鼓浪屿历史建筑带肋方形钢筋的物理性状和腐蚀原因分析

Analysis on physical properties and corrosion causes of ribbed square steel bars in Gulangyu historic building

从鼓浪屿历史建筑(1920~1930年)中实地取样了3种带肋方形钢筋,采用统计分析和微观测试方法,对钢筋的物理性状和腐蚀原因进行了深入研究和分析。结果表明:鼓浪屿历史建筑中混凝土构件所用带肋方形钢筋的横肋高、横肋与纵轴夹角满足国内外现行规范要求,但横肋间距、相对肋面积不满足要求;金相显示所用带肋方形钢筋没有发现有害的带状组织、魏氏组织以及回火马氏体组织;从化学成分判断,所用钢材品种类似于现代的非合金钢(碳素钢),且多为低碳钢;多数钢筋中的磷元素和硫元素含量偏高,说明当时的钢材质量等级较低;不同历史建筑、不同混凝土构件所用方形钢筋的力学性能差异较大,1#钢筋和2#钢筋分别满足现行规范对于HRB400和HRB600的性能要求,但3#钢筋不满足规范对HRB335的性能要求;结构加固计算分析时不能仅依据钢筋的表面特征划分钢筋级别,需要对其力学性能进行检测、鉴定;钢筋的铁锈成分比较复杂,包括Fe3O4、α-FeOOH、β-FeOOH、Fe_(2)O_(3)、Fe(OH)_(3)等多种成分,据此判断混凝土碳化、海洋环境中的氯盐侵蚀以及二者的共同作用是导致鼓浪屿历史建筑钢筋腐蚀的主要原因。

Three kinds of ribbed square steel bars were sampled from Gulangyu historical buildings(1920-1930),the physical properties and corrosion causes of the steel bars were studied and analyzed in-depth by statistical analysis and microscopic test methods.The results show that the transverse rib height and the angle between the transverse rib and the longitudinal axis of the ribbed square steel bars used in the concrete components of Gulangyu historical building meet the requirements of the current norms at home and abroad,but the transverse rib spacing and the relative rib area do not meet the requirements.Metallography shows that no harmful banded structure,widmanstatten structure and tempered martensite structure is found in the ribbed square steel bars.Judging from the chemical composition,the steel used is similar to modern non-alloy steel(carbon steel),and mostly low carbon steel.However,the content of phosphorus and sulfur in most steel bars is high,indicating that the quality grade of steel is low at that time.The mechanical properties of square steel bars used in different historical buildings and different concrete components are quite different.The 1#steel bar and 2#steel bar meet the performance requirements of HRB400 and HRB600 in the current code respectively,but the 3#steel bar does not meet the performance requirements of HRB335 in the code.Therefore,in the calculation and analysis of structural reinforcement,the steel bars grade cannot be divided only according to the surface characteristics of reinforcement,and its mechanical properties need to be tested and identified.The composition of steel rust is more complex,including Fe 3O 4,α-FeOOH,β-FeOOH,Fe_(2)O_(3),Fe(OH)_(3)and other components,according to this,it is judged that concrete carbonation,chloride corrosion in the marine environment and the combined effect of the two are the main causes of steel corrosion in Gulangyu historical buildings.