Mechanical and durability properties of concrete subjected to early-age freeze–thaw cycles

This article considers energy-saving technologies for winter concreting of building structures and constructions. Various authors have studied mathematical models of the thermal regime of a three-dimensional building structure. The mathematical model of the heat balance equations in the concrete structure, the thermal conductivity coefficient, the dependences of the heat balance equations in the concrete structure and the junction, the thermal conductivity coefficient, the volumetric thermal conductivity, respectively, in the erected fragment and the previously erected part of the wall was implemented on a computer. The article considers the processes of cement and concrete strength gain during early freezing of concrete. In previous studies by various authors, it was found that with an increase in the time for gaining critical strength, the cost of electricity is reduced by 25-50%, due to the use of thermal inertia of the structure. The rate of cooling of monolithic structures at negative temperatures is revealed. The chemistry of cement hardening processes during early freezing is shown. Thermodynamic calculations set the limits of negative temperatures at which concrete strength curing stops, but under the action of repeated positive temperatures, the cement hydration process resumes and concrete continues to harden. The aluminum minerals of Portland cement clinker are usually the first to hydrate when the cement hardens with water, and in the presence of gypsum they form calcium hydrosulfoaluminate. This connection is very fragile and is destroyed by mechanical stress (repeated vibration) and over time even at normal temperatures. The article reviews the foreign experience of winter concreting and the preferred methods of work in this case.

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“…Studies by Berkovich G.M., and Heyker D.M. and others have shown the applicability of this dependence to diffusion processes as well [5].…”

Section: Research Resultsmentioning

confidence: 74%

Energy Saving Factors in Winter Concreting

Brzhanov

SADUEVA

Курбанмагомедов

et al. 2022

jour

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“…The dynamic elastic modulus describes the defects, pore characteristics, and properties of concrete with ultrasonic velocity [25,26]. The relative dynamic elastic modulus was used to characterize the effect of freeze-thaw cycles on the mechanical properties of concrete [27].…”

Section: Relative Dynamic Elastic Modulusmentioning

confidence: 99%

Dry–Wet Cyclic Sulfate Attack Mechanism of High-Volume Fly Ash Self-Compacting Concrete

Liu

Yang

et al. 2022

Sustainability

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High-volume fly ash replacing cement helps to improve the fluidity, volume stability, durability, and economy of self-compacting concrete (SCC). Sulfate attack is the most common form of the durability damage of hydraulic concrete; in particular, the performance degradation at the water level change position is more significant. Therefore, research on the influence effect and mechanism of fly ash on the durability is of great significance. In this paper, the change regularity of the SCC physical and mechanical properties with the fly ash replacement percentage and dry–wet cycles were studied by 60 dry–wet cycles of sulfate attack test. The 6 h electric flux, MIP, and SEM were used to study the performance degradation mechanism of SCC cured for 56 days, which had also been attacked by sulfate. The results show that the physical and mechanical properties of SCC increased first and then decreased with the dry–wet cycles of sulfate attack. After 10–15 cycles, the corresponding properties increased slightly, and then decreased gradually. When the fly ash content was 40%, the corrosion resistance coefficient, relative dynamic elastic modulus, and flexural strength retention were higher than those of the control specimen. However, when the fly ash content was 50%, they were close to the control and deteriorated obviously with the further addition of fly ash. For pore sizes in the range of 120–1000 nm, the porosity of SCC cured for 56 days was inversely proportional to the 6 h electric flux and the retention of mechanical properties, indicating that the porosity of the large pores is the decisive factor affecting the chloride ion permeability and corrosion resistance. The incorporation of fly ash in SCC can change the sulfate attack products and destruction mechanism. The sulfate attack damage of SCC with 40% of fly ash and the control specimen was dominated by ettringite crystallization and expansion, while those with a fly ash content of 50% and 60% had no obvious corrosion products, and the microstructures became looser. The appropriate fly ash replacement percentage could significantly improve the corrosion resistance of SCC.

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“…Therefore, improving the impermeability of concrete to chloride ions can effectively prevent steel corrosion and prolong the service life of concrete structures. By improving these two properties, the durability and service life of concrete structures can be significantly improved [12][13][14][15][16]. Numerous scholars have studied the parameters that affect the durability of concrete, and the research results indicate that the frost resistance and chloride ion permeability of concrete are mainly influenced by the mix ratio of raw materials such as cement, water, aggregates, and additives [17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Research on a Multi-Objective Optimization Design for the Durability of High-Performance Fiber-Reinforced Concrete Based on a Hybrid Algorithm

Wang,

Cui,

Cui

et al. 2023

Coatings

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To achieve durable high-performance fiber-reinforced concrete that meets economic requirements, this paper introduces a hybrid intelligent framework based on the Latin hypercube experimental design, response surface methodology (RSM), and the NSGA-III algorithm for optimizing the mix design of high-performance fiber-reinforced concrete. The developed framework allows for the prediction of concrete performance and obtains a series of Pareto optimal solutions through multi-objective optimization, ultimately identifying the best mix proportion. The decision variables in this optimization are the proportions of various materials in the concrete mix, with concrete’s frost resistance, chloride ion permeability resistance, and cost as the objectives. The feasibility of this framework was subsequently validated. The results indicate the following: (1) The RSM model exhibits a high level of predictive accuracy, with coefficient of determination (R-squared) values of 0.9657 for concrete frost resistance and 0.9803 for chloride ion permeability resistance. The RSM model can be employed to construct the fitness function for the optimization algorithm, enhancing the efficiency of multi-objective optimization. (2) The NSGA-III algorithm effectively balances durability and cost considerations to determine the optimal mix proportion for the concrete. After multi-objective optimization, the chloride ion permeability resistance and frost resistance of the high-performance fiber-reinforced concrete improved by 38.1% and 6.45%, respectively, compared to the experimental averages, while the cost decreased by 2.53%. The multi-objective optimization method proposed in this paper can be applied to mix design for practical engineering projects, improving the efficiency of concrete mix design.

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Mechanical and durability properties of concrete subjected to early-age freeze–thaw cycles

Cited by 11 publications

References 46 publications

Energy Saving Factors in Winter Concreting

Energy Saving Factors in Winter Concreting

Dry–Wet Cyclic Sulfate Attack Mechanism of High-Volume Fly Ash Self-Compacting Concrete

Research on a Multi-Objective Optimization Design for the Durability of High-Performance Fiber-Reinforced Concrete Based on a Hybrid Algorithm

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