Impact of sample crushing on porosity characterization of hardened cement pastes by low temperature calorimetry: Comparison of powder and cylinder samples

Abstract

The impact of sample crushing on the detected porosity of hardened cement pastes by low temperature calorimetry (LTC) was studied using powder and cylinder samples. Two types of cements, CEM I and CEM III, were used to prepare the pastes. A model porous material, MCM-41, was also used in order to investigate some aspects of the measurement and the evaluation approach. The powder and cylinder samples of the cement pastes were compared in terms of the calculated ice content curves, total pore volumes and pore size distribution curves. For the two studied cement pastes, the calculated ice content curves of freezing of the powder sample differed from that of the cylinder samples, especially for the paste CEM III. The results indicate that sample crushing changed the pore connectivity as compared to non-crushed samples. One important difference between the powder sample and the cylinder samples of the paste CEM III was that the determined maximum ice content in the powder sample was much higher than that in the cylinder samples, the relatively difference being about 40-50%. However, this kind of marked difference was not found in the paste CEM I. The observed difference between the calculated pore volume of the powder and the cylinder samples of the paste CEM III is possibly due to some of the "isolated" pores which, presumably, cannot be fully filled with water in the preparation of the cylinder samples. However, sample crushing makes it possible to saturate the pores to a greater

Clays as SCM – Reactivity of Uncalcined Kaolinite and Bentonite, and Impact on Phase Assemblage and Strength Development of PC Mortars

“…Also, the substitution of cement paste by bentonite and kaolinite clays had limited impact on ice formation (threshold pores and percolated pore volume) in well hydrated systems, see Figure 8. The measured differences in total freezable water are within observed variations between similar samples [17]. Freezing in the clay samples started at relatively higher temperature, indicating less super-cooling (facilitated ice nucleation).…”

Influence of fly ash on the pore structure of mortar using a differential scanning calorimetry analysis

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Advanced NMR Cryoporometry

“…Hence, in these materials finite size effects may affect the transition behavior and their analysis without appreciating the finite-size effects may lead to structure misinterpretations. Indeed, the effect of grain sizes has experimentally been proven in experiment [116,167,168]. Whether or not are the finite-size effects important, is difficult to predict in advance.…”