Search Results (14)

Chloride ion penetration is one of the most aggressive threats to reinforced concrete, as it triggers the electrochemical corrosion of steel reinforcement, compromising structural integrity and durability. Chloride ingress occurs through the porous structure of concrete, making permeability control crucial for enhancing structural longevity. Fiber-reinforced concrete (FRC) is widely used to improve durability; however, the effects of different fiber types on chloride resistance remain unclear. This study examines the influence of glass and polypropylene fibers on concrete’s microstructure and chloride penetration resistance. Cylindrical specimens were prepared, including a reference mix without fibers and mixes with 0.25% and 0.50% fiber content by volume. Both fiber types were tested for chloride resistance. The accelerated non-steady-state migration method was employed to determine the resistance coefficients to chloride ion penetration, while X-ray macrofluorescence (MacroXRF) mapped the chlorine infiltration depth in the samples. Compressive strength decreased in all fiber-reinforced samples, with 0.50% glass fiber leading to a 56% reduction in strength. Nevertheless, the XRF results showed that a 0.25% fiber content significantly reduced chloride penetration, with polypropylene fibers outperforming glass fibers. These findings highlight the critical role of fiber type and volume in improving concrete durability, offering insights for designing long-lasting FRC structures in chloride-rich environments. Full article

The production of concrete and the manufacturing process of cement result in a significant carbon footprint, contributing to a large portion of global emissions in structures such as buildings, bridges, roads, and tunnels. Although concrete is an ideal building material that is durable and long-lasting, it can be susceptible to micro-cracks. These micro-cracks in concrete can allow water and chlorine ions to penetrate the structure, leading to the degradation of the concrete and corrosion of the reinforcement, posing an unacceptable level of structural risk. Self-healing concrete is not a new material in the construction industry but can be characterized by the capability of concrete to repair its cracks autogenously or autonomously. Recent advancements in concrete research and technology have given us a better understanding of concrete’s healing properties. Self-healing concrete combines durability with sustainability while offsetting the high carbon output of concrete manufacturing and production and associated life-cycle costs. Technologies such as microbially induced calcite (calcium carbonate) precipitation, shape-memory polymers, encapsulation methods, hydration, and swelling agents can potentially reduce carbon emissions while enhancing resilience and longevity. This paper examines these technologies and their applications in the construction industry by comprehensively reviewing the literature and available case studies. This study concluded that there are promising advancements and innovations in concrete, particularly when improving upon its autogenous healing properties. The recommendations for future research include exploring more ways to bring the concrete industry and cement manufacturing toward net-zero carbon emissions. Full article

In this paper, four water–binder ratios (w/b) of 0.29, 0.33, 0.39, and 0.46 were designed. A variable test temperature was implemented in the drying–wetting cycle test according to the temperature fluctuations in the actual service environment, and the constant temperature test was established as the control group. The mechanical properties and chloride corrosion resistance of concrete with different w/b ratios under variable temperature drying–wetting cycles, as well as the microstructure changes, phase composition, and damage mechanism inside the concrete, were investigated. The results showed that the mechanical properties of concrete increased first and then decreased with drying–wetting cycles increasing, whereas the chloride corrosion resistance continued to decline. A higher w/b exacerbated the deterioration of the concrete performance. A higher w/b increased the porosity, chloride diffusion depth, and chloride content, thus reducing the resistance of chloride corrosion. Compared with w/b = 0.29, the compressive strength, splitting tensile strength, mass, and relative dynamic elasticity modulus of w/b = 0.46 exposed to 60 drying–wetting cycles decreased by 54.50%, 52.44%, 0.96%, and 6.50%, respectively, while the porosity, peak chloride content, and erosion depth increased by 45.12%, 70.45%, and 45.00%. Compared with the drying–wetting cycle with a constant temperature, the cumulative damage caused by the drying–wetting cycle with a variable temperature was greater, resulting in more severe deterioration of concrete performance. The increase in the test temperature significantly accelerated the diffusion rate, penetration depth, and chemical binding capacity of chloride ions. After 60 drying–wetting cycles, the peak chlorine content and erosion depth of w/b = 0.46 under variable temperature cycles were 15.38% and 10.32% higher than those under a constant temperature, while the compressive strength, splitting tensile strength, mass, and relative dynamic elastic modulus were reduced by 7.76%, 14.81%, 0.33%, and 2.40%, respectively. Microscopic analysis confirmed that higher w/b and variable temperature cycles accelerated the decay of mechanical properties and the decline of chloride corrosion resistance. According to the numerical fitting analysis, the w/b should be 0.29~0.39 under the condition that the mechanical properties and chloride corrosion resistance of concrete are met. Full article

This study comprehensively investigates the rheological properties of self-compacting concrete (SCC) and their impact on critical parameters, including the migration coefficient, penetration depth of chlorine ions, specific electrical resistance, and compressive strength. A total of 43 mix designs were meticulously examined to explore the relationships between these properties. Quantitative analysis employed a backpropagation neural network model with a single hidden layer to accurately predict the resistant and durable characteristics of self-compacting concrete. The optimal number of neurons in the hidden layer was determined using a fitting component selection method, implemented in MATLAB software(2021b). Additionally, qualitative analysis was conducted using sensitivity analysis and expert opinions to determine the priority of research additives. The main contributions of this paper lie in the exploration of SCC properties, the utilization of a neural network model for accurate prediction, and the prioritization of research additives through sensitivity analysis. The neural network model demonstrated exceptional performance in predicting test results, achieving a high accuracy rate using 14 neurons for predicting parameters such as chlorine penetration depth, compressive strength, migration coefficient, and specific electrical resistance. Sensitivity analysis revealed that xanthan gum emerged as the most influential additive, accounting for 43% of the observed effects, followed by nanomaterials at 35% and micro-silica at 21%. Full article

This work aims to show the advantages of using GGBS (Ground Granulated Blast Furnace Slag) and ACBFS aggregate (Air-Cooled Blast Furnace Slag) on the tensile strength and durability properties of infrastructure concrete at the reference age of 28 days. Three concrete mixes were prepared: the first one was a control sample; the second one had 15% GGBS (instead of Portland cement) and 25% ACBFS (instead of natural sand); and the third had 15% GGBS (instead of Portland cement) and 50% ACBFS (instead of natural sand). The studies on mortars focused on the ratio of compressive strength (CS) in correlation with the specific surface area (obtained by the Blain method). The microstructure of the prepared mortars was examined at the age of 28 days by X-ray diffraction, SEM electron microscopy with an energy-dispersive EDX spectrometer, and NMR nuclear magnetic resonance relaxometry. The results of the tests carried out afterwards on the concretes containing slag (15% GGBS and 25% or 50% ACBFS) showed values that met high-quality criteria for exfoliation (S₅₆ < 0.1 kg/m²), carbonation, and gelling G100 (with a loss of resistance to compression η < 25%). The slag concretes showed a degree of gelation of G100 (with a loss of compressive strength below 25%), low volume losses below 18,000 mm³/5000 mm² (corresponding to wear class 4, grade I), and moderate penetration of chlorine ions (according to the RCPT test). All of these allow the concrete with slag (GGBS/ACBFS) to be recommended as an ecological road concrete. Our study proved that a high-class road concrete of BcR 5.0 can be obtained, with tensile strengths of a minimum 5 MPa at 28 days (the higher road concrete class in Romania, according to national standards). Full article

Nano-particles and fibers-modified cementitious composite (NFCC) can greatly overcome the shortcomings of traditional cementitious materials, such as high brittleness and low toughness, and improve the durability of the composite, which in turn increases the service life of the structures. Additionally, the polymer coatings covering the surface of the composite can exert a good physical shielding effect on the external water, ions, and gases, so as to improve the permeability and chloride ion penetration resistance of the composite. In this study, the effect of three types of polymer coatings on the water contact angle, permeability resistance, and chloride ion penetration resistance of the NFCC with varied water–binder ratios were investigated. Three kinds of polymers (chlorinated rubber coating, polyurethane coating, and silane coating) were applied in two types of coatings, including single-layer and double-layer coatings. Three water–binder ratios of 35 wt.%, 40 wt.%, and 45 wt.% were used for the NFCC. The research results revealed that the surface of the NFCC treated with polymer coatings exhibited excellent hydrophobicity. The permeability height and chloride diffusion coefficient of the NFCC coated with different types of polymer coatings were 31–48% and 36–47% lower, respectively, than those of the NFCC without polymer coatings. The durability of the NFCC was further improved when the polymer coatings were applied to the surface in two-layer. Furthermore, it was discovered that increasing the water–binder ratio of the NFCC would lessen the positive impact of polymer coatings on the durability of NFCC. Full article

The chemical characteristics of Ordovician formation water and its relationship with hydrocarbons in the Halahatang depression (Tabei Uplift, Tarim Basin, NW China) were analyzed on the basis of the detailed formation water test data. The formation water in the Halahatang depression can be characterized as CaCl₂ type with high total dissolved solids (TDS) generally. The TDS concentration has a weak negative relationship with the depth, and is above 200 g/L in the North Region (north of the pinch-out line), then gradually decreases to the south, but is still greater than 50 g/L. The ion-proportionality coefficients of formation water, including the sodium-chlorine coefficient, desulfurization coefficient and metamorphic coefficient, reflect that the present strata are well sealed and had once experienced strong water-rock interactions. Furthermore, the source and evolution of the formation water presents a closed relationship with the hydrocarbon accumulation. The meteoric source of the formation water indicates the denuding by the Ordovician formation and the damage from the previous oil and gas reservoirs. The reservoir quality was also improved due to the strong karstification during the denudation, which was beneficial for hydrocarbon accumulation. The distribution of the TDS concentration is controlled by the caprock (Sangtamu Formation) and the high salinity fluids from overlying strata and adjacent regions. A geological model was established, the high salinity fluids penetrated the Ordovician strata resulting in the TDS increases in the northern part. Whereas, the South Region (south of the pinch-out line) was less affected due to the shielding layer of the O₃s. The favorable preservation conditions reflected by the high TDS and ion-proportionality coefficients correspond to the stable subsidence of strata since the Triassic era, the oil and gas reservoirs formed in the Himalayan can be preserved. Full article

The adverse effects of a hostile marine environment on concrete structures inevitably result in great economic loss and may contribute to catastrophic failure. There is limited information on the durability of concrete in a tensile stress-chloride ion-carbon dioxide (TCC) multiple-corrosion environment. The objective of this study is to explore the impact of a TCC multiple-corrosion environment on concrete considering three coupled factors of compressive strength, Cl⁻ penetration, and carbonation. Dry–wet cycle tests were conducted to determine the strength degradation and Cl⁻ penetration concentration of concrete in a hostile multiple-corrosion marine environment. The results show that the effects of water-soluble chloride ions (Cl⁻), carbon dioxide (CO₂), and tensile stress on concrete are not a simple superposition, but involve obvious interaction. The compressive strength of a concrete specimen first increases and then decreases in chlorine salt-carbon tests. The Cl⁻ concentration and tensile stress affect the carbonation depth of concrete, which increases with an increase in Cl⁻ concentration, and with the application of tensile stress. The Cl⁻ concentration has an obvious effect on the carbonation depth. In addition to experimental observations, a stepwise regression equation was established based on the multiple linear regression theory. A correlation analysis considering different factors was conducted to reflect the corrosion results more directly. Full article

In order to study the durability behavior of CFRP (carbon fiber reinforced polymer) reinforced concrete, three category specimens (plain, partially reinforced, and fully reinforced) were selected to investigate its performance variation concerning chlorine salt and salt-freeze coupled environment, which included the microscopic examination, the distribution of chloride ion concentration, and the compressive properties. By observing the microscopic of the specimens, the surface and cross-section corrosion deterioration was examined with increasing exposure time, and the physical behavior of CFRP and core concrete were discussed. The chloride ion diffusion test exerted that the chloride ion concentration in plain specimens is at least 200 times higher than that of fully reinforced specimens. Therefore, the effectiveness of CFRP reinforcement will be proved to effectively hinder the penetration of chloride ions into the core section. The formula of the time-dependent effect of concrete diffusivity with salt-freeze coupling effect was presented and its accuracy verified. A time-varying finite element model of chloride ion distribution was established by using ABAQUS software. It can be seen from the axial compression test that the strength loss rate of three categories of specimens was varied when subjected to the corrosion environment. Therefore, it is proved that CFRP reinforcement can effectively reduce the deterioration of the specimen’s mechanical properties caused by the exposure environment. The research results can provide technical reference for applying the CFRP strengthened concrete in a severe salt-freeze environment. Full article

This study evaluated the mechanical properties and durability performance of latex-modified hybrid fiber-reinforced roller-compacted rapid-set cement concrete (LMHFRCRSC) for emergency repair of concrete pavement. Experimental parameters included the blend ratio of the hybrid fiber, which comprised natural jute fiber (0–0.2 vol.%) and structural synthetic fiber (0–2 vol.%). The mechanical performance of LMHFRCRSC of various blend ratios was evaluated in terms of compressive, flexural, and splitting tensile strength. Durability assessment included chlorine ion penetration and abrasion resistance measurements. Compressive and flexural strength values of 21 and 3.5 MPa, respectively, were the set targets after 4 h of curing; a compressive strength of 35 MPa, a flexural strength of 4.5 MPa, a splitting tensile strength of 4.2 MPa, and chloride ion penetration of 2000 C or less were required after 28 days of curing. Our test results confirmed that all mix proportions satisfied the target values, regardless of the blend ratio of the hybrid fiber. Specifically, the mechanical performance of the concrete improved as the blend ratio of the structural synthetic fiber increased. With regard to durability, a greater amount of jute fiber, a hydrophilic fiber, enhanced the concrete’s durability. Additionally, incorporating jute fiber of 0.6 kg/m³ provided excellent chlorine ion penetration resistance. The optimal blend ratio for the hybrid fiber was natural jute fiber at 0.6 kg/m³ and structural synthetic fiber at 13.65 kg/m³ (mix: J0.6 + P13.65); with this mix proportion, a chloride ion penetration amount of 1000 C or less and maximum mechanical performance were achieved. Full article

When an additive is used to replace a certain amount of cement, a concrete pore structure becomes dense. Thus, it results in inhibiting the penetration of chlorine ions and suppressing corrosion of reinforcing bars. However, the pH level of the concrete decreases, and it deteriorates the performance of the passive film formed on the surface of the rebars embedded in the concrete. Therefore, in this study, the service lives of reinforced concrete containing different types of concrete binders were predicted and compared. The chloride ion diffusion coefficients of concretes with various binders were measured, and the critical chloride content of the rebar was assessed by the real-time monitoring on the corrosion initiation time of the rebar embedded in concrete. Moreover, Fick’s 2nd law was applied to predict when the chloride content at the 40 mm depth of cover reached the critical chloride content based on the chloride ion diffusion coefficient. It was observed that the service life of S6 (OPC 40% + GGBFS 60%) was the highest, followed by TBC (OPC 40% + GGBFS 40% + FA 20%), S3 (OPC 70% + GGBFS 30%), and OPC (OPC 100%). Full article

This study focuses on the chloride ion penetration resistance of a magnesium phosphate cement (MPC)-based composite material coating on the surface of silicate material. By means of electrical flux method and electric acceleration corrosion tests, the anti-chlorine ion permeation and reinforcement properties of MPC-based materials and Portland cement (OPC) mortar were compared and analyzed. The experimental results show that the electrical flux of the hardened body of the MPC-based material is much lower than that of the Portland cement mortar, and the electrical flux of the hardened body of the MPC mortar can be obviously reduced by adding silica-fume (SF) and fly ash (FA), which, when combined in a suitable proportion, will make the MPC’s hardened body more dense and impermeable. The addition of short cut fibers increases the number of pores, the pore size, and the electrical flux of the cement mortar’s hardened body. The adverse effects of the three fibers on the permeability of the MPC mortar against chlorine ions were as follows: polyvinyl alcohol fiber > glass fiber > basalt fiber. The electrical flux of MPC mortar or MPC paste coated on the surface of the OPC mortar was greatly reduced. Compared with silicate mortar, the MPC-based material has excellent protective performance under the condition of accelerated corrosion. Full article

Chloride-induced corrosion and load induced concrete cracking affect the serviceability and safety of reinforced concrete (RC) structures. Once these phenomena occur simultaneously, the prediction of RC structures’ lifetimes becomes a major challenge. The objective of this paper is to propose a methodology to evaluate the effect of loading and cracking on the mechanism of chloride ion penetration in concrete. The proposed methodology will be based on Bayesian networks. Bayesian networks are useful to update the lifetime assessment based on experimental data as well as to characterize the uncertainties of the input parameters of a chlorination model including a chloride diffusion acceleration factor. The proposed methodology is illustrated with experimental data coming from tests on RC beams subjected to static and cyclic loading before being in contact with a solution containing chloride ions. The characterized parameters are then used to evaluate the effect of these two loading conditions (static and cyclic) on the corrosion initiation time and the corrosion initiation probability. The results obtained indicate that the proposed methodology is capable of integrating loading and chlorination test data for the determination of the probabilistic parameters of a model in a comprehensive way. Full article

Polypropylene-fiber-reinforced concrete impacts the early shrinkage during the plastic stage of concrete, and the fiber volume content influences the durability-related properties of concrete. The purpose of this paper was to investigate the influence of fiber volume content on the mechanical properties, durability, and chloride ion penetration of polypropylene-fiber-reinforced concrete in a chloride environment. Tests were carried out on cubes and cylinders of polypropylene-fiber-reinforced concrete with polypropylene fiber contents ranging from 0% to 0.5%. Extensive data from flexural strength testing, dry–wet testing, deicer frost testing, and chloride penetration testing were recorded and analyzed. The test results show that the addition of the fiber improves the failure form of the concrete specimens, and 0.1% fiber content maximizes the compactness of the concrete. The flexural strength of specimen C2 with 0.1% fiber shows the highest strength obtained herein after freeze–thaw cycling, and the water absorption of specimen C2 is also the lowest after dry–wet cycling. The results also indicate that increasing the fiber volume content improves the freeze–thaw resistance of the concrete in a chloride environment. Chlorine ions migrate with the moisture during dry–wet and freeze–thaw cycling. The chlorine ion diffusion coefficient (D_cl) increases with increasing fiber content, except for that of specimen C2 in a chloride environment. The D_cl during freeze–thaw cycling is much higher than that during dry–wet cycling. Full article