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Fly ash is an industrial by-product that is widely used in the cement industry. Traditional methods used to investigate the influence of fly ash on the hydration behavior of cement are destructive and cannot accomplish a continuous tracing of the hydration process. In this study, the influence of fly ash incorporation on the hydration process of cement is evaluated using measured electrochemical data obtained from the electrochemical impedance spectroscopy approach. A novel equivalent circuit model that considers the electrochemical characteristics of cement during the hydration process is proposed to investigate the electrochemical property of the blended cement. The resistance parameter of the model, Rct1, was found to have a positive correlation with hydration degree and compressive strength during hydration. With this parameter, the method can be used to non-destructively trace and characterize the effects of fly ash incorporation on the cement hydration process.

The chloride-induced corrosion of reinforcement in concrete is a serious problem. In this study, the chloride ion migration in cement materials blended with fly ash or/and slag is studied by the electrochemical impedance spectroscopy (EIS) method. A novel equivalent circuit model Rs(Q1(Rct1W1))(Q2(Rct2W2)) is established to analyze the chloride ion migration. The results indicate that increasing the amount of fly ash or/and slag enhances the resistance to chloride ion migration. The chloride ion migration depth can be qualified by an equation that is a function of the parameter (Rct1) of the circuit model. With this function, the chloride ion migration depth in cement materials replaced with fly ash or/and slag can be predicted by EIS method.

A X-ray micro-computed tomography (XCT) imaging method is proposed to measure and analysis the corrosion behavior of rebar in a marine environment. The experimental results reveal that the time-dependent corrosion morphology of rebar in the three-dimensional configuration can be clearly visualized and certain corrosion parameters can be determined. Based on the characteristics analysis of XCT image, the time point of the initial rust and corrosion-induced crack are estimated. Moreover, the whole corrosion process can be divided into three phases as corrosion initiation (chloride penetration), free expansion and cracking, which agrees with the frequently used corrosion model.

Camptothecin (CPT) is an antitumor alkaloid first isolated from Chinese tree Camptotheca acuminata Decaisne (Nyssaceae). Several attempts have been made to improve CPT production in plant, among which elicitation was considered as a useful method. In this study, camptothecin (CPT) and its derivative 10-hydroxycamptothecin (HCPT) accumulation, as well as related gene transcript profiling in C. acuminata seedlings, in response to abscisic acid (ABA, 100 µM), methyl jasmonate (MJ, 100 µM) and salicylic acid (SA, 1 mM) were examined. Results showed that all three elicitors enhanced both camptothecin and 10-hydroxycamptothecin accumulation, among which abscisic acid (ABA) exhibited the most effective elicitation with the increment of 1.44-fold for CPT (1.81 mg/g DW) and 1.21-fold for HCPT (2.6 mg/g DW) respectively. Our expression results showed a positive correlation between gene expression and alkaloid accumulation, suggesting that alkaloid accumulation may be the result of the synchronous up-regulation of several genes such as 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) and tryptophan decarboxylase (TDC) involved in CPT biosynthesis under the treatment of various elicitors. Our work provided useful information of further understanding molecular regulation mechanism of CPT biosynthesis and its metabolic engineering in C. acuminata in the future.Read Complete Article at ijSciences: V2201312375