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International Concrete Abstracts Portal

Showing 1-5 of 17 Abstracts search results

Document: 

SP168-08

Date: 

April 1, 1997

Author(s):

N. A. Cumming and 0. S. Ooi

Publication:

Symposium Papers

Volume:

168

Abstract:

A major structural repair and strengthening program was undertaken at a large grain shipping terminal on Canada’s northwest coast. The work was required to correct problems of excessive cracking and internal delamination in the silo walls. During the repair work, it was necessary to survey 42 silos to locate zones of delaminated or deteriorated concrete. This was done successfully using the impact-echo procedure. This paper describes the impact-echo survey and its findings. It further discusses correlation of test results to actual conditions encountered in the field.

DOI:

10.14359/5955


Document: 

SP168-11

Date: 

April 1, 1997

Author(s):

M . Cl. A . T h o m a s , D . W i e s e , a n d H . Caratin

Publication:

Symposium Papers

Volume:

168

Abstract:

This paper describes the application of geophysical tomography and scientific visualization techniques for evaluating the internal condition of massive concrete structures. The resulting output is a three dimensional representation of the structure showing the spatial distribution of ultrasound data. As various aspects of ultrasound data (e.g. velocity and attenuation) are related to concrete quality, the location and orientation of areas of inferior material or discontinties can be identified. In addition, specific features within the image can be highlighted and quantified. Results are presented from a preliminary study carried out to assess the potential application of this technique for evtiating the internal condition of large concrete elements. A large concrete block was constructed with a number of internal defects such as cracks, areas of poorly compacted concrete and uncemented aggregate, and large voids. A large number of measurements (ultrasonic pulse velocity) were taken to provide a network of velocities across a section. Algebraic tomographic techniques were then applied to reconstruct a two dimensional image. By taking a series of contiguous sections and stacking them together, a three dimensional model of the sample or structure was then created. Finally the three dimensional data set was visualized using advanced graphics techniques such as vohune rendering. Overall, the initial results are promising, and indicate that the presence and location of internal defects can be determined

DOI:

10.14359/5942


Document: 

SP168-02

Date: 

April 1, 1997

Author(s):

Anthony B. SlatonBarker and John W. Wallace

Publication:

Symposium Papers

Volume:

168

Abstract:

The paper describes a study of reinforced concrete bridge decks that addresses the need for an accurate evaluation method that is not hindered by an asphalt cover or extensive operator experience. The use of two antennas for Subsurface Interface Radar (SIR) surveys allows for more accurate evaluations by reducing false readings that may be associated with the use of a single antenna. A more accurate determination of the amount of deterioration is also achieved, because the different frequency antennas will detect different types and severities of defects. To assess the use of dual frequency radar for evaluation of bridge decks, both laboratory studies and field studies were conducted. The results of the research indicate that false readings are reduced by using dual frequency radar such that bridge deck repair jobs can be prioritized. The added information on the extent of deterioration also allows more accurate predictions of the time, effort and money necessary for bridge deck rehabilitation.

DOI:

10.14359/5948


Document: 

SP168-06

Date: 

April 1, 1997

Author(s):

Jiunn-Ming Lin and Mary Sansalone

Publication:

Symposium Papers

Volume:

168

Abstract:

Dilatational or P-wave speed in concrete is needed in impact-echo testing if the dimensions of structural elements or the location of flaws is to be determined. Previously the P-wave speed had to be determined from cores or from performing a test on a portion of the structure having known dimensions and no flaws. In cases where neither approach was possible, an estimate had to be made of the wave speed. This paper presents the details of a method for independently determining P-wave speed in concrete using a Rayleigh-wave speed measurement between two points on the surface. Such a procedure increases the power, versatility, and ease of use of the impact-echo method. In this paper the Rayleigh wave speed procedure is explained. Systematic errors involved in the measurement procedure areexamined, and the accuracies that can be expected using the procedure in conjunction with the impact-echo test procedure are discussed. Appropriate uses of the procedure are given, and the limitations of the method are stated. It is shown that the Rayleigh wave technique is an easy to use technique for estimating wave speeds. Typically, speeds within about 4% of the actual wave speed can be obtained.

DOI:

10.14359/5953


Document: 

SP168-09

Date: 

April 1, 1997

Author(s):

Randall Poston and Mary Sansalone

Publication:

Symposium Papers

Volume:

168

Abstract:

This paper presents both a brief explanation of the impact response of bar-like structures and an application involving the use of the impact-echo method for detecting cracks in the beams and columns of a post-tensioned parking garage structure. The information gained from the impact-echo tests was used to aid in specifying repair measures for the structure. In the process of implementing repair measures, selected impact-echo results were verified. This field study was performed in 1991. This paper was presented at the AC1 Fall Convention in 1992.

DOI:

10.14359/5956


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