International Concrete Abstracts Portal

International Concrete Abstracts Portal

The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

Showing 1-5 of 63 Abstracts search results

Document: 

SP79-43

Date: 

May 1, 1983

Author(s):

V. Ramakrishnan and V. Srinivasan

Publication:

Symposium Papers

Volume:

79

Abstract:

This paper presents the results of an investigation to determine the performance characteristics of fiber reinforced concretes containing condensed silica fume. The plastic concrete properties studied are slump, air content, unit weight, and Vebe-time. The hardened concrete properties investigated are compressive strength, flexural strength, toughness index, tensile strength, pulse velocity, static modulus of elasticity, and absorption co-efficient. These hardened concrete properties are compared at ages 3 to 90 days. A total of 17 mixes were made using type I cement, with the addition of condensed silica fume, steel fibers, and superplasticizers. Seven cement contents varying from 160 to 560 kg/m3 (270 to 945 lb/cu.yd.) were investigated with W/C ratios varying from 0.28 to 1. In all mixes condensed silica fume was added at 20 percent by weight of cement and steel fibers at 47.5 kg/m3 (80 lb/cu.yd.). The results indicate that the addition of condensed silica fume and steel fibers had reduced the workability consid-erably, however the workability can be restored with the addition of an appropriate amount of superplasticizer. In general the finishability of fiber reinforced concrete is improved with the addition of condensed silica fume. The unit weight of fiber reinforced condensed silica fume concrete is higher than the normal concrete. The addition of condensed silica fume is beneficial for fiber reinforced concretes with low cement content; it was shown that high strength fiber reinforced concretes could be made with low cement contents. The moisture absorption capacity of the con-crete is reduced with the addition of condensed silica fume. For the selected 20 percent addition of condensed silica fume, there is an optimum cement content and water content that considerably improves the performance characteristics of the steel fiber rein-forced concrete.

DOI:

10.14359/6726


Document: 

SP79-44

Date: 

May 1, 1983

Author(s):

J.I. Skrastins and N.G. Zoldners

Publication:

Symposium Papers

Volume:

79

Abstract:

This paper describes the use of condensed silica fume in the ready-mixed concrete plant at St. Eustache, P.Q., Canada. The effect of this admixture on the properties of fresh and har-dened concrete is discussed. Efficiency factors for the silica fume-modified concrete are given for different strength levels. Transportation of the fume and special installations at the ready-mixed concrete plant for the handling of condensed silica fume are described.

DOI:

10.14359/6727


Document: 

SP79-45

Date: 

May 1, 1983

Author(s):

David J. Cook and P. Suwanvitaya

Publication:

Symposium Papers

Volume:

79

Abstract:

The utilization of agricultural residues for building mater-ials is particularly attractive in developing countries where indigenous resources for building are hard pressed to cope with the demand. In this paper the use of rice husks, essentially a waste material in most countries, as a source for a pozzolanic material is described. The behaviour of lime - rice husk ash mixes in terms of strength, shrinkage, durability and microstructure are examined. It is shown that although maximum strengths are achieved with low lime mixes, lime leaching could seriously impair the durability and indeed the long term strength of these mixes. Accordingly, it is proposed that the optimum ratio of lime : rice husk ash should be about 1 : 1. Further, it is shown that within the limits of carbon contents likely to be encountered in the field, strength development is unaffected, though some retardation in initial and final set may occur. Finally, examination of the microstructure through x-ray diffraction analysis indicates that the hydrated matrix consists of calcium silicate hydrate of the CSH (II) type.

DOI:

10.14359/6728


Document: 

SP79-46

Date: 

May 1, 1983

Author(s):

M. Regourd, B. Mortureux, and H. Hornain

Publication:

Symposium Papers

Volume:

79

Abstract:

At early ages, blended cement mortars with 30 % hydraulic slags or active pozzolans have lower mechanical strengths than mortars incorporating 100 % Portland cement. The action of 5 % condensed silica fume replacement for slag or pozzolan or material considered as inert has been studied from 7 days to 3 months by measuring the mechanical strengths of mortars made according to IS0 test method and by observing the microstructure of fractured samples. This action of the condensed silica fume is a function of the nature of the additive. With hydraulic slags, there is a competition between slag and silica fume for the available lime. With slightly or slowly reactive pozzolans (volcanic rock, fly ash) mechanical strengths and microporosity of mortars show improve-ment at 28 days. With inert materials (crystalline slag or quartz), the improvement is more marked. This is due to the formation of dense C-S-H, strong cement paste-aggregate bond and 20 % increase in mechanical strengths.

DOI:

10.14359/6729


Document: 

SP79-47

Date: 

May 1, 1983

Author(s):

J.W. Meusel and J.H. Rose

Publication:

Symposium Papers

Volume:

79

Abstract:

A new plant for producing ground water granulated blast furnace slag has been constructed at Sparrows Point, Maryland. - The facility was specially designed to water granulate 800,000 tons per year of blast furnace slag produced by one of the largest and most modern blast furnaces in the world. Molten slag is alternately supplied to one of four granulators. Granulated slag is collected in an agitating tank where vapors are condensed and from which slag slurry is pumped to a dewatering filter bed. Granulation water is cleaned, cooled, and recycled for the next furnace tap and slag granulation. The entire granulation system is environmentally clean with no discharge of water or gases. After the slag is dewatered, it is removed from the filter beds and transported to stockpile at the grindingandprocessing plant. Slag recovered from stockpiles is dried in a fluid bed dryer and fed to two 16.5m x 4.6m 6000 HP grinding mills for finish grinding. Ground slag is stored in two 20,000-ton concrete silos from which the ground slag is loaded into barges and ships for shipment to bulk distribution terminals along the East Coast of the United States. Data are presented on the use of separately ground granulated blast furnace slag and its physical proper-ties in portland cement concrete. It is shown that where granulated slags are used in proportions of 30 to 50 percent of the total cementitious material, improved qualities may be found in both plastic and hardened properties of concrete. The data confirm that granulated slag used as a separate cementitious material does exhibit marketing potential in today's construction industry.

DOI:

10.14359/6730


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