RESUMO
This study is devoted to assessing the hygroscopic and durability properties of a clay composite with the addition of a natural polymer. Modified polymer-retrograded starch hydrogel (RSH) of various concentrations (2.5, 5.0, 7.5, and 10.0%) and heating times (3 and 5 h) were used as clay stabilizers. The introduction of retrograded starch tends to increase the drying rate of clay composites at the early period of 0-4 days without the formation of shrinkage defects. Moisture uptake increased by 29% (from 140 to 180 g/m2) over the control clay composite without RSH. The hysteresis rate of the clay samples modified with RSH decreased by half (from 0.3 to 0.15%), but the hygroscopic properties were better. The use of RSH polymer increased the durability (water erosion resistance) of the clay composite. The obtained composite has great potential for indoor use due to its high moisture-regulating and durability properties.
RESUMO
The paper analyses the properties (chemical and mineral composition, microstructure, density, etc.) of recycled tannery sludge (TS) and the possibilities for using it in cement mortar mixture. Mortar specimens containing 3-12% of tannery sludge by weight of cement and 3-9% of tannery sludge by weight of sand were tested. Flowability, density, ultrasonic pulse velocity (UPV), flexural and compressive strength, water absorption and sorptivity of the mortar were analysed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis of tannery sludge and mortar are presented. The tests revealed that replacement of 6% of cement with tannery sludge in the mix increased flexural and compressive strength and UPV values, whereas water absorption decreased. SEM and XRD analysis revealed that specimens with tannery sludge contained lower amounts of ettringite and higher amounts of portlandite; the obtained structure was denser and contained more calcium hydrosilicates (C-S-H). Chromium leaching values in cement mortars were found not to exceed the limit values set forth in Directive 2003/33/EC.
RESUMO
Large amounts of centrifuging waste of mineral wool melt (CMWW) are created during the production of mineral wool. CMWW is technogenic aluminum silicate raw material, formed from the particles of undefibred melt (60-70%) and mineral wool fibers (30-40%). 0.3-0.6% of organic binder with phenol and formaldehyde in its composition exists in this material. Objective of the research is to investigate the possibility to use CMWW as an additive for the production of ceramic products, by neutralising phenol and formaldehyde existing in CMWW. Formation masses were prepared by incorporating 10%, 20% and 30% of CMWW additive and burned at various temperatures. It was identified that the amount of 10-30% of CMWW additive influences the following physical and mechanical properties of the ceramic body: lowers drying and firing shrinkage, density, increases compressive strength and water absorption. Investigations carried out show that CMWW waste can be used for the production of ceramic products of various purposes.
