Aproveitamento de resíduos cerâmicos e de diatomita na fabricação de agregados leves

Abstract

The use of lightweight aggregates (LWAs) in engineering works and services is becoming increasingly common. Their properties of density, water absorption and mechanical resistance favour their use in a wide range of applications. However, the manufacture of LWAs depends on the consumption of natural resources. In view of this, various research projects have been trialling the use of by-products in the manufacture of LWAs. At the same time, the disorderly manufacture and use of diatomite and ceramic materials has resulted in severe environmental impacts. In China, tens of thousands of tonnes of diatomite waste (DW) are produced every year, wasting natural resources, emitting CO2 into the atmosphere and leaching nitrogenous substances into the soil. In turn, red ceramic waste (RCW) is one of the main by-products generated by ceramic materials. However, no tests have been found on the application of DW or RCW in expandable LWAs. For this reason, the main objective of this work is to evaluate the possibility of producing LWAs from the reuse of DW and RCW. Initially, all the starting materials were processed and characterised by X-ray florescence, laser granulometry, X-ray diffraction, scanning electron microscopy and simultaneous thermal analysis. Next, 31 different formulations were prepared according to the main protocols for developing LWAs. The mixtures were dried and then sintered at a temperature range of 1100 to 1250°C, resulting in 124 different samples. Tests to determine expandability, density, porosity, water absorption, mechanical strength, loss of mass, microstructure, mineralogy and thermogravimetric behaviour were carried out in order to typify the samples obtained. Subsequently, the commercial potential of each of the manufactured specimens was assessed. The samples produced had a particle density ranging from 1.14 to 2.46 g/cm³. The maximum values for swelling index, mass loss and crushing strength were 48.3 per cent, 11.9 per cent and 40.52 MPa, respectively. Meanwhile, the minimum values for closed porosity and water absorption were 2.8% and 0.1%, in that order. The results revealed that the mineralogical composition of the clay and ceramic residue exerted a strong influence on the swelling phenomenon, influencing the release of gases and acting as a substitute for the aluminosilicate matrix. In all, 78 specimens showed physical and mechanical properties within the criteria required for the use of LWAs in commercial applications. Of these, many aggregates were made exclusively from waste. The results obtained in this study show that it is technically possible to produce lightweight aggregates by replacing clay with red ceramic waste and/or diatomite waste. It was also found that RCW, when sintered at high temperatures, is effective in reducing particle density and that The use of lightweight aggregates (LWAs) in engineering works and services is becoming increasingly common. Their properties of density, water absorption and mechanical resistance favour their use in a wide range of applications. However, the manufacture of LWAs depends on the consumption of natural resources. In view of this, various research projects have been trialling the use of by-products in the manufacture of LWAs. At the same time, the disorderly manufacture and use of diatomite and ceramic materials has resulted in severe environmental impacts. In China, tens of thousands of tonnes of diatomite waste (DW) are produced every year, wasting natural resources, emitting CO2 into the atmosphere and leaching nitrogenous substances into the soil. In turn, red ceramic waste (RCW) is one of the main by-products generated by ceramic materials. However, no tests have been found on the application of DW or RCW in expandable LWAs. For this reason, the main objective of this work is to evaluate the possibility of producing LWAs from the reuse of DW and RCW. Initially, all the starting materials were processed and characterised by X-ray florescence, laser granulometry, X-ray diffraction, scanning electron microscopy and simultaneous thermal analysis. Next, 31 different formulations were prepared according to the main protocols for developing LWAs. The mixtures were dried and then sintered at a temperature range of 1100 to 1250°C, resulting in 124 different samples. Tests to determine expandability, density, porosity, water absorption, mechanical strength, loss of mass, microstructure, mineralogy and thermogravimetric behaviour were carried out in order to typify the samples obtained. Subsequently, the commercial potential of each of the manufactured specimens was assessed. The samples produced had a particle density ranging from 1.14 to 2.46 g/cm³. The maximum values for swelling index, mass loss and crushing strength were 48.3 per cent, 11.9 per cent and 40.52 MPa, respectively. Meanwhile, the minimum values for closed porosity and water absorption were 2.8% and 0.1%, in that order. The results revealed that the mineralogical composition of the clay and ceramic residue exerted a strong influence on the swelling phenomenon, influencing the release of gases and acting as a substitute for the aluminosilicate matrix. In all, 78 specimens showed physical and mechanical properties within the criteria required for the use of LWAs in commercial applications. Of these, many aggregates were made exclusively from waste. The results obtained in this study show that it is technically possible to produce lightweight aggregates by replacing clay with red ceramic waste and/or diatomite waste. It was also found that RCW, when sintered at high temperatures, is effective in reducing particle density and that