The construction sector is responsible for around 37% of global emissions of the carbon dioxide to the atmosphere. Therefore, reducing gas emissions, in this construction sector, is particularly important ,given the progressing climate change. For this reason, limiting its emissions and limiting the emission of other greenhouse gases in this sector, is of particular importance in view of the progress of climate change. It is important that new construction products have less impact on the environment during their entire life cycle, and their production has been decoupled from the use of primary energy. In this work, selected properties of geopolymeric materials were examined. Geopolymers are inorganic aluminosilicate polymers with an amorphous microstructure, which may be an alternative in certain applications, for products based on Portland cement. Here, the properties of geopolymer mortars, i.e. porosity, microstructure and mechanical strength, were compared. The influence of the composition of reaction mixture on these properties, defined by the appropriate SiO2/Al2O3 and SiO2/Na2O molar ratios, was also defined. The results show that increasing the content of SiO2 in relation to Al2O3 in the composition of the reaction mixture, reduces porosity. Thus, leading to a more compact microstructure and higher mechanical strength. A similar effect occurs when a higher NaOH solution concentration is used, in comparison to the sodium silicate [Na2SiO3] solution.

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Abstract. The paper presents the volumetric strain test results of differently composed cement mortar samples during the phase transformation of water into ice, and juxtaposes the results with other relevant indicators, such as the water absorption and the degree of filling pores with water. It also presents the possibility of using these observations in terms of frost resistance diagnostics. The investigation covered non-airentrained mortars, which were also subjected to the vacuum treatment and vibration to reduce the air content. It was found experimentally that the volumetric strain of mortar samples soaked in water under vacuum at ∆V/V < 2‰ means the mortar of high frost resistance. ∆V/V > 4‰ indicates that the mortar requires air-entraining regardless of the microstructure and kind of cement.

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%.

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