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It is essential that concrete structures should withstand the conditions for which it has been designed for long periods of time. The lack of durability may be caused either by the environment to which the concrete is exposed or by the concrete itself. In this study, the resistance to freezing and thawing of high-slag content concrete(HSC concrete), which is one of the external causes, have been discussed for the purpose of utilizing the ground granulated blast furnace slag (GGBS) as an ingredient of cement. The slag content in cement ranged from 0 to 9.5 % by weight of total cementitious materials and the fineness of slag was 816 m*/kg. The resistance of air entrained (AE) concrete with a slag content of 70% was superior or comparable to that of slag free concrete, whereas AE concretes have questionable performance in the case of slag content of 85%, and have less ability in the case of 95% slag content with respect to freezing and thawing resistance. HSC concretes could have satisfactory high resistance to freezing and thawing by using an air-entraining high range water-reducing admixture(AEHW admixture), even if the slag content was 95%. Then, the concretes with AEHW admixture, which is called SP concrete, would be recommended for freezing and thawing conditions with respect to the use of HSC concrete.

A study on application of recycled concrete for structural concrete was carried out under the concept of life cycle assessment (LCA) for environmental management of construction utilizing recycled products. Such products are often discarded, when existing electric power plants are rebuilt or upgraded in order to meet increasing power demands. In pursuing the reuse of these recycled materials, the basic policy was composed of three items: (1)the assurance of quality; (2)the reduction of environmental impact; and, (3)construction cost. The study is divided into two main parts: feasibility study on the reuse of recycled concrete and, experimental study on the quality of recycled aggregate and recycled aggregate concrete. This quality o Paper aper presents the result of the experimental study on the recycled aggregate and recycled aggregate concrete. Based on the investigation and the analysis of results, valuable data were obtained regarding concept and practice as to the reuse of construction debris based on LCA.

This Symposium Publication contains the proceedings of the Fourth CANMET/ACI/JCI International Conference held in Tokushima, Japan, in June 1998. Sixty-two refereed papers were accepted for presentation at this conference and for this publication. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP179

from Prince Edward Island, Canada’s smallest Transportation to and province, has been by ferry for the past century. The cost to operate the ferry system became an increasing burden for the Canadian government and a proposal call was solicited in 1987 to the private sector to construct and operate an alternate system to the Province of Prince Edward Island. A proposal was accepted for a private consortium to build a 12.9 km bridge from the mainland to Prince Edward Island. The bridge was completed in May, 1997. A precast concrete, post-tensioned segmental box girder structure was selected for the site. A requirement of the Government of Canada w as that the design and construction of the bridge provide a structure with a design life of 100 years. The bridge is located in a harsh marine environment, with some 100 annual cycles of freezing and thawing. Ice floes which originate in Northern waters pass through the Northumberland Strait in the winter and early spring months. Water temperatures vary from about -2 C in the winter months to +18 C in summer. The salinity of the water in the Northumberland Strait is approximately 3.5%. This paper presents some of the durability concerns which were considered during the design and construction of the bridge and describes how these concerns were addressed.

High volume waste concrete (HVWC) containing hundreds of kg of waste-derived materials in unit volume of concrete as raw materials was prepared to examine the workability, strength development, hydration of cement, composition and structure, and dissolution of harmful elements from hardened concrete to increase the amounts of waste-derived material that can be used for manufacturing concrete.The waste-derived materials tested in this experiment were incineration ash of urban refuse and sintered coal ash as the substitution for fine aggregates, and sintered sewage sludge and glass cullet as the substitution for coarse aggregates. It was determined that HVWC could keep good workability without segregation and developed higher strength than ordinary concrete even if the amounts of waste-derived aggregates in concrete exceeded 6OOkg/ms. Increase in combined water in hardened HVWC and the production of cement hydrates including C-S-H with age was normal and the influence of trace elements contained in waste-derived aggregates on the cement hydration was negligible. Decrease in the amounts of Ca(0I-Q and increase in C-S-H which was estimated from the pore volume of 3 to 6 mn in diameter was recognized in later age in the case when blastfumace slag or fly ash was used as a binder. Non-uniformity in distribution of aggregate, large pore and microgroove between aggregate and cement paste which might occur by the use of large amounts of waste-derived aggregate was not observed. There was no remarkable difference in type and quantitie of elements between HVWC and ordinary concrete dissolved from them. From the results described above, it is considered that the use of HVWC is a very promising technique to safely consume large amounts of wastes.