engleski

Lightweight Concrete Foam from Saponified Almond Shell Extract

Lightweighted concretes are cement materials with enhanced porosity. Two type can be distinguished: 1) chemically foamed concrete using aluminium powder and autoclave reaction and 2) physically foamed concrete using surfactants. Different mechanisms of foaming affect porosity and morphology of hardened cement paste. Chemical foaming yields macroporous microstructure, while surfactants shift the microstructure into meso- and microporous region. This control over microstructure development allows preparing of new materials with specific functional behaviour, such as new porous insulation materials with low thermal conductivity, or new porous binders for thermal and sound insulation composite materials. In this work the extraction of soluble organic components from waste almond shell and their employment as aerating agents for cement paste was investigated. Extraction was carried out in a batch process where milled almond shell (1:10 mass fraction) and water were mixed at 300 rpm and heated to 60 °C for 3 hours. Mixing the extracted solution into cement paste should yield saponification of soluble organic compounds from almond shells due to high alkalinity of the cement paste, with the aid of heat released from cement paste hydration. Further mixing should form foam that would allow development of porous structure of the cement paste. Such aerated paste with new properties could be used as a solid block of mineral-bound foam or as a binder for functional composite material from the waste almond shell and the dried residue of the extraction process. The feasibility of the proposed process was evaluated in this research. It was found that high content of organic compounds extracted from almond shell acted as superplasticizers and retarded the cement hydration, which consequently affected the formation of foamed microstructure. Further investigation of these phenomena is necessary.

lightweight concrete, almond shell, saponification, microporosity

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