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The main goal of this study is to investigate the strength and compaction characteristics of soil stabilized by fly ash with multiwalled carbon nanotube (MWCNT) as an additive. The materials used in the study were characterized using microscopic techniques like scanning electron microscopy-energy dispersive spectroscopy (SEM–EDS), and X-ray diffraction (XRD). The soil in the current study was replaced up to 50% by fly ash in the presence of MWCNT and sodium hexametaphosphate (SHMP) in different concentrations. The findings demonstrate that the Atterberg limits and specific gravity decrease with the increase in fly ash, MWCNT, and, SHMP. The maximum (46%) and minimum (24.2%) values of the liquid limit were recorded at 0% and 50% fly ash content, respectively. The maximum (34%) and minimum (20.2%) values of the plastic limit were observed at 0% and 50% fly ash content respectively. The specific gravity of natural soil decreases from the maximum value of 2.68 to the minimum value of 2.53 at 0% and 50% fly ash content, respectively. The optimum moisture content also decreases with the increase in fly ash, MWCNT, SHMP, and vice versa for maximum dry density. 0.01% w/w MWCNT + 80% Soil + 20% Fly Ash + 2% SHMP is the optimal mix. It gives maximum unconfined compressive strength (UCS) value in all the durations of curing, i.e. 0.50, 0.725, and 0.984 MPa at 1, 7, and 28 days of curing, respectively. The UCS value of this combination is 147% more than the UCS value of normal soil cured for 28 days. An economic analysis is also conducted to understand the feasibility of the application of MWCNTs in soil-fly ash mix. [ABSTRACT FROM AUTHOR]

Growing concern over the combustion cost and environment has made road engineers and scientists to explore the possible use of locally available materials for the construction of roads. The present study evaluated the strength and durability characteristics of five sites having locally available silty soils using lime and cement–sand stabilization technique. The test results showed that the cement–sand stabilization technique using 6% cement and 5% local sand resulted in higher strength and durability as compared to lime stabilization. There is also a significant increase in the value of the soaked California bearing ratio (CBR). As unconfined compressive strength (UCS) attained the threshold strength as prescribed by IRC SP 72 2015 for the granular sub-base (GSB) layer, by the use of sand cement stabilization, this technique of stabilization for local silty soils could be used for GSB for low volume road (LVR) construction. As observed from microstructural results which were performed by analysing SEM images, sand cement stabilisation leads to CSH gel and agglomerate formation thereby increasing strength and durability properties. The cost analysis for the replaced stabilized GSB layer showed that using sand–cement stabilization, the estimated cost can be reduced by 56% of the total cost as compared to the conventional method. [ABSTRACT FROM AUTHOR]

Durability of bituminous mixes is affected by presence or intrusion of moisture into it. The intrusion and amount of trapped moisture largely depend on the air voids present in the mixes. This study explores the combined influence of air voids and hydrated lime (HL, as anti-stripping agent) on moisture-induced damage of bituminous mixes prepared from two different aggregate sources. The aggregates used in the study are siliceous sandstone and basalt. Tensile Strength Ratio (TSR) test was used to determine the moisture susceptibility of bituminous mixes. A higher value of TSR depicts that the mixes are more moisture resistant. TSR was reaffirmed to be lowest at an air void range of about 5% to 13% which is termed as pessimum air void range. At this air void range, moisture gets trapped within the mix, resulting in moisture-induced damage. TSR results showed that bituminous mixes prepared with siliceous sandstone is more susceptible to moisture-induced damage as compared to mixes prepared with basalt. Boil water test reconfirmed the results. Use of HL in bituminous mixes improved its moisture-induced damage resistance only marginally. Thus, moisture-induced damage control at pessimum air void range using anti-stripping agent is not always sufficient. Observations show that air void plays a critical role in moisture-induced damage and control of air void during construction needs to be ensured. [ABSTRACT FROM AUTHOR]