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 78 Abstracts search results

Document: 

SP91-45

Date: 

February 1, 1986

Author(s):

P. J. Robins and S. A. Austin

Publication:

Symposium Papers

Volume:

91

Abstract:

Condensed silica fume, at up to 30% by weight, was used as a partial cement replacement in lightweight aggregate concrete. The results of round and deformed bar cube pull-out tests, with and without applied lateral stress, show that condensed silica fume increases ultimate bond strength and affects the mechanism of failure. The influence of condensed silica fume on bond stress of round bars was similar at all lateral stresses, producing a 50% increase at 20% by weight replacement of cement. For deformed bars the increase in bond strength was more pronounced at higher levels of lateral stress, producing increases approaching 70% at 20% silica fume content. The improvements in ultimate bond strength with condensed silica fume are shown to only partly result from the associated increases in compressive strength, the greater part resulting from the modified properties of the concrete matrix.

DOI:

10.14359/10105


Document: 

SP91-46

Date: 

February 1, 1986

Author(s):

M. Buil, P. Witier, F. de Larrard, M. Detrez, and A. M. Paillere

Publication:

Symposium Papers

Volume:

91

Abstract:

The adsorption of a naphthalene sulfonate formaldehyde (NSF) superplasticizer on the surface of a silica fume (SF) has been studied by adsorption isotherms and zeta potential measure-ments. A model is proposed for the fixation of NSF on a SF surface in the presence of cement, which can explain the high efficiency of this type of superplasticizer on the Portland cement - SF - Water system. The rheological efficiencies of several SF have been eva-luated by the determination of the water content of one fresh SF mortar composition at a constant workability. An hypothesis is suggested for explaining the higher water demands by the five silicon or ferro-silicon SF tested in this study, compared to a zirconia SF.

DOI:

10.14359/10106


Document: 

SP91-47

Date: 

February 1, 1986

Author(s):

R. F. Feldman

Publication:

Symposium Papers

Volume:

91

Abstract:

Pore structure changes in silica fume-portland cement blend mortars fabricated with 0, 10 and 30% silica fume at a water/binder ratio of 0.60 and a sand/cement ratio of 2.25 have been monitored by mercury porosimetry while being cured for 1 to 180 days. The threshold value for pore intrusion increases with pore size and becomes less abrupt with silica fume addition; it is in the 0.5 to 20 x l03 nm region. Mortars were also made with and without 10% silica fume at a water/cement ratio of 0.60 and sand/cement ratios of 0, 1.0, 1.5, 1.8, 2.0, 2.25 and 3.0; the sand passed ASTM C109. Mercury intrusion measurements were carried out after 14 days of curing. In the presence of silica fume pore volume in the 0.5 to 20 x 103 nm pore diameter range increased with sand/cement ratio. Mortar prisms were subjected to freezing and thawing cycles (two cycles in 24 h) according to ASTM standard test method C 666, Procedure B. Freezing and thawing resistance was monitored by measuring changes in residual length and weight. Results indicate that if the sand/cement ratio is 2.25 or over, expansion is less than 0.02% after 500 cyles. At lower sand/cement ratios 10% silica fume gives little protection.

DOI:

10.14359/10107


Document: 

SP91-48

Date: 

February 1, 1986

Author(s):

Olav Gautefall

Publication:

Symposium Papers

Volume:

91

Abstract:

This report presents the results of the diffusivity of chloride ions in hardened cement paste. The experiments were carried out at 20°C and both ordinary portland cement and blended cement with 10% fly ash have been investigated. Other experimental variables were water-to-(cement + condensed silica fume) ratio of 0.5, 0.7 and 0.9. The condensed silica fume was used as a cement replacement, the replacement levels being 5.10 and 15% by weight of cement.

DOI:

10.14359/10108


Document: 

SP91-49

Date: 

February 1, 1986

Author(s):

Mitsunori Kawamura, Kunio Takemoto, and Shigemasa Hasaba

Publication:

Symposium Papers

Volume:

91

Abstract:

The expansion of mortars containing up to at least 10% silica fume by weight of cement were about three times as great as that of the additive-free mortar. Concentrations of calcium and alkalies within opal grains in the silica fume mortars were determined by energy dispersive x-ray analysis(EDXA). The intrusion of smaller amounts of calcium into opal grains in the mortars at early ages seems to show that the conversion of alkali-silica gels into sols was delayed by the presence of silica fume. The delay of this conversion was also confirmed by microhardness measurements.

DOI:

10.14359/10109


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