Study on Autogenous Deformation of Concrete Incorporating MgO as Expansive Agent

Liu, Shu Hua; Fang, Kun

doi:10.4028/0-87849-983-0.155

Cited by 3 publications

(4 citation statements)

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“…To validate the model, the strain calculated by using the hyperbolic model with temperature history input from the site was compared with the strain directly obtained from the same test points, and the deviation varied from 14% to 33% [ 75 ]. In Equation (2), the effects of MgO and fly ash contents on deformation are both considered; the coefficient k 1 relates to the MgO content, and the coefficient k 2 relates to the fly ash content [ 76 ]. Both k 1 and k 2 are determined through regression analysis of the experimental results.…”

Section: Estimation Of Deformationmentioning

confidence: 99%

Deformation and Cracking Resistance of MgO-Incorporated Cementitious Material: A Review

Pan

Li³

et al. 2023

Materials

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In China, MgO-based expansive agent (MEA) has been used for concrete shrinkage compensation and cracking control for over 40 years. The expansive behavior of MEA in cementitious materials could be manipulated to some extent by adjusting the calcination process of MEA and influenced by the restraint condition of the matrix. It is key to investigate the factors related to deformation and cracking resistance so that the desired performance of MEA in certain concrete structures could be achieved. This paper reviews the influence of key parameters such as hydration reactivity, dosage, and calcination conditions of MEA, the water-to-binder ratio, supplementary cementitious material, aggregates, and curing conditions on the deformation and cracking resistivity of cement paste, mortar, and concrete with an MEA addition. The numerical simulation methods and deformation prediction models are then summarized and analyzed for more reasonable estimations.

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Section: Estimation Of Deformationmentioning

confidence: 99%

Deformation and Cracking Resistance of MgO-Incorporated Cementitious Material: A Review

Pan

Li³

et al. 2023

Materials

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“…Using simulation techniques, G. Zhang et al (2002Zhang et al ( , 2005 [12][13][14] comprehensively analysed the influences of concrete elastic modulus growth, creep degree with age and temperature on the amount of magnesium oxide expansion and studied the influences of curing temperature and dam concrete temperature on the effective compensation. S. Liu et al (2006) [15] established a mathematical model of the relationships between MgO concrete autogenous volume deformation and MgO content, fly ash content and temperature. P. Xu et al proposed the equivalent age method for calculating the spontaneous volume deformation of MgO concrete.…”

Section: Introductionmentioning

confidence: 99%

“…P. Xu et al proposed the equivalent age method for calculating the spontaneous volume deformation of MgO concrete. (2008) [16]. Other models, such as the arctangent curve model of C Chen et al (2008) [17], have also been proposed.…”

Section: Introductionmentioning

confidence: 99%

A Mathematical Model of the Expansion Evolution of Magnesium Oxide in Mass Concrete Based on Hydration Characteristics

Feng¹,

Zhao

Yu³

et al. 2021

Materials

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The low swelling property of magnesium oxide concrete is a significant feature that can be used to control the cracking of mass concrete. Based on the characteristics of the chemical reaction, this work proposes a coupled hydro-thermo-mechanical model that can be implemented with the finite element method for predicting the autogenous volumetric deformation of magnesium concrete. By introducing the degree of the hydration reaction of magnesia and the degree of the hydration reaction of cementitious materials as intermediate variables of the chemical reaction system, a prediction model of the concrete temperature and chemical fields is established, and using this model, the effect of the temperature on the reaction rate can be considered in real time. In addition, by combining the relationship between the degree of the hydration reaction of magnesium oxide and the comprehensive expansion of concrete, a mathematical model for calculating the expansion stress of magnesia concrete was established. The algorithms were derived by mathematical equations, and the simulation results were compared to the experimental temperature and autogenous volumetric strain curves, which showed that the hydration model provides a relatively high accuracy. The model was also applied to an arch dam, and the coupled thermo-chemical-mechanical responses of mass concrete during construction were investigated. Simulation results show that the increase in temperature (hydration of cementitious material) and expansion volumetric deformation (hydration of MgO) of the concrete on the upstream and downstream surfaces lags obviously behind that of the inner regions. Quantitative analysis for differences of internal and external expansion is worthy of further attention and study on a basis of further experimental data as well as monitored data.

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“…A mathematical model of spontaneous deformation of concrete with MgO as an expansion agent is established, which clearly reveals the characteristics of spontaneous deformation of concrete with MgO as an expansion agent [20]. e effects of calcination conditions on the microstructure, hydration activity, and expansion performance of MgO-type expansion agent MEA were studied, and a new MEA expansion model was proposed [21]. Based on isothermal calorimetry and thermo gravity analysis, the hydration behavior of CEA in cement slurry was studied, the hydration kinetics was analyzed, the apparent hydration activation energy of CEA was calculated, and a chemical-mechanical model was established to predict the expansion performance and crack resistance of concrete containing the CEA agent [22].…”

Section: Introductionmentioning

confidence: 99%

Study on the Effect of Isotropic Initial Stress on the Anchoring Performance of Self‐Expanding Bolts

Liu

Hong-ya

et al. 2021

Advances in Civil Engineering

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In order to study the anchoring performance of a new type of self-expanding, high-strength, precompression anchoring technology with a large amount of expansion agent (ω ≥ 5) cement slurry as anchoring solids under confined surrounding rock conditions, a rock mass anchoring device and methods that simulate in situ stress are developed, and real-time monitoring of expansion stress and anchor pull-out tests are carried out. The results show that the internal interface stress has a loss effect over time, and the stress loss value shows a linear increase trend with the dosage, but the loss rate shows a linear decreasing relationship with the dosage. This paper defines the coordinated additional stress and obtains its temporal and spatial evolution law in the rock mass. It is pointed out that there is a lag time difference between the peak of internal interface stress and the peak of coordinated additional stress, explaining its mechanical mechanism from the perspective of stress transfer. The strong restraint of the sealing section of the anchor hole causes the anchor solid to form a “shuttle-shaped” microexpanded head with thin ends and a middle drum under the expansion stress. During the drawing process, the microexpanded head is “stuck” in the anchor hole and moves upward to form the unique “load platform effect” of the anchoring system. And the mechanical mechanism diagram of this effect is obtained. It is pointed out that this effect can greatly improve the ductility of the anchoring system and the ultimate energy consumption value of damage. A prediction model for the ultimate pull-out force of self-expanding bolts is established. It is pointed out that the initial confining stress value has an exponential effect on the ultimate pull-out force. It shows that the surrounding rock with strong confinement constraints can greatly increase the ultimate pull-out resistance of the bolt. The self-expanding strengthening coefficient λ and the surrounding rock stress influence coefficient k are introduced, the bolt interface mechanics formula and energy equation of the self-expanding anchor system are established, and the feasibility of the formula is verified by the calculation example. It is concluded that the ultimate pull-out resistance of the anchorage with ω = 30 is increased by 3.38 times compared with the ordinary anchorage under the initial confining stress condition of 0.7 MPa, the prepeak displacement of the bolt is increased by 2.08 times, and the prepeak energy consumption of the anchoring system is increased by 7.34 times. The cost only increased by 0.023% based on the literature example.

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Study on Autogenous Deformation of Concrete Incorporating MgO as Expansive Agent

Cited by 3 publications

References 0 publications

Deformation and Cracking Resistance of MgO-Incorporated Cementitious Material: A Review

Deformation and Cracking Resistance of MgO-Incorporated Cementitious Material: A Review

A Mathematical Model of the Expansion Evolution of Magnesium Oxide in Mass Concrete Based on Hydration Characteristics

Study on the Effect of Isotropic Initial Stress on the Anchoring Performance of Self‐Expanding Bolts

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