In-situ testing of near-surface concrete - the foundation for service life prediction

摘要

Assessing the quality of concrete using indirect strength and workability testing has the advantage of being convenient and well-accepted but has been found to be largely unrelated to the durability of concrete. In-situ strength testing, whilst useful in assessing the variations in strength which occur on site, needs to be complemented by permeability testing in order to give a much better measure of the likely durability. Based on an holistic model relating permeability to durability the experience gained from the use of the 'Autoclam' permeability test, which is convenient and easy to use on site as well as in the laboratory, is presented. Details are included of a laboratory study correlating the Autoclam permeation properties with the results of carbonation and freeze-thaw tests. In addition, the results of a field study on a motorway bridge are given. It is concluded that in-situ permeability and strength testing can be used to develop durability-based design criteria for concrete and to assess the remaining life of existing structures.