Determination of apparent activation energy of concrete by isothermal calorimetry

Alkali activated materials (AAM) are generally cured at high temperatures to compensate for the low reaction rate. Higher temperature accelerates the reaction of AAM as in cement-based materials and this effect is generally predicted using Arrhenius equation based on the activation energy. While apparent activation energy is calculated from parallel isothermal calorimetry measurements at different temperatures, instantaneous activation energy is typically measured using a differential scanning calorimeter. Compared to the apparent activation energy, instantaneous activation energy has minimal effects on the microstructural changes due to the variation in temperature. In this work, the evolution of activation energy was determined by traditional methods and was compared with the instantaneous activation energy. It was found that while the activation energy changed with the progress of reaction over traditional methods, the instantaneous activation energy did not show any changes / or remained the same. The instantaneous activation energy was also found to be higher compared to the apparent activation energy determined with traditional methods.

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Thermal Properties of Calcium Sulphoaluminate Cement as an Alternative to Ordinary Portland Cement

Materials ◽

10.3390/ma14227011 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7011

Author(s):

Małgorzata Gołaszewska ◽

Barbara Klemczak ◽

Jacek Gołaszewski

Keyword(s):

Activation Energy ◽

Portland Cement ◽

Apparent Activation Energy ◽

Thermal Behaviour ◽

Ordinary Portland Cement ◽

Isothermal Calorimetry ◽

Heat Of Hydration ◽

Curing Temperature ◽

Cement Pastes ◽

Calcium Sulphoaluminate

This paper presents the results of research into the heat of hydration and activation energy of calcium sulphoaluminate (CSA) cement in terms of the dependence on curing temperature and water/cement ratio. Cement pastes with water/cement ratios in the range of 0.3–0.6 were tested by isothermal calorimetry at 20 °C, 35 °C and 50 °C, with the evolved hydration heat and its rate monitored for 168 h from mixing water with cement. Reference pastes with ordinary Portland cement (OPC) were also tested in the same range. The apparent activation energy of CSA and OPC was determined based on the results of the measurements. CSA pastes exhibited complex thermal behaviour that differed significantly from the thermal behaviour of ordinary Portland cement. The results show that both the w/c ratio and elevated temperature have a meaningful effect on the heat emission and the hydration process of CSA cement pastes. The determined apparent activation energy of CSA revealed its substantial variability and dependence, both on the w/c ratio and the curing temperature.

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Determination of the Apparent Activation Energy of Concrete by Adiabatic Test

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.477.411 ◽

2011 ◽

Vol 477 ◽

pp. 411-417

Author(s):

Jia Chun Wang

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Temperature Rise ◽

Adiabatic Temperature Rise ◽

Study Results ◽

Stage Development ◽

Concrete Hydration ◽

Apparent Activation Energies ◽

Influence Of Hydration

It is known that apparent activation energy of the binders in concrete characterizes the sensitivity of concrete hydration processes to temperature. In this paper the apparent activation energies of concretes containing different complex binders have been determined through adiabatic temperature rise test. The influence of hydration emission heat on the apparent activation energy of concrete is studied. The study results show that the apparent activation energy is decreasing with the hydration of binder stage development.

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