Evaluation of mechanical and microstructural properties of eggshell lime/rice husk ash alkali-activated cement

•Alkali-activated cements (AAC) were prepared using eggshell lime (ESL) and rice husk ash (RHA);•The ESL/RHA ratio (Ca/Si) was the most statistically significant factor in binder strength and stiffness;•AAC was optimized with 30/70 ESL/RHA, 3 % alkali content, 60 °C curing temperature;•XRD patterns...

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Veröffentlicht in:Construction & building materials 2023-01, Vol.364, p.129931, Article 129931
Hauptverfasser: Ferreira, Flávio Antônio, Desir, Jean Marie, Lima, Gustavo Emilio Soares de, Pedroti, Leonardo Gonçalves, Franco de Carvalho, José Maria, Lotero, Andres, Consoli, Nilo Cesar
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Sprache:eng
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Zusammenfassung:•Alkali-activated cements (AAC) were prepared using eggshell lime (ESL) and rice husk ash (RHA);•The ESL/RHA ratio (Ca/Si) was the most statistically significant factor in binder strength and stiffness;•AAC was optimized with 30/70 ESL/RHA, 3 % alkali content, 60 °C curing temperature;•XRD patterns and FTIR spectra confirmed CSH gel formation. Searching for innovative solutions to produce alternative construction materials using residues is a need to reduce the exploitation of natural resources. Alkali-activated cements (AACs) have been studied in recent years and pointed out as a possible alternative to Portland cement (PC). AACs can still be produced from waste and/or by-products from different sectors of the economy. In this sense, this research proposes the development of an alkali-activated binder produced from rice husk ash (RHA) and eggshell lime (ESL), activated with NaOH or KOH. A dosage study using a second-order composite design sought to evaluate the influence of parameters such as ESL/RHA ratio, alkali content (%Alk), water-binder ratio (w/B), curing temperature (TEMP) and type of alkaline activator (TYPE). Specimens were produced, thermally cured for 24 h and tested at 3 days of age. Unconfined compression strengths (UCS) and ultrasonic pulse velocities (UPV) were determined. Results indicated the ESL/RHA 30/70 ratio, 3 % alkali content, and curing temperature of 60 °C as optimal parameters, with the mixture reaching UCS of 18 MPa at 3 days of age. XRD and FTIR results show that CSH gel formation increases when increasing ESL/RHA ratio up to 30 %, alkaline content up to 3 %, and curing temperature up to 60 °C. Above these values, the formation of CSH tends to decrease. Binders activated by KOH obtained UCS results on average 10 % higher than those activated by NaOH.
ISSN:0950-0618
1879-0526
DOI:10.1016/j.conbuildmat.2022.129931