Durability Of Concrete Research Articles

Durability evolution of RC bridges under the coupled action of fatigue effect and chloride attack

The main factors affecting the durability of a reinforced concrete bridge are the fatigue effect brought on by continuous traffic loads and chloride ion erosion, but studies on how these two factors interact have been scarce. As a result, concrete structure durability analyses need to be more thorough and accurate. The fatigue model from continuum damage mechanics is used to determine the equivalent stress range of traffic loads, and poroelasticity is used to establish the link between volumetric strain and porosity. Following a change in the porosity's function, the chlorine ion diffusion coefficient is covered. Finally, a proposed coupling analysis method that takes many physics into account is presented. This method takes into account fatigue stress, body strain, porosity, chlorine ion diffusion coefficient, and corrosion rate. The multiphysics finite element program and the associated theoretical equations can be used to simulate the chloride ion diffusion, erosion states, corrosion rate, and bearing capacity of the main sections in various stages. As a result, the reinforced concrete bridge's evolutionary durability can be fully attained. Fatigue loading can accelerate corrosion of reinforcement and chloride ion diffusion, which accelerates the loss of a bridge's flexural strength. The method described in this paper can calculate the flexural load capacity, erosion state, time-varying rust rate, and chloride ion diffusion effect of the main bridge sections at various times, which can show the detailed evolution of reinforced concrete bridge durability and offer useful theoretical and technical support for decisions about bridge durability assessment and maintenance

Study on the Effect of XYPEX Admixture on the Performance of Panel Concrete and Microscopic Mechanism

The influence of different XYPEX content on the performance of dam panel concrete was studied through laboratory tests. The test results show that a certain amount of XYPEX can improve the compressive strength and impermeability of panel concrete. According to the scanning electron microscope photos, XYPEX admixture has a good filling effect on the internal pores of concrete in the microstructure, and the macro performance is improved for impermeability, but the effect on the visible cracks on the surface of concrete is small. The research results fill the gap in the research field of XYPEX admixture in dam panel concrete, provide a new idea for improving the durability of panel concrete, and provide technical support and data support for the future application of XYPEX admixture in water conservancy and hydropower projects.

Investigation of mechanical properties of high-performance concrete via multi-method of regression tree approach

Concrete's workability and durability are influenced by its mechanical properties, including Tensile and Compressive strength. High-performance concrete exhibits non-linear relationships between its compressive and tensile strength characteristics and the proportions of its constituent materials, such as water, aggregate, cement, and admixtures. The investigation of the relations between the constituents of concrete and its mechanical properties has posed a challenging issue. This paper seeks to develop a range of single, hybrid, and ensemble models to resolve the problem of accurately estimating the mechanical properties of concrete according to its constituent components as input variables. In this regard, various frameworks incorporating a machine learning technique called decision tree and four metaheuristic optimization algorithms were utilized in model development to emulate the values of tensile and compressive strength. The findings indicated that the decision tree-dynamic arithmetic optimization algorithm hybrid model produced results with an correlation of determination of 0.9919 in compressive strength and 0.9933 in tensile strength, which were on average 1–3 % higher than that of the decision tree-dandelion optimizer algorithm, decision tree-arithmetic optimization algorithm, and decision tree-coot optimization algorithm, indicating superior optimization performance of dynamic arithmetic optimization algorithm. Additionally, the powerful prediction capability of the decision tree + dynamic arithmetic optimization algorithm + dandelion optimizer algorithm + coot optimization algorithm + arithmetic optimization algorithm ensemble model was noticeable with R2 of 0.9882 and 0.9936 in compressive and tensile strength estimation reliable to be used for various data produced in the future. In general, the utilization of coupling techniques to generate hybrid and ensemble models can enhance the accuracy of predictions while reducing the time and costs associated with experimental procedures.

High-performance lightweight foam concrete enabled by compositing ultra-stable hydrophobic aqueous foam

The major limitations of lightweight foam concrete are inferior mechanical properties and durability. This study designs a novel high-modulus hydrophobic foam to produce high-strength and durable foam concrete. Poly (methyl hydrogen)siloxane (PMHS) was employed to construct a hydrophobic boundary of hydroxypropyl methylcellulose (HPMC) foam. The produced hydrophobic foam bubbles exhibit a high modulus, fine bubble size, and exceptional thermodynamic stability. A dense foam wall of 8 μm in thickness functions as a structure for chemical loadings of inorganic-organic particles onto the viscoelastic bubble film. This facilitates their interaction effect of adsorption and chemical bonding, contributing to the hydrophobic nature of the foam wall. The resulting hydrophobic foam concrete shows low water adsorption and high mechanical strength. The hydrophobic foam concrete demonstrates superior chemical resistance and anti-chloride diffusion compared with normal concrete. This study might provide a practical strategy for designing high-performance lightweight foam concrete with significant potential as structural elements.

Increasing Concrete Durability Against Organic Acid Corrosion with Coal Fly Ash and Bagasse Fly Ash as Cement Replacements

Increasing Concrete Durability Against Organic Acid Corrosion with Coal Fly Ash and Bagasse Fly Ash as Cement Replacements

Study on the Effect of Fly Ash on Mechanical Properties and Seawater Freeze–Thaw Resistance of Seawater Sea Sand Concrete

When using seawater and sea sand as mixes, the mechanical properties and durability of concrete are adversely affected because the raw materials themselves contain harmful ions. Fly ash is the tailings formed in the process of industrial production, the use of which does not require the burning of clinker, reducing CO2 emissions. Moreover, it belongs to a new type of cementitious materials with low emissions and high environmental protection. Fly ash enhances the properties of concrete and reduces the effect of harmful ions on concrete. Based on the above considerations, the corresponding specimens were prepared and subjected to cubic compressive strength, flexural strength, and seawater freezing and thawing resistance tests by using fly ash admixture as the main variable. A combination of macro-analysis and micro-analysis was used to investigate the effect of fly ash on the performance of seawater sea sand concrete. The results showed that fly ash significantly enhanced the mechanical properties and resistance to seawater freezing and thawing of seawater sea sand concrete. The best improvement in compressive strength and resistance to seawater freezing and thawing was achieved at a substitution rate of 20%. The maximum increase in compressive strength was 13.22%. The maximum reduction in mass loss rate was 57.26% and the strength loss rate was 43.14% after the specimens were subjected to seawater freezing and thawing 75 times. The maximum enhancement in flexural strength was 17.06% for a substitution rate of 10%. Through microanalysis, it can be seen that the incorporation of coal ash can enhance the compactness of concrete through the microaggregate effect as well as the volcanic ash reaction to promote the secondary hydration reaction, so as to strengthen the seawater freeze–thaw resistance of seawater sea sand concrete. Finally, the damage prediction model established using the mean GM (1, 1) model of gray system theory meets the requirements of the first level of prediction accuracy and can accurately predict the damage of seawater sea sand concrete under seawater freezing and thawing.

Enhancement of Compressive Strength and Durability of Sulfate-Attacked Concrete

This experimental study is carried out in order to improve the properties of sulfate-attacked concrete. The concrete specimens were immersed in 15% Na2SO4 solution before being protected with a concrete repairing agent (CRA). The effects of sulfate corrosion time, the curing time after being attacked, and the concrete repairing agent on concrete were investigated. The experimental results indicate that the properties slightly increased after being attacked by sulfate for 60 days than for 30 days. However, they decreased after being attacked by sulfate for 90 days. CRA could effectively improve the properties of sulfate-attacked concrete. After being re-cured for 7 days, the properties of the sulfate-attacked concrete were significantly improved in comparison with those of the specimens taken out from the sulfate solution immediately. When the specimens were attacked for three months, the compressive strength of specimens coated with CRA was increased by 6.1%, 6.4%, and 6.4% compared to that of the specimens without CRA after being cured for 7 to 56 days, respectively. The carbonation depth of concrete specimens with CRA was reduced by 4.6%, 8.3%, and 4.9%, respectively. However, the chloride ion permeation coefficient of concrete with CRA decreased by 20.3%, 28.5%, and 28.7%, respectively, for the concrete immersed in sulfate for one month.

Long-term performance of magnesium phosphate cement concrete prepared in the winter

Previous studies have established the strength development of magnesium ammonium phosphate cement (MAPC) concrete and magnesium potassium phosphate cement (MKPC) concrete at sub-zero temperatures. However, the long-term performance of these magnesium phosphate cement (MPC) concrete, prepared at low temperatures and exposed to complex environmental effects of cold regions, remains underexplored. This study monitored the mechanical properties and durability of MAPC concrete at different ages for 520 d, which fully demonstrated the feasibility of MAPC concrete for winter construction in cold regions. At the age of 520 d, MAPC concrete had a compressive strength of over 65 MPa and excellent resistance to chloride ion penetration with a measured charge of 129.1 C, and could endure more than 250 rapid freeze-thaw cycles. In contrast, MKPC concrete exhibited significant disadvantages in terms of freeze-thaw resistance during natural freeze-thaw cycles. No expansive substances or damage were found in MKPC concrete that was prepared at low temperatures and subsequently experienced temperature increases along with accelerated hydration. The relatively poor freeze-thaw resistance of MKPC concrete could be attributed to a combination of factors including larger capillary size and volume, reduced air content, greater air-void spacing factor, wider and weaker interface zone between cement mortar and coarse aggregate.

Enhancing concrete durability and strength: An innovative approach integrating abrasion and cement slurry treatment for recycled coarse aggregates

AbstractThis study introduces a novel approach to enhance the durability and strength of concrete by integrating abrasion and cement slurry treatments on surface‐treated recycled coarse aggregates (STRCA). Initial abrasion treatment removes aged mortar from the recycled coarse aggregate (RCA) surface, while subsequent cement slurry modification provides a fresh surface, reinforcing the bond with the concrete matrix. Through detailed material analyses including x‐ray diffraction, scanning electron microscopy, and energy‐dispersive x‐ray, microstructural changes are evaluated alongside compressive strength, drying shrinkage, electrical resistivity, and chloride ion penetration of STRCA‐based concrete. Results indicate significant improvements in mechanical properties and durability as the treatments eliminate mortar and enhance the interfacial connection with cement paste. Notably, a substantial 29.37% strength enhancement is observed at 25% replacement (STRCA 25), demonstrating treatment efficacy. While a reduction of 11.58% occurs at 100% replacement (STRCA 100), up to 75% replacement shows minimal strength loss, with optimal enhancements at 50% replacement. Additionally, STRCA concrete exhibits lower drying shrinkage (11%–20% reduction) and increased electrical resistivity (28%–36% rise), indicating improved durability at 100% replacement. Enhanced resistance to chloride ion penetration is also evident, with a 22%–28% increase at 100% replacement compared to conventional RCA. Overall, this study highlights the effectiveness of dual treatments for enhancing concrete properties using STRCA.

Durability analysis of metakaolin recycled concrete under sulphate dry and wet cycle

This study aims to enhance the durability, cost-effectiveness, and sustainability of recycled fine aggregate concrete (RFAC) subjected to the combined effects of wet-dry cycles and sulfate erosion. Dry–wet cycle tests were conducted in RFAC with different admixtures of biotite metakaolin (MK) and 15% fly ash (FA) mix (M) under 5% sulfate erosion environment. The effect of 0%, 30%, 60% and 90% recycled fine aggregate (RFA) replacement of natural fine aggregate on mass loss, cubic compressive strength, relative dynamic modulus test of RFAC, damage modeling and prediction of damage life of concrete were investigated. The results showed that the concrete cubic compressive strength and relative dynamic modulus were optimal for recycled concrete at 15% MK biotite dosing and 60% RFA substitution, and its maximum service life was accurately predicted to be about 578 cycles under 5% sulfate dry–wet cycling using Weibull function model. This study is pioneering in addressing the durability of RFAC under sulfate attack combined with wet-dry cycling, employing a novel approach of incorporating MK and FA into RFAC. The findings highlight the practical application potential for using MK and FA in RFAC to produce durable and sustainable construction materials, particularly in sulfate-exposed environments. This research addresses a critical challenge in the construction industry, providing valuable insights for developing more durable and eco-friendly construction materials and contributing to long-term sustainability goals.

Application of Thermal Spraying Technology in Concrete Surface Ceramic-Based Coating

Enhancing the durability and extending the service life of concrete are crucial for promoting its sustainable development. Applying surface coatings is the primary technical method used to improve concrete durability. In this study, based on the plasma thermal spraying technology, a thermal-sprayed, ceramic-based coating was prepared on a concrete surface and evaluated using the drawing method, X-ray diffraction scanning electron microscopy with energy dispersive spectroscopy, X-ray computed tomography (X-CT), and frictional wear. Subsequently, performance tests were conducted. The test results showed that mullite powder was a suitable ceramic-based coating material. The coating had a good interfacial bonding ability with the concrete surface; moreover, the bonding site exhibited a chimeric state with an adhesion strength of 3.82 MPa. The wear rate of the coating material (0.02‰) is lower than that of the concrete matrix (0.06‰), resulting in improved surface wear resistance. SEM analysis reveals that the coating contains a considerable amount of amorphous or microcrystalline phases. The internal structure of the coating exhibits porous characteristics, with a total porosity of 10.35% and pore diameters predominantly ranging from 4 μm to 16 μm. At a distance of 80 μm from the coating site, the elements Al, O, and Si significantly contribute to the mullite components. The porous structures within the coating products are further verified using X-CT. This study offers a new possibility for ceramic coatings on hydraulic concrete.

Influence of waste glass on concrete strength and permeability during dry-wet cycles

A series of experiments were carried out to explore the impact of waste glass on the durability of concrete. In this study, waste glass was incrementally incorporated to replace sand as the fine aggregate in creating 240 concrete specimens, with substitution rates of 0%, 10%, 30%, and 50%. The concrete specimens were subjected to early strength testing on the 3rd and 7th day, followed by evaluation of strength and permeability after curing for 28 days with dry-wet cycles. Furthermore, ultrasonic wave analysis was conducted on the waveform, and the concrete’s internal phases and chemical composition were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS). The results led to the following observations: (1) The inclusion of glass sand lowered the early compressive strength of concrete, with the lowest drop being 24.78%. However, when it was cured for 28 days and the content of glass sand was not more than 30%, the change rate of its compressive strength was between −2.85% and 3.19%, so it was practically negligible. (2) Glass sand substitution rates ranging from 10% to 30% greatly enhanced the strength of concrete under dry-wet cycles, and the 50% substitution rate significantly improved the permeability properties, although it adversely affected the strength.

Effect of Recycled Fibers on the Mechanical Properties and Durability of Sand Concrete

Recycling waste in construction materials is part of a sustainable development approach aimed at creating new materials with characteristics that have been shown to be competitive with traditional materials. In this context, this study aims to recover steel, copper and aluminum wastes from blacksmiths’ workshops together with the reuse thereof in the form of reinforcing fibers in sand concrete. However, in order to assess the impact of this waste on the concrete properties, we introduced such wastes in the form of fibers at different proportions (0.4 %, 0.8 % and 1.2 %). Further, a series of tests was then carried out to determine the evolution of the concrete characteristics in the fresh state (workability and density) and in the hardened state (compressive strength, flexural strength, compressive strength obtained using a sclerometer and the speed of ultrasonic waves), as well as the concrete’s durability (absorption coefficient by immersion, by capillarity and the porosity accessible to water). In closing, the behavior of the concrete was assessed in the face of a chemical attack by H2SO4 and HCl by measuring mass loss. In virtue of thus, the results obtained demonstrated a positive evolution of certain properties of sand concrete as a function of the type and percentage of fibers incorporated into the composition of the concrete.

The effect of freeze-thaw cycles and sulfuric acid attack separately on the compressive strength and microstructure of 3D-printed air-entrained concrete

3D-printed concrete (3DPC) is a promising technique for constructing structures and intricate designs. To ensure the successful performance of these structures throughout their service life, it is essential to understand their long-term properties and durability. While the use of air-entraining additives can enhance the durability of concrete against freeze-thaw cycles, investigating their impact on other properties is crucial. This study examines the effect of freeze-thaw cycles and sulfuric acid attack on the durability of 3D-printed concrete containing air-entraining additives. The results indicate that, in addition to improving resistance to freeze-thaw cycles, air-entraining additives also increases resistance to sulfuric acid attack. The drop in compressive strength of the samples containing air-entrained additive (0.08–0.12 % AEA) is 1.4–5.3 % less than the control samples against the freezing and thawing cycles. Examining the mechanisms of action of these invasive agents also shows this. Creating intentional voids to reduce the internal pressure of water expansion during freezing and reducing the number and width of possible microcracks are the dominant mechanisms of air-entraining additives against freeze-thaw cycles. Besides, their performance mechanisms during acid attacks are somewhat similar. Analysis of elements created in the matrix of the samples after acid attack indicates a decrease in calcium concentration and an increase in silica concentration. Among the observed reactions, the second reaction prevails, leading to the breakdown of the C-S-H structure into gypsum and silica hydroxide. This phenomenon is associated with changes in acid concentration. However, the presence of air bubbles causes surplus plate-like Calcium hydroxide crystals resulting from the elevated cement content in printed mixes to form within these bubbles, making them susceptible to damage and fracture during freeze-thaw and acid attacks.

Effect of Superabsorbent Polymers and Presoaked Coarse Recycled Shale Lightweight Aggregates on Relative Humidity Development in Early-Age Concrete

Self-desiccation-induced shrinkage may result in cracking at an early age, which is averse to the durability of concrete. Internal curing (IC) agents, such as superabsorbent polymers (SAP), are normally used for moisture regulation and shrinkage reduction. In addition, the make-up of recycled shale lightweight aggregate (RSLA) results in a good absorbing capacity, which makes it a potential candidate for IC. In this paper, the synergistic effect of SAP and RSLA on the relative humidity (RH) variation in early-age concrete under sealed conditions is investigated experimentally in terms of the setting time, relative humidity, and autogenous shrinkage. The results indicate that adding SAP and presoaked RSLA can significantly postpone the initial and final setting times. The initial setting time of RSLA30 and SAP06 is delayed by 127 and 171 min, respectively, compared to the benchmark mixture. In addition, increasing the amounts of SAP and presoaked RSLA can effectively extend the duration of the vapour-saturated stage, reducing the decrease in RH and autogenous shrinkage at 28 days. When the RSLA dosage increases from 0 to 10%, 20%, and 30%, the duration of the vapour-saturated stage is extended by 2, 9.4, and 26 days, respectively. Moreover, due to different water desorption behaviours, more IC water released by RSLA during the initial stage can slow the water release of SAP and lead to a higher RH level at 28 days.

Study on the Resistance of Concrete to High-Concentration Sulfate Attack: A Case Study in Jinyan Bridge.

Concrete structures face significant challenges in sulfate-rich environments, where sulfate attack can affect their durability and structural integrity. This study explores innovative approaches to enhancing concrete performance by integrating hydrophobic and densification technologies. It emphasizes the critical role of anti-sulfate erosion inhibitors in mitigating sulfate-induced damage, reducing water absorption, and inhibiting corrosive reactions. This research addresses prevalent issues in Chinese engineering projects where high sulfate concentrations are common, necessitating robust solutions for sulfate resistance. Through rigorous testing, including wet-dry cycling tests with 5% and 10% Na2SO4 solutions following the GB/T 50082-2009 standard, concrete formulations achieved exceptional long-term sulfate resistance, meeting or exceeding KS200-grade requirements. These findings provide valuable insights into optimizing concrete durability in sulfate-rich environments, offering practical strategies to enhance infrastructure resilience and reduce maintenance costs.

A Comprehensive Microstructural Analysis for Enhancing Concrete’s Longevity and Environmental Sustainability

The environmental factors lessen the durability of concrete by changing the way the elements are linked together. To maximize the building's longevity, the concrete needs to be impermeable. Samples of Portland slag cement concrete of grade M20 that had been produced with and without admixtures as well as with and without reinforcement were taken into account for the current investigation. Samples were initially cured in potable water for 28 days, following which they were subjected to additional exposure in environments containing hydrochloric acid and sulphuric acid for challenging conditions for a subsequent 28-, 56- and 90-day period. All specimens exposed to various environmental circumstances showed a similar pattern of enriching in physical characteristics and diminishing in water absorption, therefore enriching the durability qualities, when the data gathered at intervals of 28, 56, and 90 days of curing were examined. SEM examination revealed a notable refinement in pore structure with aging, confirming age-related pore refinement. XRD analysis performed for phase identification revealed the presence of silica and calcium carbonate in the concrete specimens. This research intends to offer important insights about the appropriateness of Portland Slag Cement in strengthening the resilience and durability of concrete.

Durability performance of superabsorbent polymer incorporated concrete modified by nano-silica addition in seasonal frozen regions

In seasonal frozen regions, ion erosion and freeze-thaw (F-T) cycles threaten pavement concrete durability. This study evaluates the suitability of superabsorbent polymer (SAP) concrete modified by nano silica (NS) for enhancing durability. Tests were conducted to analyze chloride impermeability and frost resistance effects on modified SAP concrete. The coupling impact of ion erosion and freeze-thawing was also evaluated. Mercury intrusion porosimetry (MIP), scanning electron microscopy, and energy dispersive spectrometry were employed to investigate microstructure characteristics. Results demonstrated that NS-modified SAP concrete exhibited high resistance to ion erosion and F-T cycles. Adding 3 % NS reduced the relative dynamic elastic modulus (RDEM) loss by 23.21 % after 300 F-T cycles. The enhancement was more pronounced under the coupled action of ion erosion and freeze-thawing, and the RDEM loss and scaling quantity per unit area of NS-3 % decreased by 13.21 % and 41.48 % respectively, and compressive strength was 28.33 % higher than that of SAP concrete after 135 salt-frost cycles. MIP testing indicated that 3 % NS significantly improved pore structure, reducing deterioration in much harmful pores by 12.82 %. SAP promoted the efficient pozzolanic reaction of NS, generating high-density C-S-H. Additionally, second-hydration products were adsorbed by the ionization of SAP microgel, densifying its shrinkage voids and delaying ITZ width and micro-crack propagation, thereby enhancing concrete durability.

Synergistic effects of graphene oxide and limestone calcined clay cement on mechanical properties and durability of concrete

Synergistic effects of graphene oxide and limestone calcined clay cement on mechanical properties and durability of concrete

Research on the effect of different content of rice husk ash on the microstructure of concrete

Mercury injection porosimetry test is used to study the microstructure of rice husk ash cement paste with different content. The influence of rice husk ash on the microstructure of cement paste is analyzed through porosity, pore size distribution, the most probable pore size, pore size gradation and critical pore size analysis. The results show that with the increase of rice husk ash content, the porosity of cement paste decreases, and the pore size distribution and the most probable pore size decrease, which indicates that the addition of rice husk ash can improve the pore structure of concrete and improve the durability of concrete. With the increase of rice husk ash content, the number of harmful holes of cement paste decreases, the number of harmless holes increases, and the critical pore diameter decreases, which indicates that the addition of rice husk ash can improve the strength and impermeability of concrete.