The single use of CaO has been regarded as relatively unsuccessful in fly ash activation when no other additives are used together, as it produces a considerably lower strength compared to other types of activators (e.g., alkaline activators). This study investigated two potential additives of nitrate compounds (i.e., Ca(NO3)2 and NaNO3) to improve the strength of a CaO-activated fly ash system. The results showed that the use of Ca(NO3)2 was greatly beneficial in the strength improvement of the binder system primarily due to the significant increase in (1) the dissolution degree of fly ash, (2) C–S–H formation, and (3) pore size refinement from early days; however, NaNO3 was much less advantageous in strength improvement, although it also aided in dissolving fly ash.

中文翻译：

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硝酸钙和硝酸钠对生石灰（CaO）活化 F 类粉煤灰体系强度发展和性能的影响

当没有一起使用其他添加剂时，单独使用 CaO 被认为在粉煤灰活化中相对不成功，因为与其他类型的活化剂（例如碱性活化剂）相比，它产生的强度要低得多。本研究调查了硝酸盐化合物的两种潜在添加剂（即 Ca(NO3)2 和 NaNO3），以提高 CaO 活化飞灰系统的强度。结果表明，Ca(NO3)2 的使用极大地有益于提高粘结剂体系的强度，这主要是由于（1）飞灰溶解度的显着增加，（2）C-S-H 的形成， (3) 早期的孔径细化；然而，虽然 NaNO3 也有助于溶解飞灰，但它在强度提高方面的优势要小得多。