碳纤维(CF)不参与水泥水化,对水化产物初始缺陷无法发挥作用。氧化石墨烯(GO)可以调节水泥水化,但其无法限制较大尺寸裂缝的扩展。为实现CF和GO的优势互补,将CF和GO掺入混凝土中,研究了两者单掺和复掺对混凝土力学性能的影响,并探讨了CF与GO对混凝土力学性能的复合改性效果及机理。结果表明:CF与GO均可提高混凝土的抗压和抗折强度,且CF和GO的最佳掺量分别为0.2%、0.15%。在掺加0.2% CF(或0.15% GO)的基础上,复掺GO(或CF)可以进一步提高混凝土的力学性能。当CF和GO复掺,且两者掺量分别为0.2%、0.15%时,混凝土的力学性能最佳。CF和GO具有“正混杂效应”,其对混凝土抗压和抗折强度的提高效果优于单掺CF和单掺GO时两者提高效果之和,表现出“1+1＞2”的效果。CF/混凝土基体界面处结构疏松,而当CF与GO混掺时,CF/混凝土基体界面结合较好,且界面处C-S-H(水化硅酸钙)晶体的含量增多。GO可以调节CF/混凝土基体界面处的水化,增强CF与混凝土基体的界面结合,促进CF作用的发挥。

Carbon fiber (CF) does not participate in the hydration of cement,and cannot mitigate the initial defects of hydration products.Graphene oxide (GO) can regulate the hydration of cement,but it cannot limit the growth of larger cracks.In order to realize the complementary advantages of CF and GO,CF and GO were mixed into concrete.The effects of single and compound addition of CF and GO on the mechanical properties of concrete were studied,and the co-modification effects and mechanisms of CF and GO on the mechanical properties of concrete were further explored.The results showed that both CF and GO could improve the compressive strength and flexural strength of concrete,with optimal dosages of CF and GO of 0.2% and 0.15%,respectively.On the basis of adding 0.2% CF (or 0.15% GO),adding GO (or CF) could further improve the mechanical properties of concrete.The best mechanical properties of concrete were achieved when CF and GO were compound added with contents of 0.2% and 0.15%,respectively.CF and GO exhibited a “positive hybrid effect”,and their combined improvement effect on the compressive strength and flexural strength of concrete was better than the sum of the two single addition,showing the effect of “1+1>2”.The interface structure of CF/concrete matrix was loose,but when CF and GO were compound added,the interface of CF/concrete matrix was well combined,and the content of C-S-H (calcium silicate hydrate) crystal at the interface increased.GO could regulate the hydration at the interface of CF/concrete matrix,enhance the interface combination of CF and concrete matrix,and promote the effectiveness of CF.