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International Concrete Abstracts Portal

Showing 1-5 of 26 Abstracts search results

Document: 

SP148-01

Date: 

September 1, 1994

Author(s):

R. N. Swamy, M. Sakai, and N. Nakamura

Publication:

Symposium Papers

Volume:

148

Abstract:

Presents a detailed investigation of the role and effectiveness of ground granulated blast furnace slag and a high-range water reducer (HRWR) on the quality of concrete in terms of bleeding, setting times, heat evolution, strength development, and pore structure. The tests were carried out in two parts. In the first, a slag of normal fineness was used, and both the replacement level and water-binder ratio were varied. It was found that both the slag and HRWR acted as set retarders in terms of setting times and heat evolution. The water-binder ratio was the predominant factor affecting the rate of bleeding. The presence of slag, on the other hand, caused low-early strength and slow strength development, but had significant beneficial influence on the total pore volume and pore size distribution. In the second part, fineness of slag was varied from 453 to 1160 m 2/kg and the replacement level was kept constant at 50 percent. It was then possible to obtain compressive strength in excess of 30 MPa at 3 days and 100 MPa at 28 days, with substantial reductions in total porosity and water permeability. The bleeding rate was also reduced and the setting times also improved. The overall conclusion of this study is that a judicious combination of HRWR and slag fineness can lead to a very effective synergic interaction to produce concretes of high strength, high modulus, and low porosity.

DOI:

10.14359/4100

Document: 

SP148-20

Date: 

September 1, 1994

Author(s):

H. Wang, S. Tysl, and J. E. Gillott

Publication:

Symposium Papers

Volume:

148

Abstract:

Two well-understood and defined reactions in concrete are known as alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). These two reactions are extremely detrimental to the integrity of concrete structures. It is known that lithium-based chemical compounds can control and/or eliminate the expansion caused by ASR. Based on this technology, a commercial chemical admixture has been developed. The admixture is a ready-to-use liquid product formulated to meet ASTM C 494 requirements as a Type A water-reducing admixture. This product is not intended to control ACR-induced expansion. Therefore, identification of the types of alkali-aggregate reactions is necessary to effectively control concrete expansion.

DOI:

10.14359/4111

Document: 

SP148-14

Date: 

September 1, 1994

Author(s):

K. Yokoyama, S. Hiraishi, Y. Kasai, and K. Kishitani

Publication:

Symposium Papers

Volume:

148

Abstract:

Paper addresses shrinkage and cracking at early ages of highly flowable flowing concrete with a special admixture (unit amount of water of 185 kg/m 3) and of normal high-strength, viscous concrete with high-range AE water-reducing agents (unit amount of water of 170 kg/m 3) under constant air flow. Results are as follows: 1) shrinkage at early ages of flowing concrete and normal high-strength concrete increased with a decrease in water-cement ratio. Shrinkage of normal high-strength concrete varied according to the admixture composition; 2) cracking of both flowing concrete and normal high-strength concrete within a restricting steel frame initiated at an earlier age and became significant with decreasing water-cement ratio. Time and amount of crack initiation of normal high-strength concrete varied according to admixture composition.

DOI:

10.14359/4282

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: 

SP148-23

Date: 

September 1, 1994

Author(s):

J. Hrazdira

Publication:

Symposium Papers

Volume:

148

Abstract:

Gypsumless portland cements (GPC) are inorganic binders that may be described as systems of ground portland clinker with a specific surface of 400 to 500 kg/m 2 (Blaine), a superplasticizer with hydroxyl groups, and a hydrolyzable alkali metal salt. The major feature of GPC is the use of a low water-cement ratio (under 0.30), based on the strong liquefying action of the superplasticizer and alkali salt in suspension of ground clinker in the absence of gypsum. The effect of the dosage of sodium lignosulfonate in combination with sodium carbonate on compressive strength, setting time, and consistency of cement paste was studied. It was found that paste properties strongly depend on dosage and mutual ratio of the admixtures. The optimum composition of the setting and liquefying regulator causes high compressive strengths 3 to 7 hr after mixing of binders (15 to 45 MPa).

DOI:

10.14359/4114

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