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International Concrete Abstracts Portal

Showing 1-5 of 23 Abstracts search results

Document: 

SP131-08

Date: 

March 1, 1992

Author(s):

Bryant Mather

Publication:

Symposium Papers

Volume:

131

Abstract:

Most authoritative works that discuss the issue of whether or not calcium chloride should be used as an accelerating admixture in concrete made with Type V sulfate-resisting cement warn against its use. The origin of this warning is reviewed, and the conclusion is reached that it is probably not harmful to obtaining the desired level of sulfate resistance (for which the use of Type V cement was specified) to use calcium chloride in normally acceptable amounts as an accelerating admixture in such concrete to mitigate the effects of cold weather.

DOI:

10.14359/1207


Document: 

SP131-07

Date: 

March 1, 1992

Author(s):

Sidney Diamond and Michael Penko

Publication:

Symposium Papers

Volume:

131

Abstract:

Among the important stages of the overall SR process as it occurs in concrete is the conversion of alkali sulfate dissolved from the cement to alkali hydroxide. The results of laboratory studies are presented to provide an understanding of this process and its effects. This conversion process depends on continued formation of ettringite and does not take place until the cement gypsum is exhausted. Provision of a large excess of gypsum or interference with early ettringite production by high-temperature exposure may postpone or prevent it, thus reducing the OH - ion concentration and the possibility of ASR reaction.

DOI:

10.14359/1206


Document: 

SP131-06

Date: 

March 1, 1992

Author(s):

D. M. Roy, D. Shi, B. Scheetz, and P. W. Brown

Publication:

Symposium Papers

Volume:

131

Abstract:

The principal mechanism for the deterioration of concrete is transport of fluids either into or out of the pore structure of hardened body. The fluid transport occurs via a complex network of interconnected porosity incorporating both the cementitious matrix and matrix/aggregate interfacial regions. Paper describes the development of an experimental method and a mathematical background for a rapid water-permeability measurement method and a mathematical model relating porosity, described in terms of a log-normal distribution, to permeability.

DOI:

10.14359/1205


Document: 

SP131-05

Date: 

March 1, 1992

Author(s):

F. R. Montgomery, P. A. M. Basheer and A. E. Long

Publication:

Symposium Papers

Volume:

131

Abstract:

Good curing is now recognized as essential to achieving good durability of concrete and other cementitious material surfaces. However, it has not been easy to judge whether or not it has been achieved on site, so surface failures continue to occur. The Department of Civil Engineering at the Queen's University of Belfast is developing a number of test techniques to allow the measurement of surface strength, surface absorption and permeability, and surface abrasion-resistance of structures on site. These have been used to assess the performance of various curing regimes for concrete and mortar, first to see if the test methods can extract meaningful measurements of durability-related properties, and secondly to get an indication of the magnitude of the changes in these properties for different curing regimes and water-cement ratios. It is hoped that they may eventually provide a means to assess a surface in terms that could allow an objective judgment of its durability.

DOI:

10.14359/1204


Document: 

SP131-04

Date: 

March 1, 1992

Author(s):

M. J. Simon, R. B. Jenkins, and K. C. Hover

Publication:

Symposium Papers

Volume:

131

Abstract:

Experiments were conducted to determine the influence of immersion vibration on the air-void system parameters of air-entrained concrete, as a function of both radial distance and depth from the point of vibrator insertion. For a 1½ in. (40 mm) diameter immersion vibrator, one could conclude that vibration has little or no effect on air-void systems at distances of 5, 8, or 10 in. (125, 200, or 250 mm) from the point of insertion. The same vibrator in the same concrete can reduce the total air content by 50 percent, and increase specific surface by as much as 100 percent directly at the point of vibrator insertion. Which particular effect one may observe in hardened concrete, therefore, depends on the selection of core location relative to point of vibrator insertion. These observations have implications for specifying, casting, and testing air-entrained concrete.

DOI:

10.14359/1203


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