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International Concrete Abstracts Portal

Showing 1-5 of 26 Abstracts search results

Document: 

SP148-07

Date: 

September 1, 1994

Author(s):

M. Kayaga, H. Tokuda, M. Kawakami, and T. Kaneko

Publication:

Symposium Papers

Volume:

148

Abstract:

High-strength concrete with air-entraining high-range water-reducing admixture, 0.35 water-cement ratio, 148 kg/m 3 unit water content, and about 60 MPa compressive strength, was produced, and the admixture content and sand percentage were varied. The consistency property was measured by the slump test, and the compaction property and segregation resistance were determined by the flow time through an inverted slump cone. An appropriate mixture that balanced these properties relative to the admixture content and sand percentage was determined from the test. The appropriate mixture can be consolidated by using a shorter vibrating time and lower frequency than in the case of ordinary concrete.

DOI:

10.14359/4275


Document: 

SP148-17

Date: 

September 1, 1994

Author(s):

J. J. Schemmel, v. Arora, and J. Williams

Publication:

Symposium Papers

Volume:

148

Abstract:

High-performance concretes (HPC) typically have low w/c to achieve the desired levels of strength and durability. As a result, HPC have a tendency to be stiff and lose their workability rather quickly. Often, high-range water-reducing admixtures (HRWRA) are used to improve the workability of HPC. Care must be exercised when using any admixture, or combination of admixtures, to insure that there are no detrimental side effects that might shorten the life of the concrete. Research has shown that, although retempering concrete with an HRWRA will generally improve workability and maintain the strength of low-w/c concretes, it may also reduce freeze-thaw resistance. Therefore, an experimental study was

DOI:

10.14359/4025


Document: 

SP148

Date: 

September 1, 1994

Author(s):

Editor: V.M. Malhotra

Publication:

Symposium Papers

Volume:

148

Abstract:

In October, 1994, CANMET in association with the American Concrete Institute sponsored a fourth conference on the superplasticizers and chemical admixtures in Montreal. The objective of this conference was to bring to the attention of the concrete community the new developments in chemical admixtures since the last conference in 1989. A total of 25 papers were accepted for publication in this special proceedings from the conference. If you are involved with superplasticizers and chemical admixtures, this special publication is a must. 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. SP148

DOI:

10.14359/14188


Document: 

SP148-22

Date: 

September 1, 1994

Author(s):

A. A. Jeknavorian, N. S. Berke, and D. F. Shen

Publication:

Symposium Papers

Volume:

148

Abstract:

Among the requirements for Type C and E accelerators in the ASTM C 494 Specification on Admixtures, limits for set and strength performance are stipulated for concrete mixed and cured at 23 C (73 F). However, set-accelerating admixtures are predominantly used for cold weather concreting operations, where they can significantly increase the rate of early strength development at low temperatures, thereby reducing the curing and protection periods necessary to achieve specified strength. Paper discusses a laboratory program designed to evaluate the effectiveness of various set-accelerating admixture formulations. The scope of the program includes measuring set, strength, and air-entraining performance over a wide range of mix and curing conditions, and selection of cementitious materials. Furthermore, considering that a wide range of soluble inorganic salts, used over a relatively large dosage range, has been shown to accelerate the setting early hardening of portland cement, protocol for evaluating the corrosive potential of accelerator formulations containing these salts is discussed.

DOI:

10.14359/4113


Document: 

SP148-21

Date: 

September 1, 1994

Author(s):

E. I. Tazawa, A. Yonekura, M. Takahashi, S. Miyazawa, and K. Kawai

Publication:

Symposium Papers

Volume:

148

Abstract:

Various types of superplasticizer that maintain concrete slump for longer periods have been extensively investigated. A new type of superplasticizer with high-range water-reducing slump-maintaining capacities, composed of sulfonic acid polymer with methacrylic acid derivatives, has recently been developed. In this study, influence of cement type, concrete temperature, and pozzolans on properties of fresh and hardened concrete with this type of superplasticizer was investigated. Two reference superplasticizers were widely used naphthalene-based and amino sulfonic acid-based. A significant increase in water-reducing capacity to obtain the same consistency was observed at a much lower dosage. Absolute value of zeta potential of cement particles with the superplasticizer increased with elapsed time until 90 min after mixing, which explains the high-slump-retention capacity of the concrete. Plasticizing effects of superplasticizers were more pronounced for concretes with fly ash or blast furnace slag as blending agents. Concrete bleeding decreased slightly. Properties of hardened concrete, such as compressive strength and drying shrinkage, were at nearly the same level as those of concrete with naphthalene-based superplasticizer.

DOI:

10.14359/4112


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