Research Agenda for Test Methods and Models to Simulate the Accelerated Aging of Infrastructure Materials: Report of a Workshop by Board on Infrastructure & the Constructed Environment

Author:Board on Infrastructure & the Constructed Environment
Language: eng
Format: epub
Tags: Engineering and Technology : Materials
Publisher: NATIONAL ACADEMY PRESS
Published: 1999-07-06T00:00:00+00:00

The defining conditions for a good structure, Hanson said, are adequate strength, acceptable serviceability, and long-term durability. Mechanical response factors, (i.e. load resistance, stability, fatigue resistance, and fracture resistance) must be addressed to ensure structural integrity.

According to Professor Hanson, the mechanisms of deterioration of the primary construction materials (i.e., concrete, steel, masonry, and timber) are quite well known, at least at the level required of an engineer. Concrete materials, as well as masonry materials, may be subject to scaling due to freezing and thawing, chemical attack, alkali-silica reaction, and corrosion of embedded reinforcements. The deterioration of structural steels is mainly due to corrosion, and the deterioration of timber is due mainly to decay. The rate of deterioration (i.e., durability) is greatly affected by environmental factors, as well as the details of construction. However, our understanding of these mechanisms is currently not sufficient to enable us to make quantitative life predictions. Additional research to enhance understanding of the basic mechanisms is critical to improving the durability of materials and structures.

Professor Hanson emphasized however, that reviews of many infrastructure failures have shown that very few occurred because of deterioration, except when the structure or system had an underlying design or construction defect. Some forms of deterioration seem to slow down or even stop after a period of time. Thus, the deterioration of a material or structure does not necessarily affect safety (See, for example, NRC, 1997 and Levy and Salvadori, 1992). Proper maintenance can prolong the life of materials by slowing their rate of deterioration.

Professor Hanson concluded his presentation by stating that, although the development of a concrete that does not shrink or creep or a steel that does not corrode would be of great benefit to the construction industry, the likelihood of such a material being developed is considered to be very small. Of course, advancements have been, and continue to be, made, but accurate tests for assessing the effects of environmental conditions on their lifetimes will require a much better fundamental understanding of the damage process before they can test results could be used for making life predictions. The adoption of these materials will also depend on their economic advantage in a highly competitive market. Thus, Hanson believes that the lifetimes of structures are more likely to be extended by improvements in the quality of construction, than the use of new materials.

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