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International Concrete Abstracts Portal

Showing 1-5 of 50 Abstracts search results

Document: 

SP173-29

Date: 

September 1, 1997

Author(s):

J. Norberg, 0. Peterson and P. BillbergJ. Norberg, 0. Peterson and P. Billberg

Publication:

Symposium Papers

Volume:

173

Abstract:

Different superplasticizers have been tested in order to evaluate their effect on concrete properties and to express concrete’s rheology in fundamental parameters such as yield stress and plastic viscosity. Measurements were made on concrete’s rheology with two different viscometers, one for mortar and one for concrete. Tests were also made using the more traditional slump cone. By using results from slump tests at different times after mixing, slump losses by means of time required to lose 30 mm of slump and time required to lose half the initial slump value were calculated. The time necessary before trowelling was also measured. Results show that viscosity-measurements on mortar give useful information about the fresh concrete’s properties, information that cannot be attained with the traditional methods, such as slump, spread, etc. The method of evaluating trowelling hardness very efficiently measures the admixture’s effects on retardation. Only those superplasticizers containing new types of acrylic and vinyl polymers show effects efficient enough to belong to the second generation.

DOI:

10.14359/6203


Document: 

SP173-04

Date: 

September 1, 1997

Author(s):

A. A. Jeknavorian, L. R. Roberts, L. Jardine, H. Koyata and D. C. Darwin.

Publication:

Symposium Papers

Volume:

173

Abstract:

A new family of comb polymers has been developed that have been found to overcome many performance shortcomings typically exhibited by conventional high range water reducing agents, commonly referred to as superplasticizers. This paper discusses some theoretical considerations associated with comb polymer type super-plasticizers, and reports on several key performance advantages such as extended slump life without prolonged set time, minimal variation in slump and air performance as a function of cement brand, and linear dosage response in mortar flow tests.

DOI:

10.14359/6178


Document: 

SP173-02

Date: 

September 1, 1997

Author(s):

Hiroshi Uchikawa and Shunsuke Hanehara

Publication:

Symposium Papers

Volume:

173

Abstract:

The relationships among the amounts of adsorption admixtures to cement particles, the interactive force between cement particles and the zeta potential of cement particle and the fluidity of cement paste prepared at the W/C ratio of 0.3 with lignin sulfonic acid-based admixture (LS), aminobenzene sulfonic acid-based admixture (AS) or melamine sulfonic acid-based admixture (MS) was studied in this paper, aiming at obtaining the basic data for elucidating the effects of the characters of sulfonic acid-based organic admixtures on the fluidity of concrete. The amount of adsorption of the sulfonic acid-based admixture by cement particles are logarithmically related to the molecular weight of the admixtures. The lower the molecular weight, the more the amount adsorbed are. The zeta potential of cement particle in cement paste depends upon the content of sulfonate group in the admixture and the adsorption state of admixture. The interactive force between cement particles are linearly related to the fluidity of cement paste. The steric repulsive force considerably contributes to the dispersion of particles even in the addition of sulfonic acid-based admixture which has been considered so far to disperse the particles mainly by the electrostatic repulsive force. The steric repulsive force is related to the molecular weight of the sulfonic acid-based admixture except AS. The rate of contribution of electrostatic repulsive force to the total repulsive force accounting for the interactive force correlates with the content of sulfonate group in the admixture. The reason why the action of AS is different from those of the other admixtures is probably because the adsorption state of AS is different from those of the others.

DOI:

10.14359/6176


Document: 

SP173-30

Date: 

September 1, 1997

Author(s):

M. Shonaka, K. Kitagawa, H. Satoh, T. lzumi and T. Mizunuma

Publication:

Symposium Papers

Volume:

173

Abstract:

High range water reducing agents (superplasticizers), in general, adsorb on the surface of cement particles and disperse the particles by means of electric force. Recently, the authors have developed a new type of high range water reducing agents which have characteristically long chains of polyethylene oxides (EO) as branches. When the new molecules adsorb on the particles, it is considered that long EO chains are expanded in the water / cement mixture and that each particle disperse due to their steric repulsion instead of electric. So, it can bring good workability to the concrete mix and retain fluidity for a longer period without retarding on the setting. Therefore, it can be applied to various concrete, such as high and ultra high strength concrete.

DOI:

10.14359/6204


Document: 

SP173-18

Date: 

September 1, 1997

Author(s):

Shinzou Nishibayashi, Akira Yoshino, K. Yamura, Y. Okawa and M. A. Peres Lara

Publication:

Symposium Papers

Volume:

173

Abstract:

This paper describes the effects of properties of powder such as specific surface and solid volume percentage on the plastic viscosity of fresh paste with admixtures. Eight types of blended powder and three types of high-range water-reducing admixtures (HRWRA) were used, and the plastic viscosity of paste mixed with these materials was measured, keeping the yield value of paste constant. The fresh paste is considered to be a type of highly concentrated suspension, so the authors propose a method to predict plastic viscosity based on this concept. In this method, the ratio of powder content, the specific surface, and solid volume percentage of powder, the type of admixture, and other factors are taken into account.

DOI:

10.14359/6192


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