scholarly journals Investigations on Presence of Biopolymer Producing Microorganism in Marine Soils & Enhanced Potential of Marine Soil by Using Isolated Microorganism

2021 ◽  
Vol 12 (3) ◽  
pp. 3135-3149
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Screening Method ◽  
High Water ◽  
Soil Strength ◽  
Infrastructure Development ◽  
Aquatic Life ◽  
Environmentally Sustainable ◽  
Coastal Belt ◽  
Marine Soil

Gujarat has a very extended coastal belt, and due to type, the properties of available soil in the coastal regions vary from place to place. These soil properties are not suitable for infrastructure development. Many techniques were already developed for the improvement of marine soil strength. Some of them are very costly; some method is not suitable due to high water table in the region. Some have adverse effects on aquatic life. This study has an approach to give sustainable, eco-friendly, and economical techniques to increase the unconfined compressive strength of marine soil of the different regions. The entire colonies available in soil are studied by series dilution and spread plate technique. Microorganisms produce exopolysaccharides (EPS) in excess carbohydrates, which provides by the screening method in nutrient agar broth (N. agar). Microbial Biopolymer such as exopolysaccharides can act as an eco-friendly binder of soil. EPS-producing organisms work as an environmentally sustainable method to improve soil strength. More exopolysaccharides-producing and fastest-growing microorganisms were selected by EPS extraction from all microorganisms found in a survey. The result was also compared with the unconfined compressive strength achieved by bio cement and a mixture of biopolymer and biocement. The biopolymer shows an increase in result (1.625– 1.891) times from 14 days to 28 days. Biocement showed an increase in the result, which ranges from (1.763–1.955), and the mixture of both shows a tremendous increment of (1.635-1.885).

Modeling unconfined compressive strength of fine-grained soils: Application of pocket penetrometer for predicting soil strength

CATENA ◽  
2021 ◽  
Vol 196 ◽  
pp. 104890
Author(s):  
Fatemeh Mousavi ◽  
Ehsan Abdi ◽  
Shaaban Ghalandarayeshi ◽  
Deborah S. Page-Dumroese
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Soil Strength ◽  
Fine Grained

scholarly journals Microbial-Induced Carbonate Precipitation for Strengthening Soft Clay

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
J. Z. Xiao ◽  
Y. Q. Wei ◽  
H. Cai ◽  
Z. W. Wang ◽  
T. Yang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
Soft Clay ◽  
High Water ◽  
High Water Content ◽  
Carbonate Precipitation ◽  
Experimental Conditions ◽  
Strength Enhancement ◽  
Complex Chemical Composition

Currently, calcite produced in sediments by microbial-induced carbonate precipitation (MICP) is mainly used as a strengthening binder in sand because sands are porous and have good permeability. Conventional wisdom does not consider MICP to be suitable for use in soft clay because of the clay particles’ small size and its minimal porosity. Because of the clay’s high water content and complex chemical composition, very little research has been done and not much is known about the use of MICP in soft clay for strength enhancement. For this paper, soft clay specimens were prepared by mixing a solution containing Sporosarcina pasteurii bacteria, solutions with different concentrations of nutrient salts, and soft clay. Unconfined compressive strength tests were carried out on these specimens after they had cured for 28 days in a moisture-controlled environment. These laboratory tests were used to study the chemical reactions, the clay’s strength, and other influencing factors. The results are as follows: (1) directly mixing a S. pasteurii solution, nutrient salts, and soft clay considerably improves the uniformity of the spatial distribution of the bacteria and the nutrients in the soft clay. Directly mixing these constituents promotes the formation of calcium carbonate and greatly simplifies soft clay sample preparation. (2) It is feasible to use MICP to increase the strength of soft clay. Compared to control specimens cured under the same conditions but without introduced nutrients and bacteria solution, the unconfined compressive strength of MICP-treated specimens can be increased by as much as 2.42 times to an unconfined compressive strength of 43.31 kPa. The water content in MICP-treated specimens was significantly reduced by the MICP reactions and in one case decreased from 40% to 30.73%. (3) The strength enhancement of microbially solidified soft clay is the result of two processes: urea hydration catalyzed by enzymes consumes water in the clay and the bacterially precipitated calcite forms in the sediment’s pores. (4) The micro-organism-produced calcite in the soft clay increases the calcite abundance from 0% to as much as 3.5%. (5) The MICP-treated strength of soft clay varies with the concentration of the nutrients provided. For the experimental conditions used for this paper, the optimum concentration of the CaCl2·2H2O and CH4N2O nutrients is 0.5 mol/L.

scholarly journals The Role of Superabsorbent Polymer on Strength and Microstructure Development in Cemented Dredged Clay with High Water Content

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1069 ◽  
Author(s):  
Xia Bian ◽  
Lingling Zeng ◽  
Yongfeng Deng ◽  
Xiaozhao Li
Keyword(s):  
Compressive Strength ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
High Water ◽  
High Water Content ◽  
Strength Increase ◽  
Primary Role ◽  
Superabsorbent Polymer ◽  
Microstructure Development

This paper presents the role of superabsorbent polymer (SAP) on strength and microstructure development in cemented clays with notably high water content. A series of unconfined compressive strength (UCS), scanning electron microscope (SEM) and X-ray diffraction (XRD) tests were performed to identify strength behavior and microstructure. Results showed that SAP significantly influenced the mechanical behavior of cemented clays with notably high water content, characterized by an increase in the unconfined compressive strength and a decrease in the after-curing water content with SAP content. This revealed that the strength increase due to SAP was directly related to the water absorption by SAP. Meanwhile, XRD results showed that the hydration products were controlled by cement and lime content, regardless of SAP content. That meant there was no chemical reaction between SAP particles used in this study and cement or lime. The microstructure analysis by SEM revealed that SAP played an important role in the microstructure of cemented clays. With an increase in SAP content, the water absorbed by SAP increased significantly, leading to a decrease in the pore volume and a denser soil fabric. This behavior indicated that the primary role of SAP on strength increase was to absorb and fix water in cemented clays. Consequently, the clay–cement cluster distance decreased with an increase in solid mass (soil particles and swollen SAP particles) and a decrease in pore water. The corresponding tighter flocculated fabric due to SAP eventually led to the strength increase.

scholarly journals Analysis of Influencing Factors and Mechanism of Strength of Cement-Modified Silty Sand

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Weidong Jin ◽  
Zhe Wang ◽  
Yongming Ai ◽  
Chenyang Liu
Keyword(s):  
Compressive Strength ◽  
Power Function ◽  
Unconfined Compressive Strength ◽  
Cement Content ◽  
Soil Strength ◽  
Silty Sand ◽  
Logarithmic Relationship ◽  
Cement Soil ◽  
Comprehensive Characterization ◽  
Curing Age

The unconfined compressive strength of cement-modified silty sand in Jilin Province was investigated in this study. For this purpose, various tests were conducted, including the screening test, compaction test, CBR test, X-ray fluorescence detection, and unconfined compressive strength test. Effects of compaction degree, soil quality, water quality, cement content, and curing age were considered. The results show that CBR value is positively correlated with compactness. Two kinds of different water qualities have little effect on unconfined compressive strength of cement-improved soil; with the increase in cement content, the unconfined compressive strength increases, and the power function equation established by the two is significantly correlated. The logarithmic relationship between cement-soil strength and curing age is approximately linear. Through regression analysis, the comprehensive characterization parameters of cement-soil strength, such as water-cement ratio, cement content, and curing age, are put forward. The unconfined compressive strength of cement-modified silty sand has a good power function relationship with the comprehensive characterization parameters, and the fitting degree between the strength prediction formula and the existing research and test data exceeds 90%, which verifies the effectiveness of the comprehensive characterization parameters.

Influence of Fly Ash on Unconfined Compressive Strength of Cement-Admixed Clay at High Water Content

2010 ◽  
Vol 22 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Pornkasem Jongpradist ◽  
Narongrit Jumlongrach ◽  
Sompote Youwai ◽  
Somchai Chucheepsakul
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Content ◽  
Unconfined Compressive Strength ◽  
High Water ◽  
High Water Content

Rapid determination of soil unconfined compressive strength using reflectance spectroscopy

2021 ◽  
Vol 80 (5) ◽  
pp. 3923-3938
Author(s):  
Fatemeh Mousavi ◽  
Ehsan Abdi ◽  
Parviz Fatehi ◽  
Abbas Ghalandarzadeh ◽  
Hossein Ali Bahrami ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Rapid Determination ◽  
Reflectance Spectroscopy

scholarly journals Compression and Strain Predictive Models in Non-Structural Recycled Concretes Made from Construction and Demolition Wastes

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3177
Author(s):  
Evelio Teijón-López-Zuazo ◽  
Jorge López-Rebollo ◽  
Luis Javier Sánchez-Aparicio ◽  
Roberto Garcia-Martín ◽  
Diego Gonzalez-Aguilera
Keyword(s):  
Compressive Strength ◽  
Predictive Models ◽  
Unconfined Compressive Strength ◽  
Image Correlation ◽  
Peak Strain ◽  
Compression Tests ◽  
Maximum Peak ◽  
3D Digital Image Correlation ◽  
Granulometric Analysis ◽  
Physical And Chemical

This work aims to investigate different predictive models for estimating the unconfined compressive strength and the maximum peak strain of non-structural recycled concretes made up by ceramic and concrete wastes. The extensive experimental campaign carried out during this research includes granulometric analysis, physical and chemical analysis, and compression tests along with the use of the 3D digital image correlation as a method to estimate the maximum peak strain. The results obtained show that it is possible to accurately estimate the unconfined compressive strength for both types of concretes, as well as the maximum peak strain of concretes made up by ceramic waste. The peak strain for mixtures with concrete waste shows lower correlation values.

Risk of Mercury exposure during childhood: a review of Sri Lankan situation

2020 ◽  
Vol 35 (3) ◽  
pp. 229-232
Author(s):  
Himan K. A. Galappaththi ◽  
Inoka Suraweera
Keyword(s):  
Sri Lanka ◽  
Health Effects ◽  
Fish Consumption ◽  
Public Awareness ◽  
Mercury Level ◽  
Fluorescent Light ◽  
Aquatic Life ◽  
Hair Mercury ◽  
Coastal Belt ◽  
High Mercury

AbstractSri Lanka had ratified the Minamata convention in the year 2017 and is planning to phase out Mercury by 2020. Mercury thermometers and compact fluorescent light bulbs are abundant at hospitals, households and schools. Limitations in safe disposal and containment mechanisms have enhanced the unregulated e-waste collection and extraction. Sri Lanka has plentiful lagoons, fishing bays, and inland irrigation systems. Fish consumption is high, especially around the coastal belt. Mercury can bioaccumulate in humans by the consumption of fish from contaminated sources. Children are at risk of exposure in their living environments and via food. A multicountry study done across three oceans on Mercury threat to women & children revealed, lagoon pollution from industrial Mercury emissions in Sri Lanka, possessing high Mercury among local females who consume fish from that lagoon. The mean hair Mercury level in coastal areas with high fish consumption exceeded the reference dose even among children. Aquatic life and crop studies revealed a mixed picture of Mercury levels which some are lower and some are higher than the permissible levels. Studies on environmental Mercury levels and correlations with health effects among children will help to fill the data gap. Public awareness of the health effects of Mercury and mechanisms of Mercury disposal should be established.

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