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.

在主要实验取向的亚项目TP1中，循环载荷引起的降解以及其对外部提供的碱的运输机制的影响，是研究的重点。关于由于逼真的循环交通和混凝土内的约束应力而导致的降解，将在各种应力水平和各种数量的负载周期下测试大型混凝土梁。混凝土MI裂解中的变化将通过测量梁表面的超声运行时间来描述。循环载荷后，相关的裂纹参数作为长度，宽度和裂纹数量在微观上被删除。因此，可以量化预损伤的程度。这些参数表征降解并验证数值模型（来自TP3）。通常，微型结构降解不会导致疲劳失败。然而，它影响了在很大程度上向混凝土供应的碱的运输机制。液体在tp1下损伤的样本中的渗透行为将通过在压力和毛细管中评估水吸收的评估来确定。因此，根据预损伤程度，可以评估对液体/碱的渗透的影响，以验证数值模型。 Fur-ther，将在修饰的迁移细胞中评估asrevant Na-ions的穿透行为。超卷轮胎对外部提供碱的穿透行为的影响也将在亚项目tp1中进行实验评估。因此，未污损的和预损害的混凝土梁将被装载的轮胎覆盖；同时在表面上应用了NaCl-solution。在所需的超卷中数量后，将评估碱的穿透深度。因此，可以定义预损伤程度与穿透深度之间的直接相关性。结论性地，所获得的样品样品将存储在发动ASR的环境中，并且将根据降解和外部碱供应量来评估ASR-strain-poditials。在第一个资金期间，重点放在有关循环载荷引起的降解和液体穿透行为引起的降解的研究。在第二个融资期间，特别是通过过度滚动轮胎和最终评估由此产生的ASR的外部提供的碱的渗透。通过评估子项目TP4（3D-CT，LIBS），TP5（KWL）和TP6（机电参数）中的其他参数，TP1中获得的结果将得到补充。此外，通过TP1的实验获得的结果，将验证来自子项目TP3和TP6的相应数值模型。