纳米SiO_(2)改性纤维增强普通硅酸盐水泥-硫铝酸盐水泥复合材料早期性能及微观结构

Effect of Nano-SiO_(2) on Early Properties and Microstructure of Fiber-Reinforced Ordinary Portland Cement-Sulphoaluminate Cement Composites

为优化纤维增强普通硅酸盐水泥-硫铝酸盐水泥复合材料(OPC-CSA-ECC)的性能,拓宽纳米SiO_(2)的应用范围,本文系统探讨了纳米SiO_(2)对OPC-CSA-ECC凝结时间、强度和韧性的影响,并结合XRD和SEM分析了体系的微观结构和改性机制。结果表明:纳米SiO_(2)缩短了复合胶凝体系的凝结时间,且掺量越大凝结时间越短;纳米SiO_(2)可提高OPC-CSA-ECC的强度和韧性,纳米SiO_(2)的适宜掺量在1.5%(质量分数),对应的7 d和28 d龄期抗压强度分别为59.1 MPa和85.4 MPa,等效弯曲韧性分别为195.82 kJ/m^(3)和256.51 kJ/m^(3)。纳米SiO_(2)没有改变水化产物的种类,但促进了C-S-H凝胶生成且消耗了部分portlandite晶体。SiO_(2)通过提高基体密实度增大了基体与纤维之间的粘结性能,有助于应变硬化行为的实现。

In order to optimize the properties of fiber-reinforced ordinary Portland cement-sulfoaluminate cement composites(OPC-CSA-ECC) and extend the use of nano-SiO_(2),this study discussed the effects of nano-SiO_(2)on the setting time,strength and toughness of OPC-CSA-ECC.Microstructure and modification mechanism of OPC-CSA-ECC were analyzed by XRD and SEM.The results show that,nano-SiO_(2)shortens the setting time of the composite cementitious,and the greater the content,the shorter the setting time.Nano-SiO_(2)improves the strength and toughness of OPC-CSA-ECC.The appropriate content of nano-SiO_(2)is 1.5%(mass fraction),the corresponding compressive strength at 7 d and 28 d is 59.1 MPa and 85.4 MPa,and the equivalent flexural toughness is 195.82 kJ/m^(3) and 256.51 kJ/m^(3),respectively.Nano-SiO_(2)doesn’t change the type of hydration products,but promotes the formation of C-S-H gel and consumes some portlandite crystals.SiO_(2)increases the adhesion between the matrix and fiber by increasing the density of the matrix,which contributes to improve strain hardening ability.