engleski

Mechanical and durability properties of cement mortars with built-in sewage sludge ash

Sewage sludge is being generated as a by- product of nearly all technological processes on wastewater treatment plants. Its disposal, in accordance with the current legislation, is expensive and environmentally and socially sensitive process. In accordance with the principles of sustainable development and circular economy, special emphasis is put on the possibilities of recycling and/or use of the sewage sludge or ash obtained as by-product of sludge thermal treatment. Due to the chemical composition based on oxides of calcium, silicon, aluminium and iron and possible pozzolanic properties of sewage sludge ash, there is a possibility of its use as a replacement for part of the cement in mortars and concrete. Results of previous research conducted on mortars and concrete point to significant potential for the use of sewage sludge ash in the concrete industry, from the standpoint of preserving mechanical properties. In this study, ash generated by combustion of sludge from the wastewater treatment plant Varazdin, in laboratory conditions in an electric furnace at temperatures 800 – 1000 °C, was used for the preparation of mortar samples. The paper analyses the influence of incineration temperature and ash replacement ratio on the properties of the mortars in the fresh state, mechanical (compressive and flexural strength) and durability (gas permeability) properties of mortar, as well as the impact on the corrosion resistance of steel during exposure to 3.5% NaCl solution. Results indicate that the addition of ash causes decrease in workability of mortars, as well as its strength. It is also found that it tends to reduce resistance to corrosion of reinforcing steel during exposure to 3.5% NaCl solution, while at the same time, because of the so- called "filler effect" occurs partially reduced permeability, which is confirmed by lower values of the gas permeability coefficient for some of the tested mortars.

pepeo iz mulja s UPOV-a ; recikliranje ; cementni mort ; čvrstoća ; trajnost ; korozija

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