Externer Alkalieintrag in mechanisch/thermisch vorgeschädigtes Betongefüge

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进入混凝土微观结构的运输机制的影响是研究的重点。关于混凝土中实际叠加循环交通和约束应力造成的退化，大型混凝土梁将在各种应力水平和各种荷载循环次数下进行测试。混凝土微结构内部的变化将通过测量梁表面的超声运行时间来描述。循环加载后，在微截面上确定了裂缝的长度、宽度和裂纹数等相关参数。因此，预损伤程度可以量化。这些参数表征了退化并验证了数值模型（来自TP3）。一般情况下，微观结构的退化不会导致疲劳失效。然而，它在很大程度上影响了外源碱进入混凝土的输送机制。在子项目TP1中，液体在预损伤试样中的渗透行为将通过评估压力下的吸水性和毛细吸力来确定。因此，根据预损伤的程度，可以评估对液体/碱渗透的影响，以验证数值模型。此外，asr相关的钠离子的渗透行为将在修饰的迁移细胞中进行评估。在子项目TP1中，还将实验评估过滚轮胎对外源碱渗透行为的影响。因此，未完工的和预损坏的混凝土梁将被一个满载的轮胎辗压；同时在表面涂上氯化钠溶液。在达到所需的滚压次数后，将评估碱的渗透深度。因此，可以定义预损伤程度与侵彻深度之间的直接相关关系。最后，采集的样品将被储存在asr激发的环境中，并评估asr菌株对降解和外部碱供应的依赖性。在第一个资助期，重点是研究循环载荷引起的降解和液体的渗透行为。特别是在第二个供资期间，将评估外源碱在滚压轮胎中的渗透情况以及最终产生的ASR。通过对子项目TP4 （3D-CT、LIBS）、TP5 （KWL）和TP6（裂缝力学参数）的进一步参数评估，TP1的结果将得到补充。此外，将通过TP1的实验结果验证TP3和TP6子项目中相应的数值模型。

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.