详情

RES2013-18: Lightweight Concrete for Tennessee Bridge Decks

项目名称：	RES2013-18: Lightweight Concrete for Tennessee Bridge Decks
摘要：	The major focus of the research performed on the project described in this Final Report was directed toward learning more about the effective use of a ternary blend mix for lightweight concrete, including the identification of an surface resistivity (SR) value that could be reasonably chosen as a lower limit expectation for bridge deck concrete. Based on available literature, the choice of expanded slate as the lightweight coarse aggregate, rather than expanded shale or expanded clay is a sound one. However, there are some special considerations that affect the use of lightweight concrete (LWC) and which have some influence on any chosen acceptance criteria. Based both on research reported in available literature and experience on this project, one can argue that proper aggregate saturation is the primary quality control concern for LWC. The positive effect of internal curing only occurs with properly saturated aggregate. Poorly saturated aggregate leads to difficulty in pumping. One motivating objective of this project was to identify a reasonable minimum SR value to specify for mix designs to achieve an adequate resistance to chloride ion penetration. Work to accomplish this objective evolved into a study of the effects several variables have on Surface Resistivity. However, the surprising discovery of the large effect that cement brand had on the test results, coupled with the differences between lab and field mixes, made the specification of a lower bound SR value essentially impossible. The report also found that shrinkage of properly saturated lightweight concrete is not appreciably different from that of normal weight concrete. The inspection of five bridge decks indicated only minor cracking but raised potential concerns because of one difference between lightweight and normal weight aggregates. Lightweight aggregate tends to float closer to the top than normal weight, a phenomenon which is particularly exacerbated by improper aggregate saturation. The grinding exposes the lightweight aggregate near the surface which is then ground smooth. This aggregate exposure is a potential issue for porous aggregate as the pore connectivity potentially allows some chloride ion penetration into the deck. Whether or not this is a problem was not reviewed as part of this report.
状态：	Completed
资金：	179713
资助组织：	Tennessee Department of Transportation
执行机构：	University of Tennessee, Knoxville
开始时间：	20130801
预计完成日期：	20150801
主题领域：	Bridges and other structures；Materials；Pavements