硅灰与超塑化剂对钢纤维与水泥基体界面的影响

用两端带弯钩的钢纤维制作钢纤维增强混凝土梁形试件,研究了用硅灰代替不同量的普通硅酸盐水泥并通过掺加超塑化剂以降低混凝土的水灰比,发现当用硅灰代替10％水泥并同时使水灰比由0.5降至0.37,可使钢纤维增强混凝土小梁的抗弯极限强度与韧性分别提高了79％和63％,拔出试验结果表明,掺硅灰并同时掺塑化剂以降低水灰比有助于提高钢纤维与水泥砂浆的界面粘结强度。对钢与水泥基体界面区微观结构的研究结果表明,掺硅灰与降低水灰比可减少CH晶体在界面区的富集并消弱其取向性,增加C-S-H凝胶的含量并使界面区的孔结构得以明显改善,钢纤维增强混凝土的宏观力学性能与纤维——水泥基体的界面区微结构密切相关。

EFFECTS OF SILICA FUME AND SUPERPLASTICIZER ON INTERFACE BETWEEN STEEL FIBRE AND CEMENT MATRIX

When 10% of portland cement by weight is replaced by silica fume and W/C ratio of concrete is re- duced by adding superplasticizer, MOR and toughness of steel fibre reinforced concrete (SFRC) test beams can be enhanced considerably. The results of pull-out test also show that under these conditions the average interfacial bond strength between steel fibre and cement matrix is thus increased. According to the investiga- tion of interface between steel and cement matrix it is proved that the macro-mechanical properties of SFRC may be closely related to the microstructure of the interface between the fibre and the matrix.