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Theoretical models to evaluate the effect of SiO2 and CaO contents on the long‑term compressive strength of cement mortar modified with cement kiln dust (CKD)

Abdalla Aso A., Salih Mohammed Ahmed

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e105

EN

Cement kiln dust (CKD) is a fine powder similar to Portland cement in appearance and produced during grinding and burning of the raw material in the cement kiln. Large amounts of CKD have accumulated in the cement factories annually. It is necessary to re-use this waste material in the construction field instead of landfilling, causing environmental problems, such as the death of vegetation and groundwater pollution. One of the choices to re-use CKD is replacing Portland cement in cement-based mortar and reducing greenhouse gas emissions like carbon dioxide to the atmosphere. This study evaluated the effect of the main two components of CKD, such as SiO2 and CaO, on the long-term compressive strength of cement-based mortar up to 360 days of curing. For that purpose, 167 data of cement-based mortar samples modified with CKD were collected from literature and analyzed. Water-to-binder ratio (w/b) was ranged from 0.34 to 0.76, CKD content ranged from 0 to 50% (dry weight of cement), different CaO and SiO2 of CKD and cement are ranged from 17.64 to 25.45%, and 51.45 to 65.57%, respectively. Several soft computing models, such as multi-expression programming (MEP), artificial neural network (ANN), nonlinear regression (NLR), and full quadratic (FQ), were developed to predict the compressive strength of the cement mortar modified with CKD. Statistical assessment tools were also used to evaluate the proposed models. It was obtained from the modeling results that are increasing SiO2(%) increased the compressive strength of the mortar, and increasing CaO (%) decreased compressive strength for CKD content from 0 to 15% and increasing compressive strength for CKD content of 15-50%. According to the assessment criteria, the ANN model predicted compressive strength up to 360 days of curing better than other developed models with high R2 and a20-index and low RMSE, MAE, SI, and OBJ. The second-best model was the MEP model. Based on the sensitivity analysis, the curing time is the most influential parameter in compressive strength prediction of cement-based mortar modified with CKD.

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Evaluation of different binder combinations of cement, slag and ckd for s/s treatment of tbt contaminated sediments

Lindh Per, Lemenkova Polina

Acta Mechanica et Automatica

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2021

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Vol. 15, no. 4

236--248

EN

The seabed in the ports needs to be regularly cleaned from the marine sediments for safe navigation. Sediments contaminated by tributyltin (TBT) are environmentally harmful and require treatment before recycling. Treatment methods include leaching, stabilisation and solidification to remove toxic chemicals from the sediments and improve their strength for reuse in the construction works. This study evaluated the effects of adding three different binder components (cement, cement kiln dust (CKD) and slag) to treat sediment samples collected in the port of Gothenburg. The goal of this study is to assess the leaching of TBT from the dredged marine sediments contaminated by TBT. The various methods employed for the treatment of sediments include the application of varied ratios of binders. The project has been performed by the Swedish Geotechnical Institute (SGI) on behalf of the Cementa (HeidelbergCement Group) and Cowi Consulting Group, within the framework of the Arendal project. An experiment has been designed to evaluate the effects of adding CKD while reducing cement and slag for sediment treatment. Methods that have been adopted include laboratory processing of samples for leaching using different binder combinations, followed by statistical data processing and graphical plotting. The results of the experiment on leaching of TBT for all samples are tested with a varied ratio of cement, slag, CKD and water. Specimens with added binders 'cement/CKD' have demonstrated higher leaching compared to the ratio 'cement/slag/CKD' and 'cement/slag'. The 'CKD/slag' ratio has presented the best results followed by the ‘cement/slag/CKD’, and can be used as an effective method of s/s treatment of the sediments. The results have shown that the replacement of cement and slag by CKD is effective at TBT leaching for the treatment of toxic marine sediments contaminated by TBT.

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Czynnik FGF23 - nowy parametr rokowniczy w przewlekłej chorobie nerek?

Bobilewicz Dagna

Laboratorium Medyczne

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2019

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nr 1

10--13

PL

Czynnik wzrostu fibroblastów FGF23 produkowany w osteoblastach i osteocytach jest określany jako istotny element w regulacji gospodarki wapniowo-fosforanowej, zwiększając wydalanie fosforanów i w nadmiarze prowadząc do hipofosfatemii. Działa również poprzez zahamowanie syntezy witaminy 1,25 (OH)2 D. Szczególna rola jest mu przypisywana w indukowaniu tak pośrednio, jak i przez bezpośredni wpływ na przerost lewej komory, niekorzystnych zmian w układzie sercowo-naczyniowym, będących przyczyną zwiększonej śmiertelności w przewlekłej niewydolności nerek, charakteryzującej się wzrostem stężenia FGF23. Brak jest jeszcze udokumentowanych klinicznych badań randomizowanych potwierdzających korzyści z obniżania stężenia FGF23 w PChN.

EN

Fibroblast growth factor 23 (FGF23) produced in osteoblasts is described as a new element regulating calcium-phoshate metabolism. It increases phosphate urinary excretion and in excess causes hypophoshatemia. It also acts by inhibiting vitamin 1.25 (OH)2 D synthesis. It plays particular role in inducing cardiovascular changes indirectly as well as by a direct impact on left ventricular hypertrophy. These changes are responsible for increased mortality in chronic kidney disease, in which the serum level of FGF23 is elevated. However there are still no randomized clinical trials demonstrating better outcome associated with the therapeutic reduction of FGF23 in CKD.

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Early stage of chronic kidney disease by using statistical evaluation of the previous measurement results

Akben S. B.

Biocybernetics and Biomedical Engineering

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2016

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Vol. 36, no. 4

626--631

EN

Chronic kidney disease (CKD) that causes the progressive losses in kidney functions is one of the major public health problems. Expert medical doctors can diagnose the CKD through symptoms, blood and urine tests in its early stages. However, the diagnosis of CKD might be difficult for expert medical doctors in case of the questionable measurement result. Therefore a new mathematical method that would be helpful to the expert medical doctors is required. It can be said that there is no studies related with automatic diagnosis of CKD in the literature. This study aims to remedy this shortcoming in the literature. In this study, for each of test and symptom values, averages of measurement results were calculated separately for healthy subjects and patients. Then the measured values were marked as ‘‘0’’ or ‘‘1’’ (healthy or patient) according to closeness to average values. Finally, the classification was performed by averaging the values marked for each subject. The success rate of the proposed method is between 96% and 98% according to the age ranges. In conclusion section of the study, how to implement the proposed method in real life is offered.