在役桥梁混凝土碱-集料反应检测

为寻找在役桥梁结构混凝土出现大量裂缝且周边有些伴随白色、黄褐色析出物现象的原因,对混凝土碱-集料反应的可能性做诊断检测。通过现场观察桥梁混凝土裂缝数量、分布密度和方向、宽度及与结构的空间关系等特征,了解渗流物特征和结构变形特征,钻取混凝土芯样进行岩相分析、电子探针分析和分离粗骨料鉴定碱活性。结果表明桥梁各桥墩以及不同结构部位混凝土裂隙发育差异性明显;岩相分析可见碱活性矿物含量很少;显微结构分析可知混凝土水泥基体发育裂纹或沿着骨料的边缘延伸或止于骨料边界,粗、细集料边缘界线清晰;电子探针分析骨料周边没有碱成分富聚的迹象;粗骨料用砂浆长度法测得膨胀率甚小显示其无潜在的碱活性反应危害。因而得出该工程混凝土没有出现碱-集料反应的结论。

Inspection on alkali-aggregate reaction of concrete in servant bridge

In order to explore causes of crack emerges in concrete of servant bridge,alkali-aggregate reaction was thought one of the possible causes and then carried out to investigate.In situ,crack feature of number,scale,width,distribute and relation with structure were inspected.So did characteristic of educts along cracks and structural deformation.Concrete cores were drilled for petrography study,electron-probe microanalysis and determine of alkali activity in coarse aggregate.The results revealed that difference of cracks in various pier and structural position was evident.There were less mineral with alkali activity on petrography.Rims of aggregates were clear,and cracks in matrixes of concrete were elongated besides borders of aggregates or stopped till borders of aggregates.There no indication on assemble of alkali constitute near borders of aggregates by electron-probe microanalysis.Coarse aggregate was implied to be potential nuisanceless on alkali activity due to lower expansibility measured by method of JGJ52-2006.Finally,that was concluded that there was no alkali-aggregate reaction in the concrete of bridge.