Properties of concrete intended for further testing measured by the Impact-Echo and the ultrasonic pulse method

O Karel,P Schmid,I Rozsypalova,R Dvorak

doi:10.1088/1757-899x/385/1/012025

Abstract

The aim of the paper is non-destructive measurement of differently degraded specimens by high temperature intended for further testing of joints of stainless steel helical reinforcement glued into the groove and differently degraded concrete. Measurement intended for determination of possibilities of estimation of future properties of named joints is performed by the Impact-Echo method and by the ultrasonic pulse velocity method on specimens of dimensions 400 × 100 × 100 mm made of concrete of the C20/25 strength class degraded by different elevated temperature. Five sets of specimens were manufactured - four sets of specimens were heated in the furnace at temperatures of 400 °C, 600 °C, 800 °C and 1000 °C and one set was kept intact as reference. Specimens will be afterwards additionally strengthened at the tensile side of specimens and broken by four-point flexural strength test. The non-destructive measurement aims to evaluate the residual physical-mechanical properties of plain concrete in terms of resonance frequency of test specimen, and sound velocity in tested specimen before and after the temperature degradation. This assessment will serve as material information basis for interpretation of the expected behaviour of used helical reinforcement for a retrofitting process and the thermally damaged concrete reaction to such intervention.

Highlights

Due to economical and serviceability demands on structures either in housing or industry buildings, a building structures damaged by fire is more often rehabilitated by retrofitting methods
Presented paper focus on the inspection process of thermally degraded concrete before the application of retrofitting tool – in this case a stainless steel helical reinforcement glued into groove in tensile area of test specimen
The recorded signal is converted by Fast Fourier Transform [11] into a spectrum that can be analyzed

Summary

Introduction

Due to economical and serviceability demands on structures either in housing or industry buildings, a building structures damaged by fire is more often rehabilitated by retrofitting methods. There are many possible approaches and tools to strengthen, retrofit and repair the damaged elements such as partial replacement of structure elements, concrete or steel jacketing and retrofitting of structural members by fiber reinforced polymers (FRP) or stainless steel helical reinforcement [1]. Presented paper focus on the inspection process of thermally degraded concrete before the application of retrofitting tool – in this case a stainless steel helical reinforcement glued into groove in tensile area of test specimen. The inspection process in relation to retrofitting by this reinforcement is not described yet. This kind of additional reinforcement is made of high strength (800 – 1300 MPa depending on type and manufacturer) stainless steel which is twisted due to better cohesion with mortar used to bond reinforcement with basic material. Its cross-section ensures that even if it is able to carry a large load the worker is still able to bend it by hands to desired shape – this advantage is very useful for structure retrofitting [2]

Objectives

Methods

Results

Conclusion