Differential scanning calorimetry of high-performance concrete with burnt clay shale addition

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Mineral additives are used in concrete primarily due to a positive effect on its mechanical properties. Using the differential scanning calorimetry, it is possible to observe thermophysical changes in concrete samples containing such additives at the microstructural level. In our study high-performance concrete samples with a different mass% of a burnt clay shale addition were prepared. The burnt clay shale is a pozzolana active material which can be used as a partial replacement for the cement binder. The aim of this paper is to investigate the hydration and pozzolanic reaction in a high-performance concrete with the burnt clay shale addition using differential scanning calorimetry (DSC) and thermogravimetry (TG). The investigation was performed in the temperature range from 25 to 1000 °C with a heating rate 5 °C/min in an argon atmosphere.cf201

Estimation of the thermal diffusivity in a large electroceramic body by an invere method

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.We investigate the temperature dependence of the thermal diffusivity for a large ceramic body of a cylindrical shape during firing up to 900 °C. The body was made of a ceramic material used in the production of electroporcelain insulators. We describe the corresponding heat transfer by the standard heat equation and solve the inverse problem by the Levenberg-Marquardt method. The results show that the method allows one to detect the physical-chemical processes occurring in the material during firing, namely, the liberation of physically bound water in the range up to 250 °C, the phase transformation of kaolinite into metakaolinite (dehydroxyla-tion) in the range ~ 450 °C – 650 °C, and solid-state sintering starting at ~ 700 °C.cf201

Investigation of sintering in electroceramics by thermodilatometry

Solid-state sintering was investigated in electroceramic samples using thermodilatometric measurements. The samples were studied in the isothermal regime at the temperatures 500, 600, 700, 800, 900, 1000 and 1050°C. The relative expansion was measured for a period of 8 h. At a given temperature a dominant diffusion mechanism for the sintering process was determined, and the corresponding porosity together with the pore size distribution was also measured

Measuring the Flexural Strength of Ceramics at Elevated Temperatures – An Uncertainty Analysis

The flexural mechanical strength was measured at room and elevated temperatures on green ceramic samples made from quartz electroporcelain mixture. An apparatus exploited the three-point-bending mechanical arrangement and a magazine for 10 samples that are favorable at the temperature measurements from 20 °C to 1000 °C. A description of the apparatus from the point of possible sources of uncertainties is also given. The uncertainty analysis taking into account thermal expansion of the sample and span between the supports is performed for 600 °C. Friction between the sample and supports as well as friction between mechanical parts of the apparatus is also considered. The value of the mechanical strength at the temperature of 600 °C is 13.23 ± 0.50 MPa, where the second term is an expanded standard uncertainty. Such an uncertainty is mostly caused by inhomogeneities in measured samples. The biggest part of the uncertainty arises from the repeatability of the loading force which reflects a scatter of the sample properties. The influence of the temperature on the uncertainty value is very smal

Lime-Pozzolan Plasters with Enhanced Thermal Capacity

Abstract-A new type of lightweight plaster with the thermal capacity enhanced by PCM (Phase Change Material) addition is analyzed. The basic physical characteristics, namely the bulk density, matrix density, total open porosity, and pore size distribution are measured at first. For description of mechanical properties, compressive strength measurements are done. The thermal properties are characterized by transient impulse techniques as well as by DSC analysis that enables determination of the specific heat capacity as a function of temperature. The resistivity against the liquid water ingress is described by water absorption coefficient measurement. The experimental results indicate a good capability of the designed plaster to moderate effectively the interior climate of buildings

Acoustic Emission During Firing of the Illite-Based Ceramics with Fly Ash Addition

In this work, illite-based ceramic body with power plant fly ash addition (60 wt.% of illite, 30 wt.% of fly ash and 10 wt.% of illite fired at 1100°C) was investigated by the thermal analysis techniques (differential thermal analysis, thermodilatometry and thermogravimetry) and the acoustic emission technique. The green body was heated up to 1100°C at three different rates 2.5, 5, 10 K/min. The most intense acoustic emission was recorded at the highest rate 10 K/min. Mutual correlations between thermal analyses and acoustic emission data were also examined. The first acoustic emission response appears at 430°C, corresponding to a small endotherm on the DTA curve, where the thermal decomposition of mineral portlandite takes place. In the temperature range from 600 to 900°C, high acoustic emission activity correlates with dehydroxylation and expansion of the sample. At temperatures higher than 800°C, the source of acoustic emission signals is the thermal decomposition of calcite. The amorphous phase created from illite at 920°C becomes pyroplastic, therefore it is not documented by the acoustic emission technique

Electric properties of anorthite ceramics prepared from illitic clay and oil shale ash

Electrical properties during firing of anorthite ceramic prepared from mixtures of illitic clay (from Northeastern Hungary) and fly ashes (obtained from circulating fluidized bed combustion – IA4 and pulverized firing – ID4) with high content of CaO were investigated. Mixtures were prepared with 60 wt% of illitic clay and 40 wt% of oil shale ash. The ashes were hydrated prior to mixing, to prevent the reaction of free lime with water during sample preparation. The mixtures were subjected to thermal and structural analyses to describe the processes induced by thermal treatment. The contraction of the IA4 and ID4 samples reached 1.8% and 2.5%, respectively, at 1100 °C, which is significantly lower than that of the illitic clay (7%). X-ray diffraction (XRD) analysis revealed a presence of diopside, gehlenite, cristobalite, and leucite minerals as additional mineral phases in the prepared anorthite ceramics. Measurement of AC conductivity showed that after the decomposition of the CaCO3 at ∼880 °C, Ca2+ ions became the dominant charge carriers, and the electrical current was carried by a hopping mechanism throughout the studied temperature region. The electrical conductivity and the relative dielectric constant of the ID4 sample was higher compared to that of the IA4 sample. The relative dielectric constant reached values of 6 (sample IA4) and 8 (sample ID4) at 140 °C (after drying)