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Shear performance of plain UHPC (ultrahigh-performance concrete) construction joints is studied in both experimental and analytical ways. In push-off tests, three different contact surfaces of the construction joint were considered, while the case without any joint was provided for the reference. Test results indicate that the geometry of contact surfaces greatly affects shear performance of the construction joint. With simplifying structural behavior of contact surfaces and UHPC substrate, the finite-element analysis model is developed for every case studied by utilizing the ABAQUS software and validated against the test results. Agreement between experimental and numerical simulation results is excellent especially in terms of displacement, strength, and failure mechanism. It is expected that the present work provides a basis for further study on reinforced UHPC construction joints.

Close-packed structures of uniformly sized spheres are ubiquitous across diverse material systems including elements, micelles, and colloidal assemblies. However, the controlled access to a specific symmetry of self-assembled close-packed spherical particles has not been well established. We investigated the ordering of spherical block copolymer micelles in aqueous solutions that was induced by rapid temperature changes referred to as quenching. As a function of quench depth, the quenched self-assembled block copolymer micelles formed three different close-packed structures: face-centered cubic (fcc), random stacking of hexagonal-close-packed layers (rhcp), and hexagonal-close-packed (hcp). The induced hcp and rhcp structures were stable for at least a few weeks when maintained at their quench temperatures, but heating or cooling these hcp and rhcp structures transformed both structures to fcc crystallites with coarsening of the crystal grains, which suggests that these noncubic close-packed structures are intermediate states. Time-resolved scattering experiments prove that the micellar rhcp structures do not originate from the rapid growth of competing close-packed structures. We speculate that the long-lived metastable hcp and rhcp structures originate from the small size of crystal grains, which introduces a nonnegligible Laplace pressure to the crystal domains. The reported transitions from the less stable hcp to the more stable rhcp and fcc are experimental observations of Ostwald's rule manifesting the transition order of the key close-packed structures in the crystallization of close-packed uniform spheres.

Inhibitor is one of the most accepted method to reduce, prolong the initiation of steel corrosion and increase the threshold value of Cl− and CO32− ions. In present study, we have mixed sodium salt of phosphate and benzoate along with benzo triazole in water to prepare the inhibitor. Open circuit potential (OCP) results show that 5 v/v% inhibitor was exhibited most positive (nobler) potential than others at its prolonged exposure in simulated concrete pore (SCP) + 3.5 wt% NaCl solution. The OCP of 3 and 5% inhibitor containing solution proved that these concentrations are away from under corrosion region of steel rebar even after 192 h of exposure in SCP + 3.5 wt% NaCl solution. Electrochemical impedance spectroscopy (EIS) results show that the charge transfers resistance (Rct) to be highest for 5% inhibitor and gradually decreased once the concentration was reduced with exposure periods. Potentiodynamic studies reveal that inhibitor shows passive properties due to adsorption of inhibitor molecules on steel surface and enhance the corrosion resistance properties. The efficiency was calculated using Rct and corrosion current density (Icorr) process and found that 3 and 5% inhibitor exhibit around 89 and 96%, respectively after 1 h of exposure in SCP + 3.5 wt% NaCl solution.

The stress due to volume change causes cracking in concrete, so that construction joint is intentionally prepared for an efficient construction and crack controlling in mass concrete structure. Cold joint means a weak joint area which may occur due to imperfect treatment of pre-placed concrete surface and delayed concrete delivery. Many researches have been performed for a quantitative evaluation of chloride ingress in cold joint concrete, which puts an emphasis on the more rapid penetration of chloride ions. The applied loading condition is one of the major reasons for concrete cracking and it also has a great effect on chloride penetration before the stage of cracking. Steel corrosion in concrete is accelerated when concrete cover has unsound area such as crack and cold joint. Chloride diffusion behavior varies with reduction of porosity and enhancement of hydrates, so called time effect on chloride diffusion. The effect of time and of cold joint on chloride diffusion is an important parameter for quantitative durability design for RC (Reinforced Concrete) structures exposed to various loading conditions. This paper investigates changes in chloride diffusion coefficient in cold joint concrete considering time effect and various loading conditions. Concrete samples with 0.6 of w/b (water to binder) and 40% replacement ratio of GGBFS (Ground Granulated Blast Furnace Slag) were prepared, and the chloride diffusion coefficients were measured for 1 year-cured concrete considering tensile and compressive loading conditions. The results were analyzed with the previous results in 91 days-cured concrete for evaluation of time effect. In the work, the time dependent chloride diffusion behaviors were quantitatively evaluated and discussed considering various effects of GGBFS, tensile and compressive stress levels, and cold joint.

In this study,Al–Zn and Al–Mg coatings were deposited on steel substrates by an arc thermal spray process.X-ray diffraction and scanning electron microscopy were used to characterize the deposited coatings and corrosion products.Open circuit potential（OCP）,electrochemical impedance spectroscopy,and potentiodynamic studies were used to assess the corrosion characteristics of these coatings after exposure according to the Society of Automotive Engineers（SAE）J2334 solution of varying durations.This solution simulates an industrial environment and contains chloride and carbonate ions that induce corrosion of the deposited coatings.However,the Al–Mg alloy coating maintained an OCP of approximately-0.911 V versus Ag/Ag Cl in the SAE J2334 solution even after 792 h of exposure.This indicates that it protects the steel sacrificially,whereas the Al–Zn coating provides only barrier-type protection through the deposition of corrosion products.The Al–Mg coating acts as a self-healing coating and provides protection by forming Mg6Al2（OH）16CO3（Al–Mg layered double hydroxides）.Mg6Al2（OH）16CO3has interlocking characteristics with a morphology of plate-like nanostructures and an ion-exchange ability that can improve the corrosion resistance properties of the coating.The presence of Zn in the corrosion products of the Al–Zn coating allows dissolution,but,at the same time,Zn5（OH）6（CO3）2and Zn6Al2（OH）16CO3are formed and act to reduce the corrosion rate.

In the recent years, development and use of nanomaterials are gaining importance in the construction industries due to the advancement of science and technology. In the present investigation, nanosilica (NS) was synthesized from rice husk ash and characterized using XRD, Particle size analysis and SEM techniques. 1% NS by weight was used in cement mortar along with carbon nano tube (0.01%–0.07%) as a cement replacement materials and rock dust (RD) was used as a replacement for river sand. Five different mix combinations were formulated. Polycarboxylate based water reducing admixture was used for improving the workability of the mix. All the combination of mixes derived were subjected to compression, split tensile test, and durability studies such as sorptivity, water absorption, and chloride penetration test. Potentiodynamic polarization study was carried out to understand the corrosion performance of the composite cement mortar. SEM and XRD studies were carried out for the hydrated products of the composite cement mortar. The results showed that NS and CNT increased the compressive strength by 12%–76% and enhanced the corrosion resistance properties than the control.

Electrochemical chloride removal is one of the superior healing methods for chloride affected reinforced (RC) concrete structures. In the present study, the effect of electrochemical chloride removal (ECR) of chloride contaminated concrete consisting of embedded rebar in corroded condition was assessed by measuring the corrosion rate and rebar potential after the ECR treatment at a current density of 0.5, 1.0 and 2.0 mA/m2 and by using three types of anodes namely, TiSA, SSA and, CCPA. Here, ‘current ON’ (ONC) and ‘current OFF’ (OFFC) method was adopted to obtain an efficient and uniform ECR throughout the specimen. From the results, it is found that the increase in current density (1.0 and 2.0 A/m2) increases the chloride removal efficiency. However, the corrosion rate of the rebar was increased at higher current densities and some damage on the CCPA anode material was noticed due to the hydrogen gas evolution in the rebar. It is found that the CCPA is more stable and the chloride removal efficiency was improved at 0.5 A/m2 current density and hence it is suitable for long-time application of ECR process under ONC and OFFC method. This approach allows the easier passage of chloride ions from the cathode to the anode and the current OFFC period allows the system to re-establish the equilibrium between the anode and cathode. From this study, it was found that the ‘‘ONC and OFFC method’’ increases the chloride removal efficiency and thereby preventing the rebar from corrosion.

In this study, an embeddable in-situ corrosion monitoring electrode based on Ce-doped NiFe2O4 was fabricated, and their corrosion performance of the steel rebar was evaluated in the simulated concrete environment under passive and active conditions. The passive and active environment consists of simulated concrete pore solution (SCPS) without and with 3% NaCl. The corrosion performance of embedded steel rebar in concrete was monitored by exposing the concrete specimens under alternate dry and wet condition in 3% NaCl solution. The corrosion behavior of the steel rebar was studied by using open circuit potential, AC-impedance, and potentiodynamic polarization studies. The relative corrosion performance of the embeddable steel rebar was assessed with fabricated corrosion monitoring electrode (FCME) and compared with the surface mounted electrode (SME) by using saturated calomel electrode (SCE). The results revealed that the FCME could use as an in-situ electrode for assessing the corrosion monitoring of the reinforced concrete structures.

Zeolitic imidazolate frameworks (ZIFs) have attracted significant attention as excellent materials for removing toxic substances from wastewater. Herein, a comprehensive first-principles and cluster DFT study was performed to investigate the interaction mechanism of sulfur mustard (HD) simulant, 2-chloroethyl ethyl sulfide (CEES) with ZIF-8 and ZIF-67. The primitive cell of ZIF-8 was optimized using some exchange functional methods, and excellent agreement between experimental and computed cell parameters was found using revised PBE functional. The optimization of several conformations by first-principles DFT calculations showed that the CEES molecule is favorably adsorbed into ZIFs. The adsorption was found to be due to long-range interactions between the CEES molecule and ZIFs' framework. The charge density difference (CDD) iso-surfaces showed no evidence of coordination between CEES molecule and ZIFs, confirming the physisorption mechanism. The ZIF-67 framework showed more negative adsorption energy compared to ZIF-8. On the other hand, cluster DFT calculations showed that clusters with open metal defects could electrostatically interact with the CEES molecule through electron-deficient metal centers. The present conclusions can be used as a reference for the future design of ZIF-based adsorbents.

High fluidity concrete exhibits an excellent self-compacting property. However, the application of typical high-fluidity concrete is limited in the normal strength range (18~35 MPa) due to the large amount of binder. Therefore, it is important to solve these problems by adding a viscosity modifying agent (VMA) with a superplasticizer (PCE), which helps to improve the fluidity of the concrete. In addition, the rheology and stability of the concrete with VMA can be improved by preventing bleeding and segregation issues. Current studies focused on the physical phenomena of concrete such as the fluidity, rheological properties, and compressive strength of normal-strength, high-fluidity concrete (NSHFC) with different types of a polycarboxylate-based superplasticizer (NPCE). The obtained results suggested that the combinations of all-in-one polycarboxylate-based superplasticizers (NPCE) did not cause any cohesion or sedimentation even stored for a long time. The combination of three types of VMA showed the best fluidity (initial slump flow of 595~630 mm) without any segregation and bleeding, and the compressive strength at 28 days was also found to be the highest: 34–37 MPa. From these results, the combination of PCE (2.0%) + HPMC (0.3%) + WG (0.1%) + ST (0.1%) showed an 18% higher plastic viscosity and -4.4% lower yield stress than Plain.

Particulate matters (PMs) generated on construction sites can pose serious health risks to field workers and residents living near construction sites. PMs are generated in a wide range of locations, therefore, they must be managed in real time at various locations within construction sites for practical management of the PMs. However, no such systems exist currently. Therefore, this study aims to develop a system that can manage PMs in real time at multiple locations in a construction site using the Internet of Things technology. Accordingly, measuring instrument, network, and program services were developed as system components, while considering the characteristics of construction sites, and the construction site PM monitoring system was developed by integrating these components. Finally, performance certification and field application tests were performed to verify the developed system. The construction site PM monitoring system (CPMS) achieved grade 1 for reproducibility, relative precision, and data acquisition rate, and grade 2 for accuracy and coefficient of determination. Thus, it received a performance certification of grade 2, in total. In particular, regarding accuracy, which is a shortcoming of the light-scattering method and represents the accuracy of measurements, the CPMS was found to have an accuracy of 74.2%.

Benzimidazole derivatives have been widely investigated as corrosion inhibitors due to their unique chemical reactivity with different metal surfaces. Herein, the effect of heterocyclization on corrosion inhibition mechanisms and bonding of two 2-mercaptobenzimidazole derivatives (MBIs) − 2,3-dihydrobenzo[4,5]imidazo[2,1-b]thiazole (2HBIT) and 3,4-dihydro-2H-benzo[4,5]imidazo[2,1-b]thiazole (3HBIT) – with Fe(1 1 0) surface was comprehensively evaluated using dispersion-corrected density functional theory (DFT). The interaction energies computed from DFT calculations successfully predicted the experimental inhibition performance. The effect of protonation on the adsorption strength of molecules was also investigated. We have found strong covalent bond formation between S, C, and N atoms of molecules and Fe-atoms. The excellent charge transfer between molecules’ atoms and Fe(1 1 0) surface was further confirmed by the projected density of states and electron density difference plots. The adsorption energy of MBI adsorbed on Fe(1 1 0) surface was also determined for comparison purposes. This study showed that the heterocyclization of 2-mercaptobenzimidazole increased the charge transfer and bonding between MBIs and the Fe(1 1 0) substrate, thereby improving their corrosion inhibition performance.

Blended cement is widely used in critical structures mainly because of its enhanced corrosion resistance concerning its durability. This paper presents the long term corrosion performance of blended cements namely; Portland pozzolana cement (PPC) and Portland slag cement (PSC) concrete under the three marine exposure conditions such as, atmospheric zone (AZ), immersion zone (IZ) and splash zone (SZ). Offshore Platform Marine Electrochemistry Center (OPMEC), Tuticorin, Tamil Nadu, India was selected as an exposure station. The concrete cubes were exposed over the period of 10 years and their physicochemical properties such as compressive strength, alkalinity, free chloride content and sulphate content, bio-fouling attachment and electrochemical properties like, AC-impedance and potentiodynamic polarization were carried out and the results obtained were compared with Ordinary Portland Cement (OPC) concrete. XRD and SEM studies were also carried out for both OPC, PPC and PSC concrete samples exposed under various zones. It was observed that the strength and alkalinity of the blended cement concretes were relatively equal to that of OPC concrete. In addition, the pH values of the blended cement concretes are above the threshold limit recommended for depassivation. Furthermore, the resistance to chloride ion penetration was significantly reduced for blended cement concretes than that of OPC concrete and also exhibited very high amount of bio-fouling attachment. The electrochemical studies revealed that the blended cement concretes are having higher corrosion resistance in all three exposure zones than that of OPC concrete. From the results it is observed that the blended cement concretes are technically viable from the durability point of view and highly recommended for aggressive marine environments rather than OPC concrete.

Lauric acid (LA), an eco-friendly fatty acid, is used as phase change materials (PCMs) and tetraethyl orthosilicate (TEOS) as the precursor solution of SiO2 for sol-gel process. In the present study, various core-shell ratios are taken for the microencapsulation of LA with SiO2. The effect of different core-shell ratios on the chemical, structural, and thermal properties are studied by different techniques such as Fourier transform-infrared spectroscope (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). FT-IR, XRD, XPS, SEM, and TEM results confirmed the proper microencapsulation of LA with SiO2 shell while DSC and TGA revealed about excellent thermal stability of the microencapsulated LA. Core-shell ratios played a vital role on the microencapsulation of LA with SiO2 which affected the overall performance and structure of the encapsulated PCMs. PCMs with the highest core-shell ratio i.e., LATEOS6, exhibited the highest encapsulation ratio (92.39%), encapsulation efficiency (93.48%) as well as excellent thermal reliability even after 30 cycles of heating and cooling. These results suggested that microencapsulated LA would be a promising material for thermal energy storage as well as construction building materials (CBMs) to solve mass concrete problems.

Dyeing wastewater from textile industries is often contaminated with chemical pollutants, which causes severe water pollution problems that are challenging to treat. Herein, we report the development of laminated membranes consisted of polysulfone (PSf)/polyetherimide (PEI) layers coated on Nylon-fiberglass-Nylon support by spin/spray-coating technique for the removal of reactive black 5 (RB5) and basic red 18 (BR18) from aqueous solutions via membrane Ultrafiltration (UF). In addition to a pristine polysulfone (PSf) membrane, composite membranes were prepared with 25 wt% (CM25), 30 wt% (CM30), and 35 wt% (CM35) of PEI, and characterized in terms of morphological, wetting, mechanical, and water transport properties along with surface charge and mean pore diameter. Morphological characterization by SEM showed homogeneous and uniform distribution of PSf/PEI membrane layer on the Nylon-fiberglass-Nylon support. Moreover, mechanical tests showed that the stress and strain at the breaking point of membranes were remarkably changed after coating it with Nylon-fiberglass-Nylon support. The addition of PEI had a significant influence on the hydrophilic character of prepared membranes. Filtration results indicated that the incorporation of PEI in composite membranes improved the pure water permeability (PWF) up to 79.11 L m-2 h-1 bar-1 compared to that of PSf alone (29.36 L m-2 h-1 bar-1). The combined effect of Nylon-fiberglass-Nylon support and the PSf/PEI membrane layer has certainly enhanced the filtration performance, making prepared UF membranes potential candidates for scale-up industrial applications.

In the present study, different amounts of L-arginine (LA) i.e. Zwitterion have been used as an eco-friendly corrosion inhibitor to study its effect on the mitigation of the steel rebars corrosion in 0.17 M NaCl added simulated concrete pore (SP) solution. Potentiodynamic polarization, open circuit potential (OCP), and electrochemical impedance spectroscopy (EIS) have been used to understand the corrosion kinetics and mechanism for the formation of passive film at steel rebar/solution interface with exposure periods. The characterization of passive films after 144 h of exposures were performed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Cl− ions help in the formation of Zwitterion-(Cl)-Fe complex in the presence of LA containing solution which led to stabilize the passive film resulting improvement in polarization resistance (Rp). The steel rebar exposed to 0.115 M LA containing SP + 0.17 M NaCl solution exhibited around 96% inhibition efficiency after 144 h of exposure. Raman spectroscopy of passive film reveals adsorption of LA and formation of goethite and maghemite. A schematic has been proposed to derive the adsorption mechanism of LA in the presence of Cl− ions and form Zwitterion-(Cl)-Fe complex, therefore, enhanced corrosion resistance was observed.

Two mercaptobenzimidazole derivatives, namely the 1H-benzimidazol-2-thioyl hexane (MBI-C6) and the 1H-benzimidazol-2-thioyl dodecane (MBI-C12) were synthesized. The corrosion inhibiting potential of both compounds was studied in HCl solution (1.0 M HCl) for carbon steel. The investigation was conducted using gravimetric, electrochemical, Density Functional Theory (DFT), and molecular dynamics (MD) assessment methods. The carbon steel surfaces with or without the MBI-C6 and MBI-C12 were also assessed employing a Scanning Electron Microscope (SEM). The findings showed a high inhibition efficiency for both MBI-C6 and MBI-C12 at low concentrations, reaching 90% and 95.7% for MBI-C6 and MBI-C12 at 10−3 mol/L, respectively. Impedance results showed that the polarization resistance was greatly increased, from an initial value for the CS (in blank) of 12 up to 241 Ω cm2 for the inhibited solution (1.0 mol/L HCl with 10−3 mol/L of MBI-C12). Tested compounds inhibited CS corrosion through a physical-chemical adsorption mechanism that followed Langmuir adsorption isotherm model with a change in the free energy of adsorption from −35.97 to −38.63 kJ/mol. DFT calculations and MD simulations were used to check the effect of the molecular structure of MBI-C6 and MBI-C12 on their reactivity and, on the other hand, to explain their adsorption mode on the metal surface. By scanning electron microscopy (SEM), the adequate protection of carbon steel by the usage of MBI-C6 and MBI-C12 in 1.0 M HCl was confirmed. All the outcomes from experimental findings and theoretical calculations were in line.

As a part of an ongoing research to develop construction joints using ultra-high performance concrete (UHPC) and reinforcements, shear performance of plain concrete construction joints is experimentally examined with push-off tests. Two different sets, namely, a combined set of UHPC (180 MPa) and a set of UHPC (180 MPa) and NSC (normal strength concrete, 30 MPa) were considered, each of which had five cases of interface treatment including use of water jet, vertical joint, and three cases of a grooved joint. In addition, cases without any construction joint were also considered as a reference. Key factors affecting shear performance of individual construction joint were investigated in terms of shear strength, failure mechanism, and displacement responses. Experimental results show that steel fibers and grooved geometry greatly affect shear performance for the combined set of UHPC, while interlocking mechanism of coarse aggregates is crucial for the set of UHPC and NSC.

A set of poly(δ-valerolactone-co-d,l-lactide)-b-poly(ethylene glycol)-b-poly(δ-valerolactone-co-d,l-lactide) (PVLA-PEG-PVLA) triblock copolymers was synthesized and the solution properties were characterized using rheology, cryo-TEM, cryo-SEM, SANS, and degradation studies. This polymer self-assembles into a low viscosity fluid with flowerlike spherical micelles in water at room temperature and transforms into a wormlike morphology upon heating, accompanied by gelation. At even higher temperatures syneresis is observed. At physiological temperature (37 °C) the hydrogel’s average pore size is around 600 nm. The PVLA-PEG-PVLA gel degrades in about 45 days in cell media, making this unique hydrogel a promising candidate for biomedical applications.

Exposure of concrete structures to chloride-bearing solutions such as sea water or de-icing salts brine can affect their durability to stand against deterioration caused by corrosion of steel reinforcement. In order to monitor the chloride ingress into concrete, embedded chloride sensors can be used in concrete structures. Through the sensors, they monitor the initiation of corrosion of steel reinforcement with time, and measure the open circuit potential and polarisation of steel reinforcement, humidity inside the concrete, chloride content and many more. This paper provides an overview of the latest development of chloride permeation measurement in concrete by evaluating the current techniques being used in industry and highlighting a new approach to monitor chloride ion progress in concrete structures wirelessly.

Concrete cast at low temperatures can have an adverse effect on the concrete quality owing to both a delay in the hydration reaction of the concrete and the occurrence of early frost damage. Therefore, a heating sheet was developed, which exploited the exothermic reaction between quicklime and water. A form with the heating sheet attached experienced a temperature rise and had a high compressive strength. TG-DTA analysis confirmed that a larger amount of the Ca(OH)2 hydration product was generated in the form with the heating sheet attached, while SEM analysis visually confirmed the size and shape of the hydration product.

It is proved that inhibitors control or reduce the onset time of corrosion of steel rebars. The nitrite based i.e. sodium or calcium nitrite corrosion inhibitor is very popular and significantly reduces the corrosion of steel rebars. In this study, the effect of LiNO2 was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic studies. This inhibitor showed 63.67% efficiency at [Cl−/NO2−] = 0.6 in Ca(OH)2 solution contaminated with 0.99 g/L NaCl. LiNO2 works as mixed type corrosion inhibitor by stabilizing the iron oxides/hydroxides in their stable form and stifle the corrosion of steel rebar.

The effect of calcium nitrite (Ca(NO2)2) was assessed by electrochemical means such as open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic studies in saturated Ca(OH)2solution contaminated with 0.99 and 7.91 g/L NaCl. The preliminary results of OCP showed that the potential is shifted towards positive (noble) side as content of inhibitor increased. The EIS results indicate that Ca(NO2)2works effectively in reduction and initiation of corrosion of steel rebar in NaCl contaminated Ca(OH)2solution. Potentiodynamic studies revealed the pitting tendency of steel rebar exposed in 0.99 g/L NaCl at [Cl−/NO2-] = 1.2 attributed to low conductivity of passive film which causes interference for Cl−ions attack during anodic polarization. The 85.75% efficiency is found in 0.99 g/L at [Cl−/NO2-] = 1.2. The Ca(NO2)2inhibitor transformed the unstable iron oxides/hydroxides into stable and protective oxides/hydroxides due to its strong oxidizing nature. Therefore, this inhibitor is sufficiently and significantly reducing the corrosion of steel rebar at even its low concentration with 0.99 and 7.91 g/L NaCl solution.

A solid-state alkaline stable polymer coated Ag/AgCl sensor was fabricated for chloride sensing in concrete structures. The Ag/AgCl sensor was fabricated by sintering the AgCl powder with Ag wire. Polypyrrole (PPy) was prepared by simple chemical synthesis. The unwavering character of the prepared PPy coated Ag/AgCl sensor in saturated KCl solution was exemplified by potentiodynamic polarization studies followed by half-cell potential (HCP). The alkaline stability of the Ag/AgCl and PPy coated Ag/AgCl sensor in synthetic concrete pore solution (SCPS) was characterized by HCP, X-ray diffraction (XRD) and scanning electron microscopic (SEM) studies. The PPy coated chloride sensor was calibrated in saturated KCl, distilled water and SCPS with various concentrations of chloride ions. The results showed a good relationship between the sensitivity of the sensor regarding the potential to the logarithm of chloride activity. Further, it was noticed that the potential value remained stable with increasing immersion time.

The chloride diffusion coefficient is considered to be a key factor for evaluating the service life of ground-granulated blast-furnace slag (GGBS) blended concrete. The chloride diffusion coefficient relates to both the concrete mixing proportions and curing ages. Due to the continuous hydration of the binders, the capillary porosity of the concrete decreases and the chloride diffusion coefficient also decreases over time. To date, the dependence of chloride diffusivity on the binder hydration and curing ages of slag-blended concrete has not been considered in detail. To fill this gap, this study presents a numerical procedure to predict time-dependent chloride diffusion coefficients for slag-blended concrete. First, by using a blended cement hydration model, the degree of the binder reaction for hardening concrete can be calculated. The effects of the water to binder ratios and slag replacement ratios on the degree of the binder reaction are considered. Second, by using the degree of the binder reaction, the capillary porosity of the binder paste at different curing ages can be determined. Third, by using the capillary porosity and aggregate volume, the chloride diffusion coefficients of concrete can be calculated. The proposed numerical procedure has been verified using the experimental results of concrete with different water to binder ratios, slag replacement ratios, and curing ages.

Worldwide increase in the amount of slag production, a by-product of steel manufacturing, has led to efforts to recycle the slag into value-added products. However, the presence of unstable constituents like free CaO limits the applications of electric furnace slag, which is stabilized by the aging process. Herein, by measuring the free CaO content as a function of aging period, source region, company, and storage position, using the ethylene glycol method, the feasibility of using electric furnace slag as a construction material is confirmed. The free CaO contents of electric furnace oxidizing slag (EOS) samples were found to be below 0.5%. This satisfies the criteria specified in KS F 4571, which states that the CaO content should be below 40% and CaO/SiO2 ratio should be below 2.0. In addition, it was confirmed that free CaO content difference appears to be dependent on the aging period and storage position.

Changes in the salt attack resistance of concrete using ground granulated blast furnace slag (GGBFS) were examined based on different curing conditions. These conditions were divided into air and underwater curing. Three concrete mixes with GGBFS replacement ratios of 0% (control group), 30% and 60% were fabricated. Then, evaluation of concrete compressive strength, evaluation of chloride ion diffusion coefficient and electrochemical impedance spectroscopy (EIS) were performed. As the GGBFS replacement ratio increased, the concrete compressive strength of the air cured specimens decreased compared to the underwater cured specimens. With respect to the chloride ion diffusion coefficient measurements, the coefficient decreased as the GGBFS replacement ratio increased. However, the diffusion coefficient of the air cured specimen relative to the underwater cured ones increased up to two times. The EIS results showed that as the GGBFS replacement ratio increased, |Z| increased in every frequency range. However, the |Z| of the air cured specimen was lower than the underwater cured one. This showed the same tendency as the evaluation results of the chloride ion diffusion coefficient.

We designed a flexible chloride ion selective sensor that directly monitors electrochemical reactions of chloride ions without using a reference electrode. A flexible polytetrafluoroethylene (PTFE) substrate was utilized to provide bendability to the fabricated sensor. As an ion selective material, Ag nanoparticles (NPs) were employed on the multi-walled carbon nanotubes (MWCNTs) loaded on the PTFE substrate. Enhanced adsorption property of the fabricated sensor toward chloride ions was achieved by incorporating hydrophilic copper benzene-1,3,5-tricarboxylate (Cu-BTC), which has significant flexibility and stability. Accordingly, compared with the bare sensor, the sensing performance of the Cu-BTC-treated Ag NPs/AgCl electrode sensor was improved as indicated by an approximately four times reduction in the response and recovery times. This indicated that the Cu-BTC layer could function as an effective medium between the surface of Ag NPs and the electrolyte containing chloride ions. It is observed from contact angle measurement that the hydrophilicity significantly increased in the Cu-BTC-treated sensor because the exposed surface of the sensor not treated by Cu-BTC largely consisted of hydrophobic MWCNTs. Furthermore, the Cu-BTC layer could hold the electrolyte for effective adsorption of analytes with a large specific surface area.

Calcined Hwangtoh (HT) clay is a very promising supplementary cementitious material (SCM). In this work, the development of the mechanical properties and microstructures of HT-blended cement paste was studied after substituting the binder with HT powder calcined at 800 &deg, C. The water-to-binder (w/b) ratios of the paste used were 0.2 and 0.5, and the quantities of HT powder added to the mixture were 0, 10, and 20%. The compressive strength test indicates that the addition of the HT powder increases the compressive strength of the paste after seven days of curing, and the highest compressive strength is obtained with the 10% HT substitution, regardless of whether the w/b ratio is 0.5 or 0.2. X-ray fluorescence (XRF), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), isothermal calorimetry, thermogravimetric analysis (TGA), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis show that the HT powder not only has a physical effect (i.e., nucleation effect and dilution effect) on cement hydration but also has a chemical effect (i.e., chemical reaction of HT). The results of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analysis show that the paste has more ettringite during the early stage, and the microstructure is refined after the addition of the HT powder. In addition, the relationships between chemically bound water, hydration heat, and compressive strength are presented.

The carbonation rate of reinforced concrete is influenced by three parameters, namely temperature, relative humidity, and concentration of carbon dioxide (CO2) in the surroundings. As knowledge of the service lifespan of reinforced concrete is crucial in terms of corrosion, the carbonation process is important to study, and high-performance durable reinforced concretes can be produced to prolong the effects of corrosion. To examine carbonation resistance, accelerated carbonation testing was conducted in accordance with the standards of BS 1881-210:2013. In this study, 10&ndash, 30% of micro palm oil fuel ash (mPOFA) and 0.5&ndash, 1.5% of nano-POFA (nPOFA) were incorporated into concrete mixtures to determine the optimum amount for achieving the highest carbonation resistance after 28 days water curing and accelerated CO2 conditions up to 70 days of exposure. The effect of carbonation on concrete specimens with the inclusion of mPOFA and nPOFA was investigated. The carbonation depth was identified by phenolphthalein solution. The highest carbonation resistance of concrete was found after the inclusion of 10% mPOFA and 0.5% nPOFA, while the lowest carbonation resistance was found after the inclusion of 30% mPOFA and 1.5% nPOFA.

The draft genome sequence of the halophilic bacterium Halobacillus mangrovi KTB 131, isolated from Topan salt of the Jeon-nam in Korea, was established. The genome comprises 4,151,649 bp, with a G + C content of 41.6%. The strain displays a high number of genes responsible for secondary metabolite biosynthesis, transport, and catabolism compared to other Halobacillus bacterial genus members. Numerous genes responsible for various transport systems, solute accumulation, and aromatic/sulfur decomposition were detected. The first genomic analysis encourages further research on comparative genomics and potential biotechnological applications. The whole draft genome sequence of Halobacillus mangrovi KTB 131 is now available (Bioproject PRJNA380285).

The consumptions of artificial light especially in urban area leads to carbon footprints and global warming. The introduction of light-transmitting concrete (LTC) enables light to be transmitted through opaque concrete and reduces building energy consumptions. The aesthetic value and the light transmittance properties of LTC attracted the attention among researchers on the investigations and development of this type of concrete. However, the application of LTC in construction industry is still immature due to several reasons including intensive labour cost and complexity of the manufacturing process, insufficient reliable data on the mechanical properties and durability, as well as the lack of design modelling. This paper reviewed the types of LTC as well as the research findings regarding the mechanical properties, durability, microstructure analysis as well as the light transmittance properties. This paper also critically discussed the assessment, design modelling, theoretical studies and cost analysis of LTC based on various parameters. LTC was proven to reduce the total energy consumptions of a building significantly. More investigations are required to examine the light transmitting properties and durability of LTC especially when exposed to the various environmental conditions.

Utilization of upgraded fine fly ash in cement-based materials has been proved to be an effective method to improve compressive strength at early ages. The addition of fine fly ash has introduced dilution effect, enhanced pozzolanic reaction effect, nucleation effect and physical filling effect into cement-fly ash system. In this study, an integrated reaction model is adopted to quantify the contributions from cement hydration and pozzolanic reaction to compressive strength. A modified model related to the physical filling effect is utilized to calculate the compressive strength increment considering the gradual dissolution of fly ash particles. Via combination of these two parts, a numerical procedure has been proposed to predict the compressive strength development of fine fly ash mortar considering fly ash fineness and replacement ratio. The reliability of the model is validated through good agreement with the experimental results from previous articles. In addition, parametric analyses are performed to further analyze the effects of fly ash fineness and replacement ratio on compressive strength. The results indicate that compressive strength increases linearly with the increase of fly ash fineness. While its slope is less affected by fly ash replacement ratio, it increases along with the extension of curing time. Moreover, the fineness of fly ash can improve the relationship between compressive strength and replacement ratio. For ultrafine fly ash mortar, the 28-day compressive strength of mortar shows an evident trend of first increase and then decrease with the increase of replacement ratio. Under the condition of ensuring the same compressive strength, upgraded finer fly ash can replace more cement, thus realizing energy saving and CO2 emission reduction.

In the present studies, the Al coating deposited by arc thermal spraying process was treated with different concentrations of ammonium phosphate mono basic ((NH4)H2PO4) and caesium nitrate (CsNO3) to improve the morphology and corrosion characteristics of the coating. As coated (AC) sample exhibits pores and defects onto the surface but once the treatment was carried out, the coating shows reduction in porosity as observed by scanning electron microscopy (SEM). The treated coatings contain caesium aluminum oxide (CAO: Cs2Al2O3) and ammonium aluminum hydrogen phosphate hydrate (AHP: (NH4)3Al5H6(PO4)8.18H2O) as composite oxides identified by X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) results reveal that as the exposure periods are increased, the resistance to coating/treatment (Rc/t) and charge transfer resistance (Rct) of AC and 0.5 M NH4H2PO4 and 0.0025 M CsNO3 (CN2) are increased with exposure periods in artificial ocean water solution. The improvement in total impedance values at 0.01 Hz of AC sample is attributed to formation of corrosion products which fill the pores/defects of coating while CN2 sample owing to the treatment film i.e. AHP and CAO and transformation of AHP into stable form. As the amount of NH4H2PO4 and CsNO3 is increased up to 1 M and 0.005 M i.e. CN3, the AHP film dissolved and enhances the corrosion reaction. Thus, cracking is observed in corrosion products. The enhancement in corrosion resistance of CN2 sample is attributed to the formation of α-Al(OH)3 (bayerite) and Al3(PO4)2(OH)3(H2O)5 (Aluminium hydroxide phosphate hydrate: AHPH) in greater amount as corrosion products. These corrosion products of CN2 sample are stable, sparingly soluble and protective.

Hwangtoh clay is a type of kaolin clay, which is used as an environment-friendly material in constructions. This study presents multiple experimental studies on the hydration, strength, and durability properties of ternary or binary composites, with calcined Hwangtoh clay and limestone powder. The replacement levels of calcined Hwangtoh clay and limestone powder in the composite were in the ranges of 0%–30%, and 0%–15%, respectively. Multiple experimental studies involving compressive strength tests, isothermal calorimetry, thermogravimetric analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electrical resistivity, and carbonation were performed. The corresponding experimental results indicated the following: 1) among all the mixtures, the ternary composite with a 15% replacement level provided the most optimal mixture, and 30% replacement level was the threshold level for achieving a similar strength as that of plain concrete; 2) for all the mixtures aged 3–270 days, there was a linear relationship between the strength and combined water; 3) for the ternary composite, the contents of hemicarboaluminate (Hc) became more evident as the amount of Hwangtoh was increased, which showed a synergic relation between the calcined clay and limestone; 4) for the ternary composite, as the replacement levels of limestone and Hwangtoh were increased, the electrical resistivity increased significantly, and so did the carbonation degree; and finally, (5) compared to strength, the combined water was a better indicator for judging the carbonation resistance of the blended concrete.

Compared with fly ash, addition of ultrafine fly ash manufactured by mechanical grinding will significantly improve the performances of the cement-based materials. In this paper, firstly the cement hydration is simulated based on the modified shrinking core model with the concept of multi components. Then it is combined with the fly ash pozzolanic reaction via the contents of capillary water and calcium hydroxide (CH) in the blended cement paste. The effects of the heterogeneous nucleation, fineness of fly ash and local w/c augmentation are quantitatively analyzed and incorporated into the hydration models. The integrated models are validated by the contents of CH and non-evaporable water (NEW) in the (ultrafine) fly ash and cement composite The coupled evolution of cement hydration, pozzolanic reaction and porosity is presented using the integrated hydration models. Compared with the fly ash and cement composite (FAC), it is found that the extent of the pozzolanic reaction significantly increases in the ultrafine fly ash and cement composite (UFAC) while the increment of cement hydration extent due to nucleation effect is relatively small. Furthermore, the contributions of gel content by different effects are quantitatively calculated and compared between UFAC and FAC. Finally, an empirical formula is established to predict the compressive strength of the hardening UFAC. The filling effect of the ultrafine fly ash, gel content and cumulative pore volume are adopted to evaluate the development of the compressive strength. The results indicate that the physical filling effect of ultrafine grains reflected on the compressive strength of UFAC will gradually increase during the first seven days of curing and then keeps constant. With the increase of cement replacement ratio (0 ~ 0.5), the physical filling effect brought by UFA will be greatly enhanced. The analyses presented in this paper will give a better understanding on the hydration process and strength development for the FAC and UFAC.

Five different cell concentrations of Bacillus megaterium (10 × 105 to 50 × 105 cfu/ml) were introduced in structural concrete to achieve the optimum concentration of bacteria. The significant increase in the strength was obtained in the case of 30 × 105 cfu/ml at different ages. The strength of highest grade of bacterial concrete had improved (24%) as compared to lowest grade (12.8%) due to calcification mechanism. Microbial calcite precipitation was quantified using X-ray diffraction analysis, visualized by scanning electron microscopy and analyzed by energy dispersive spectrometer. It was found that the optimum concentration of B. megaterium had a positive effect on high strength structural concrete.

Based upon the extended framework of Hamilton's principle, a variational formulation in heat diffusion, as well as second sound phenomena is developed. This formulation is compatible with the initial and boundary conditions of a well-posed heat problem, and it correctly accounts for the governing partial differential equations, as its Euler-Lagrange equations. Thus, this new formulation provides a sound base to develop various unified space-time finite element methods. In order to validate the finite element representation over both space and time in the context of this formulation, two-dimensional lower-order space-time finite element methods are also developed with numerical investigations on representative examples.

Steel rebars attain passivity in concrete environment. Passive film can be destroyed by acidification through carbonation and chloride ions from NaCl in concrete. There are different techniques have been employed to mitigate the corrosion problem of steel rebars embedded in concrete. Among different methods inhibitors are very popular and frequently used. Commercially available N, N′-Dimethyl ethanol amine (DMEA) inhibitor is studied in different concentrations of NaCl in saturated Ca(OH)2 solution. The performance of inhibitor was evaluated by potential time, electrochemical impedance spectroscopy and potentiodynamic techniques. DMEA inhibitor is showing 63–74% efficiency and effectively reduces the corrosion rate.

Arc thermal metal spray coating is very efficient process to protect the steel from corrosion in industrial, humid and saline/coastal environments. This paper incorporates the experimental results for the performance of Aluminum coating deposited on mild steel substrate by arc thermal metal spray. Different electrochemical techniques, FE-SEM, Raman spectroscopy and XRD were used to assess the performance of deposited coating. Electrochemical studies revealed the enhanced corrosion resistance properties of coating in 3.5 wt.% NaCl solution. The formation of α-Al(OH)3 on coating substrate during exposure periods block the pores of coating and impede the penetration of corrosive species to react with substrate.

We previously showed that long-lived nanoemulsions, seeming initially vesicular, might be prepared simply by diluting and cooling (quenching) warm microemulsions with n-hexadecane with precooled water. In this paper, we confirm that these systems are vesicular dispersions when fresh, and they can be made with similar structures and compositional dependence using alkanes with chain lengths ranging from octane to hexadecane. The nanostructures of fresh nanoemulsions are imaged with cryogenic transmission electron microscopy (cryo-TEM). We confirm that water-continuous microemulsions give simple dispersions of vesicles (sometimes unilamellar), typically less than 100 nm in diameter; these systems can avoid separation for over 2 months. Selected samples were also prepared using halogenated alkanes to create additional contrast in the cryo-TEM, allowing us to confirm that the oil is located in the observed vesicular structures.

In this research, it used cement powder and reduction slag, which generates high hydration heat in hydration reaction without heat cure below degree. Purpose of final research is preventing freezing and thawing by making the compressive strength 5MPa in 3days below zero temperature due to own heat of concrete. and it is the result of physical characteristic and thermal property evaluation of reduction slag. Because reduction slag generates high hydration heat, compressive strength development is excellent. By generating highly hydration heat by and in reduction slag, compressive strength is developed in low temperature. In case of displacing only reduction slag without , it is indicated that quick-setting occurs by shortage of . For preventing quick-setting, gypsum is used essentially. According to this research result, in case of using reduction slag and gypsum as a ternary system, compressive strength developed 5MPa in 3 days below zero temperature. It is identified to prevent early frost damage of concrete below zero temperature.

From 1990`s, a study on the development of exothermic concrete, a concrete which electro-conductive material is mixed, has been proceeded. However, due to the difficulty of exothermic reproducibility of concrete specimen, the study has been unable to continuously carried out. Accordingly, this study was focused on developing an exothermic concrete for the purpose of snow-melting material. Cement paste and mortar specimens mixed with graphite, conductive metal powder and chemical admixture were made. The evaluation of exothermic performance and reproducibility was conducted under of low temperature. In addition, micro-chemical analysis was carried out to investigate a cause of exothermic reproducibility. As a test result, the specimen mixed with graphite and superplasticizer with air entrained showed the best exothermic performance and reproducibility. Through micro-chemical analysis, it is judged that polymer or methacrylic acid (MAA), the contents inside the superplasticizer with air entrained, gave exothermic reproducibility by generating the electrochemical reaction with graphite.

Concrete is a representative heterogeneous material and mechanical properties of concrete are influenced by various factors. Due to the fact that pores in concrete affect determining compressive strength of concrete, studies which deal with distribution and magnitudes of pores are very important. That way, studies using picture imaging have been emerged. Studies on mechanical performance evaluation of structural lightweight foamed concrete and FEM analysis based on picture image are inadequate because lightweight foamed concrete has been researched for only non-structural. Therefore, in this study, cement paste with foaming agent to evaluate mechanical performance is made, FEM analysis with picture image is conducted and young`s modulus of experiment and analysis are compared. In this study, dosage of foaming agent is determined 7 level to check pore distribution and water-binder ratio is determined 20% to progress research about structural light weight foamed concrete. Weight of unit volume is minimum at 0.8% of foaming agent dosage. However, weight of unit volume is increased over 0.8% of foaming agent dosage because of interconnection with independent pores. For FEM analysis, cement paste is photographed to use image analyzer(HF-MA C01). Consequently, the fact that Young`s Modulus of experiment and FEM analysis are same is drawn by using OOF(Object Oriented Finite elements).

Being a plant with open cellulose structure, such potential has gone untapped due to its tendency to take up excessive resin during the mixing process. Hence, this paper presents the potential of utilizing an agricultural waste; palm oil fuel ash (POFA) as micro-filler in polymer concrete (PC). Two types of POFA fillers – ground (GPOFA) as fine filler and unground (UPOFA) as coarse filler were investigated in different contents. For comparison purpose, GPOFA was paired with calcium carbonate while UPOFA was with silica sand. Filler characteristics were studied through microstructural examination, particle size distribution, nitrogen absorption test, morphology image, and thermal analyses. Forty polymer blended and polymer concrete mixes were prepared for flowability and compression tests, respectively. Then, miniature crushed specimens were tested using Mercury Intrusion Porosimetry (MIP) and Field Emission Scanning Electron Microscopy (FESEM) to investigate porosity and morphology of PC, respectively. Results showed that POFA had their physical features changed significantly after surface modifications. The ground POFA gives superior filling ability and high PC compressive strength. Additionally, good dispersion characteristic of POFA could reduce porosity in PC as well. It can be concluded that POFA can be potentially utilized as effective PC filler after being subjected to some physical modifications and mixing it with appropriate mix design.