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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 12 Abstracts search results
March 1, 2004
T. R. Naik, R. N. Kraus, Y. Chun, and R. Siddique
Three series of flowable slurry mixtures were made, each series with three different sources of wood ash (W-1, W-2, and W-3). The series of mixtures were: low-strength (0.3 to 0.7 MPa), medium-strength (0.7 to 3.5 MPa), and high-strength (3.5 to 8 MPa) mixtures. Tests were performed for flow, air content, unit weight, bleeding, settlement, compressive strength, and water permeability. Wood ashes W-1 and W-3 caused expansive reactions in CLSM mixtures resulting in little or slight (average 1%) net shrinkage of CLSM. Wood ash W-2 caused either significant net swelling (15% for Mixture 2-L, and 21% for Mixture 2-M) or no shrinkage (Mixture 2-H) of CLSM. The 91-day compressive strength of low-strength, medium-strength, and high-strength slurry mixtures was in the ranges of 0.38 to 0.97 MPa, 1.59 to 5.28 MPa, and 4.00 to 8.62 MPa, respectively. Overall, the slurry mixtures showed an average increase in strength of 150% (range: 25% to 450%) between the ages of 28 days and 91 days. This was attributed to pozzolanic and cementitious reactions of wood ash. In general, water permeability of CLSM mixtures decreased with age.
C. Meyer and S. Shimanovich
Secondary markets for waste glass have been widely developed in Europe. In the United States, on the other hand, most post-consumer glass is still being land-filled, primarily because it is mixed-color. Also, the need to clean the often highly contaminated glass constitutes a barrier against its beneficial use. For several years, an ongoing research effort at Columbia University has explored the potential of waste glass as an aggregate for concrete. The primary technical problem, caused by alkali-silica reaction, can be solved with existing means. The economics of beneficiating recycled glass in large urban areas such as New York City constitutes a more formidable barrier, because the standard aggregate that the glass would replace, whether sand or gravel, is relatively inexpensive. However, if the esthetic potential of color-sorted glass is exploited fully, the economic picture changes, and glass processors are more likely to create the link between curbside collection and concrete producer. A number of architectural concrete applications have been explored to date, and design professionals and developers have shown keen interest in adding high-quality concrete products to their palette of options. Some of these are already produced commercially. By developing a promising secondary market for recycled glass as a value-added component of architectural concrete, it is possible to offer the concrete industry new directions to shed its image of being environmentally unfriendly and to actively embrace the principles of sustainable development.
This paper addresses first the generation of construction waste in Japan, the extent of recycling, and the shortage of landfill capacity. Second, it chronicles the trend of recycling concrete rubble from 1970 until today. Third, it discusses methods of manufacturing recycled concrete aggregate and introduces the recently developed equipment and methods to produce good aggregate for concrete. Fourth, the problems associated with the use of recycled concrete aggregate are mentioned. Also, the utilization of concrete fines, eco-concrete, and slurries from ready-mix concrete plants are addressed. Land in Japan is very scarce and resources limited. These conditions are similar to those faced by Europeans and Scandinavians. Therefore, this paper should be of interest to those countries and their efforts to build closed-loop material cycles.
H. C. Scott IV and D. L. Gress
This study investigated the reactivity of concrete containing recycled concrete aggregates (RCA) that had shown distress due to alkali silica reaction (ASR). The investigation evaluated several mitigation techniques to control ASR in concrete containing potentially reactive RCA. Mitigation work was done with three different aggregate types; an igneous fine-grained quartzite aggregate locally called blue rock, a non-reactive limestone, and RCA containing blue rock aggregate. These aggregates were used to investigate various mitigation techniques to prevent ASR from occurring in concrete containing RCA. The mitigation strategies include the use of class F fly ash, ground granulated blast furnace slag (GGBFS), lithium nitrate, silica fume blended cement and low alkali cement. These materials were incorporated into concrete mixes by cement substitution and direct application. These mitigation strategies showed potential in controlling ASR distress in RCA concrete. Mortar bars and concrete prisms were used to investigate the mitigation strategies by following standard and modified versions of ASTM C 1260 and ASTM C 1293 specifications to evaluate expansion caused by ASR. The modified versions of ASTM C 1260 were found effective in evaluating potential ASR expansion using conventional aggregates.
J. S. Melton
Recycled concrete aggregate (RCA), when used appropriately, is an excellent substitute for natural aggregates in highway construction. RCA has been used successfully in unbound applications such as base course and fill, and in bound applications as aggregate in new concrete. However, a significant amount of concrete debris is still disposed of in landfills. Barriers to concrete recycling include regulatory and policy issues, economic disincentives, environmental concerns and technical questions. This paper reviews current obstacles to concrete recycling and discusses recent developments and research that will help overcome these barriers.
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