Durability Of Concrete Materials Research Articles

Experimental and Modeling Analysis of Polypropylene Fiber Reinforced Concrete Subjected to Alkali Attack and Freeze-Thaw Cycling Effect.

The durability of concrete materials in harsh environmental conditions, particularly in cold regions, has garnered significant attention in civil engineering research in recent years. Concrete structures in these areas are often damaged by the combined effects of alkali-silica reaction (ASR) and freeze-thaw cycles, leading to structural cracks and significant safety hazards. Numerous studies have demonstrated that polypropylene fiber concrete exhibits excellent crack resistance and durability, making it promising for applications in cold regions. This study elucidates the impact of alkali content on concrete durability by comparing the mechanical properties and durability of different alkali-aggregate concretes. The principal experimental methodologies employed include freeze-thaw cycle experiments, which examine patterns of mass loss; fluctuations in the dynamic modulus of elasticity; and changes in mechanical properties before and after freeze cycles. The findings indicate that increased alkali content in concrete reduces its strength and durability. At 100% alkali-aggregate content, compressive strength decreases by 35.5%, flexural strength by 32.9%, mass loss increases by 35.85%, relative dynamic elastic modulus by 39.4%, and residual strength by 97.28%, indicating higher alkali content leads to diminished durability. Additionally, this paper introduces a constitutive damage model, validated by a strong correlation with experimental stress-strain curves, to effectively depict the stress-strain relationship of concrete under varying alkali contents. This research contributes to a broader understanding of concrete durability in cold climates and guides the selection of materials for sustainable construction in such environments.

Numerical Analysis of the Thermodynamic Response of a Hollow Concrete Cylinder

The stability and durability of concrete materials are essential factors in the construction industry. Environmental conditions, such as temperature affect the tensile strength and durability of concrete structures. This work investigates the thermodynamic behaviour of hollow cylindrical concrete using the finite element method (FEM). By deploying ANSYS®, the element mesh was created, and the temperature distribution inside the hollow cylinder was calculated. The effect of the hollowness of the concrete on its heat absorption is determined. The findings demonstrate that the temperature profiles changed radially throughout the concrete thickness. Moreover, it was discovered that the temperature distribution was impacted by the airflow into the cylinder. The numerical experiment in this study was essential in providing a comprehensive understanding of the behaviour of the concrete, particularly when exposed to higher heating rates. This study contributes to the knowledge of the performance and stability of concrete materials. It also demonstrates that the hollowness of the concrete enhances its heat-shielding performance. Furthermore, the inflow of air into the cylinder affects the temperature distribution, with a higher influx of air resulting in lower temperatures. These findings can be utilised to develop appropriate measures to enhance the performance and durability of concrete structures.

Research on the effect of sand content on stress and durability of cement

With the progress of science and technology and the improvement of people’s quality of life, the demand for materials is getting higher and higher. As one of the most important civil engineering materials, concrete is widely used to repair a large number of broken infrastructures. Its production uses sand and aggregate from quarrying operation. If the use is unreasonable, a large amount of waste will be produced. In addition, there is a significant shortage of natural building raw materials in many regions (especially in developed regions). So improving the sustainability and durability of concrete materials can save transportation costs. This paper mainly discusses the influence of sand content in cement concrete on the performance of the material itself. The maximum pressure resistance of the corresponding specimen is measured by the pressure sensor and other experimental instruments, and compared with the specimen of different shape and volume under the condition of different sand rate. By changing the ambient temperature, the number of times that the specimen does not conform to the specified standard value is measured, and the durability of the specimen with different sand ratio is obtained. In this work, the optimal sand gravel ratio is successfully and relatively accurately measured. And it can be reasonably used in infrastructure construction.

An Overview of Smart Materials and Technologies for Concrete Construction in Cold Weather

Cold weather conditions pose significant challenges to the performance and durability of concrete materials, construction processes, and structures. This paper aims to provide a comprehensive overview of the material-related challenges in cold weather concrete construction, including slow setting, reduced curing rate, and slower strength development, as well as frost damage, early freezing, and freeze–thaw actions. Various innovative materials and technologies may be implemented to address these challenges, such as optimizing the concrete mix proportions, chemical admixtures, supplementary cementitious materials, and advanced construction techniques. The paper also examines the impact of weather-related challenges for personnel, equipment, and machinery in cold environments and highlights the importance of effective planning, communication, and management strategies. Results indicate that the successful implementation of appropriate strategies can mitigate the challenges, reduce construction time, and enhance the performance, durability, and sustainability of concrete structures in cold and freezing temperatures. The paper emphasizes the importance of staying updated about the latest advancements and best practices in the field. Future trends include the development of smart and functional concrete materials, advanced manufacturing and construction techniques, integrated design, and optimization of tools, all with a strong focus on sustainability and resilience.

Developing a Model Based on the Radial Basis Function to Predict the Compressive Strength of Concrete Containing Fly Ash

A supplemental pozzolanic material such as fly ash may result in a reduction in the concrete’s adverse environmental effect by reducing the discharge of carbon dioxide throughout the cement production procedure. This pozzolanic material also enhances the mechanical characteristics as well as the durability of concrete material. Considering the boundless passion for utilizing fly ash and conducting extensive research studies, the extent to which this supplement can be added to concrete has a limitation equal to almost one-third of cement material’s weight. In the current study, a model based on the Radial Basis Function (RBF) is developed to estimate the compressive strength of concrete containing various amounts of fly ash at any arbitrary age. Having parameters used as inputs in ANN modeling such as concrete additives and characteristics of fly ash, the output was compressive strength. It was concluded that the estimated results agree well with the experimental measurements with an MSE of 0.0012 for the compressive strength. Simple and practical equations are proposed to present a simple means to determine the compressive strength of fly ash-based concrete.

Experimental study on durability of basalt fiber concrete after elevated temperature

AbstractThe durability of concrete material after exposure to elevated temperatures is important for the serviceability prediction of concrete structures in a fire disaster scenario. Existing researches show that an appropriate amount of basalt fiber can significantly improve the splitting tensile strength and chloride penetration resistance of concrete. However, the mechanical properties of basalt fiber concrete after elevated temperatures and its durability properties are still not clear. In this paper, the mechanical properties, carbonization law, and chloride ion penetration law of ordinary concrete and basalt fiber concrete under high temperatures are studied. The concept of a burnt layer for concrete exposed to elevated temperatures is proposed, and the thickness of this burnt layer for concrete under different temperatures was measured. The results show that the addition of basalt fiber can inhibit the carbonization of concrete at elevated temperatures, diminish the thickness of the burnt layer, and significantly improve the chloride penetration resistance of concrete.

DEM analysis of the effect of interface transition zone on dynamic splitting tensile behavior of high-strength concrete based on multi-phase model

The tensile strength is one of the main parameters in the design of concrete structures and has an important influence on the cracking performance and durability of concrete materials. As the weak region in concrete, the strength of the interface transition zone (ITZ) directly affects the dynamic mechanical response of concrete. Meanwhile, considering that the tensile performance of concrete is far weaker than its compressive performance, the study of the strength of ITZ is of great significance to the dynamic tensile fracture characteristics and mechanical properties of concrete. In this paper, a method combining 3D scanning technology and Clump-Cluster was proposed to generate a real geometry shape model of crushable aggregate. On this basis, the 3D discrete element model (DEM) of high-strength concrete was constructed using the Flat-Joint Model (FJM). The effects of the ITZ strength on the failure mode, number of microcracks, tensile strength and strain rate effect of high-strength concrete under strain rates from 0.01/s to 100/s were studied by splitting tensile test. The simulation results indicate that the number of microcracks generated decreases with the increase of ITZ strength, and the proportion of ITZ cracks decreases obviously. When the ITZ strength exceeds the critical value of 0.8 times that of mortar, the tensile strength is almost not affected by ITZ strength. In addition, based on the numerical simulation results, a modified formula that can reflect the functional relationship between the ITZ strength and the dynamic increasing factor of the concrete tensile strength (TDIF) is proposed, and the rationality of the TDIF modified formula is verified.

Experimental study on PPP-BOTDA-based monitoring approach of concrete structure crack

Cracks are the most common lesion in water-wading structures such as dams and sluices, which have an important impact on the durability of concrete materials and the safety of structures. The emergence of cracks is also regarded as a precursor to the destruction of buildings. However, the randomness and concealment of cracks are strong, which bring great difficulty to real-time and accurate capture. This paper focuses on Pulse Pre-Pump Brillouin Optical Time Domain Analysis (PPP-BOTDA) and studies the principle and realization method of PPP-BOTDA optical fiber sensing for concrete structure strain. On this basis, several groups of monitoring experiment for crack initiation location and propagation process of concrete structures are carried out. In the paper, the relationship between force-light-opening is studied and the influence of angle between optical fiber and crack on monitoring results is analyzed. Finally, a monitoring model for concrete cracks based on optical fiber strain sensing is constructed.

Durability of Pavement Materials with Exposure to Various Anti-Icing Strategies

Anti-icing is a critical topic in durability assessment for pavement infrastructures, and it varies according to local policies. To provide sufficient information to winter maintenance agencies, and help compare the merits and shortcomings of each strategy, this review summarizes the widely used anti-icing strategies, including elastic surfaces or high-friction overlays, asphalt binders mixed with anti-icing additives, pavement heating technologies, deicers, and fixed automated spray technology, from academic and practical perspectives, as well as explore the impact of deicers on the durability of concrete materials. Furthermore, the costs of each method were compared to evaluate the feasibility of them. This review not only provides a summary of previous anti-icing strategies, but also sheds light on future research trends that may help address the challenges of current anti-icing strategies, and further enhance anti-icing efficiency and reduce life cycle costs.

Preparation of High Performance Hydrophobic Concrete Material and Experimental Study on Its Corrosion Resistance

The durability of reinforced concrete structure will be threatened because of corrosion. In view of this situation, in this study, from the perspective of super hydrophobic to improve the durability of concrete materials, a high-performance super hydrophobic concrete material is proposed. The material uses the principle of "binary coordination," which mixes fluorosilane and steel fiber into the composition of concrete, and sets up a copper net on its surface, thus forming a micro-nano-composite structure, making the concrete have a super hydrophobic surface. When characterizing the proposed concrete material, the contact angle of super hydrophobic concrete is 158.3°, rolling angle is 7.6°, and the contact between droplets and concrete conforms to Cassie Baxter model. In the study of corrosion resistance, standard maintenance environment and oxygen diffusion dry wet cycle environment are studied. During the test, a long-term immersion method is used, and the immersion period is set to (30 d, 50 d, 80 d). Compared with different environments, it is found that super hydrophobic concrete has strong corrosion resistance, which shows that the doping of fluorosilicane and steel wire can significantly improve the impermeability of concrete.

Contribution to Sustainable Environment through Examination of Durability of Materials in an Aggressive Environment

Abstract The paper presents the results of leaching tests of concrete samples with 5 wt. % cement's replacement by fly ash and applies the statistical approach to an interpretation the results. Concrete samples with of two types of fly ashes, originating from anthracite and lignite burning, respectively were exposed to solution of Al2(SO4)3 to sulphate corrosion testing. Deterioration process was manifested by leaching the elementary components of concrete (Ca, Si, Fe, Al) and particular pH changes of leachates in 5 cycles. The leached-out concentrations of elements from concrete matrix measured by X-ray fluorescence method (XRF) and measured pH values were used for the subsequent statistical analysis. A dependency between pH of leachates and leaching trends of Ca and Al, respectively, was confirmed. The correlation coefficients ranged from 0.79 to 0.85. No significant differences between durability of concrete materials based on black or brown-coal fly ashes regarding to leachability were noticed.

Development of Fly Ash Based Geopolymer as Erosion Mitigation Coating

Loss of durability of concrete materials in sewage and chemical treatment facilities exposed to acidic environments is a key issue that affects the life cycle performance. Applications of organic coating such as epoxy and acrylic usually covers the concrete surface by physical addition normally failed to act as an effective coating due to debonding when the organic coating absorbs water. In this work, geopolymer was used as alternative material for concrete coating. Preparation of geopolymer involved fly ash, a materials containing high aluminosilicate and calcium mixed with various concentrations (6, 8 and 12M) of sodium hydroxide (NaOH). Subsequently, all samples were tested and analysed through compressive strength test and gel time. Geopolymers synthesised from 12M NaOH concentration exhibited high compressive strength and low gel time, hence was chosen as a coating for the concretes for the erosion evaluation. Results show that, concretes coated with geopolymers yielded low percentage of mass loss compared to the uncoated concretes. This suggest that geopolymers has high potential to be used as erosion mitigation coating to prevent the concretes from degrading due to the acidic environment.

Advances in Hygro-Thermal Deformation of Concrete Material

The development of concrete deformation is determined by the time depended distribution of temperature and humidity in concrete resulting form the variation of temperature and humidity and also their coupling effect, which also greatly influences the durability and service life of concrete. Therefore, the coupling effect of temperature-humidity variation must be considered when study the volume deformation of concrete. The studies related to the hygro-thermal deformation of concrete were reviewed and summarized, which included the research status of concrete deformation resulting from temperature and humidity, the coupled heat and moisture transfer model and the numerical simulation method. The research status and existing problems of hygro-thermal deformation of concrete were also analyzed in detail for promoting the investigation on the mechanism of volume deformation cracking and the durability of concrete material, which will benefit to the deformation prediction and crack control technology of engineering structure. Periodically variation of environmental temperature and humidity can be used to describe the seasonal or diurnal temperature-humidity changing of concrete materials and structures in the construction and service period of concrete structure. Consideration should also be given to "fatigue effect of heat and moisture stress" when study the deformation evolution and the damage mechanism of concrete crack.

Evaluation of Relationship between Water Absorption and Durability of Concrete Materials

Environment has significant effects on the water absorption of concrete materials. This paper presents an experimental study of the influence of water absorption on the durability of concrete materials. A detailed analysis is also presented in order to establish useful relationship between them. Concrete specimens of different water absorption were prepared through different curing conditions, and results indicated that curing condition can significantly affect the surface water absorption. SEM photos also showed that different curing conditions caused different microstructure. After 28-days curing, compressive strength, permeability, sulfate attack, and chloride ion diffusion of concrete samples were investigated. As a result, both of surface sorptivity and internal sorptivity have no clear relationship with compressive strength. Results obtained also showed that only surface water absorption related to the performance of concrete including permeability, sulfate attack, and chloride ion diffusion. In addition, both impermeability and resistance to sulfate attack were linearly associated with surface sorptivity, and both correlation coefficients were not less than 0.9. Furthermore, chloride ion diffusion coefficient has exponent relation to surface water absorption with higher correlation coefficient. However, no apparent relationship was found between internal water absorption and durability like impermeability, resistance to sulfate attack, and chloride ion diffusion.

Uncertainty propagation of a multiscale poromechanics-hydration model for poroelastic properties of cement paste at early-age

The durability of concrete materials with regard to early-age volume changes and cracking phenomena depends on the evolution of the poroelastic properties of cement paste. The ability of engineers to control the uncertainty of the percolation threshold and the evolution of the elastic modulus, the Biot–Willis parameter and the skeleton Biot modulus is key for minimizing the vulnerability of concrete structures at early-age. This work presents original results on the uncertainty propagation and the sensitivity analysis of a multiscale poromechanics-hydration model applied to cement pastes of water-to-cement ratio of 0.40, 0.50 and 0.60. Notably, the proposed approach provides poroelastic properties required to model the behavior of partially saturated aging cement pastes (e.g. autogenous shrinkage) and it predicts the percolation threshold and undrained elastic modulus in good agreement with experimental data. The development of a stochastic metamodel using polynomial chaos expansions allows to propagate the uncertainties of kinetic parameters of hydration, cement phase composition, elastic moduli and morphological parameters of the microstructure. The presented results show that the propagation does not magnify the uncertainty of the single poroelastic properties although, their correlation may amplify the variability of the estimates obtained from poroelastic state equations. In order to reduce the uncertainty of the percolation threshold and that of the poroelastic properties at early-age, engineers need to assess more accurately the apparent activation energy of calcium aluminate and, later on, of the elastic modulus of low density calcium-silicate-hydrate.

Influence of polypropylene fibre on the mechanical performance and durability of concrete materials

Concrete is the most commonly used structural material in the world. This paper evaluated the influence of polypropylene fibre on the performance of concrete materials. The performance of concrete materials was determined by testing the compressive, flexural, and splitting tensile strengths, as well as the freeze-thaw resistance, impermeability, and restrained shrinkage cracking. These results indicate that the use of polypropylene fibres can significantly improve the flexural and splitting tensile strengths of concrete materials. The freeze-thaw resistance and impermeability were improved due to the addition of polypropylene fibre. When the volume of the added polypropylene fibres was increased, the concrete was able to resist more freeze-thaw cycles. Polypropylene fibres can also reduce cracking, and improve the cracking resistance of concrete materials.

The Pore Fractal Characteristics of Concrete Materials under Salt Freezing Conditions in Cold Area

For further research on durability of concrete material under salt frozen conditions in cold area, the non air-entraining concrete with water-binder ratio of 0.4 and 0.28, air-entraining concrete with water-binder ratio 0.28 and the air content 7.0% are studied respectively. The fractal dimension of three kinds of concrete pore at different pore diameter range were determined by MIP(mereury intrusion porosimetry) before and after salt freezing and were studied in a comparative way. The research shows that the fractal dimension of pore diameter at range of 50nm ~ 550nm after salt freezing changed remarkably, namely salt frozen process has greater influence on pore within this range. Objectively the pore within this range in concrete suffered supercooled water osmotic pressure is the greatest. In addition, the total porosity reduced after salt freezing injury while fractal dimension changed more obviously. The fractal dimension of concrete pore could be a good reflection of concrete structure after salt freezing injury, showing that the diameter at 50nm ~ 550nm after salt frozen injury coarsening is obvious. Thus the fractal dimension of diameter within this range can be used as a key parameters after salt freezing injury.

Degradation of permeability resistance of high strength concrete after combustion

To evaluate the remaining durability of concrete materials after combustion, the permeability of high strength concrete (HSC) after combustion was studied. The transport behavior of chloride ion, water and air in concrete after combustion and the effect of temperature, strength grade, and aggregation on the permeability of HSC after combustion are investigated by chloride ion permeability coefficient (Dc), water permeability coefficient (Dw) and air permeability coefficient (Da). The experiment results show that all three permeability coefficients commendably reflect changes of permeability. The permeability coefficient increases with the evaluation temperature. After the same temperature, the permeability coefficient of HSC is lower than that of normal strength concrete (NSC). However, the degree of degradation of permeability coefficient of HSC is greater than that of NSC. The permeability resistance of HSC containing limestone is better than that of HSC containing basalt. Combining changes of compressive strength and permeability, the remaining durability of concrete materials after combustion is appropriately evaluated.

Variation of flexural strength of cement mortar attacked by sulfate ions

Under the environment of seawater, durability of concrete materials is one of the chief factors considered in the design of structures. The decrease of durability of structures is induced by the evolution of micro-damage due to the erosion of chlorine and sulfate ions, which is characterized by the reduction of modulus, strength, and toughness of the material. In this paper, the variation of the flexural strength of cement mortar under sulfate erosion is investigated. The results obtained in present work indicate that the erosion time, concentration of sulfate solution, and water-to-cement ratio will significantly affect the flexural strength.