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Externer Alkalieintrag in mechanisch/thermisch vorgeschädigtes Betongefüge

外部碱进入机械/热损坏的混凝土结构

基本信息

批准号：
202256458
负责人：
Professor Dr.-Ing. Rolf Breitenbücher
金额：
--
依托单位：
Lehrstuhl für Baustofftechnik
依托单位国家：
德国
项目类别：
Research Units
财政年份：
2011
资助国家：
德国
起止时间：
2010-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/202256458?language=en
关键词：
Externer Alkalieintrag mechanisch thermisch vorgesch

项目摘要

Within the predominantly experimentally orientated sub-project TP1 the degradation induced by cyclic loading as well as its effects on the transport mechanisms of externally supplied alkalis into the con-crete microstructure are in the focus of the investigations. Regarding degradation due to realistic su-perposed cyclic traffic and restraint stresses within the concrete, large concrete beams will be tested under various stress levels and various numbers of load cycles. The changes within the concrete mi-crostructure will be described by measurement of the ultrasonic runtimes on the surface of the beam. After the cyclic loadings the relevant crack parameters as length, width, and crack numbers are de-termined on microsections. Thus, the degree of pre-damaging can be quantified. These parameters characterize the degradation and validate the numerical models (from TP3). Generally, the microstruc-tural degradation does not lead to fatigue failure. Nevertheless, it affects the transport mechanisms of i.e. externally supplied alkalis into the concrete largely. The penetration behavior of liquids in pre-damaged specimen in sub-project TP1, will be determined through the evaluation of the water uptake under pressure as well as capillary suiction. Thus, in dependence of the degree of pre-damaging, the effect on the penetration of liquids/alkalis can be assessed for validation the numerical models. Fur-ther, the penetration behavior of ASRrelevant Na-ions will be evaluated in a modified migration cell. The effect of an overrolling tire on the penetration behavior of externally supplied alkalis will be also experimentally assessed in sub-project TP1. Therefore, unoffended as well as pre-damaged concrete beams will be overrolled with a loaded tire; simultaneously a NaCl-solution is applied on the surface. After the desired number of overrollings the penetration depth of alkalis will be evaluated. Thus, a direct correlation between the degree of pre-damaging and the penetration depth can be defined. Conclusively, the acquired specimen samples will be stored in an ASR-provoking environment and the ASR-strain-potential depending on the degradation and the external alkali supply will be assessed. In the first funding period the focus lay on the investigations regarding the degradation caused by cyclic loading and the penetration behavior of liquids. In the second funding period especially the penetration of externally supplied alkalis by an overrolling tire and ultimately the resulting ASR will be assessed. Through the assessment of further parameters in the sub-projects TP4 (3D-CT, LIBS), TP5 (KWL) and TP6 (fracture-mechanical parameters) the results acquired in TP1 will be complemented beneficiary. Furthermore, corresponding numerical model from the sub-projects TP3 and TP6 will be validated through the experimentally acquired results from TP1.

在主要以实验为导向的子项目TP1中，循环加载引起的降解及其对外部供应的碱向混凝土微观结构传输机制的影响是调查的重点。考虑到实际循环交通和混凝土内部约束应力引起的退化，大型混凝土梁将在不同应力水平和不同荷载循环次数下进行试验。混凝土微观结构内的变化将通过测量梁表面的超声波运行时间来描述。在循环加载后，确定了相应的裂纹参数，如长度、宽度和裂纹数量。因此，预先破坏的程度可以量化。这些参数表征了退化，并验证了数值模型(来自TP3)。一般来说，组织退化不会导致疲劳失效。然而，它在很大程度上影响了外部供应的碱向混凝土中的传输机制。将通过评估压力下的吸水率和毛细管腐蚀来确定液体在TP1子项目中的预损坏试件中的渗透行为。因此，根据预毁伤的程度，可以评估对液体/碱侵彻的影响，以验证数值模型。此外，将在改进的迁移池中评估与ASR相关的Na离子的穿透行为。翻转轮胎对外部供应的碱液渗透行为的影响也将在TP1子项目中进行实验评估。因此，未受影响的以及预先损坏的混凝土梁将被加载的轮胎覆盖；同时在表面涂抹氯化钠溶液。在所需的过轧次数之后，将评估碱的渗透深度。因此，可以确定预毁伤程度和侵彻深度之间的直接关系。最后，获取的样本将被储存在引发ASR的环境中，并将根据降解和外部碱供应评估ASR应变潜力。在第一个供资期间，重点放在关于循环加载引起的降解和液体渗透行为的调查上。在第二个资助期，将对外部供应的碱液由翻滚轮胎穿透的情况进行评估，并最终对由此产生的ASR进行评估。通过对分项目TP4(3D-CT、LIBS)、TP5(KWL)和TP6(断裂-力学参数)中其他参数的评估，在TP1中取得的成果将得到受益者的补充。此外，子项目TP3和TP6的相应数值模式将通过从TP1获得的实验结果进行验证。