辅助胶凝材料改善砼微观结构的研究

Investigation of improvement of concrete microstructure with auxiliary cementing materials

以掺加复合掺合料制成的高性能细石混凝土和普通硅酸盐水泥制成的细石混凝土作为研究对象,在混凝土试样平整断面上先镀碳膜,再镀金属膜,通过扫描电镜的手段,研究了细石混凝土中的Ca(OH)2和C-S-H的形貌特征.结果表明,掺加粉煤灰后,明显取向生长的六角板状Ca(OH)2晶体数减少,C-S-H的生成量增多,混凝土内部的孔洞减少,密实性提高.说明粉煤灰的二次水化能够有效地与Ca(OH)2反应,有效改善其界面结构;矿粉也能与Ca(OH)2反应,使混凝土内部生成更多的C-S-H填充孔洞,生成有利于混凝土过渡层的大量水化物;复合掺加矿粉与粉煤灰优于单掺粉煤灰或矿粉,有效地改善了混凝土的微观结构.

Taking two sorts of concrete such as high-performance fine-grained concrete with compound mixture and common concrete with silicate cement as investigation target and plating first carbon theca on the flat surface of concrete sample and then plating metal theca on top of it, the morphological feature of Ca （OH）2 and C-S-H in the concrete with fine gravel was investigated by means of SEM. The results showed that the typical hexagonal plates of Ca（OH）2 decreased and the C-S-H gel increased in the concrete mixed with fly ash,the porosity in the concrete decreased, and its density improved, showing that the secondary hydration of the fly ash with Ca（OH）2 can improve the interface microstructure of concrete effectually. Mineral powder also hydrate with Ca（OH）2 and produce greater C-S-H gel to fill in to the pores in the concrete mixed with mineral powder, generating much hydrate to improve the interface of the concrete. The results of mixing composite additive of mineral powder and fly ash of mixing is better than that fly ash only, improving even more the microstructure of the concrete.