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- One-part formulation (2) (entfernen)
A silica residue from waste treatment of chlorosilane production was used together with solid sodium aluminate to test its applicability for the production of one-part geopolymers. The blend was activated with water and cured at 70 °C. The degree of reaction and strength were determined after 1, 3, and 7 days. The reaction products were analyzed by XRD and SEM/EDX. Until the third day of curing the degree of reaction of the residue reached 51 % and the strength was 8.9 MPa. The reaction product was identified as geopolymer containing zeolite A. Thus, the results confirmed that the residue may be used in the production of geopolymers. However, after 3 days of curing no further progress of reaction was observed and the strength slightly decreased, which was attributed to changes in the structure of the geopolymeric gel. It was further observed that even harsh vacuum drying left some water (presumably zeolitic water and surface hydroxyl groups) in the geopolymer.
One-part geopolymers offer advantages over conventional geopolymers with regard to handling and storage of feedstocks. However, they often suffer from a low degree of reaction, a high amount of crystalline byproducts, and consequently low strength. In this study, one-part geopolymers were produced from rice husk ash (RHA) and sodium aluminate, and investigated by XRD, ATR-FTIR, SEM and compressive strength testing. The compressive strength of the material was 30 MPa, i.e. significantly higher than for comparable one-part geopolymers. This is attributed to an almost complete reaction of the RHA and the absence of crystalline byproducts (zeolites) in the hardened geopolymer.