Although it has long been accepted that the spalling of concrete from corroded reinforcing bars occurs as a result of the pressure generated because the volume of rust produced is so much larger than the volume of metal which is dissolved, there have been few previous attempts to develop this model quantitatively. Apparatus has therefore been set up to determine the pressure which is necessary to cause spalling to take place. This consists of a concrete encased reinforcing bar with a void at the steel/concrete interface which simulates an active anodic area. This void may be pressurized by means of hydraulic oil which can be pumped through the centre of the bar and the pressure required to cause spalling determined. From the results which have been obtained it is suggested that the onset of cracking from the concrete/steel interface is not controlled by the strength of the concrete but by the fracture surface energy. Although the fracture surface energy of a brittle material such as concrete is normally very low, multiple cracking and crack branching may cause the effective fracture surface energy to be much larger than might otherwise be expected.

Subject
Compressive strength, Rebar, Corrosion cracking, Stress cracking, Flaws, Mechanical failure, Interfaces, Hydraulic equipment, Tensile strength, Cracking, Cracks, Concrete, Reinforcement
© 1989 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1989
Association for Materials Protection and Performance (AMPP)
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