Early-age Thermal Characteristics of Clinker Cements in Relation to Microstructure and Composition: Implications for Temperature Development in Large Concrete Elements

Ballim, Y.
Graham, P.C.
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This paper presents an assessment of the heat response of nominally similar cement clinkers from a range of cement production facilities in South Africa. Clinker samples were collected at nine cement plants and cements were prepared by grinding each clinker with a uniform quality of gypsum. XRF and optical microscope techniques were then used to characterise each clinker and cement in terms of chemical composition and cement compound morphology.
The thermal response of concrete due to hydration of cement is a predominant factor in the potential for early-age cracking of large concrete elements. An anal¬ysis of this cracking potential requires an ability to quantify both the amount of heat that is evolved by the cement as well as the rate at which this heat is evolved [1]. Both these parameters are strongly influenced by the chemical and mineralogical composition of the cement, insofar as it affects the kinetics of the hydration reac¬tions of cement. Furthermore, clinker morphology has been shown [2] to influence the compressive strength and, by inference, the hydration development of cement. Clearly, an ability to estimate the thermal response of cement in concrete, based on a knowledge of clinker characteristics would be of assistance to mass concrete