water holding capacity, thereby causing a reduction in soil plasticity (by 21% for MD and 14.5% for RHA) and optimum water content (by 2% for MD and increased by 6% for RHA) along with an increase in the UCS (for 8% MD from 97 kPa to 471 kPa and for 10% RHA from 211 kPa to 665 kPa, after 3 days and 112 days of curing, respectively). Moreover, from the oedometer test results, m v initially increased up to 6% dosage and then dropped with further increase in the preconsolidation pressure. Furthermore, the compression index dropped with an increase in the preconsolidation pressure and addition of MD/RHA, while the coefficient of permeability (k) of RHA stabilized soil was higher than that of MD-treated samples for almost all dosage levels. The formation of the fibrous cementitious compounds (C-S-H; C-A-H) increased at optimum additive dosage after 7 days and at higher curing periods. Hence, the use of 10% RHA and 12% MD as replacement of the expansive soil is recommended for higher efficacy. This research would be helpful in reducing the impacts created by the disposal of both expansive soil and industrial and agricultural waste materials.

Highlights

  • Expansive soils or soft soils are hydrophilic due to the presence of water-sensitive clay minerals resulting from environmental and seasonal moisture variations, which cause myriad problems in civil engineering works. ey are highly problematic and cause annual economic loss ranging from several millions to billions of dollars, exceeding damage caused by other geological disasters [1,2,3,4,5]

  • According to the X-ray fluorescence (XRF) analysis, the SiO2 content is higher in rice husk ash (RHA), and the combined percentage of alumina, silica, and calcium oxide totals 78.66% which conforms to the requirements of pozzolanic material as per ASTM D4943 standard. erefore, the pozzolanic nature of RHA would play a major role in improving the properties of expansive soils

  • For the soil-marble dust (MD) mixture, the LL and PL decreased from 36% to 29% and 16% to 13%, respectively, with 12% addition of MD. e reduction in LL and PL beyond 8% dosage of MD was relatively higher

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Summary

Introduction

Expansive soils or soft soils are hydrophilic due to the presence of water-sensitive clay minerals resulting from environmental and seasonal moisture variations, which cause myriad problems in civil engineering works. ey are highly problematic and cause annual economic loss ranging from several millions to billions of dollars, exceeding damage caused by other geological disasters [1,2,3,4,5]. When the RHA reacts with calcium hydroxide, they generate cementitious gels, which helps to improve the compression strength of soil [21, 43, 44] It has been established from previous studies that RHA is a very reactive pozzolanic material, and it can efficaciously stabilize high plastic expansive soils either solely or in combination with lime and/or other additives [45, 46]. To the authors’ knowledge, no study to date is available explaining the independent roles of locally produced marble waste and rice husk ash on the compression strength and consolidation behavior of clays with high plasticity cured for long curing periods in the context of microstructural tests. Preliminary investigation of the area revealed the diagonal cracking of boundary walls and the presence of polygonal desiccation cracks over the inclined face of embankments running along the pavements that could be attributed to the swelling of the expansive soil, as shown in Figures 2(a) and 2(b)

Experimental Investigation
Results and Discussion
Determination of Consolidation Characteristics
Full Text
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