Thermal Behavior of Ceramic Bodies Based on Estonian Clay from the Arumetsa Deposit with Oil Shale Ash and Clinker Dust Additives

The thermal behavior of green clay samples from the Arumetsa and Füzérradvány deposits (Hungary) and the influence of two new types of Estonian oil shale (OS) ashes and cement bypass dust (clinker dust) additives on it were the objectives of this study. Thermal and thermo-dilatometric analysis methods were applied using a Setaram Setsys 1750 thermoanalyzer coupled with a Pfeiffer Omnistar spectrometer and a Setaram Setsys 1750 CS Evolution dilatometer. The kinetic parameters were calculated based on the differential isoconversional method of Friedman. The results of the thermal analysis of clays and blends indicated the emission of physically bound water at 200–250 °C. At temperatures from 200–250 °C to 550–600 °C the release of water is caused by oxidation of organic matter and dehydroxylation of different clay minerals like illite, illite-smectite, mica and kaolin. From blends, in addition, also from the decomposition of portlandite. The emission of CO2 at these temperatures was a result of the oxidation of organic matter contained in the clays. In the temperature range from 550–600 °C to 800–900 °C, the mass loss was caused by ongoing dehydroxylation processes in clay minerals but was mainly due to the decomposition of the carbonates contained in the OS ashes and clinker dust. These processes were accompanied by contraction and expansion of the ceramic bodies with the corresponding changes in the SSA and porosity values of the samples. Therefore, the decomposition of the clays took place in one step which blends in two steps. At first, dehydroxylation of the clay minerals occurs, followed by decomposition of the carbonates. The value of the conversion-dependent activation energy E along the reaction progress α varied for the Arumetsa and illitic clay between 75–182 and 9–206 kJ mol−1, respectively. For the blends based on Arumetsa and illitic clay, the activation energy of the first step varied between 14–193 and 5–205 kJ mol−1, and for the second step, it was between 15–390 and 135–235 kJ mol−1, respectively, indicating the complex mechanism of the processes.

Thermal Analysis of Oil Shale Ash-filled High-density Polyethylene Composites

Thermal analysis was performed to evaluate the impact of the addition of oil shale ash (OSA) to high-density polyethylene (HDPE) polymer matrix using differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Extrusion and press molding processes were used to compound the OSA-filled HDPE polymer composites containing 0, 5, 15 and 25 wt% OSA, for which the thermal properties and the characteristics of the composites were studied. Investigation of the thermal properties of the OSA-HDPE composite is necessary for selecting processing conditions and the appropriate application field. The DSC results demonstrated that OSA addition only marginally affected the glass transition temperature Tg of the composite formulations. The melting temperature Tm showed a decreasing trend with increased OSA fraction, while the crystallization temperature Tcryst showed an increasing trend. The heat of fusion ∆Hm, the heat of crystallization ∆Hcryst and the percentage of crystallinity decreased on the addition of OSA filler. The TGA results demonstrated that the thermal stability of the polymer composite matches that of the neat polymer behavior up to 350 °C after which the thermal stability of the filled polymer composite increases with increased filler content. Above 360 °C, the weight loss of the neat polymer as well as of the polymer composite is accelerated up to 480 °C where all tested samples become fully degraded.

Relationship between Phase Composition and Mechanical Properties of Peat Soils Stabilized Using Oil Shale Ash and Pozzolanic Additive

Construction of road embankments in peatlands commonly involves replacement of the peat with a fill-up soil of an adequate load-bearing capacity. This usually requires a lowering of the water level, turning a peatland from a carbon sink to a source of greenhouse gases. Thus, alternatives are sought that are less costly in both economic and ecological terms. Mass-stabilization technology can provide a cheap substitute for Portland cement. Calcareous ashes (waste materials), supplemented with pozzolanic and alkali additives to facilitate and accelerate the setting and hardening processes, are attractive alternatives to soil excavation or replacement techniques. Silica fume and waterglass were used as pozzolanic agents and KOH as a soil-alkalizing agent. X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analyses and stress–strain tests were performed for the hardened samples. Crystallization of alkali feldspars was observed in all test samples. Comparable hardening of peat soil was achieved for both ashes. It was shown that the ashes of Estonian kukersite (oil shale) from both pulverized firing and a circulating fluidized bed incineration process (produced in energy sector as quantitatively major solid waste in Estonia) can be used as binding agents for peat stabilization, even without the addition of Portland cement. Hardened peat soil samples behaved as a ductile material, and the cellulose fibers naturally present in peat gave the peat–ash composite plasticity, acting mechanically in the same way as the steel or glass fiber in ordinary reinforced concrete. The effect of peat fiber reinforcement was higher in cases of higher load and displacement of the composite, making the material usable in ecological constructions.

Properties of Oil Shale Ash Filled Polypropylene Composite Material: Mechanical and Physical Characterization

The outcome of oil shale ash (OSA) filler addition on the mechanical, morphological, thermal and water uptake properties of the polypropylene (PP) matrix was investigated. The test specimens were prepared with various ratios of the mixtures that contain OSA and polypropylene in the following weight percentages: 0%, 10%, 20%, 30% and 40% OSA in polymer matrix. Composites specimens were produced by using a co-rotating twin screw extruder and a thermal press machine. The properties of the polymer composite specimens were characterized by using a universal testing machine (WDW-5) and izod impact testing machine (FI-68). The morphology of the composite samples was also characterized by using the scanning electron microscopy (SEM). Impact strength and Young’s modulus of the OSA/PP composite formulations were consistently improved on OSA inclusion. On the other hand, addition of OSA to pure polypropylene had consistently reduced the tensile stress at yield, tensile stress at rupture, tensile strain at yield and tensile strain at break. Adding OSA to polypropylene decreased the maximum flexural stress and flexural strain of maximum force. The observed SEM confirmed that the addition of OSA to pure polypropylene resulted in a significant increase in its agglomerates and filler pullout. Differential scanning calorimetry (DSC) results confirmed the addition of the OSA to pure polypropylene resulted in a significant decrease in normalized heat of crystallization, normalized enthalpy of melting. Where the degree of the crystallinity (Xc) of polymer composite decreased from 59% to 34% for 0% and 40% OSA addition, respectively. While melting temperature (Tm) of the composite did not change (167 °C) the crystallization temperature (Tc) increased from 116.6 °C to 127.1 ºC for 0% to 40% OSA addition, respectively. Water uptake, however, demonstrated different behaviour. The initial addition of OSA to polypropylene increased the water uptake property up to 4% for the 40% filler addition. The results of this study demonstrated that the OSA could be used as reinforcement material for polypropylene, as long as good mechanical properties and homogeneous morphology obtained.