纳米纤维素纤维改性水泥砂浆力学性能研究

Study on mechanical properties of cement mortar modified by cellulose nanofibrils

研究了纳米纤维素纤维(cellulose nanofibrils,CNFs)对水泥净浆流变、水化热的影响,并探讨了CNFs对水泥砂浆强度、断裂韧性和微观结构的影响。研究结果表明,CNFs可以增大水泥浆体的屈服应力和塑性黏度,延迟水泥早期水化,促进水泥后期水化;随CNFs掺量的增加,水泥砂浆的抗压强度逐渐增强,当CNFs的掺量为0.4%时,其28 d抗压强度增加9.6%,而抗折强度呈现先增后减的趋势,当CNFs的掺量为0.1%时,28 d抗折强度达到最大增幅(8.2%);CNFs对水泥砂浆的断裂韧度提高显著,当CNFs的掺量为0.2%时,断裂韧度增加85%;CNFs在水泥基体中起到了纳米晶核和纳米桥连的作用,改善了水泥基体的微观结构,提高了水泥基体的力学性能。

The effects of cellulose nanofibrils(CNFs)on the rheology and hydration heat of cement paste were studied,and the effects of CNFs on the strength,fracture toughness and microstructure of cement mortar were discussed.The results show that CNFs can increase the yield stress and plastic viscosity of cement paste,delay the early hydration of cement and promote the later hydration of cement.With the increase of the content of CNFs,the compressive strength of cement mortar gradually increases.When the content of CNFs is 0.4%,the28 d compressive strength increases by 9.6%,while the flexural strength increases first and then decreases.When the content of CNFs is0.1%,the 28 d flexural strength reaches the maximum increase(8.2%).CNFs can significantly improve the fracture toughness of cement mortar.When the content of CNFs is 0.2%,the fracture toughness increases by 85%.CNFs play the role of nano crystal core and nano bridging in the cement matrix,improve the microstructure and mechanical properties of the cement matrix.