Corrosion Resistance Of Steel Bars Research Articles

Effects of interlayer-modified layered double hydroxides with organic corrosion inhibiting ions on the properties of cement-based materials and reinforcement corrosion in chloride environment

Developing novel, environmentally friendly, and efficient corrosion inhibitors is of great significance for improving the durability of marine concrete against chloride ion erosion. This paper aims to explore the potential of layered double hydroxides (LDHs) as nanocontainers, incorporating organic corrosion inhibitors between LDHs layers to synergistically enhance their effectiveness. In this study, Mg/Al-pAB-LDH was synthesized through the interlayer modification of LDHs with an organic corrosion inhibitor, p-aminobenzoic acid (pAB), employing a calcination-rehydration method. Chloride ion (Cl−) adsorption behavior was quantitatively and qualitatively analyzed and the effect on mortar properties was investigated. The corrosion resistance of steel bars in the mortar was assessed under chloride salt simulated concrete pore solution (SCPs) and chloride salt wet-dry cycles via electrochemical tests and microscopic characterization of Mg/Al-pAB-LDH. The results demonstrate that Mg/Al-pAB-LDH efficiently captures Cl− and releases corrosion-inhibiting ions pAB, with the adsorption process conforming to pseudo-second-order kinetics and Langmuir adsorption isotherm. Mg/Al-pAB-LDH enhances the pore structure of mortar, effectively improving mechanical properties and resistance to chloride ion penetration, with the optimal effect observed at a 4 % addition rate. Mg/Al-pAB-LDH demonstrates outstanding corrosion resistance to steel bars in both SCPs and mortar. In SCPs, it serves as a corrosion inhibitor by adsorbing Cl− and releasing pAB, whereas in mortar, it functions as a corrosion inhibitor by enhancing the physical barrier effect of mortar, adsorbing Cl−, and releasing pAB. This study demonstrates the promising potential of utilizing Mg/Al-pAB-LDH as a novel corrosion inhibitor to mitigate the corrosion of steel bars in marine concrete.

Experimental investigation on Nano-Al2O3 and hydroxypropyl methyl cellulose (HPMC) modified cement-based coatings for corrosion resistance

In this work, cementitious coatings doped with nano-Al2O3 (NA) and hydroxypropyl methyl cellulose (HPMC) were prepared in order to enhance corrosion resistance of steel bar. The electro-chemical behaviors and corrosion inhibition properties of coated steel bar and tensioned coated steel bars (subjected to 10 %, 30 % and 50 % yield load) were analyzed in 3.5 wt% NaCl solution for 840 h (35 days). At the end of electrochemical test, coating overall performance was evaluated by visual inspection. In addition, scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) were used to examine microstructure and elemental composition of coatings. To comprehend the anti-corrosion mechanism of the coatings, X-ray diffraction (XRD) and infrared spectroscopy (FTIR) analysis to characterize products composition and chemical groups. Test results obtained by linear polarization resistance and electrochemical impedance spectroscopy indicated that both tensile and non-tensile coatings resistance show an increasing trend followed by a decrease with increasing NA content. Cementitious coatings incorporating 1 % NA and 0.12 % HPMC by weight of cement exhibited the best corrosion protection. The LPR fluctuates around 3700 Ω cm2, which is about twice as much as a single doped NA coating. Whether subjected to tensile loads or not, OCP values for all coated steel bar were below −0.273 V/SCE, indicating has a 90 % probability of being in active-corrosion. The corrosion resistance of tensioned coated bars decreased as time and increased load level. According to SEM and TEM image, HPMC forms a thin and continuous film on the substrate surface, which acts as a barrier to the penetration of moisture and corrosive agents. Coatings doped with 1 % NA and 0.12 % HPMC formed denser integrated polymer films at the microscopic. FTIR and XRD results showed that coating incorporated NA consumed the cement hydration product Ca(OH)2 to generate more nanofibers filling pores and microcracks. Coatings incorporating HPMC show better resistance to carbonization.

Experimental investigation into corrosion effect on buckling and low-cycle fatigue performance of high-strength steel bars

The reinforcement in marine RC structures will inevitably be corroded under long-time erosion of chloride ions, which will weaken steel mechanical properties and then structural seismic resistance. The new metallurgical technology is adopted for manufacturing high-strength steel bars (HSSB), but that may affect the corrosion resistance of steel bars at the same time. This paper experimentally investigates the effects of corrosion on monotonic and low-cycle fatigue properties of HSSB HTRB600 and normal strength steel bars (NSB) HRB400E. The HRB400E and HTRB600 steel bars were corroded to different corrosion rates by electrochemical accelerated corrosion technique. The monotonic tensile and compressive, as well as low-cycle fatigue tests of corroded steel bars were conducted to investigate the effects of corrosion on steel mechanical properties, of which corrosion levels (0–20% target corrosion mass loss), slenderness ratios (L/D=6, 8, 10, 12) and strain amplitudes (2%, 4%) are considered. Test results show that, the corrosion morphology of steel bars under electrochemical accelerated corrosion is basically consistent with that observed under natural corrosion. Compared with uncorroded HRB400E and HTRB600 steel bars, 20% corrosion mass loss leads to 38% and 35% decrease in tensile strength, as well as 33% and 28% reduction in buckling stress, respectively. The HTRB600 steel bars present slightly superior monotonic tensile and compressive corrosion resistance than HRB400E steel bars. Corrosion obviously decreases the low-cycle fatigue (LCF) life of steel bars, resulting in reductions of 44% and 36% in LCF life at 20% corrosion mass loss for HTRB600 and HRB400E steel with a L/D of 6, respectively. Moreover, the HTRB600 steel bars present more significant corrosion degradation in total hysteretic dissipated energy, compared with HRB400E steel bars. The combined effect of corrosion and inelastic buckling further exacerbates the deterioration of LCF performance of steel bars. The corresponding deterioration models are proposed to determine the LCF life and energy dissipation capacity of corroded steel bars.

Study on the strengthening mechanism of graphene-FeTCPP MOF on the corrosion resistance of steel bars in alkaline environment

Reinforced concretes are the primary materials in coastal and offshore engineering. In the strong alkaline environment of concrete, steel bars are passivated spontaneously. However, concrete carbonization and Cl− in marine environments negatively affects the passivation process of steel bars and the durability of passivation films. Considering the anodic passivation is coupled with cathodic oxygen reduction reaction (ORR) and they form the current circuit, in this paper, we propose that the passivation process would be encouraged by the catalyzed ORR. The prepared ORR catalytic agent, graphene-iron meso-tetra(4-carboxyphenyl)porphine metal-organic framework (G-FeTCPP MOF), is characterized by UV-VIS, FT-IR, XRD, XPS, SEM, TEM and TGA. G-FeTCPP MOF could be directly doped into concrete during construction to promote passivation of steel bars. G-FeTCPP MOF exhibits significant ORR catalytic activity by reducing the reaction activation energy and driving the more efficient 4-electron pathways. The passivation of steel bars is facilitated by catalytic ORR which depletes the electrons released by coupled anodic passivation. It is the first innovation point. Another newly discovered function of G-FeTCPP MOF is to hinder the generation, migration and accumulation of crystal defects (interspaceal ferrous ions, iron ions vacancy, oxygen ions vacancy and iron atomic vacancy) by forming the adsorption film outside the passivation film. It is manifested as the optimization effect on the crystal structure of passivation film which is the greatest innovation of this paper.

Improve corrosion resistance of steel bars in simulated concrete pore solution by the addition of EDTA intercalated CaAl-LDH

The main perspective of this paper is to prepare an eco-friendly corrosion inhibitor suitable for reinforced concrete. The properties of CaAl-LDHs loaded with ethylenediaminetetraacetic acid (EDTA) synthesized under different conditions were studied and the optimal condition was determined. Electrochemical tests showed that CaAl-EDTA-LDH had excellent anti-corrosion properties for steel bars in the simulated concrete pore (SCP) solution. Mechanistically, the dual protection mechanism of CaAl-EDTA-LDH on steel bars was mainly due to the fact that the organic corrosion inhibitor adsorbed on the surface of steel bars to form a protective film while consolidating chlorides.

Experimental study on precast concrete columns reinforced with bundled SFCBs under horizontal cyclic loading

The poor corrosion resistance of steel bars limits the potential application of precast concrete structures. A promising solution is the use of steel-fiber reinforced polymer (FRP) composite bars (SFCBs) as reinforcements. SFCBs consist of an inner steel bar and an outer layer of FRP, providing excellent durability and customizable post-yield stiffness. The fabrication process of precast concrete structures can be more efficient by the utilization of bundled reinforcement and the deformation capacity can be enhanced by the weakening of the bond behavior. This paper describes a quasi-static test conducted on five precast concrete columns reinforced with bundled SFCBs (PCC-B-SF), as well as one conventional reinforced concrete column. The variables of the experiment contained the number of bars in each bundle (one (SF-1-P), two (SF-2-P), and three (SF-3-P)) and the construction method used (cast-in-place, partial grouting assembly, or full-length grouting assembly). The failure modes, hysteretic behavior, energy dissipation, residual deformation, and plastic hinge length were investigated. The results show that increasing the number of bars in each bundle of PCC-B-SFs leads to higher deformation capacity, energy ductility and self-centering ability. The ultimate deformation of SF-3-P was approximately 43.8% higher compared to the single-bar reinforced concrete column. Furthermore, the energy ductility of SF-2-P, SF-3-P, and SF-3-PL (with full-length grouting) was 16.1%, 20.7%, and 79.2% higher compared to SF-1-P. However, increasing the number of bars in each bundle may have a negative impact on energy dissipation. With full-length grouting, the highly bundled PCC-B-SF (consisting of three or more bars in one bundle) was found to enhance the bearing capacity and prolong plastic hinge regions. These findings suggest that the performance of PCC-B-SFs can exceed that of cast-in-place concrete columns.

Mechanical properties and service life analysis of high strength concrete using different silica fume contents in marine environment in Vietnam

This study evaluated the durability of concrete incorporating different silica fume (SF) content and also computed the service life of this concrete in marine environments. The specimens were prepared with three different SF content (i.e. 8%, 10%, and 12% by mass of cement replaced with SF). Three water/binder ratios (0.25, 0.30, and 0.35) were used for preparing concrete specimens. The mechanical properties were assessed via compression and splitting tensile tests. The rapid chloride penetration and chloride migration experiments were employed to evaluate the durability of concrete. The results showed that the mixture with 10% SF replacement showed the best performance. The inclusion of SF not only reduced the total porosity but also refined the volume fraction of harmless and less harmful pores (< 200 nm). Consequently, the chloride ion penetration resistance of concrete was improved, which in turn reduced the potential corrosion rate of reinforcement. From the results of service life prediction using Life-365 software, it is indicated that the utilization of SF for cement replacement effectively improved the corrosion resistance of steel bars in marine reinforced concrete. The service life against salt damage can be remarkably extended by substituting cement with an appropriate SF level.

Experimental Evaluation of Quality of TMT/QST Steel Bar by Using TM Ring Test

bstract: This steel is frequently used on our construction site. However, there are numerous issues with the quality of this steel. Recently, a test method for evaluating the calibre of tempered Martensite rings on TMT steel was developed and refined. The tempered Martensite ring gives TMT rebars their strength, while the ferrite pearlite core gives them their ductility. Because of their unique properties, we use them in earthquake-resistant systems that require both strength and ductility. We bend these components at a 135-degree angle for use in stirrups. A typical 135-degree bend stirrup is seen here. Because of its superior surface crack resistance, TMT rebar will not have a cracked surface. Steel has been employed in structural applications for many decades due to its durability. Designers advocate high strength steel bars in a contemporary concept to reduce steel consumption in reinforced cement concrete (RCC) structures. Microalloying, thermomechanical treatment, cold working, and other methods are used to manufacture them. Some designers believe that thermomechanical treatment (TMT) steel bars are more sensitive to corrosive environments. Corrosion behaviours of high strength steel bars of 500W (weldable steel bar of yield strength 500MPa) grade from two different local industries in fresh water and sea water were studied and compared to weldable low strength (yield strength 300MPa) bars from the same companies. The addition of minor amounts of alloying elements such as Cr, Ni, and Cu enhances the corrosion resistance of steel bars in all test mediums, but strength levels have no effect on the corrosion rate. There is also a link between the degree of tensile property loss and the severity of corrosion damage

Comparative Studies on Steel Corrosion Resistance of Different Inhibitors in Chloride Environment: The Effects of Multi-Functional Protective Film

A corrosion inhibitor was widely used to improve corrosion resistance of steel bar in reinforcement concrete structure. A kind of multi-component corrosion inhibitor, which is composed of organic and inorganic substances, was developed in this research. This corrosion inhibitor was comparatively studied with various other inhibitors by using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) methods. The results show that the OCP values and charge transfer resistance (calculated by EIS curves) of the multi-component corrosion inhibitor remain, respectively, as high as −0.45 V and 932.19 kΩ·cm−2 after 60 days immersion, which are significantly better than other groups. Wide passivation interval and various peaks in cyclic voltammograms (CV) were applied to analyze the mechanism of adsorption (organic substance) and oxidation–reduction reactions (inorganic substance). The functional groups -OH in triethanolamine (TEA) and tri-isopropanolamine (TIPA) bond to the steel bar surface quickly, behaving as an adsorbent of organic substance in early age. An additional protective precipitate related to the reactions of Fe3+ was formed by inorganic substances (Fe2(MoO4)3 and FePO4), which is consistent with the EIS results and equivalent electrochemical circuits. As an eco-friendly substitute, multi-component corrosion inhibitors possess similar or even better protecting effects on steel bars in comparison to calcium nitrite. In addition, the concept of a “multi-functional protective film” was proposed, providing a new insight to achieve modified anti-corrosion capacity of inhibitors.

The equivalent quantization method of corrosion damage of reinforcement cage for concrete beam and its durability in island and reef environment

• The equivalent quantization method of corrosion damage of concrete beam was proposed and verified. • Effects of four factors with twelve levels on durability of concrete beam were studied. • Three types of self-produced protective materials were tested. • The relation between the linear polarization resistance and electrochemical impedance spectroscopy methods was established. The electrochemical measurement technique was used to conduct a non-destructive test the corrosion degree of reinforcement cage for concrete beam in tidal environment of island and reef region in real-time. Apart from this, the corrosion resistance of concrete beam with different concrete strength grades, steel bar, darex and migrating corrosion inhibitors, including three types of self-produced protective materials, was studied. Furthermore, based on electrochemical parameters, the relation of electrochemical measurement techniques was established. The results showed that the proposed equivalent quantization method of corrosion damage could be available for the reinforcement cage in concrete beam. In addition, the durability of concrete beam in tidal environment of island and reef region can be effectively improved by improving the concrete strength grade and the corrosion resistance of steel bar and using darex and migrating corrosion inhibitors. The polarization resistance obtained by the linear polarization resistance method and charge transfer resistance obtained by the electrochemical impedance spectroscopy method were linear. This study provides a key technology for actual reinforcement corrosion in concrete structure and some protective measures.

Synthesis and characterization of layered double hydroxides hybrid microcapsules for anticorrosion via self-healing and chloride ion adsorption

Self-healing and corrosion resistance microcapsule (S/CMC) was fabricated by solvent evaporation method with tung oil (TO) as core, layered double hydroxides (LDH) as corrosion inhibitor and ethyl cellulose (EC) as wall. The average particle size of microcapsule increased with the increase of LDH content when LDH was less than 20 wt%. LDH component was present in the wall of S/CMC by surface loading, the chlorine adsorption performance of microcapsule in neutral environment was superior to that in alkaline environment. LDH was hybridized in EC to form stable wall structure. The LDH embedded in hybrid wall captured chloride ion by surface adsorption and ion exchange to improve the corrosion resistance of steel bar. This study provides a solution for the compatibility of anti-corrosion and self-healing technology, and provides a new perspective for the anti-corrosion application of microcapsule.

Ca-LDH-modified cementitious coating to enhance corrosion resistance of steel bars

Layer double hydroxides (LDHs) are potential candidates for the application in reinforced concrete. The main perspective of this paper is to prepare cementitious coatings modified with Ca–Al–NO3 layered double hydroxides (Ca-LDH) and investigate its corrosion inhibition performance on steel bars by means of the isothermal adsorption experiment, open-circuit potential (OCP) and linear polarization resistance (LPR). The effect of Ca-LDH dosage on pore structure and chloride binding ability of cement pastes were studied. The primary aim was to design a novel composite coating applied to reinforced concrete. The results show that the incorporation of Ca-LDH increased the chloride consolidation ability of cement paste. Compared with the uncoated steel bars, the chloride concentration threshold (CCT) of the cement paste coatings with 2% and 4% Ca-LDH increased by 0.07 M and 0.06 M respectively, which effectively inhibited corrosion of steel bars in the simulated concrete pore (SCP) solution with chloride. The incorporation of Ca-LDH into cement paste reduced its porosity and strengthened the physical barrier effect. Moreover, Ca-LDH had the dual ability of consolidating chlorides and releasing corrosion-inhibiting anions.

Corrosion Experimental Research on Local Damage of Epoxy-Coated Steel Bars in Concrete Under Marine Environment

Epoxy coating has been proven to protect steel bars from corrosion. However, the damage of epoxy coating is inevitable, and this may lead to more serious corrosion of steel bar. In order to study the corrosion resistance of steel bars with damaged epoxy coating, two groups of coating-damaged bar and one group of coating-intact rebar were designed, and six specimens were made. The influence of electrolyte concentration on the corrosion rate of steel bars was studied by setting different concentrations. After 30 days of accelerated corrosion, electrochemical data were recorded by the electrochemical workstation. The experimental result shows that the steel bars with coating damage have obvious polarization curve characteristics of corrosion, and corrosion resistance decreases obviously. According to the corrosion current and potential, the larger the damaged area of the coating, the faster will be the corrosion rate. According to the polarization curve data, the polarization resistance is modified, and the result is closer to the real polarization resistance value. The calculated corrosion rate shows that the corrosion rate of reinforcement is affected by both electrolyte concentration and coating damage area, and electrolyte concentration has a greater influence on the corrosion rate.

Electrochemical and microscopic analysis on corrosion behavior of steel bars in slag/fly ash-cement paste subjected to seawater attack

A series of corrosion experiments of cement paste-steel bar specimens with different contents of slag and fly ash were performed to investigate the influence of slag/fly ash on the corrosion behavior of steel bars in concrete under seawater. In this investigation, the corrosion behavior of specimen was electrochemically monitored by open-circuit potential (OCP), Tafel polarization (TP) and electro chemical impedance spectra (EIS). Meanwhile, SEM/EDS and XRD were applied to microscopically analyze the microstructure deterioration of materials. Results showed that, replacing cement with slag/fly ash caused a decrease in Ca(OH)2 as well as an increase in C-S-H gel and Friedel's salt in concrete, which can improve the chloride-solidification ability and slow down the chloride diffusion in concrete by both physical adsorption and chemical binding, and thereafter promoting the corrosion resistance of steel bars in concrete in marine environment. Compared to slag, the equal replacing content of fly ash can contribute to a better improving effect on the corrosion resistance of reinforced concrete in marine environment. In this study, a replacement of cement by 20% slag+20% fly ash led to an optimum improving effect on its corrosion resistance. In addition, the results also indicate that the corrosion of reinforced concrete caused by seawater attack does not occur at a uniform rate, but it can firstly maintain a long-term uncorroded state, and then develops rapidly after pitting corrosion occurs.

Biomimetic Superhydrophobic Concrete with Enhanced Anticorrosive, Freeze Thaw, and Deicing Resistance

A green superhydrophobic hybridization concept that incorporates biomimetics (lotus effect), chemistry (siloxane and silane admixtures), and nanotechnology (hydrophobic coating with SiO2 nanoparticles) is used to produce superhydrophobic concrete. The fabricated samples exhibit superior hydrophobicity, contact angles (CA) up to 157.6° ± 3.1°, and roll‐off angles (RO) of 6.5° ± 1.5°, even under high surface mechanical abrasion. The superhydrophobic samples can decrease freeze‐thaw damage and maintain high freeze‐thaw resistance effectively. The modified surfaces exhibit 6 times lower deicing strength compared with the reference surfaces. Furthermore, the high water repellency helps to prevent corrosive liquids from encountering the concrete reinforcement samples and helps to improve the corrosion resistance of steel bars. These unique key properties and self‐cleaning capability make superhydrophobic concrete relevant for a wide range of commercial and practical engineering applications in construction, bridges, and transportation.

Research on the Mechanical Strengths and the Following Corrosion Resistance of Inner Steel Bars of RPC with Rice Husk Ash and Waste Fly Ash

In this paper, the slump flow and mechanical strengths (compressive and flexural strengths) of the reactive powder concrete (RPC) with rice husk ash (RHA) and waste fly ash (WFA) were investigated. The following corrosion resistance of steel bars-reinforced specimens was researched. The ultrasonic sound, the mass loss rate, the electrical resistance, and the electrical resistance time history curves were determined to reflect the corrosion resistance of steel bars. The influence of NaCl freeze–thaw cycles and dry–wet alternations was considered. Results showed that the addition of RHA and WFA demonstrated a negative effect on the fluidity of fresh RPC. The fluidity of fresh RPC with WFA was lower. Moreover, RHA and WFA could effectively improve the mechanical strengths of hardened RPC, and the enhancing effect of RHA was higher. The increasing dosage of RHA could improve the corrosion resistance of steel bars in RPC when the specimens were exposed to the environment of NaCl freeze–thaw cycles and dry–wet alternations. However, when WFA was added, the effect was the opposite. The steel bars in RPC corroded more seriously when the specimens were exposed to the environment of NaCl dry–wet alternations than the environment of NaCl freeze–thaw cycles.

Influence of Rust Inhibitor on the Corrosion Resistance of Reinforcement in Cement Paste with Chloride

The electrical resistance and polarization effect of cement paste containing reinforcement were tested to research the anti-corrosion properties of steel bars in cement paste. Moreover, the microstructure and composition of passivation film and rust on the steel bars were studied. The water–cement ratio of the cement paste in this study was 0.3, with 0.5% NaCl, 1% NaNO2, and 1% Benzotriazole, and an assembly unit of 0.5% NaNO2 + 0.5% Benzotriazole by mass of cement was added to the cement to provide a chloride environment. X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were applied to research the composition of the passivation film and the microstructure of the cement paste, respectively. The results indicated that the samples with the assembly unit of 0.5% NaNO2 + 0.5% Benzotriazole showed the highest electrical resistance and polarization electrical resistance, while the specimens with 1.0% Benzotriazole showed the lowest electrical resistance and polarization electrical resistance. Moreover, the passivation film of steel bars weakened with increasing distance from the surface of the steel bars. Therefore, the corrosion of steel bars becomes more serious with increasing distance. Finally, the influence of the rust inhibitor on the corrosion resistance of steel bars in the specimens decreased in the following order: 0.5% NaNO2 + 0.5% Benzotriazole &gt;1.0% NaNO2&gt;1.0% Benzotriazole.

Effects of coral sand powder and corrosion inhibitors on reinforcement corrosion in coral aggregate seawater concrete in a marine environment

AbstractThis paper investigates the effects of coral sand powder (CSP) and corrosion inhibitors (SBT®‐ZX(V), SBT®‐RMA(II)) on reinforcement corrosion in coral aggregate seawater concrete (CASC) in a marine environment. A reasonable time‐variation model for reinforcement corrosion in CASC is proposed and verified. Based on the time‐variation model and chloride diffusion model, the cracking time and service life of CASC are predicted. The results show that the replacement of cementitious materials by 5% CSP can improve the corrosion resistance of steel bar in CASC. Both SBT®‐ZX(V) and SBT®‐RMA(II) can reduce the corrosion rate of steel bar in CASC, and this effect of SBT®‐RMA(II) is more effective than that of SBT®‐ZX(V). Among all CASC, CASC containing 5% CSP and SBT®‐RMA(II) possesses the best corrosion resistance. The results also reveal that the corrosion current density of steel bar in CASC increases firstly and then decreases over time. The ascending segment of the fitting curves for reinforcement corrosion in CASC conforms to the logarithmic‐type time‐variation model, and the descending segment of the fitting curves for reinforcement corrosion in CASC conforms to the exponential‐type time‐variation model. The cracking time and service life of CASC containing 5% CSP and SBT®‐RMA(II) will reach more than 10 years when the thickness of protective layer is 30 mm.

Research on the Influence of Carbonation on the Content and State of Chloride Ions and the Following Corrosion Resistance of Steel Bars in Cement Paste

In this paper, the changes of free chloride ion concentration and bound chloride concentration in cement paste with different total and proportion of mineral admixtures under carbonation were studied. Moreover, the following corrosion resistance of steel bars buried in cement paste under carbonation was researched by testing the electrical resistance and alternating current (AC) impedance spectroscopy of reinforced cement paste. Results indicated that fly ash and granulated blast furnace slag powder with the content less than 20% by mass ratio of total binder hindered the solidification of chloride ions in cement-based materials, and blast furnace slag powder with the content higher than 20% promoted the solidification of chloride ions in cement paste. The carbonation effect was able to decrease the amount of solidified chloride ion and increase the amount of free chloride ions leading to accelerating the corrosion of reinforcement. Meanwhile, the blast furnace slag powder with the content higher than 20% could effectively promote the corrosion resistance of steel bars.

Hydration process of rice husk ash cement paste and its corrosion resistance of embedded steel bar

Thermogravimetric analysis and electrical resistivity were used to determine the hydration process of cement paste with rice husk ash (RHA) (0–15%) and water-cement ratio of 0.4 in this work. X-ray diffraction (XRD) method and scanning electron microscopy (SEM) were used to survey crystal composition and microstructures of specimens cured for 3 h, 1 d, 7 d and 28 d. Finally, electrical parameters (electrical resistance and AC impedance spectroscopy) of steel bars reinforced cement paste were investigated to study the effect of RHA on the corrosion resistance. Results showed that RHA could affect the cement hydration by hydration promotion and pozzolanic effect. The evaluation function for electrical resistivity and curing ages fitted well with linear increasing function. The addition of RHA higher than 5% demonstrated a decreasing role in the electrical resistivity of cement paste at earlier curing ages (3–7 d). Meanwhile, when at later curing ages (7–28 d) the result was the opposite. Moreover, RHA demonstrated positive effects on corrosion resistance of steel bars in cement paste.