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International Concrete Abstracts Portal

Showing 1-5 of 63 Abstracts search results

Document: 

SP79-03

Date: 

May 1, 1983

Author(s):

Val R. Sturrup, R. Doug Hooton, and T. Gerry Clendenning

Publication:

Symposium Papers

Volume:

79

Abstract:

Since before the first utilization of imported fly ash by Ontario Hydro as a pozzolan in mass concrete in 1950, research programs on many aspects of its influence on durability were undertaken. Majo. areas addressed have been: 1. thermal crack resistance in mass concrete; 2. reduction of alkali reactivity; 3. freezing and thawing resistance, and 4. sulphate resistance (preliminary). When the first fly ash was produced by Ontario Hydro from thermal plants used for peak load power, the problems with utilizing variable and often high carbon content fly ash were also studied. This problem was overcome by selective storage along with provisior for fineness and carbon content checks for each tanker of ash leaving the plant. Major findings of the research include: 1. Fly ash has and is being used successfully in lieu of both CSA Types 20 and 40 (ASTM Types II and IV) moderate and low-heat cements to control temperature rise and thermally induced cracking in mass concrete. 2. The replacement of 25 percent of normal portland cement with fly ash has been found to be effective in reducing alkali silicate expansions. 3. As long as adequate air contents are obtained, carbon content does not adversely affect the freezing and thawing resistance of concrete at least within the 12 percent CSA and ASTM limits. As long as carbon contents are established for each delivery of fly ash, dosages of air entraining agents can be modified easily.

DOI:

10.14359/6686

Document: 

SP79-40

Date: 

May 1, 1983

Author(s):

S. Lessard, P.C. Aitcin, and Micheline Regourd

Publication:

Symposium Papers

Volume:

79

Abstract:

A low heat of hydration blended cement for structural applications has been developed. This cement is composed of 50 percent of a Canadian cement, CSA Type 20, (ASTM Type II), 35 percent of a slowly reactive slag, and 15 percent of condensed silica fume. The heat of hydration measured at 20°C of this blended cement is 30 percent lower than that of the pure Type 20 cement whereas the 28 d compressive strength of standard mortars is about the same. The peak temperature of an insulated mass of concrete having a 28 d compressive strength of 30 MPa is reduced from 44.4°C to 34.4°C when using this composition instead of the Type 20 cement. A microstruc tural study has shown th at when using this blended cement the CSH formed is ve ry dense and amorpho us-like.

DOI:

10.14359/6723

Document: 

SP79-37

Date: 

May 1, 1983

Author(s):

Eigil V. Sorensen

Publication:

Symposium Papers

Volume:

79

Abstract:

Scale ctioning of concrete due to freezing and thawing action with the use of chemicals has become a severe concrete durability problem. The present paper reports results of freezing and thawing experiments performed to evaluate 4 the effect of microsilica (beneficiated condensed silica fume) addition to concrete in that respect. Tests performed using a fied method show that the drying rewetting standard and a modify history of the concrete prior to freezing and thawing has a sig-nificant influence on conventional concrete, whereas microsilica concrete is relatively unaffected. Air entrainment has a marked beneficial effect on both conventional and microsilica concrete, I although microsilica concrete with relatively low cement contents can be manufactured to be frost resistant without air entrain-ment.

DOI:

10.14359/6720

Document: 

SP79-20

Date: 

May 1, 1983

Author(s):

Karim W. Nasser and H.M. Marzouk

Publication:

Symposium Papers

Volume:

79

Abstract:

This investigation is a study of the structural properties of concrete made with sulphate-resisting cement (Type V) and Saskatchewan fly ash. Tests were performed on cylinders exposed to temperatures of 70° to 450°F (21.4° to 232°C) for periods of six months and over. The properties of strength, elasticity, creep and creep recovery were studied for both sealed and unsealed specimens. Test results revealed that temperature had a minor effect on strength and stress-strain relationship for both sealed and unsealed specimens; however, the modulus of elasticity showed a continual decrease with a rise in temperature. Creep of unsealed concrete increased with an increase in temperature up to 160°F (70°C) and decreased thereafter, while creep of sealed specimens decreased with a rise in temperature, except at 350°F (177°C) where it was one and a half times that at 70°F (21.4°

DOI:

10.14359/6703

Document: 

SP79-09

Date: 

May 1, 1983

Author(s):

Eddie Rossouw and Japie Kruger

Publication:

Symposium Papers

Volume:

79

Abstract:

Several countries have specifications for additions that are used in concrete, such as fly ash (pulverised fuel ash) or other pozzolans and virtreous blast-furnace slag, shile other countries are preparing specifications for such materials. This paper lists the more important existing specifications and summarises, compares and discusses their specific requirements. The differences and similarities of nomenclature, requirments and methods of test are indicated. Attention is given to the relationship between the results obtained from a test and the materials performance in use. Specificaiton test results may not always be valid criteria for forecasting the performance of a material.

DOI:

10.14359/6692

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