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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2023

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Effect of microsilica addition on properties of geopolymer composites

Smoleń W., Marczyk J., Łach M., Nguyen T. X., Korniejenko K.

Journal of Achievements in Materials and Manufacturing Engineering

2023

Vol. 121, nr 1

46--59

Purpose Geopolymers are modern, inorganic aluminosilicate materials that, through their high mechanical properties, are used in many industries and can be an excellent alternative to Portland cement-based concrete. The study aims to determine the effect of adding microsilica on the properties of geopolymer composites. Design/methodology/approach Reference samples were made by mixing pozzolanic material such as fly ash (50 wt.%) with sand (50% wt.%). The effect of the additive was analysed by introducing microsilica (T180) into the material in shares of 5%, 10% and 15% by weight, each time replacing part of the fly ash with microsilica. The samples were activated with a 10 M sodium hydroxide solution mixed with an aqueous sodium silicate solution. Laser particle size analysis, mineralogical analysis and SEM observations were carried out on the raw materials. Phase identification analysis, SEM observations, density tests, compressive and flexural strength tests, water absorption and thermal conductivity tests were carried out on the produced geopolymer composites. Findings The results obtained based on the compressive strength test showed that the strength of the material decreases with the increase of the silica content in the material. Increasing the silica addition by each subsequent 5% resulted in a decrease in strength of about 20-30%—addition of silica at 5 wt.% resulted in a decrease in flexural strength compared to the reference sample of over 15%. However, adding 10% and 15% causes a decrease in flexural strength by more than 50% compared to the value for the reference sample. The thermal conductivity coefficient decreases with increasing silica content in the composite, which means introducing this additive improves the thermal insulation properties of geopolymer composites. Practical implications Adding microsilica introduced into the geopolymer matrix in 10% ensures a good correlation between thermal conductivity and strength. The compressive strength of this composite is over 25 MPa, which makes it a construction material with improved thermal insulation by approximately 15% compared to the reference material. The investigated materials are dedicated to application in the construction industry. Originality/value The article provides a new voice in a discussion connected with the role of microsilica in geopolymers because microsilica was not previously investigated as an additive for the fly ash used by the authors.