International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 12 Abstracts search results

Document: 

SP92-11

Date: 

June 1, 1986

Author(s):

A. Lammke

Publication:

Special Publication

Volume:

92

Abstract:

After actual fires with plastic materials involved concrete surfaces are often infested with high chloride concentrations, causing a serious risk of corrosion of the reinforcement. Absorption techniques with lime paste have been recommended to remove chlorides from concrete surfaces. To study this reaction concrete beams with different chloride contents, added as sodium chloride, were cast. The chloride distribution in the concrete before and after lime paste treatment and the chloride content of the used lime were determined analytically. The results show that the lime does not absorb chlorides, and within the concrete, the chlorides are redistributed. Further tests were made to study the rate of chloride absorption from aqueous solutions by lime, acti-vated carbon and ion exchange resins. The amount of absorbed chloride was very low. Corresponding the absorption of chlorides by fresh pastes of different cements and completely hydrated cements was studied. An effect of absorption but much more of chemical bond was shown.

10.14359/6519


Document: 

SP92-10

Date: 

June 1, 1986

Author(s):

P. J. E. Sullivan and G. A. Khoury

Publication:

Special Publication

Volume:

92

Abstract:

Generalised response curves for the transient thermal strain behaviour of concrete have been developed from a series of tests employing a wide range of materials and a lower than normal heating , rate. The latter allowed detailed assessment of underlying "material" behaviour to be made which was not complicated by "structural" effects that develop at a fast heating rate. The temperature, stress and moisture conditions within a cylindrical test specimen have been investigated and a study of the behaviour of individual constituents has confirmed that aggregate thermal stability is a critical factor. Thermal strains during virgin heating were separated into "Free" and "Load Induced" components possessing different and distinct properties allowing successful prediction of residual strains. A master with te m first h analysis the mast While t effect 0 clearly sensitiv thermal curve connecting Load Induced perature up to 450°C was found eating for different concretes of heated concrete structures er curve signified onset of c ransient creep did not occur duringf cracking caused bv thermal inc evident. Strain measurements, the indicators cycle. of damage taking Thermal Strain to exist during thus simplifying Departure from concrete damage. ing cooling, the ompatibility was harefore, proved place during the

10.14359/6518


Document: 

SP92-09

Date: 

June 1, 1986

Author(s):

T T. Lie, T. J. Rowe, and T. D. Lin

Publication:

Special Publication

Volume:

92

Abstract:

A study was carried out to assess the residual strength of reinforced concrete columns after exposure to a standard fire for various lengths of time, and cooling. The use of a mathematical model, an ultrasonic pulse test method and a load test method are investigated. Calculated temperatures and residual strengths of test columns were compared with those measured. Comparisons were also made between calculated and measured pulse velocities. The results indicated that using the calculation procedure and the method of measuring pulse velocity described in the study, the residual strength of concrete columns can be assessed with an accuracy sufficient for practical purposes.

10.14359/6517


Document: 

SP92-08

Date: 

June 1, 1986

Author(s):

K. D. Hertz

Publication:

Special Publication

Volume:

92

Abstract:

The paper describes a new technique developed by the author for heating concrete rapidly by application of microwave power. Using an appropriate thermal insulation it is found to be possible to heat dry concrete specimens 10°C per minute and 20°C per minute avoiding the development of thermal stresses within the specimens. A series of 90 specimens has been heated 10°C per minute to various maximum temperature levels. The residual compressive strength was measured, and the results are compared to the similar results of the same concrete heated slowly. Applications for the technique are outlined, and a possible future development; is presented.

10.14359/6516


Document: 

SP92-07

Date: 

June 1, 1986

Author(s):

L. Krampf and A. Haksever

Publication:

Special Publication

Volume:

92

Abstract:

The present paper is intended to give an overall information on temperatures which may have occured in concrete cross-sections affected by a fire Firstly the paper contains a catalogue of circumstances and vestiges which can be found when the affected building is visited and which allow conclusions concerning the intensity of the fire and the resulting value of damages to the structural elements. For this purpose, residual contents of the building (fire load), the state of building materials, and the evident condition of the concrete structure itself are used. In the second part of the paper, general informations are given on the development of natural fires and on the parameters which in-fluence it. On the basis of two series of experiments - Metz and Lehrte - which gave temperature-time developments in compartments where wood cribs or furniture were burnt, temperature fields are presented for square concrete cross-sections affected from all sides, and for T-shaped sections affected from three sides. It is stated that the presented figures can only be rough approaches for practical work. Short, only introductory informations on residual changes of material properties due to temperature influences are added to facili-tate judgements and decisions. It stands to reason that, if findings won by this guide lead to the conclusion that the structure may be worthy to be kept, more intense and detailed investigations have to be done.

10.14359/6515


Document: 

SP92-06

Date: 

June 1, 1986

Author(s):

K. Kordina, W. Wydra, and C. Ehm

Publication:

Special Publication

Volume:

92

Abstract:

Experiments were carried out ith measurements of the total defo ission in order to investigate the evelopment and deformation behavio y temperature conditions.S purpose specimens were loaded wi th different stress le- on normal concrete specirmation and of the acou-correlation between ur of concrete during vels and heated up to maximum temperatures between 150 "C and 750 OC. After a holding period the specimens were cooled under load. The creep deformations showed strongly increasing rates at about 450 OC during heating and at the beginning of the cooling phase. , In the heating phase the activity of acoustic emissions increased considerably. During the holding period no remarkable activity e observed. A new increase of the acoustic activity could rly observed at the beginning of the cooling phase. rmal concrete specimen, the main a.ctivity in the damaging occurs during unsteady temperature conditions, and is nt on the maximum temperature reac hed. parison between acoustic emission activity and creep de-formations shows that the acoustic emission activities are high at e time that creep deformations areI high.

10.14359/6514


Document: 

SP92-05

Date: 

June 1, 1986

Author(s):

Richard A. Muenow and Melvin S. Abrams

Publication:

Special Publication

Volume:

92

Abstract:

Evaluation of fire-damaged concrete has been made using field-applicable test techniques which are valuable but limited. With the advent of reliable non-destructive testing methods, a much more comprehensive assessment of damage is available. The objective of this paper is to present. information on Pulse-Echo, magnetic and microwave testing techniques. Pulse-Echo non-destructive testing can be conducted on insitu concrete for: measuring thickness of damaged concrete assessing bond loss between concrete and reinforcing steel detecting internal cracks and their orientation determining degree and extent of cement matrix microcracking estimating insitu concrete compressive strength Accompanying the Pulse-Echo method are steel reinforcement location techniques that involve microwave and magnetic principles. These tests can determine remaining concrete cover and additional data for engineering the required repairs. Of equal importance to the assessment of damage is the evaluation of the performed repairs to determine that the repairs satisfy all the structural requirements of the original specifications.

10.14359/6513


Document: 

SP92-04

Date: 

June 1, 1986

Author(s):

A. K. Tovey

Publication:

Special Publication

Volume:

92

Abstract:

The purpose of this paper is to outline some of the proposed changes to the Concrete Society Technical Report 15 which is the most comprehensive UK document dealing with assessment and repair of fire-damaged concrete structures. The publication is being updated to take into account changes of practice and methods of assessment since 1978. Repair techniques other than Gunite are to be included with particular comment in respect to resin repairs.

10.14359/6512


Document: 

SP92-03

Date: 

June 1, 1986

Author(s):

Peter Smith

Publication:

Special Publication

Volume:

92

Abstract:

A major three span highway bridge in Southern Ontario was 1nvYived in a construction fire while it was being widened 25 years ago. Concrete, ranging in age from 6 days to 20 years, in an abutment, the adjacent arch rings and spandrel columns was severely damaged. The structure is now revisited to assess the long term performance of the remedial works and to consider whether the investigation and repairs might have taken a different course if today's testing, analytical and repair techniques had been available then. The strengthening of the damaged arch springings and the shotcrete restored concrete sections exposed to a harsh environment have stood the test of time. The review of investigative and repair methods identifies advances made in recent years, and justifies long term confidence in o'lder procedures which are still in use.

10.14359/6511


Document: 

SP92-02

Date: 

June 1, 1986

Author(s):

M. Diaz-Llanos, V. Sanchez Velasco, and I. Cerezo Preysler

Publication:

Special Publication

Volume:

92

Abstract:

In some cases, it is necessary to evaluate and document structures which were subjected to fires during construction. Due to the lack of official regulations on the subject, the analyses and documentation on these incidences, when reported to the regulatory authorities, implied unconventional activities, both for the utility and the A/E. The paper describes several fires affecting nuclear power plant concrete structures. They were all caused by inadvertent human actions. The presence of highly combustible auxiliary cons-truction materials contributed to their propagation. It is recommended that the cost (purchase and installation) of these auxiliary materials be evaluated against the use of alter nate (noncombustible)ones before making any decision, sufficiently in advance to avoid costly and time-consuming changes that may affect a usually tight schedule. As a result of visual inspection, followed by "in situ" and laboratory tests and engineering analyses of the affected elements, some elements had to be demolished and reconstructed while others were found to be acceptable.

10.14359/6510


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