Double Feedback Control Method for Determining Early-Age Restrained Creep of Concrete Using a Temperature Stress Testing Machine

He, Zhaoyi; Li, Qingbin; Hu, Yu; Ma, Rui

doi:10.3390/ma11071079

Cited by 23 publications

(5 citation statements)

References 36 publications

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“…As the above described testing system mainly allows for the effects of restrained linear shrinkage to be examined, the traditional TSTM has been recently modified and improved by numerous researchers, in order to enable thermally insulated and regulated concrete specimens to be examined. These improvements include temperature and humidity control, insulation, simultaneous measurements on restrained and unrestrained specimens, as well as the addition of a closed loop computer‐controlled system 70,82,85,88,113–122 …”

Section: State Of the Art Review Of Longitudinal Testing Devicesmentioning

confidence: 99%

Longitudinal restraining devices for the evaluation of structural behaviour of cement‐based materials: The past, present and prospective trends

Kanavaris

Azenha

Schlicke

et al. 2020

Strain

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The problem of thermal and shrinkage cracking in concrete has been long recognised by researchers and engineers as it can jeopardise the intended serviceability of a concrete structure. This has led researchers to develop testing devices which aim to simulate the behaviour of concrete under restrained deformations. Such devices are discerned in passive and active, depending on how concrete's movement is restrained, whilst a new type of devices has been developed to account for the combined effects of intrinsic restrained deformations and externally imposed actions. This paper presents a detailed and critical literature review on the developed restraining devices and an analysis of the capabilities, complexities and peculiarities associated with their use. Further to this, the challenges the developers of testing devices are faced with, the gaps and uncertainties with the methods found in the literature and recommendations for potential improvements in the field are discussed. K E Y W O R D Screep and shrinkage, heat of hydration, restraining devices, restraint, shrinkage cracking, thermal cracking, viscoelasticity

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Section: State Of the Art Review Of Longitudinal Testing Devicesmentioning

confidence: 99%

Longitudinal restraining devices for the evaluation of structural behaviour of cement‐based materials: The past, present and prospective trends

Kanavaris

Azenha

Schlicke

et al. 2020

Strain

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“…The specimen would drive the universal joint to move when the specimen length changed with the temperature history. Then the stepping motor would push or pull the universal joint to its original position when the absolute value of the total strain of the restrained specimen exceeded the threshold value [ 17 , 25 , 36 ], as shown in Figure 5 . A compensation cycle is repeated at increments of threshold value to recover the shrinkage strain [ 18 , 31 , 37 ].…”

Section: The Temperature Stress Testmentioning

confidence: 99%

Research on the Crack Risk of Early-Age Concrete under the Temperature Stress Test Machine

et al. 2018

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A new temperature stress test machine (TSTM) was developed to improve temperature control accuracy and efficiency. As there is no uniform standard for the threshold value of TSTM, quite different threshold values are used in the test, which results in the influences of the threshold value on the evaluation of thermal stresses and crack risk of concrete not being determined. To illustrate the importance of an appropriate threshold value, different threshold values were used to evaluate the influences on the thermal stresses and cracking resistance of concrete specimens under a complete restraint test with semi-adiabatic temperature development. The results show that the maximum compressive stress of a concrete specimen with a threshold value 3 με was slightly larger than that of 1.5 με when the growth rate of tensile stress of the concrete specimen with the threshold value 3 με was slightly greater than that of concrete specimen with the threshold value 1.5 με. Based on the combination of crack risk coefficient and restraint degree, a new system for evaluating the crack resistance of concrete was proposed, in which different threshold values were used to estimate their influences on the crack risk of concrete. Thus, an appropriate range of threshold values could be determined.

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“…Existing studies have shown that the Temperature Stress Testing Machine (TSTM) is a powerful instrument for studying the early-age anti-cracking of concrete under the combined effects of temperature and constraint. TSTMs can accurately control the constraint conditions of the cast-in-place concrete specimens and simulate the tensile damage and cracking process of concrete [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. Riding et al [ 31 ] used a rigid cracking frame to measure the uniaxial stress of concrete containing different fly ashes under restrained conditions, and the results showed that fly ashes reduced the cracking risk because of the decrease in the heat of hydration of the cementitious materials.…”

Section: Introductionmentioning

confidence: 99%

Development and Preliminary Application of Temperature Stress Test Machine for Cast-in-Place Inner Shaft Lining

et al. 2023

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Over the past 20 years, as the depth and diameter of shaft lines increased in China, the cracking and water leakage of the inner walls of frozen shafts have become increasingly severe, resulting in significant safety threats and economic losses. Understanding the stress variation patterns of cast-in-place inner walls under the combined effects of temperature and constraint during construction is a prerequisite for evaluating the crack resistance performance of inner walls and preventing water leakage in frozen shafts. The temperature stress testing machine is an important instrument for studying the early-age crack resistance performance of concrete materials under the combined effects of temperature and constraint. However, existing testing machines have shortcomings in terms of applicable specimen cross-sectional shapes, temperature control methods for concrete structures, and axial loading capacity. In this paper, a novel temperature stress testing machine suitable for the inner wall structure shape, capable of simulating the hydration heat of the inner walls, was developed. Then, a reduced-scale model of the inner wall according to similarity criteria was manufactured indoors. Finally, preliminary investigations of the temperature, strain, and stress variations of the inner wall under 100% end constraint conditions were conducted by simulating the actual hydration heating and cooling process of the inner walls. Results show that the hydration heating and cooling process of the inner wall can be accurately simulated. After approximately 69 h of concrete casting, the accumulated relative displacement and strain of the end-constrained inner wall model were −244.2 mm and 187.8 με, respectively. The end constraint force of the model increased to a maximum value of 1.7 MPa and then rapidly unloaded, causing the model concrete to crack in tension. The temperature stress testing method presented in this paper provides a reference for scientifically formulating technical approaches to prevent cracking in cast-in-place concrete inner walls.

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Double Feedback Control Method for Determining Early-Age Restrained Creep of Concrete Using a Temperature Stress Testing Machine

Cited by 23 publications

References 36 publications

Longitudinal restraining devices for the evaluation of structural behaviour of cement‐based materials: The past, present and prospective trends

Longitudinal restraining devices for the evaluation of structural behaviour of cement‐based materials: The past, present and prospective trends

Research on the Crack Risk of Early-Age Concrete under the Temperature Stress Test Machine

Development and Preliminary Application of Temperature Stress Test Machine for Cast-in-Place Inner Shaft Lining

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