Enhancing Subbase Strength: CBR Evaluation of Lime Sludge-Cement Stabilized Soil | InformativeBD

Roxette C. Galdo, and Vera Karla S. Caingles, from the institute of Philippines. wrote a Research Article about, Enhancing Subbase Strength: CBR Evaluation of Lime Sludge-Cement Stabilized Soil. Entitled, Evaluation on the california bearing ratio of lime sludge-cement stabilized subbase course soil. This research paper published by the Journal of Biodiversity and Environmental Sciences (JBES). an open access scholarly research journal on Biodiversity. under the affiliation of the International Network For Natural Sciences| INNSpub. an open access multidisciplinary research journal publisher.

Abstract

In designing a pavement, aside from the types and properties of the surface layer (flexible or rigid), the soil properties of subgrade, subbase, and base materials are also important parameters. This research study was performed to determine the effects of lime sludge (LS) mixed with cement for use as stabilizers for road subbase course material. Laboratory tests to determine the engineering properties and California bearing ratio (CBR) were conducted on treated and untreated soil samples. There were two (2) sets of treated soil samples, Set 1: (Subbase soil + LS) added with varying percentages of lime sludge of 8, 10, 12, 14 and 16; and Set 2 (Subbase soil + LS + OPC) which contained lime sludge content of 8, 10, 12, 14 and 16 percent each coupled with 2% cement. For Mixture Set 1, laboratory test results indicated that treated samples with LS of 10%, 12%, 14% and 16% showed CBR values higher than the untreated sample. Highest CBR in this set of mixtures was recorded from the treated sample with 14% LS. Moreover, when 2% cement was added for Mixture Set 2, CBR values of subbase soil+LS mixtures increased, obtaining the highest value from the mixture with 10%LS and 2% cement. Therefore, the experimental result showed that the LS combined with cement can effectively improve the CBR value of the subbase course material.

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Introduction

Civil engineering structures are necessary infrastructures built to strengthen native terrains. The soil is the definitive base of all constructions and its geotechnical properties significantly contribute to the stability of these structures. The pavement’s design takes into account the types and properties of the surface layer, its flexibility or rigidity, as well as the soil layers such as subgrade, subbase, and base materials as vital parameters. The subbase course layer is on top of the subgrade which is identified as native soil or improved compacted soil; and, the base course layer is between the surface and the subbase course layer. The subbase course layer contains assorted types of smaller rocks and fragments, sometimes with troughs or holes, compressed to produce a strong surface. It assists in distributing the wheel load to mitigate stress on the subgrade layer (Joe and Rajesh, 2015). Hence, a good quality subbase material is vital in a pavement structure.

Soil stabilization technique improves the characteristics of soil (Kowalski and Starry, 2007). It treats soil to increase its strength and durability beyond their original classification that are suited for construction (Alhassan and Mustapha, 2007). More importantly, it increases bearing capacity or reduces settlement, water permeability, or risks of liquefaction (Zorluer and Gucek, 2020). The stabilization process is categorized into two broad fields, mechanical and chemical stabilizations. Mechanical stabilization requires compaction, aggregate mixing, gradient improvement, and asphalt cement extension. On the other hand, chemical stabilization utilizes chemicals like lime, asphalt, or fly ash as compaction supports to soil. According to Guyer (2011), additives such as cement, lime, bitumen, among others, contribute to the improvement of soil in terms of strength and stiffness, and permit to reduce the design thickness of layer being stabilized. Among the chemicals applied for soil stabilization, cement is commonly used (Firoozi, et al., 2017). However, the construction cost of a stabilized road using cement has remained financially high because of the over-dependence on the use of manufactured additives. This is one of the reasons underdeveloped countries still struggle to make quality road networks (Alhassan and Mustapha, 2007). Also, it has been reported that Portland cement, by the nature of its chemical components, produces large quantities of CO2 for every ton of its final product (Rubenstein, 2012). Thus, the use of available industrial waste having similar chemical composition with cement as soil stabilizer in the locale would be a good alternative means to construct stabilized roads at a possibly reduced construction cost.

Various engineering scholarly studies opined about the effectiveness of using industrial wastes as stabilizers highlighting their potential as replacements of chemicals such as cement and lime. Researchers were conducted on the by-product from paper milling and sugar milling companies called lime sludge (Chandak, 2015; Nagaraju and Kumar, 2017; Daleon and Lorenzo, 2018; Suthar and Aggarwal, 2018) and hyposludge (Usha, 2016), the by-product from rice milling company called rice husk ash (Hossain et al., 2018), the by-product from coal-fired thermal power plant called fly ash (Simatupang et al., 2020; Turan et al., 2020; Diallo and Unsever, 2019; Sharma and Hymavathi, 2016; Dahale et al., 2016) and by-products of other industrial wastes.

Lime sludge produced from the lime calcining process is an industrial by-product from paper and sugarmilling companies. It is identified as one of the prospective soil stabilizer substitute to lime. Limestone and lime sludge have the same composition except that the latter is found to be smoother. In the study conducted by (Daleon and Lorenzo, 2018), the lime sludge from BUSCO Sugar Milling Co. Inc. contained similar chemical compounds with Portland cement. A major proportion of lime sludge such as Silicon Dioxide (

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), Aluminum Oxide (

) and Calcium Oxide (CaO), is the same as the major compounds evident in cement. Thus, this study examined the potential of the sugar mill’s by-product as soil stabilizer in order to improve the engineering properties of road subbase/base material.

Reference

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