Development of Improved Electrodeposition Method for Repair of Reinforced Concrete Structures

Deterioration of reinforced concrete members and their repair methods have been reported in various concrete published reports. Electrodeposition method is one of these repair methods for repairing deteriorated concrete members using an electrochemical mechanism. The purposes of the electrodeposition method are to fill cracks in concrete and to coat the concrete surface by electrodeposits of chemical compounds. This can be accomplished by passing a weak direct current (1.0–3.0 A/m2 of concrete surface area) between a reinforcing steel bar (cathode) in concrete and an external electrode (anode) located in an external solution near the concrete surface. This method also accomplishes corrosion protection and desalination/re-alkalization, as well as crack closure or surface coating by the electrodeposits. Therefore, it is considered that the electrodeposition is effective in repairing deteriorated concrete members because of chloride attack or carbonation. However, there is very little work on the selection of appropriate electrodeposition conditions such as the type of the cation, its concentration, or type of external electrode for repairing existing reinforced concretes. Therefore, the objective of this paper is to investigate the electrodeposition conditions such as external solution or an external electrode for repairing reinforced concrete structures. From this study, the most suitable electrodeposition conditions to repair deteriorated concrete members are found to be a magnesium acetate-based external solution and an aluminum sacrificial electrode

Hamilton-Jacobi-Bellman equation of nonlinear optimal control problems with fractional discount rate

This paper derives the Hamilton-Jacobi-Bellman equation of nonlinear optimal control problems for cost functions with fractional discount rate from the Bellman's principle of optimality. The fractional discount rate is described by Mittag-Leffler function that can be considered as a generalized exponential function

Repair Inspection Technique Based on Elastic-Wave Tomography Applied for Deteriorated Concrete Structures

Applying elastic wave tomography as an innovative NDT method, the evaluation of velocity distribution in three-dimensional (3D) before and after the repair is introduced in this study. The increase in the velocity with penetration of the repair material according to the repair effect is identified visually and quantitatively. The 3D tomography technique is newly proposed for one-side access inspection, using drill hammering to generate an elastic wave. Accordingly, the elastic wave velocity distribution result enables to visualize the internal quality of concrete after patch repair is successfully done. In addition, an attempt for reinforced concrete (RC) slab panels is made to confirm the effectiveness of the repair by comparing the velocity distribution of elastic waves obtained from acoustic emission (AE) tomography analysis, before and after the repair. Thus, the velocity recoveries due to injection are found in all the slab panels, and it is confirmed that the elastic wave velocities obtained using this technique can serve as an indicator for examining the state of crack and void filling with injected material. Further, a good correlation is found between the low-velocity region before repair and the amount of injection. These results show the potential of the AE tomography technique to be used as a method for estimating the effect of injection repair

A novel replication-independent histone H2a gene in mouse

BACKGROUND: An uncharacterized histone H2a-coding transcript (E130307C13) has been cloned from a mouse full-length cDNA library. This transcript is encoded on chromosome 6, approximately 4 kb upstream of a histone H4 gene, Hist4h4. The proteins encoded by this transcript and the human H2afj mRNA isoform-2 have the highest amino acid similarity. In this paper, we characterize it from the expression pattern given by quantitative RT-PCR. RESULTS: Quantitative RT-PCR indicated that the gene that encodes E130307C13 (E130307C13) is regulated in a replication-independent manner, and therefore it is H2afj. Certainly, H2afj transcript lacks a stem-loop structure at the 3'-UTR but contains a poly (A) signal. In addition, its promoter region has a different structure from those of the replication-dependent histone H2a genes. CONCLUSION: The bioinformatics imply that E130307C13 is a replication-independent H2a gene. In addition, quantitative RT-PCR analysis shows that it is replication-independent. Thus, it is H2afj, a novel replication-independent H2a gene in mouse

Investigation on the Corrosion of Coated Steel Plates with Impact Defect using Divided Steel Plates

A method utilizing divided steel plates was used to investigate the corrosion of coated steel plates with impact defect while continuously submerged in 3% NaCl solution. The polarization behavior of circular divided steel plates was first compared to that of undivided ones. Half-cell potential and polarization resistance results show similar trend in divided and undivided form especially at the later stages of exposure. The method of using circular divided steel plates was then used to monitor the macrocell as well as microcell corrosion in coated steel plates induced with defect. The test results show that the defect causes macrocell corrosion to occur between the defect and sound portions. The impact defect also caused the reduction in the polarization resistance and consequently higher microcell corrosion at the neighbouring sound coated portions

Reduction of dissolved oxygen in minimizing corrosion

Concrete structures are susceptible to corrosion especially when exposed to marine environment. In order to minimize the corrosion in reinforced concrete, reduction of dissolved Oxygen (DO) in mixing water is recommended. The DO is the measurement of the amount of free Oxygen that is dissolved in water which is proportional to the corrosion rate of steel bars inside concrete. In this paper, the use of industrial waste/by-products, agricultural waste, natural minerals, and green inhibitors as additive for cement in reducing the DO level of the mixing water was explored. Candidate materials from different types of agricultural waste, industrial waste, natural minerals, and green inhibitors. The percentage difference of DO were computed for all types of materials as ash or powder or extract in room temperature. This is the percentage difference of DO level in distilled water and the solution mixed with the candidate material having a mass ratio of 3 : 2 and/or 3 : 1. Results showed that more than 90% reduction of DO level were achieved when mixed with ginger extract, ginger powder, aloe vera extract, ginger pulp, and rice hull ash. Future experimental studies using the candidate materials producing reinforced concrete specimens with high reduction of DO level in mixing water is recommended

Development of a Damage Detecting Method for RC Slabs by Means of Machine Learning

It is beneficial to understand damage conditions of RC structural members by non-destructive methods. In this study, K-means clustering method was applied to the AE wave data in order to develop a damage detection method. From the result of this study, the damaged area had the relatively large number of AE hits and AE energy. In addition, from the result of the K-means clustering of the power spectral density of AE waves, the data could be separated into the obviously damaged area and other areas

Comparative analysis of expression of histone H2a genes in mouse

BACKGROUND: At least 18 replication-dependent histone H2a genes are distributed in 3 Hist gene clusters on different chromosomes of the mouse genome. In this analysis we designed specific PCR primers for each histone H2a transcript and studied the expression levels and patterns using quantitative RT-PCR (qRT-PCR). In addition, we compared histone H3 K9 acetylation levels in the promoter regions of H2a genes by ChIP (chromatin immunoprecipitation) – quantitative PCR (qPCR) analysis. RESULTS: RT-PCR analysis indicated that all 20 histone H2a genes assessed in this study are expressed. The replication-dependent histone H2a genes have different expression levels but similar expression patterns. Among the 20 histone H2a genes, the expression-level of H2afz, a replication-independent gene, was highest, and that of Hist1h2aa, a replication-dependent gene, was lowest. Among 18 replication-dependent H2a genes, the expression level of Hist3h2a was highest. The ChIP-qPCR analysis showed that histone H3 K9 acetylation levels in promoter regions of both H2afz and Hist3h2a are clearly higher than that in the promoter region of Hist1h2aa. The H3 K9 acetylation level in the promoter of Hist1h2aa is similar to that in the γ-satellite region. CONCLUSION: These results strongly suggest that histone H3 K9 acetylation plays a role in the expression of histone genes

Effect of Blast Furnace Slag Powder and Fly Ash on Durability of Concrete Mixed with Seawater

According to the report of the United Nations, it is said that two-third of world population would be influenced by water shortage before 2050. To use fresh water effectively, the usage of seawater in concrete industry seems imperative. However, the usage of seawater as concrete material is prohibited in almost all the standards or specifications around the world. In this article, the usage of seawater as a material of concrete based on the results of experimental works and deterioration prediction was discussed. Especially, the effects of by-products such as blast furnace slag or fly ash on the durability of concrete mixed with seawater were evaluated. In the experimental works, the measurements of the material diffusivity/permeability such as chloride ion diffusivity, carbonation rate, and oxygen permeability in concrete/mortar were conducted. Also, the time-dependent changes of corrosion rate of steel bar embedded in mortar were periodically measured. At the same time, immobilization ability of cement matrix and corrosion threshold chloride ion content of steel bar were evaluated. Based on the above data, the initiation and propagation periods were predicted, and the durability of concrete mixed with seawater and the effectiveness of adding by-products were discussed. Based on the results of the present article, it was said that the period before the generation of cracks due to steel corrosion in concrete mixed with seawater was almost same with that with fresh water under severe chloride attack environment. Also, it could be concluded that the addition of blast furnace slag powder or fly ash might contribute significantly to the corrosion resistance of steel bar as well as low penetrability of materials

Effect of Crack Repair by Bio-Based Materials Using Alginate and Bacillus Subtilis under Wet and Dry Environment Part-II

This study examined durability of mortar after repairing crack using alginate gel films (1.5wt.%) mixed with healing agents under seawater splayed condition. The healing agents consist of Bacillus subtilis (natto) as an aerobic microorganism and glucose as an organic carbon source, thereby producing insoluble calcium carbonate in the gel films in the presence of calcium ions. In this study, repaired mortar was dried under room condition for half year and exposed at seawater splayed condition for another half year. After that, surface condition, elastic wave velocity was measured. In addition, the inside situation in the crack was observed by X ray computed tomography. Based on the results of elastic wave velocity, the property of repair material in mortar was improved under the seawater splayed condition. Additionally the substance in crack derived from healing agents was remained even after seawater splayed exposure