The performance of zinc anodes embedded in mortar enhanced with lithium chemicals was studied in laboratory test blocks, larger test slabs, and a demonstration field trial. Environments studied included an indoor setting at 55% and 80% relative humidity, an outdoor setting in northeast Ohio, and a parking garage field site.

All tests indicated that use of a combination of lithium nitrate (LiNO3) and lithium bromide (LiBr) resulted in the best performance. This combination of chemicals resulted in protective currents of about 0.2 mA/ft2 (2 mA/m2) for periods in excess of 2 years. Lithium hydroxide (LiOH) was relatively ineffective as an enhancing agent. Tests on larger slabs indicated that epoxy-coating of the reinforcing steel in the immediate vicinity of the anodes was useful for directing protective current outside the patch to areas of greater risk, and for extending the service life of the zinc anodes. Proper spacing of the zinc anodes ranged from 12 to 40 inches (30-100 cm) depending on conditions such as chloride content and steel density. It was demonstrated in a field trial that properly constructed and placed zinc anodes could deliver sufficient protective current to meet NACE 100-mV criterion in the area immediately surrounding the patch.

It was concluded from these results that this technology has the capability to mitigate the “anode ring effect” and significantly extend the service life of concrete patch repair.

Subject
Electric current, Concrete repair, Anodic protection, Cathodic protection, Rebar, Zinc anodes, Slabs, Lithium, Anodic current, Steel, Electric potential, Half cell potential, Concrete
Keywords:
anodes, cathodic protection, concrete, concrete patch repair, corrosion, lithium chemicals, reinforcing steel, zinc
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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