Use of transmixer washing water in geopolymer composite production

In this study, physical, mechanical and durability properties of transmixer wash water and fly ash added geopolymers were investigated. Binder dosage in the mixtures was chosen as 1000 kg/m3. 25% and 50% fly ash (UK) was used instead of ground blast furnace slag, which is the main binder of the mixtures. Sodium metasilicate powder was used as alkali activator at the rate of 7,5% and 15% of the total binder. Setting end times of the mixtures vary between 165-230 minutes. As the UK ratio increased, the final setting times increased. All mixtures have a flow diameter of more than 150 mm. Oven-dry densities of the mixtures are less than 2000 kg/m3. As the UK ratio increased, the fresh and oven-dry densities decreased. As the UK ratio increased, the porosity and water absorption values of the mixtures increased. The mixer washing water did not have a significant effect on the fresh and physical properties of the mixtures. A compressive strength of about 20 MPa was obtained on the 3rd day, while a compressive strength of more than 80 MPa was obtained on the 180th day. As the UK ratio increased, the compressive and flexural strengths generally decreased. As the UK ratio increased, the mass loss decreased after high temperature. However, lower compressive and flexural strengths were obtained after high temperature in mixtures with UK. After 120 freeze-thaw cycles, a mass loss of 7-15% occurred in the mixtures. The compressive strength of the mixtures decreased below 50 MPa. While the increase in UK ratio did not contribute to acid resistance, it contributed positively to the sulfate effect. In addition, more weight loss occurred in mixtures with UK exposed to the effect of NaCl. Increasing the UK ratio generally decreased the ASR expansions. As a result, the performance of the composites decreased as the UK ratio increased. However, in terms of sustainability, 25% UK can be used. In addition, it has been observed that the transmixer washing water can be used up to 100%. Thanks to the obtained composites, it has been shown that a sustainable building material can be obtained by reducing the environmental pollution considerably. KEYWORDS: Geopolymer, Sustainability, Sodium metasilicate, Fly ash, Durabiliy