Chloride Ingress in Cement Mortars Exposed to Acidithiobacillus thiooxidans Bacteria

Concrete structures placed in aggressive aqueous environments are vulnerable to degradation. Majority of studies have linked structural failures to the ingress of deleterious ions into the cement matrix. Some microbial activities may accelerate the penetration of harmful materials into the cement matrix and hence cause pronounced deterioration. This work reports a laboratory-simulated study carried out to determine the extent of chloride ingress in cement mortars exposed to Acidithiobacillus thiooxidans. Test prisms were cast from Portland pozzolana cement (PPC) and ordinary Portland cement (OPC) with water-to-cement ratio maintained at 0.5. Acidithiobacillus thiooxidans bacterial solution of concentration 1.0 × 10 7 cell/mL was used to prepare microbial mortar prisms, whereas distilled water was used to prepare the control mortar prisms. The test prisms were subjected to porosity and accelerated chloride ingress after 28th day of curing. Compressive strength was determined after the 2nd, 7th, 28th, and 56th days of curing. Apparent diffusion coefficients (Dapp) were estimated from the solutions to Fick’s second law of diffusion. After the 56th day of curing, the microbial-treated mortars exhibited a significant reduction in compressive strength. The resultant percentage decrease in compressive strength was 30.74% and 19.88% for OPC and PPC, respectively. Further, microbial-treated mortars demonstrated both high porosity and chloride ingress as compared to the control test mortars. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses showed the formation of new deleterious products in the microbial-exposed mortars.

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Chloride Ingress in Chemically Activated Calcined Clay-Based Cement

Journal of Chemistry ◽

10.1155/2018/1595230 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8 ◽

Cited By ~ 10

Author(s):

Joseph Mwiti Marangu ◽

Joseph Karanja Thiong’o ◽

Jackson Muthengia Wachira

Keyword(s):

Compressive Strength ◽

Portland Cement ◽

Ordinary Portland Cement ◽

Strength Development ◽

Chloride Ingress ◽

Calcined Clay ◽

Apparent Diffusion Coefficients ◽

Apparent Diffusion ◽

Lower Porosity ◽

Lower Chloride

Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800°C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC) at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na2SO4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC), and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients (Dapp) were estimated from solutions to Fick’s second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of Dapp, compared to OPC, PPC, and nonactivated PCC35.

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Influence of Starkeya novella on Mechanical and Microstructural Properties of Cement Mortars

Journal of Chemistry ◽

10.1155/2020/8212396 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

Onesmus Mulwa Munyao ◽

Joseph Karanja Thiong’o ◽

Jackson Muthengia Wachira ◽

Daniel Karanja Mutitu ◽

Romano Mwirichia

Keyword(s):

Compressive Strength ◽

Sem Analysis ◽

Chloride Ingress ◽

Microstructural Properties ◽

Alkali Aggregate Reaction ◽

Cement Mortars ◽

Water Curing ◽

Structural Failures ◽

Mechanical And Microstructural Properties ◽

And Control

Cement-based materials are subject to degradation during their service life. Most of the structural failures have been associated with corrosion of the rebar due to chloride ingress, alkali aggregate reaction, and/or sulfate attack. Microbial activities, especially in waste water collection points such as sewer lines, may compromise the integrity of concrete structures. This study reports an experimental work carried out to determine the effect of Starkeya novella bacteria species on mechanical and microstructural properties of cement mortars. Mortar prisms were prepared from selected ordinary Portland cement (OPC) and Portland pozzolana cement (PPC) in Kenyan markets. Bacterial solution of 1.0 × 107 cell/mL concentration was used as either mix water, curing media, or both. Distilled water was used to prepare mortar prisms for control samples. Compressive strength was determined after the 7th, 28th, 56th, and 90th day of curing. Scanning electron microscopy (SEM) was tested on both bacterial and control mortar prisms after the 28th day of curing. Both PPC and OPC exhibited significant decrease in compressive strength for bacterial-prepared mortars as compared to controls. SEM analysis showed extreme erosion on the microstructure of the microbial mortars. This was denoted by massive formation of ettringite and gypsum which are injurious to mortar/concrete.

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Chloride Diffusion in Concrete Protected with a Silane-Based Corrosion Inhibitor

Materials ◽

10.3390/ma13082001 ◽

2020 ◽

Vol 13 (8) ◽

pp. 2001 ◽

Cited By ~ 2

Author(s):

Luigi Coppola ◽

Denny Coffetti ◽

Elena Crotti ◽

Gabriele Gazzaniga ◽

Tommaso Pastore

Keyword(s):

Diffusion Coefficient ◽

Corrosion Inhibitor ◽

Sharp Decrease ◽

Chloride Diffusion ◽

Cement Matrix ◽

Water Repellent ◽

Chloride Ingress ◽

Chloride Diffusion Coefficient ◽

Apparent Diffusion ◽

Corrosion Risk

One of the most important parameters concerning durability is undoubtedly represented by cement matrix resistance to chloride diffusion in environments where reinforced concrete structures are exposed to the corrosion risk induced by marine environment or de-icing salts. This paper deals with protection from chloride ingress by a silane-based surface-applied corrosion inhibitor. Results indicated that the corrosion inhibitor (CI) allows to reduce the penetration of chloride significantly compared to untreated specimens, independently of w/c, cement type, and dosage. Reduction of chloride diffusion coefficient (Dnssn) measured by an accelerated test in treated concrete was in the range 30–60%. Natural chloride diffusion test values indicate a sharp decrease in apparent diffusion coefficient (Dapp) equal to about 75% when concrete is protected by CI. Mechanism of action of CI in slowing down the chloride penetration inside the cement matrix is basically due to the water repellent effect as confirmed by data of concrete bulk electrical resistivity.

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Apparent Diffusion Coefficients in Spinal Cord Transplants and Surrounding White Matter Correlate With Degree of Axonal Dieback After Injury in Rats

Yearbook of Neurology and Neurosurgery ◽

10.1016/s0513-5117(08)70341-7 ◽

2006 ◽

Vol 2006 ◽

pp. 156-157

Author(s):

B.C. Bowen

Keyword(s):

Spinal Cord ◽

White Matter ◽

Diffusion Coefficients ◽

Apparent Diffusion Coefficients ◽

Apparent Diffusion

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Incorporation of Iraqi Rocks in the Production of Eco-Friendly Cement Mortar

Engineering and Technology Journal ◽

10.30684/etj.v38i10a.1479 ◽

2020 ◽

Vol 38 (10A) ◽

pp. 1522-1530

Author(s):

Rawnaq S. Mahdi ◽

Aseel B. AL-Zubidi ◽

Hassan N. Hashim

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Compressive Strength ◽

Water Absorption ◽

Structural Properties ◽

Mechanical Milling ◽

Cement Mortar ◽

Cement Mortars

This work reports on the incorporation of Flint and Kaolin rocks powders in the cement mortar in an attempt to improve its mechanical properties and produce an eco-friendly mortar. Flint and Kaolin powders are prepared by dry mechanical milling. The two powders are added separately to the mortars substituting cement partially. The two powders are found to improve the mechanical properties of the mortars. Hardness and compressive strength are found to increase with the increase of powders constituents in the cement mortars. In addition, the two powders affect water absorption and thermal conductivity of the mortar specimens which are desirable for construction applications. Kaolin is found to have a greater effect on the mechanical properties, water absorption, and thermal conductivity of the mortars than Flint. This behavior is discussed and analyzed based on the compositional and structural properties of the rocks powders.

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Feasibility of Quantitative Diffusion Weighted MR Imaging with Calculated Apparent Diffusion Coefficients in Characterization of Pediatric Head and Neck Masses

Indian Journal of Public Health Research & Development ◽

10.37506/v10/i12/2019/ijphrd/192433 ◽

2019 ◽

Vol 10 (12) ◽

pp. 1577

Author(s):

Ahmed Gabr ◽

Ayman M. Nada ◽

Mohammed Gomaa ◽

Rania Hashem ◽

Ahmed Shokry ◽

...

Keyword(s):

Mr Imaging ◽

Head And Neck ◽

Diffusion Coefficients ◽

Apparent Diffusion Coefficients ◽

Neck Masses ◽

Diffusion Weighted ◽

Apparent Diffusion ◽

Head And Neck Masses

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Baseline apparent diffusion coefficients: Validation study of new predictor of survival in patients with unresectable hepatocellular carcinoma following chemoembolization

Journal of X-Ray Science and Technology ◽

10.3233/xst-200827 ◽

2021 ◽

pp. 1-10

Author(s):

Lichao Xu ◽

Shiqin Wang ◽

Shengping Wang ◽

Ying Wang ◽

Wentao Li ◽

...

Keyword(s):

Hepatocellular Carcinoma ◽

Roc Curve ◽

Cox Regression ◽

Response To Treatment ◽

Roc Curve Analysis ◽

Adc Value ◽

Apparent Diffusion Coefficients ◽

Apparent Diffusion ◽

Response Biomarker ◽

The Difference

OBJECTIVES: To investigate whether the baseline apparent diffusion coefficient (ADC) can predict survival in the hepatocellular carcinoma (HCC) patients receiving chemoembolization. MATERIALS AND METHODS: Diffusion-weighted MR imaging of HCC patients is performed within 2 weeks before chemoembolization. The ADC of the largest index lesion is recorded. Responses are assessed by mRECIST after the start of the second course of chemoembolization. Receiver operating characteristic (ROC) curve analysis is performed to evaluate the diagnostic performance and determine optimal cut-off values. Cox regression and Kaplan–Meier survival analyses are used to explore the differences in overall survival (OS) between the responders and non-responders. RESULTS: The difference is statistically significant in the baseline ADC between the responders and non-responders (P < 0.001). ROC analyses indicate that the baseline ADC value is a good predictor of response to treatment with an area under the ROC curve (AUC) of 0.744 and the optimal cut-off value of 1.22×10–3 mm2/s. The Cox regression model shows that the baseline ADC is an independent predictor of OS, with a 57.2% reduction in risk. CONCLUSION: An optimal baseline ADC value is a functional imaging response biomarker that has higher discriminatory power to predict tumor response and prolonged survival following chemoembolization in HCC patients.

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Properties of Calcium Sulfoaluminate Cement Mortar Modified by Hydroxyethyl Methyl Celluloses with Different Degrees of Substitution

Molecules ◽

10.3390/molecules26082136 ◽

2021 ◽

Vol 26 (8) ◽

pp. 2136

Author(s):

Shaokang Zhang ◽

Ru Wang ◽

Linglin Xu ◽

Andreas Hecker ◽

Horst-Michael Ludwig ◽

...

Keyword(s):

Compressive Strength ◽

Flexural Strength ◽

Bond Strength ◽

Cement Mortar ◽

Retention Rate ◽

Methyl Cellulose ◽

Tensile Bond Strength ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

Cement Mortars

This paper studies the influence of hydroxyethyl methyl cellulose (HEMC) on the properties of calcium sulfoaluminate (CSA) cement mortar. In order to explore the applicability of different HEMCs in CSA cement mortars, HEMCs with higher and lower molar substitution (MS)/degree of substitution (DS) and polyacrylamide (PAAm) modification were used. At the same time, two kinds of CSA cements with different contents of ye’elimite were selected. Properties of cement mortar in fresh and hardened states were investigated, including the fluidity, consistency and water-retention rate of fresh mortar and the compressive strength, flexural strength, tensile bond strength and dry shrinkage rate of hardened mortar. The porosity and pore size distribution were also analyzed by mercury intrusion porosimetry (MIP). Results show that HEMCs improve the fresh state properties and tensile bond strength of both types of CSA cement mortars. However, the compressive strength of CSA cement mortars is greatly decreased by the addition of HEMCs, and the flexural strength is decreased slightly. The MIP measurement shows that HEMCs increase the amount of micron-level pores and the porosity. The HEMCs with different MS/DS have different effects on the improvement of tensile bond strength in different CSA cement mortars. PAAm modification can improve the tensile bond strength of HEMC-modified CSA cement mortar.

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Classification of paediatric brain tumours by diffusion weighted imaging and machine learning

Scientific Reports ◽

10.1038/s41598-021-82214-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jan Novak ◽

Niloufar Zarinabad ◽

Heather Rose ◽

Theodoros Arvanitis ◽

Lesley MacPherson ◽

...

Keyword(s):

Diffusion Coefficient ◽

Apparent Diffusion Coefficient ◽

Posterior Fossa ◽

Brain Tumours ◽

Diffusion Weighted Imaging ◽

Regions Of Interest ◽

Apparent Diffusion Coefficients ◽

Diffusion Weighted ◽

Apparent Diffusion ◽

Paediatric Brain Tumours

AbstractTo determine if apparent diffusion coefficients (ADC) can discriminate between posterior fossa brain tumours on a multicentre basis. A total of 124 paediatric patients with posterior fossa tumours (including 55 Medulloblastomas, 36 Pilocytic Astrocytomas and 26 Ependymomas) were scanned using diffusion weighted imaging across 12 different hospitals using a total of 18 different scanners. Apparent diffusion coefficient maps were produced and histogram data was extracted from tumour regions of interest. Total histograms and histogram metrics (mean, variance, skew, kurtosis and 10th, 20th and 50th quantiles) were used as data input for classifiers with accuracy determined by tenfold cross validation. Mean ADC values from the tumour regions of interest differed between tumour types, (ANOVA P < 0.001). A cut off value for mean ADC between Ependymomas and Medulloblastomas was found to be of 0.984 × 10−3 mm2 s−1 with sensitivity 80.8% and specificity 80.0%. Overall classification for the ADC histogram metrics were 85% using Naïve Bayes and 84% for Random Forest classifiers. The most commonly occurring posterior fossa paediatric brain tumours can be classified using Apparent Diffusion Coefficient histogram values to a high accuracy on a multicentre basis.

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