Abstract
Low bearing capacity soils may pose serious construction concerns such as reduced bearing capacity and excessive hydro-associated volume changes. Proper soil remediation techniques must be planned and implemented before commencing any construction on low bearing capacity soils. Environmentally friendly soil stabilizers are gradually replacing traditional soil stabilizers with high carbon dioxide emissions such as lime and cement. This study investigated the use of an alternative pozzolanic mix of nano-additives (i.e., nano-silica and nano-alumina) and cement to reduce the usage of cement for achieving competent soil stabilization outcomes. A series of unconfined compressive strength (UCS), direct shear, and durability tests were conducted on marl specimens cured for 1, 7, and 28 days stabilized with nano-additives (0.1~1.5%), 3% cement, and combined 3% cement and nano-additives. The UCS and shear strength of stabilized marl increased with nano-additives up to a threshold nano-additive content of 1% which was further intensified with curing time. Nano-additive treated cemented marl specimens showed long durability under the water, while the cemented marl decomposed early. The microfabric inspection of stabilized marl specimens showed significant growth of calcium silicate hydrate (CSH) products within the micro fabric of nano-silica treated marl with reduced pore-spaces within aggregated particles. The results confirmed that nano-additives can replace cement partially to achieve multi-fold improvement in the strength characteristics of the marl.
Highlights
Soil stabilization incorporates processes to alter one or more properties of soil to achieve overall improved mechanical characteristics and engineering performance under ongoing and future stress conditions
The maximum dry unit weight of the marl was reduced by 4.7% and 3.8% with the addition of 1.5% nano-silica and 1.5% nano-alumina, respectively
Nano-silica treated marl achieved a slightly higher dry unit weight compared to the nano-alumina treated marl that can be linked with the lower particle size and high specific surface of nano-silica particles compared to those of nano-alumina particles (Table 2)
Summary
Soil stabilization incorporates processes to alter one or more properties of soil to achieve overall improved mechanical characteristics and engineering performance under ongoing and future stress conditions. Chemical stabilization improves the engineering characteristics of soil by mixing the soil with additives such as lime, cement, bitumen, and fly ash. The default choice for soil stabilization amongst most engineers is the use of traditional calcium-rich additives, such as cement or lime and, to some extent, fly-ash, which all have been traditionally proved to work well for improving the mechanical behavior of reactive clays, soft clays, and other low bearing capacity soils (i.e., high compressibility and heave, insufficient stiffness, and shear/compressive strength) [1,2,3,4,5,6,7,8,9,10]. Marls are carbonate-rich, fine-grained soft soils that pose engineering concerns including settlement, low bearing capacity, instability, and water sensitivity [60] This type of soil is frequently found in Iran especially in the northwest. The current study investigated the impact of the proportionate amount of two different nano-additives (i.e., nano-silica and nano-alumina) on the compressive and shear strength of cemented marl
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