不同损伤源对玄武岩纤维增强混凝土孔隙结构变化特征的影响

Effects of different damage sources on pore structure change characteristics of basalt fiber reinforced concrete

为了研究玄武岩纤维增强混凝土在高温和力学两种损伤源下的孔隙结构变化特征,采用核磁共振(NMR)和扫描电镜(SEM)技术,观察试件T2谱分布、孔径分布、孔洞和裂隙发育情况。结果表明,高温作用后基准混凝土、短玄武岩纤维增强混凝土、长玄武岩纤维增强混凝土均呈微孔数量不断减小、介孔数量不断增加的趋势。通过对比发现,长玄武岩纤维增强混凝土T2谱主峰孔隙数量最多,孔径分布最大。以长玄武岩纤维增强混凝土为例,研究在高温和力学两种损伤源下玄武岩纤维增强混凝土的孔隙结构变化特征。发现弛豫时间在0.1~10 ms内高温损伤下玄武岩纤维增强混凝土的孔隙数量大于力学损伤下的孔隙数量,且随着温度升高,T2谱主峰向右偏移,随着荷载增加,T2谱主峰几乎不发生变化,表明温度升高更能加剧损伤,每级温度作用下新生孔径不断增大。T2谱主峰幅值和孔径分布随温度升高不断增大,随荷载增加出现先减小后增大的现象,表明高温作用对混凝土直接构成损伤,而力学作用使混凝土先密实再产生损伤,SEM观察得到了相同的结论。

In order to study the pore structure change characteristics of basalt fiber reinforced concrete under two sources of damage,high temperature and mechanics,nuclear magnetic resonance(NMR)and scanning electron microscopy(SEM)techniques were used to observe the T2 spectrum distribution,pore size distribution and flaw development of the basalt fiber reinforced concrete.The results show that normal concrete,short basalt fiber reinforced concrete and long basalt fiber reinforced concrete show a trend of decreasing the number of micropores and increasing the number of mesopores after high temperature.By comparison,it is found that long basalt fiber reinforced concrete has the largest number of pores in the main peak of the T2 spectrum and the largest pore size distribution.The long basalt fiber reinforced concrete was taken as an example to illustrate the change characteristics of pore structure under two kinds of damage sources.The number of pores under high temperature damage with a relaxation time of 0.1–10 ms is greater than the number of pores under mechanical damage.And the main peak of T2 spectrum shiftes to the right as the temperature increases.However,the main peak of T2 spectrum hardly changes with the increase of load,indicating that the increase in temperature can aggravate the damage more than mechanical.And the new pore diameter increases continuously under each temperature.The main peak of T2 spectrum and pore size distribution increase with temperature increasing,and decrease at first and then increase with increasing load,which indicates that the high temperature directly causes damages to the concrete,while the mechanical makes the concrete dense at first and then damage.The same conclusion is obtained by electron microscope observation.