Retardation effect and corrosion detection of blended cement pastes

AbstractDifferent blended cement pastes were prepared from OPC+10%, 20% and 30% slag (air cooled) by using a water/solid ratio (W/S) of 0.25 (by weight). The hydration was conducted for various time intervals at 1, 3, 7, 28 and 90days. Each hardened cement paste was tested for its physico-chemical and mechanical characteristics under normal curing conditions. In addition, the phase compositions of the formed hydration products were identified by means of X-ray diffraction (XRD). Moreover, the electrical conductivity and corrosion detection measurements were also carried out for all the previous blended cements under investigation. The results showed that the combined water contents increase gradually with hydration time for all hardened cement pastes and the partial replacement of OPC by slag cause a notable drop in the combined water content for all blend pastes. The compressive strength values obtained for the hardened blended cement pastes is less than that of neat OPC pastes at all ages of hydration up to 90days but the sample with 30% slag+70% OPC had the highest compressive strength. The electrical conductivity of the studied blended cement pasts was lower than that of OPC due to less alkali hydroxides when cement is diluted by the added slag. The significance of low potentials of steel bars in these pastes indicates inhibition of corrosion. As a result, it can be concluded that the mineral admixtures retards the hydration and inhibit the corrosion for cement pastes

XYF3 (X=Ag, K ve Y=Mg, Ni, Zn, Co, Mn) malzemelerinin yapısal ve elastik özelliklerinin teorik olarak incelenmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Genel formülü ABF3 (A: Alkali metaller, B: Alkali toprak metaller) olan Florid Perovskitler fotolüminesans, piezoelektriklik, ferromagnetiklik ve magnetik direnç gibi ilginç özellikleri nedeniyle dikkatleri üzerlerine çekmişlerdir. Bu eşsiz özellikleri, ABF3 bileşiklerini optik uygulamalarda, lenslerde, magnetik tünel eklemlerinde ve medikal uygulamalarda kullanılmak üzere elverişli duruma getirmiştir. Bununla birlikte bir malzemenin teknolojik veya endüstriyel uygulamalarda kullanılabilir olup olmadığını anlamak için özellikle onun elastik ve mekanik özelliklerinin de bilinmesi gerekmektedir. Bu tezde, XYF3 (X=Ag,K and Y=Mg, Ni, Zn, Co, Mn) bileşiklerininyapısal ve elastik özellikleri yoğunluk fonksiyonel teorisi ve genelleştirilmiş gradyan yaklaşımı kullanılarak hesaplanmıştır. Çalışılan malzemelerin örgü parametrelerinin daha önceki deneysel sonuçlarla uyum içinde olduğu bulunmuştur. Ayrıca, çalışılan tüm malzemeler için Shear modülü, Young modülü, Poisson oranı, Kleinman parametresi, elastik anizotropik faktörü ve Lame katsayıları da hesaplanmış ve detaylı bir şekilde tartışılmıştır. Bunun yanı sıra B/G oranı ve Poisson oranı sonuçları kullanılarak, çalışılan tüm malzemelerin esnek ya da kırılgan olup olmadıkları tanımlanmıştır.Fluoride Perovskites with the general formula ABF3 (A: Alkali metals, B: Alkaline earth metals) have received great attention because of their interesting properties such as photoluminescence, piezoelectricity, ferromagnetism and magnetoresistivity. These unique properties of ABF3 compounds make them favorable materials to use in optical applications, lenses, magnetic tunnel junctions and medical applications. However, in order to determine whether a material can be used in technological or industrial applications, it is necessary to know especially its elastic and mechanical properties. The structural and elastic properties of XYF3 (X=Ag,K and Y=Mg, Ni, Zn, Co, Mn) compounds have been calculated by using generalized gradient approximation within the density functional theory in this thesis. The calculated lattice parameters of studied compounds have been found in good agreement with the corresponding experimental results. Additionally, the shear modulus, Young's modulus, Poisson's ratio, Kleinman parameter, elastic anisotropic factor and Lame's coefficients for all studied compounds are also calculated and discussed in detail. Besides, the ductile and brittle characters of the studied compounds have been determined using B/G ratio and Poisson's ratio

The Effect of Using Commercial Red and Black Iron Oxides as a Concrete Admixtures on its Physiochemical and Mechanical Properties

Study discuss the effect of using commercial red and black iron oxides (RIO and BIO) as a concrete admixtures in percentages do not exceeded 2.5% of each oxide from the amount of cement, this study tested the effect of every portion from each oxide at different ages on the compressive strength as well as the workability represented as a values of slump. We conclude that the optimum portion of RIO is 2.5%, but for BIO is 1%, while the proposed uses of RIO in concrete technology are retarder through slump increment reach to 50%, coloring material and mineral admixture through Compressive Strength increment (7-365 days) 5.5-12.8%. On the other hand BIO will propose as, coloring material and mineral admixture through Compressive Strength increment (7-365 days) 22.2-30.8%. SEM-images are clearly show the formation of Calcium hydroxide phase at 7-days while at 1-year the CSH phase is a predominate one, in both cases of RIO and BIO. XRD-pattern is supported the results outcomes through SEM-images

Effect of Alkali Concentration on Physico -Chemical and Mechanical Properties of Slag Based Geopolymer Cement.

In this article we studied the effects of sodium hydroxide pellets (SH) and sodium silicate liquid (SSL) as an activator on the physico chemical and mechanical Properties of ground granulated blast furnace slag (GGBFS) geopolymer pastes. Various mixes are prepared using different liquid/solid ratios (L/S) by weight. The hydration characteristics of the various mixes have been tested through determination of total porosity, compressive strength, bulk density, chemically combined water, and XRD analysis at different time intervals from 2 days up to 90 days under relative humidity 100%. The results elucidated that as the quantity of alkali activator increases up to (15% SSL, and 15% SH), the compressive strength increases up to 90 days. The combined water content of all mixes increases up to 90 days. Also the bulk density raises and the total porosity minimizes, this is due to the addition of the pozzolanic materials. All mixes showed good stability of its compressive strength values in 5 % MgSO4 solution. The data showed that mix S6 (100% GGBFS) activated by (15% SSL, and 15% SH) is the most appropriate binding material (geopolymer cement) that has good properties so it can be used as alternative binding materials to the ordinary Portland cement

An investigation of the mechanical properties of ternary blend cement pasts containing a large amount of cement kiln dust

Cement kiln dust is a by-product of the cement industry composed of particles of feedstock and condensed volatilized inorganic salts. The effect of Cement kiln dust (CKD) on the mechanical properties of ternary blend cement pastes was studied by preparing different mixes using 40%CKD, 10% OPC and 50% of three different pozzolanic material (ground granulated blast furnace slag (GGBFS), metakaolin (MK), and ground clay brick (GCB)). The mechanical properties were tested via the determination of compressive strength, bulk density, total porosity, and chemically combined water content at 3, 7, 28, 90, and 180 days. The hydration products were evaluated using x-ray diffraction analysis. The result indicated that 40%CKD greatly enhances the activation of GGBFS, MK, and GCB. The paste that contains (10% OPC, 40% CKD, and 50% GGBFS) gives the highest compressive strength, while (10% OPC, 40% CKD, and 50% GCB) gives the lowest compressive strength

The relationship between associative learning, transfer generalization, and homocysteine levels in mild cognitive impairment

Previous studies have shown that high total homocysteine levels are associated with Alzheimer's disease (AD) and mild cognitive impairment (MCI). In this study, we test the relationship between cognitive function and total homocysteine levels in healthy subjects (Global Dementia Rating, CDR = 0) and individuals with MCI (CDR = 0.5). We have used a cognitive task that tests learning and generalization of rules, processes that have been previously shown to rely on the integrity of the striatal and hippocampal regions, respectively. We found that total homocysteine levels are higher in MCI individuals than in healthy controls. Unlike what we expected, we found no difference between MCI subjects and healthy controls in learning and generalization. We conducted further analysis after diving MCI subjects in two groups, depending on their Global Deterioration Scale (GDS) scores: individuals with very mild cognitive decline (vMCD, GDS = 2) and mild cognitive decline (MCD, GDS = 3). There was no difference among the two MCI and healthy control groups in learning performance. However, we found that individuals with MCD make more generalization errors than healthy controls and individuals with vMCD. We found no difference in the number of generalization errors between healthy controls and MCI individuals with vMCD. In addition, interestingly, we found that total homocysteine levels correlate positively with generalization errors, but not with learning errors. Our results are in agreement with prior results showing a link between hippocampal function, generalization performance, and total homocysteine levels. Importantly, our study is perhaps among the first to test the relationship between learning (and generalization) of rules and homocysteine levels in healthy controls and individuals with MCI

Effect of Pb+2 ion on physico chemical properties of fly ash -slag geopolymer pastes

The aim of this work is to examine the stabilization or immobilization of heavy metals such as Pb (NO3)2 in a various paste of slag and slag-FA based and on geopolymer pastes. Geopolymer prepared by 100% slag and partially substitution of slag by 15% Fly ash (FA) [85% slag+15%FA]. The alkaline activator is (1:1) liquid sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution (the concentration of sodium hydroxide is 5 Molar). Different percentages of Pb (NO3)2 were added to the alkali activation mixture, 0.5%, and 1% by mass% of the solid binder. The obtained geopolymer specimens are cured in water for 90 days. The compressive strength test, combined water content, X-ray diffraction (XRD), Atomic absorption, and Transform infrared spectrometry (FTIR) are examined. The results showed that the used lead nitrate caused a retarding effect for the hydration of the investigated geopolymer mixes.The best mix for immobilization were 99.98% in mix SF1[85%slag+15%Fly ash +0.5%Pb+2]

Statistical Inference of Marshall-Olkin Extended Exponential Distribution Based on Progressively Type-I Censored Data

In this article, we intend to study the progressive Type-I censoring (PT-TC) that has been examined, employing the Marshall-Olkin extended exponential (MOEE) distribution as the fundamental lifetime distribution. The censoring technique is believed to be independent and non-informative. Because maximum likelihood (ML) estimators cannot be derived in closed form, ML estimates (MLEs) are calculated via Newton-Raphson method approaches. In this approach, MLEs and asymptotic confidence intervals for unknown parameters are produced. Under squared error and linear exponential (LINEX) loss functions, the Bayes estimations of unknown parameters with gamma priors are evaluated. Once both parameters are unknown, the Bayes estimators cannot be computed explicitly. Then, the Markov Chain Monte Carlo (MCMC) technique is employed to construct Bayes estimates using the Metropolis-Hasting (MH) algorithm. The highest posterior density (HPD) credible intervals of the unknown parameter are calculated. Simulation studies are carried out to explore the finite sample effectiveness of the recommended estimators, as well as data set analyses at various schemes of PT-TC samples

Effects of administration of 10 nm or 50 nm gold nanoparticles (AuNPs) on blood profile, liver and kidney functions in male albino rats

This work aimed to investigate the effect of acute and chronic administration of gold nanoparticles (GNPs) on liver and kidney functions, blood glucose concentration, lipid profile, and haematological parameters in male albino rats. Two experiments were conducted. In acute study: Fifty-four adult mature male rats were randomly assigned into three equal groups (18 per group). Group 1 (control group): in which rats were received intramuscular (i.m) injection of 1 ml normal saline 0.9%. Group 2 (50 nm GNPs group): rats were i.m. injected with a single dose of 75 µg 50 nm GNPs/kg body weight (bwt). In Group 3 (10 nm GNPs group): rats were i.m. injected with a single dose of 75 µg 10 nm GNPs/kg bwt. In chronic study: Eighteen adult male rats were randomly divided into three equal groups (6 per group). Group І (control): rats were intramuscular (i.m) repeatedly injected with 1 ml normal saline 0.9% once/week 5 for weeks. Group 2 (50 nm GNPs): rats were i.m. injected with once/week with a dose of 75 µg 50 nm GNPs/kg bwt) for 5 weeks. In Group 3 (10 nm GNPs): male rats were i.m. injected with once/week with a dose of 75 µg 50 nm GNPs/kg bwt for 5 weeks, followed by 3 weeks washout period for all groups. Blood was collected at 3, 7, and 60 days in acute experiment, while, they were collected only before and after 2 months in chronic experiment. Acute and chronic administration of GNPs (10 or 50 nm size) in male albino rats induced no significant alterations for liver and kidney functions, lipid profile parameters and different haematological parameters at days 3 and 60 of the study. However, on day-7 post-treatment, GNPs-treated rats showed significantly (P <0.05) higher serum ALT, AST, ALP, urea, creatinine, glucose, and different lipid profile and decreased HDL level. Chronic administration of 10 nm or 50 nm GNPs significantly (P <0.05) decreased serum glucose levels. In conclusion acute or chronic administration of 10 nm or 50 nm GNPs could alter the liver, kidney functions and blood profile on day 7 post-treatment, however, these values returned to the normal levels on day 60 post- injection. Also, the chronic administration of GNPs induced a hypoglycemic effect in male albino rats

Adaptive inertial Yosida approximation iterative algorithms for split variational inclusion and fixed point problems

In this paper, we present self-adaptive inertial iterative algorithms involving Yosida approximation to investigate a split variational inclusion problem (SVIP) and common solutions of a fixed point problem (FPP) and SVIP in Hilbert spaces. We analyze the weak convergence of the proposed iterative algorithm to explore the approximate solution of the SVIP and strong convergence to estimate the common solution of the SVIP and FPP under some mild suppositions. A numerical example is demonstrated to validate the theoretical findings, and comparison of our iterative methods with some known schemes is outlined