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International Concrete Abstracts Portal

Showing 1-5 of 31 Abstracts search results

Document: 

SP68-06

Date: 

January 1, 1981

Author(s):

Hiroshi Tokuda, Masami Shoya, Makoto Kawakami, and Makoto Kagaya

Publication:

Symposium Papers

Volume:

68

Abstract:

This paper describes the results of an investigation to improve the drying shrinkage, thermal diffusivity and coefficient of thermal expansion of comparatively rich-mix concrete by the use of admixtures. Three types of superplasticizers were examined. Shrinkage tests were performed on 100x100x400 mm prismatic speci-mens in a controlled room where the temperature and the humidity were kept at 20°C and at 50 % R.H.. Two series of tests were made, one to make clear the character of shrinkage of concretes of low water-cement ratio and another to examine the effect of dosage of superplasticizer on shrinkage. Thermal diffusivity tests and the tests for the coefficient of thermal expansion were carried out using 10x20 cm cylindrical specimens of gravel concretes having a maximum cement content of 700 kg/m3, and attempts were made to improve these thermal properties by reducing the unit water content by the addition of a certain superplasticizer. It was found that the addition of superplasticizer to reduce the unit water content by about 20 percent, while maintainingthe constant consistency of concrete, gave a maximum increase of thermal diffusivity of more than 14 percent, a maximum decrease of coefficient of thermal ex-pansion of about 7 percent and a maximum decrease of drying shrinkage of almost 12 percent at 350 days drying. It is concluded that a suitable choice and use of superplasticizers should be used more specifically to improve drying shrinkage and thermal properties.

DOI:

10.14359/6467


Document: 

SP68-17

Date: 

January 1, 1981

Author(s):

Paolo De Lama and Salvatore Tavano

Publication:

Symposium Papers

Volume:

68

Abstract:

This paper describes the results of research into energy savings and noise abatement in a precasting plant. Optimum beneficial results were obtained through the use of superplasti-cizers and control of vibration frequency.

DOI:

10.14359/6478


Document: 

SP68-01

Date: 

January 1, 1981

Author(s):

Kirsten Eriksen and Pal/e Nepper-Christensen

Publication:

Symposium Papers

Volume:

68

Abstract:

Use of a naphtalene-based superplasticizer at high dosages in concretes made with fly ash (100-150 kg/m3) and a moderate content of portland cement (250-300 kg/m3) results in great water reductions and high strengths (75-80 MPa after 28 days) for concretes with normal workability (slump 5-10 cm). Laboratory investigations concerning mixture proportions and pro-perties of the fresh and hardened concretes with a discussion of physical and chemical influences of the use of the superplasticizer are presented. Increasing problems with the supply of good, in-expensive, natural coarse aggregates may be solved through combined additions of superplasticizers and fly ash to the concrete. This paper further presents experimental evidence of mixture proportions and phy-sical data for socalled "sand-concrete", i.e. concrete without coarse aggregates but with "normal" contents of portland cement and water obtained by the addition of rather large amounts of fly ash and superplasticizers.

DOI:

10.14359/6462


Document: 

SP68

Date: 

January 1, 1981

Author(s):

Editor: V.M Malhotra

Publication:

Symposium Papers

Volume:

68

Abstract:

SP-68 A collection of 30 papers from 11 countries. Principal topics: water-reduced and high-strength concrete, physical and mechanical properties of concrete using superplasticizers, freeze-thaw durability, energy conservationand by-product utilization, slump loss and rheology, surface phenomena, and special applications.

DOI:

10.14359/14120


Document: 

SP68-11

Date: 

January 1, 1981

Author(s):

L. R. Roberts and P. Scheiner

Publication:

Symposium Papers

Volume:

68

Abstract:

Previous workers have shown that the air-void system in air-entrained concrete containing a superplasticizer tends toward larger bubbles. This effect leads to spacing factors larger than the 0.2 mm normally accepted as a requirement for durability. Nevertheless, concretes containing such admixtures generally have been found to be frost-resistant. The present work is an attempt to understand the reasons for durability when the accepted 0.2 mm spacing factor requirement is not met. The distribution of air-void sizes in air-en-trained concretes made with and without a naphthalene sulfonate type superplasticizer were examined, using a new microprocessor-based Rosiwal linear traverse apparatus. The individual chord intercepts available with this system were fitted to a zeroth-order logarithmic distribution function, and the parameters of the fitted function were related to frost resistance as tested for by ASTM: C 666, procedure A. Concretes containing the superplasticizer were frost-resistant, despite spacing factors in excess of 0.2 mm. The most frequently encountered chord lengths in superplasticizer-con-taining concrete did not change relative to equal slump refer-ence concrete.

DOI:

10.14359/6472


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