NDT of Mechanical Damaged Concrete Specimens by Nonlinear Acoustic Spectroscopy Method

Dvořák

Pazdera

2017

MSF

One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The concrete structural components still must be able to withstand dead and live loads without collapse even though the rise in temperature causes a decrease in the strength and modulus of elasticity for concrete and steel reinforcement. In addition, fully developed fires cause expansion of structural components and the resulting stresses and strains must be resisted. This paper reports the results of measurements by Acoustic Emission method during three-point bending test on concrete specimens. The Acoustic emission method is a non-destructive technique used widely for structural health monitoring purposes of structures. The sensors are mounted by beeswax on the surface of the material or structure to record the motion of the surface under the elastic excitation of the cracking sources. The concrete specimens were heated in a programmable laboratory furnace at a heating rate of 5 °C/min. The specimens were loaded at six temperatures, 200 °C, 400 °C, 600 °C, 800 °C, 1000 °C, and 1200 °C maintained for 60 minutes. The results are obtained in the laboratory.

Section: Discussionmentioning

confidence: 99%

The Assessment of High-Temperature Degraded Concrete Specimens of Different Mixtures by Acoustic Emission Method during Three-Point Bending Test and Pulse Velocity Method in Comparison with Destructive Tests

Dvořák

Pazdera

2017

MSF

“…1). Acoustic emission signals were taken by measuring equipment DAKEL XEDO with six acoustic emission sensors MTPA-15 with preamplifier 35 dB [10]. Table 1 introduces the composition and designation of selected mixtures evaluated in this paper.…”

Section: Methodsmentioning

confidence: 99%

“…Detection sensitivity can be increased by using waveguide. The typically case in civil engineering is the location of a waveguide into the prepared hole in wood or concrete [9,10].…”

Section: Introductionmentioning

confidence: 99%

Applying Method of Acoustic Emission for Monitoring of Different Concrete Mixture during Setting and Hardening

Misák

Kocáb

et al. 2016

SSP

Non Destructive Testing is a powerful tool for determination of properties, durability and lifetime of concrete structures. Acoustic Emission Method is an unusual technique which describes only active defects or changes into structure arising as a consequence dangerous tension into structure. The method is appropriate to be used in homogenous structures as metal structures when cracks are highly active (generates sound). Its application in civil engineering is not so much used because building structures are inhomogeneous. This article shows possible application of Acoustic Emission Method for monitoring of concrete structure changes during its lifetime. The main aim of the article is to show the application of Acoustic Emission Method during the early age to 28 days after mixing. It is believed that early age of concrete structure is very important for its quality. Common concrete cube specimens have been tested after the production by Acoustic Emission Method with using waveguides. The results of acoustic emission method will be compared to classical parameters of fresh concrete e.g. the value water-cement ratio, air void content measured by different methods (pressure methods, AVA) and similar. In the results will be compared four mixtures when two mixtures were aerated and two mixtures were without aeration.

“…Analysis of the obtained data assumes Fourier transform of obtained signal to the frequency spectrum. The aim is to determine dominant frequencies [7,8,9].…”

Section: Impact-echomentioning

confidence: 99%

NDT Monitoring of Alkali-Activated Material Carbonation

Plšková

Matysík

et al. 2020

KEM

Production of Portland cement is relatively environmentally demanding (high CO2 emissions, extraction of raw materials for its production). Alkali-activated materials are an alternative to conventional Portland cement in the production of concrete. For alkali-activated binder concretes, their ability to withstand corrosive environments and their ability to protect steel reinforcement must be assessed. It is also necessary to know the suitability of non-destructive methods for monitoring the degradation process of these concretes. The paper deals with the carbonation monitoring of concrete with alkali-activated binder (slag) by the impact-echo method. Slag activated by sodium hydroxide (NaOH) was used as a binder. The specimens were tested by the non-destructive method (Impact-echo, ultrasound velocity). We focused on the shift of the dominant frequency obtained by the Impact-echo method.