Cement Mortar Porosity by Modified Analysis of Differential Scanning Calorimetry Records

Abstract

A modified method of interpreting a heat flux differential scanning calorimetry records in pore structure determination is presented. The method consists of determining the true phase transition energy distribution due to the melting of water during a differential scanning calorimetry (DSC) heating run. A set of original apparatus functions was developed to approximate the recorded calorimetric signals to the actual processes of the water phase transition at a given temperature. The validity of the proposed calorimetric curves-based algorithm was demonstrated through tests on a cement mortar sample. The correct analysis required taking into account both the thermal inertia of the calorimeter and the thermal effects that are associated with water transitions over the fairly narrow temperature ranges close to 0 °C. When evaluating energy distribution without taking the shifts of the proposed modified algorithm into account, the volume of the pores with radii bigger than 20 nm was greatly overestimated, while that of the smaller pores (rp < 20 nm) was underestimated, in some cases by approximately 70%.

The Use of Thermoporometry in the Study of Frost Resistance of Rocks

“…The recorded exothermic (during water freezing) and endothermic (related to ice melting) thermal effects were shifted due to the calorimetric measurement system's inertia. For the endothermic part of the phase change energy distribution (related to the ice melting for the heating stage), the thermal inertia of the apparatus was taken into account using the algorithm described in the paper [41]. The exothermic part of the heat flows was left unchanged due to the initial stage of freezing.…”

“…Importantly, the calculations additionally took into account the inertia of the system. The algorithm described in the paper [41] was used to analyze the thermograms. This algorithm makes it possible to take into account the influence of the thermal inertia of the differential scanning calorimetry measurement system (DSC) on the recorded signals, for the part related to the melting of ice.…”

Differential Analysis of Volumetric Strain Method Characterization in the Context of Phase Change of Water in Carbonate Rocks

“…There are known methods to limit the impact of this phenomenon on the precision of calculations used in calorimetric tests. In the case of the DAVS method, the method of elimination or partial elimination of this unfavorable phenomenon is different [ 23 , 24 ]. One method to reduce the effect of system inertia is to reduce the rate of cooling and heating of the material.…”

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

“…In order to partially eliminate this phenomenon, a proprietary analytical procedure was used that allows more precise adjustment of specific amounts of energy to the actual temperatures in which the phase transition occured. The algorithm was described thoroughly in [19]. Figure 2 shows original and corrected plots of water phase transition energy during the endothermic stage (heating).…”