Project Details
Projekt
Externer Alkalieintrag in mechanisch/thermisch vorgeschädigtes Betongefüge
Applicant
Professor Dr.-Ing. Rolf Breitenbücher
Subject Area
Construction Material Sciences, Chemistry, Building Physics
Structural Engineering, Building Informatics and Construction Operation
Structural Engineering, Building Informatics and Construction Operation
Term
from 2011 to 2020
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 165295427
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.
DFG Programme
Research Units
