Statistical view of evaluating concrete-surface-layer permeability tests in connection with changes in concrete formula

Hrubý

Topolář

et al. 2021

SSP

The paper summarizes partial results of a study of degradation of materials based on alkali-activated blast-furnace slag (AAS) and comparative on cement CEM III/A 32.5 R after exposure to aggressive environments. It further specifies the possibilities for utilising destructive and non-destructive techniques to determine the progress of degradation and characterizes the degree of their correlation. After 28 days of ageing in a water environment, the produced test specimens (40×40×160 mm beams) were placed in aggressive media (ammonium nitrate solutions; sodium sulfate, rotating water) and after subsequent 28, 56 and 84 days of degradation were subjected to testing. Testing comprised both a destructive form (determination of compressive strength and flexural strength) and a selected non-destructive technique (Impact-echo method). The partial outputs were supplemented by the results acquired from monitoring weight changes. In addition, the development of Ultrasonic Pulse Velocity in relation to the progress of the degradation processes was also monitored. While the exposure of both test specimens to water and sodium sulfate did not result in any significant changes, the exposure to the ammonium nitrate solution exhibited rapid signs of degradation associated with a significant reduction in functional characteristics.

Section: Testing Methodsmentioning

confidence: 99%

Degradation of Materials Based on Alkali-Activated Blast-Furnace Slag after Exposure to Aggressive Environments

Hrubý

Topolář

et al. 2021

SSP

“…Or, the so-called pulse-echo method, reflects from the end wall of the object under investigation and goes backwards, and if there is some reflection in addition to the end echo, it indicates that there has been some anomaly. Where the ultrasound is bounced, the defect is located [9,10].…”

Section: Introductionmentioning

confidence: 99%

Detection of Reinforced Concrete Thermal Damage by Nonlinear Ultrasonic Spectroscopy

Matysík

Chobola

2019

SSP

Nonlinear Ultrasonic Spectroscopy (NUS) methods investigates nonlinear phenomena that occur when the sound or ultrasound waves pass through the material. This paper focuses on the use of these methods for nondestructive testing of reinforced concrete damaged by high temperature. For this research, reinforced concrete beams with one steel rod were made and the NUS measuring equipment was assembled. An appropriate nonlinear parameter was selected to assess the damage. The nonlinear behavior of thermally damaged reinforced concrete was manifested by the deformation of ultrasound waves passing through the measured samples, resulting in nonlinear effects in the frequency spectra of the recorded signal.

“…One of the promising nondestructive methods for monitoring concrete damage is nonlinear acoustic spectroscopy. It has great potential in the field of concrete defectoscopy [4]. Methods based on nonlinear acoustic spectroscopy are based on the effects that arise when the elastic waves passes through material.…”

Section: Introductionmentioning

confidence: 99%

The Possibility of Using Nonlinear Acoustic Spectroscopy with a Single Excitation Signal for Testing of Concrete Elements Damaged by High Temperature

Matysík

Chobola

2019

KEM

This paper focuses on the use of nonlinear acoustic spectroscopy with one excitation signal for NDT of concrete parts exposed to high temperature. The rate of the temperature rise, the highest achieved temperature, time of exposure to elevated temperature and the cooling rate has an influence on the overall damage of concrete structures affected by fire. The test specimens described in this paper have been heated for various periods of time and at a different temperature. Nonlinear acoustic spectroscopy method was performed before and after heat load.