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International Concrete Abstracts Portal

Showing 1-5 of 7 Abstracts search results

Document: 

SP158-03

Date: 

January 1, 1996

Author(s):

Nam Chau; and Vern C. Rogers

Publication:

Symposium Papers

Volume:

158

Abstract:

Interest in the use of reinforced concrete structures in LLW disposal facilities has preceded the development of a comprehensive understanding of the long-term performance of these disposal technologies. With this in mind, Rogers and Associates Engineering Corporation has developed a new assessment computer model, restrict, that adopts a more complete, mechanistic approach to modeling concrete degradation, groundwater infiltration, leaching, and radiological risks.

DOI:

10.14359/1432

Document: 

SP158-02

Date: 

January 1, 1996

Author(s):

Nam Chau; Robert D. Baird; and Vern C. Rogers

Publication:

Symposium Papers

Volume:

158

Abstract:

Several engineered disposal technologies involving concrete structures have been proposed for low-level radioactive waste disposal. The long-term performance and behavior of reinforced concrete structures in disposal units have been examined. Under most conditions, the reinforcing steel and concrete work well together to withstand the natural forces. Under certain conditions, however, the reinforcement and concrete may be subject to environmental attack which may cause degradation of the reinforced concrete. Water infiltration through the structure may increase as a result of cracking and increasing permeability and thereby increase the potential for contaminant release. The model for estimating time to onset of reinforcing steel corrosion due to presence of chloride is presented. Requirements for design of reinforced concrete structures for low-level radioactive waste disposal facilities are suggested.

DOI:

10.14359/1431

Document: 

SP158

Date: 

January 1, 1996

Author(s):

Editors: A.A. Al-Manaseer and D.M. Roy

Publication:

Symposium Papers

Volume:

158

Abstract:

SP-158 The Building Code Requirements for Masonry Structures will provide solutions to the most complex masonry construction questions. Replacing all existing masonry code, these important new ACI/ ASCE documents have been especially prepared to facilitate adoption, by reference, in a general building code. They have been adopted by B.O.C.A. and SBCC (model code groups). The code contains: a standard construction specification as part of the design standard; provisions for analytical and empirical design; provisions for seismic design; and provisions for design of brick and block composite and cavity walls. Other topics covered by the new code include: permits and drawings; quality assurance; materials; placing embedded items; strength and serviceability; flexural and axial loads; shear; walls; columns; pilasters; beams and lintels. The quality, inspection, testing and placement of materials used in construction are covered by reference to specifications and the appropriate ASTM Standards.

DOI:

10.14359/14198

Document: 

SP158-06

Date: 

January 1, 1996

Author(s):

Parviz Soroushian and Abdulrahman Alhozaimy

Publication:

Symposium Papers

Volume:

158

Abstract:

Water is generally involved in every form of concrete deterioration; the permeability of concrete usually determines the rate of deterioration. Since the permeation of water into concrete takes place through the capillary pores, a reduction in the volume of large (greater than about 0.01 micron) capillary voids in the paste matrix will reduce permeability. This can be assisted by the partial substitution of cement with fly ash in the paste. As a pozzolanic material, fly ash reacts chemically with the calcium hydroxide resulting from cement hydration to form compounds (mainly calcium silicate hydrate) with cementitious properties. The effects of fly ash type and content on the permeability characteristics of concrete materials subjected to two different curing conditions were investigated. Four different fly ash contents and three different fly ash types were considered to provide sufficient data for powerful statistical analysis of results. Fly ash was observed to be capable of reducing the permeability of concrete, even at early ages. Selection of fly ash type (Class F vs. Class C), the level of cement substitution with fly ash, and curing conditions had important effects on the permeability characteristics of fly ash concrete. The interactions between these factors were also generally important.

DOI:

10.14359/898

Document: 

SP158-05

Date: 

January 1, 1996

Author(s):

Barry E. Scheetz and Jefferson P. Hoffer

Publication:

Symposium Papers

Volume:

158

Abstract:

The cement/silicate method of solidifying wastes was investigated. Emphasis was placed on the interaction between aqueous sodium silicate and portland cement hydration reactions. A definition of the role which the alkali- silicate plays in increasing the ability of cement hydration reactions to immobilize waste ions was the principal objective. Characterization relied upon calorimetry, X-ray diffraction, microstructural examination by scanning electron microscopy, and monitoring strength development of the waste forms. Increasing additions of sodium silicate to cement pastes accelerate hydration reactions, specifically the hydration of C 3 A and C 3 S, and decrease the presence of portlandite. Effects on compressive strengths of cement pastes were varied; at a water-cement ratio of 0.83, strengths increased with moderate sodium silicate additions, while at higher water-cement ratios, sodium silicate additions decreased strengths.

DOI:

10.14359/897

12

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