冻融循环作用后玄武岩纤维混凝土的断裂性能

Fracture Properties of Basalt Fiber Reinforced Concrete after Freeze Thaw Cycles

关键词:  混凝土  玄武岩纤维  冻融循环  数字图像相关  断裂性能  弯曲韧性

Key words:  concrete  basalt fiber  freeze thaw cycle  digital image correlation（DIC）  fracture property  flexural toughness

摘要:

在带切口梁的三点弯曲试验中,采用数字图像相关（DIC）技术观测玄武岩纤维混凝土（BFRC）试件的全场变形,基于DIC技术的水平应变云图和水平位移云图确定试件的起裂荷载和裂缝开口位移,并研究冻融循环次数和玄武岩纤维掺量对BFRC试件断裂能、延性指数和等效断裂韧度的影响.结果表明：玄武岩纤维的掺入能够提高BFRC试件在冻融条件下的断裂能,但提高程度不如冻融损伤带来的下降程度大;BFRC试件的延性指数随玄武岩纤维掺量的增加呈现先增大后减小的趋势,而随冻融循环次数的增加呈现上升趋势;冻融损伤主要降低了BFRC试件在微变形阶段和小变形阶段的等效断裂韧度,在中变形阶段的降低程度有限,在大变形阶段降低程度已不显著,而玄武岩纤维的增韧作用在混凝土变形的各个阶段都比较显著,且增韧程度为微变形阶段最小,小变形阶段较低,中变形阶段较高,大变形阶段最高.

Abstract:

The full field deformations of notched concrete prisms were observed inrealtime in three point bending test by using the digital image correlation(DIC) technology. The horizontal strain and displacement nephogram based on DIC technology were used to determine the initial cracking load and the crack mouth opening displacement. The effects of freeze thaw cycles and basalt fiber dosage on the fracture energy, ductility index and equivalent fracture toughness of basalt fiber reinforced concrete(BFRC) were investigated. The results show that the fracture energy of BFRC can be improved by adding basalt fiber under freeze thaw cycle condition, but the degree of improvement is smaller than that of the decline caused by freeze thaw cycles. The ductility index of BFRC increases first and then decreases with the increase of basalt fiber dosage, and increases with number freeze thaw cycles. The flexural toughness of BFRC reduces significantly with number freeze thaw cycles at micro and small deformation stages, followed in the middle deformation stage, and that is not significant in the large deformation stage. The toughening effect of the basalt fiber is significant in all deformation stages and the effect from low to high is in the order as follows:the micro deformation stage, the small deformation stage, the middle deformation stage, and the large deformation stage.