Finite-Size Effects for Classical Lattice Models

Institute of Theoretical PhysicsÚstav teoretické fyzikyFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Thermal Properties of High-Performance Concrete Containing Fine-Ground Ceramics as a Partial Cement Replacement

Some types of industrial waste can be used in concrete as a partial replacement of a cement binder. One such material is fine-ground ceramics, which is a waste produced during brick cutting. The ground ceramic can be used as a pozzolana active material which can improve final properties of concrete. This fine powder was used in this study as a partial replacement of the cement binder up to 60 mass% and its thermal and mechanical properties were studied using the differential scanning calorimetry, thermogravimetry, and thermodilatometry. It was shown that the differential scanning calorimetry is a suitable method for observing thermal changes in concrete samples containing such additives at the microstructural level. In particular, it allows one to investigate the hydration and pozzolanic reaction in the studied concrete. The investigation was performed in the temperature range from 25 °C to 1000 °C.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7160</p

Influence of fly ash added to a ceramic body on its thermophysical properties

We study thermal expansion, mass changes, heat capacity, and thermal diffusivity and conductivity for a ceramic body with 20 mass% and without fly ash content, using the TDA, TG, DTA, DSC, and flash method. The measurements were performed (a) for green samples either isothermally or by a linear heating up to a temperature 600°C, 1050°C, or 1100°C, depending on the measurement method; (b) at the room temperature for samples preheated at 100°C, 200°C, ..., 1100°C. In case (a) addition of fly ash changes the final contraction only above ~900°C, while the thermal properties remain almost unchanged. In case (b) the final contraction of samples at 1100°C is the same. The thermal diffusivity is nearly identical up to 700°C, and fly ash causes the diffusivity to stay almost constant up to 1000°C

Effects of Secondary Porosity on Microstructure and Mechanical Properties of SAP-Containing Lime-Based Plasters

Despite the many benefits associated with the utilization of superabsorbent polymers (SAPs), several drawbacks have been reported. In particular, the effect of SAPs on microstructure, together with its consequences for mechanical properties, is not fully understood yet for some composite materials. This study analyzes the role of SAPs in the formation of the microstructure of lime composites, taking into account their chemical composition. The obtained experimental results show that the particle size and cross-linking density of used SAPs are crucial parameters affecting both the microstructure and mechanical performance of the analyzed composites. Coarser SAPs with low cross-linking density in the dosage of 0.5 and 1 wt.% are found as the most suitable solution, leading even to a slight improvement of mechanical parameters. The secondary porosity formed by swelled hydrogels is identified as a very significant factor since hydrogel-filled voids do not contribute to the strength parameters. The formation of the affected zone around SAP cores depends on the chemical composition of SAPs considerably as the higher cross-linking density influences the desorption rate. Based on achieved results, utilization of SAPs in building materials should be studied at a more detailed level with particular importance on the definition of SAP-related voids and affected zone around SAP particles