BD43/90 (1990) ‘Criteria and material for the impregnation of concrete highway structures’ was published by the Highways Agency (HA) in 1990. This document specified the requirements for new HA structures to be treated with hydrophobic pore-lining impregnants to provide protection against the ingress of de-icing salts. There was also a requirement to apply impregnants to all in-service structures provided that their condition was suitable.
Since 1990 it has been assumed that all new bridges have been treated and that the maintaining agents responsible have implemented the policy of treating in-service bridges. The HA commissioned TRL to carry out a survey of the 14 maintaining agents in England to assess the extent and effectiveness of treating bridges which have been constructed since 1990 and the older in-service bridges. The survey involved inviting the maintaining agents to complete questionnaires designed to yield information on the number of new and in-service bridges that had been treated and seek their opinions on the effectiveness of the policy.
Within the scope of the project, it was only possible to obtain detailed information from two maintaining agents. The results from one of the agents showed that over 90% of the post-1990 structures had been treated compared with 30% for the pre-1990 structures. Information from the other agent showed that some of their pre-1990 structures had been treated. No information was supplied for the post-1990 structures.
The results from the survey have highlighted the limitations in the current record keeping of impregnation and associated monitoring. It is considered that it would be highly desirable for HA to set up a system which requires maintaining agents and authorities responsible for new construction to record information on impregnation to assist with planning future maintenance strategies. The information should be in a form that can be easily entered into the Highways Agency Database (SMIS).

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