Degree of hydration-based description of mechanical properties of early age concrete

Schutter, Geert De; Taerwe, Luc

doi:10.1007/bf02486341

Cited by 288 publications

(169 citation statements)

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“…6,9,15,16,[19][20][21][22] The coeffi cient used for slag cement of 461 was selected from literature values ranging from 355 to 461. 9,23,24 A three-parameter exponential degree of hydration was used to model the hydration development, as shown in Eq.…”

Section: Background: Existing Methods For Heatmentioning

confidence: 99%

Modeling Hydration of Cementitious Systems

Riding

Poole²,

Folliard³

et al. 2012

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heat loss is measured and minimized by the use of insulation. The concrete adiabatic temperature rise is then back-calculated with the increased heat of hydration rate from the higher temperatures in adiabatic conditions taken into account. Semiadiabatic calorimetry is much easier to perform than adiabatic calorimetry, and it can even be performed in the fi eld. Higher temperature speeds the rate of the cementitious material hydration reactions. The infl uence of temperature on the hydration rate can be accounted for by the use of a maturity function. The equivalent age maturity function is commonly used with strength or degree of hydration calculations, as shown in Eq. (1 where t e (hours) is the equivalent age or time that the concrete would take to achieve the same property while being cured at an isothermal temperature at the reference temperature T r (K); E a is the apparent activation energy (J/mol); R is the universal gas constant (8.314 J/mol/K [10.732 ft 3 psia/°R/ lb-mol]); T C is the temperature of the concrete (K); and ∆t is the time step used. In practical terms, the equivalent age of a concrete mixture is the amount of time that the concrete mixture would need to be cured at an isothermal reference temperature to reach the same property as the concrete under the different time-temperature history. The equivalent age maturity method has been shown to well account for the effects of different placement temperature 3 and curing conditions 1 on the concrete heat of hydration development. The apparent activation energy term is a measure of the temperature sensitivity of the hydration reaction.2,4,5 A mechanistic-empirical model was developed for predicting E a by Poole 6 from isothermal calorimetry experiments, as shown in Eq. (2) INTRODUCTION Concrete temperature development during hydration is a major factor in determining the long-term strength, permeability, durability, and cracking probability. The mixture proportions, curing, and construction schedule can be optimized to control concrete temperature and improve concrete performance. To determine optimum mixture proportions and placement conditions, heat transfer software can be used to model the combined effects of the weather, member geometry, insulation, boundary conditions, and concrete heat of hydration to predict internal concrete temperatures. Such software requires the rate and amount of concrete heat generation as input parameters. Measuring the rate and amount of heat released during hydration to provide input for a model can take a week or longer per mixture in a specialized calorimeter and can be costly. Therefore, a comparison of several candidate mixtures using laboratory test results could require several weeks. A predictive model for the concrete heat released during hydration, based on the constituent materials and mixture proportions, would reduce the need for this costly testing. This study documents the test methods, materials, and statistical methods used to develop and validate a model for predicting the concrete heat release...

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Section: Background: Existing Methods For Heatmentioning

confidence: 99%

Modeling Hydration of Cementitious Systems

Riding

Poole²,

Folliard³

et al. 2012

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show abstract

“…(3). 4,[8][9][10][11] (3) where α equals the degree of hydration at time t, H(t) equals the heat evolved from time 0 to time t (J/gram), and H u equals total heat available for reaction (J/gram).…”

Section: Mechanistic Model To Quantify Heat Of Hydrationmentioning

confidence: 99%

“…4,[8][9][10][11] Because heat evolution is measured directly with isothermal calorimetry, this test method would seem to be a better indication of the extent of hydration than compressive strength. There are, however, discrepancies in the literature on exactly how to calculate E a from isothermal calorimetry data.…”

Section: Introductionmentioning

confidence: 99%

Methods for Calculating Activation Energy for Portland Cement

2007

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INTRODUCTIONThe chemical reactions between cement and water during setting and hardening are exothermic, which results in a rise in the temperature of the hardening concrete. Characterization of temperature rise is useful for a variety of reasons. The curing temperature of concrete is arguably the one variable that has the most significant effect on the rate of hydration. 1 Early research by Saul 2 on the effects of temperature on concrete was driven by the desire to predict strength of steam-cured concrete, which led to the development of the "maturity" concept. ASTM C 1074 3 defines maturity as "the extent of the development of a property of a cementitious material." For mass concrete elements, accurate characterization of the progress of hydration is necessary to predict temperature gradients, maximum concrete temperature, thermal stresses, and relevant mechanical properties.Accurate prediction of temperature development in mass concrete requires knowledge of the adiabatic temperature rise of a particular concrete mixture. Adiabatic calorimetry is the best test to obtain this information. Unfortunately, adiabatic calorimeters are not common. Semi-adiabatic calorimeters are much more common, because the test setup is much simpler. Therefore, semi-adiabatic calorimeters are more commonly used to characterize the heat evolution of a concrete mixture. Corrections must be made to semi-adiabatic temperature measurements to approximate the results obtained from an adiabatic system. 4 The Arrhenius theory is used to capture the temperature sensitivity of a particular mixture so that its behavior may be modeled under different temperature conditions. In this manner, semi-adiabatic calorimetry data may be used to model what would be experienced under adiabatic conditions. The Arrhenius equation uses the concept of activation energy E a to define the sensitivity of a particular reaction to temperature. The Arrhenius theory for rate processes is the equation of choice for the study of chemical kinetics, 5 and is the most commonly used relationship to characterize the temperature sensitivity of portland cement. Portland cement, however, is much more complex than the materials for which the Arrhenius equation was originally developed. Several researchers have discussed determination of the rate constants for use in the Arrhenius equation. 6,7 Currently, ASTM C 1074 3 uses compressive strength of mortar cubes to determine the activation energy for strength estimating purposes.The cumulative heat of hydration at a particular point in time relative to the total potential heat of hydration of the system is often used to quantify the degree of hydration. 4,[8][9][10][11] Because heat evolution is measured directly with isothermal calorimetry, this test method would seem to be a better indication of the extent of hydration than compressive strength. There are, however, discrepancies in the literature on exactly how to calculate E a from isothermal calorimetry data.Arrhenius' theory does not describe the temperature sensitivity o...

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“…[1] In previous research, in case of traditional binder systems consisting of Portland cement or blast furnace slag cement, the degree of hydration is shown to be a fundamental parameter, enabling a detailed study and accurate prediction of the early-age mechanical behavior, including basic creep. [2][3][4][5][6][7][8][9] Nowadays, in view of improved sustainability of cementitious materials, binder systems tend to become more complex, consisting of a blend of different powders. Where initially, waste powders have been incorporated in cementitious materials mainly because of environmental reasons, nowadays the sustainability pressure on concrete technology is more and more leading to a complete rethinking of the concept of cementitious binders.…”

Section: Introductionmentioning

confidence: 99%

Degree of hydration-based creep modeling of concrete with blended binders: from concept to real applications

Schutter

Liu

Yuan

2014

Journal of Sustainable Cement-Based Materials

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The mechanical behavior of hardening concrete is to a large extent determined by the evolving microstructure as a result of the hydration process. For traditional binder systems, consisting of Portland cement or blast furnace slag cement, the degree of hydration is known to be a fundamental parameter in this respect, enabling a detailed study and accurate prediction of the early-age mechanical behavior, including basic creep. Nowadays, in view of improved sustainability of cementitious materials, binder systems tend to become more complex, consisting of a blend of different powders. As the hydration process and microstructure development are influenced by the inclusion of powders into the binder, the question is raised whether the degree of hydration concept is still applicable to concrete based on complex blended binder systems. In this paper, some experimental results are summarized and the application to real structures is illustrated. Basic creep of hardening concrete with complex blended binders can still be modeled following the degree of hydration concept.

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Degree of hydration-based description of mechanical properties of early age concrete

Cited by 288 publications

References 5 publications

Modeling Hydration of Cementitious Systems

Modeling Hydration of Cementitious Systems

Methods for Calculating Activation Energy for Portland Cement

Degree of hydration-based creep modeling of concrete with blended binders: from concept to real applications

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