Petr Lehner

Investigation of Fracture and Electrical Resistivity Parameters of Cementitious Composite for their Utilization in Deterioration Models

The paper is focusing on the investigation of the effective crack length obtained from bending test on concrete notched beams with the complementary measurements of electrical resistivity of the tested concrete. The electrical resistivity measurements are performed on several stages of the fracture process along the specimen ligament for each tested notched beam. Gained results of the concrete resistivity during the fracture process, i.e. its dependence on the crack length or opening, provide information which should be taken into account in structural durability analyses. The fracture tests are conducted for a set of specimens differing in the notch length. Changes of the concrete resistivity with increasing effective crack length are observed and discussed.

Variation of Diffusion Coefficient for Selected Binary and Ternary Concrete Mixtures Considering Concrete Aging Effect

The paper deals with the variation of resistance of selected High Performance Concrete (HPC) materials against chloride ion penetration. The resistance of chloride penetration is described by means of the diffusion coefficient and it is derived from emerging non-destructive tests. It is computed from the measurements of surface electrical resistivity (see e.g. AASTHTO TP-95 specification) data. The effect of concrete aging on the diffusion coefficient is taken into account as the concrete properties are time dependent and it is significantly important for High Performance Concrete (HPC) materials.

Analysis of Durability of High Performance and Ordinary Concrete Mixtures with Respect to Chlorides

The paper is focused on the evaluation of chloride ingress considering high performance and ordinary concrete mixtures. The effect of concrete maturing is investigated as well. The selected laboratory measurements are used for the description of resistance of concrete against ingress of chlorides. The Finite Element-based numerical model is applied in order to evaluate the effect of concrete type as well as the effect of aging.

Stochastic analysis for short edge cracks under selected loads

The article is focused on the exploration of fatigue damage to bridges and steel structures subjected to cyclic loading. Computational model is focused on fatigue crack propagating from the surface and it is based on linear elastic fracture mechanics utilizing the Paris-Erdogan’s law. The behavior of the carrier element susceptible to fatigue damage is experimentally investigated on specimens with various types of load and it is expressed by a calibration function. For the prediction of fatigue damage over time, calibration functions for short edge cracks were derived based on the results of the experiment, and the acceptable size of the fatigue crack in damaged structural component under analysis was determined. Using the derived relationships, a stochastic analysis of the selected element was performed and the results are discussed.The article is focused on the exploration of fatigue damage to bridges and steel structures subjected to cyclic loading. Computational model is focused on fatigue crack propagating from the surface and it is based on linear elastic fracture mechanics utilizing the Paris-Erdogan’s law. The behavior of the carrier element susceptible to fatigue damage is experimentally investigated on specimens with various types of load and it is expressed by a calibration function. For the prediction of fatigue damage over time, calibration functions for short edge cracks were derived based on the results of the experiment, and the acceptable size of the fatigue crack in damaged structural component under analysis was determined. Using the derived relationships, a stochastic analysis of the selected element was performed and the results are discussed.

Experimental and numerical evaluation of SCC concrete durability related to ingress of chlorides

The article focuses on the sample chloride ingress induced corrosion initiation evaluation of the traditional and self-compacting concrete. Surface electrical resistivity measurements is used as material parameter related to the diffusion coefficient. The presented calculations and results are part of a campaign that includes also steel fibers reinforced concrete however the effect of fibers is not covered herein due to long term experiments. The input parameters for the time-dependent diffusion coefficient model are presented. The time to onset of corrosion including the effect of delay of chloride concentration load and the aging effect is evaluated.

Influence of the Extent of Fracture on the Resistance against Chloride Penetration into Cementitious Composite

The paper presents data obtained in own experimental campaign focused on the investigation of the effect of fracture propagation on the change in values of electrical resistivity and ultrasound pulse passing time in notched beam specimens. Test geometry of three-point bending was utilized to propagate the crack through the specimen ligament in several loading−unloading cycles, between which the electrical resistivity and ultrasonic measurements over the fractured region in the centre of the beam were performed. Equivalent elastic crack length was estimated at those loading stages. Relationships among the changes in the investigated, non-destructively gained parameters, the effective crack length and the distance from crack tip are discussed with respect to two variants of treatment of the specimens’ surface during testing: the pre-dried and the wet one.