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.

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.

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.

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.

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.