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International Concrete Abstracts Portal

Showing 1-5 of 90 Abstracts search results

Document: 

SP132-89

Date: 

May 1, 1992

Author(s):

C. Alfes

Publication:

Symposium Papers

Volume:

132

Abstract:

In High-Strength Concrete in general high-quality aggregate is used. This aggregate has a high compressive strength and often a high modulus of elasticity. This high modulus of elasticity of the aggregate strongly influences the deformation behaviour of high-strength concrete. Results show that there is a direct and linear relationship between the shrinkage value and the modulus of elasticity of the concrete. The highest modulus of elasticity of concrete was 85 GPa. The compressive strength at the age of 28 days was in the range from 102 to 182 MPa. A design aid is given to show the interrelation between modulus of elasticity and shrinkage strain of the concrete on one side and modulus of elasticity of the aggregate, modulus of elasticity of the matrix and matrix content on the other side.

DOI:

10.14359/17148


Document: 

SP132-88

Date: 

May 1, 1992

Author(s):

J. Hrazdira

Publication:

Symposium Papers

Volume:

132

Abstract:

Gypsumless Portland cements (GPC) are inorganic binders, which may be described aas system of: ground Portland clinker (specific surface of 400-500 m2/kg - Blaine), a surface-active agent with hydroxyl groups and a hydrolyzable alkali metal salt (carbonate, bicarbonate, silicate). New cements, developed in recent years, are able to reach both higher strengths and fracture toughness than ordinary Portland cement (1,2,3). New developments in the making of very strong cements have resulted from modifying cement compositions and manipulating the microstructures (4).

DOI:

10.14359/17147


Document: 

SP132

Date: 

May 1, 1992

Author(s):

Editor: V.M. Malhotra

Publication:

Symposium Papers

Volume:

132

Abstract:

SP-132 Published in two volumes...The first volume contains papers dealing with fly ash and natural pozzolans. The second volume consists of papers dealing with condensed silica fume and ferrous and non-ferrous slags.

DOI:

10.14359/14164


Document: 

SP132-32

Date: 

May 1, 1992

Author(s):

H. Ohga and S. Nagataki

Publication:

Symposium Papers

Volume:

132

Abstract:

Heavy damage due to alkali-aggregate reaction has been observed in concrete structure in and along the sea. An accelerated test is performed on mortar to evaluate effectiveness of fly ash for controlling alkali-aggregate reaction in the marine environment. Mortar bars using Pyrex as aggregate and cements with 0.6 and 1.1% of equivalent sodium oxide are made. The alkali content in the mixture is adjusted by adding NaOH or NaCl. Specimens are stored in distilled water, NaCl solution, and under more than 95% of relative humidity. The controlling effect of fly ash and the effect of internal and intruded chloride ion in mortar on alkali-aggregate reaction is studied by measuring the expansion of mortar. Expansion of mortar depends on the type of cement and chemical reagents used for alkali adjustment, the amount of fly ash used and the exposure condition. Even with the same equivalent sodium oxide in the mixture, mortar using NaCl for alkali adjustment shows higher expansion than mortar using NaOH. The highest expansion is revealed for mortar cured in NaCl solution. The controlling effect of fly ash also depends on the type of cement and the exposure condition.

DOI:

10.14359/10027


Document: 

SP132-60

Date: 

May 1, 1992

Author(s):

O. S. B. Al-Amoudi, Rasheeduzzafar, S. N. Abduljauwad, and M. Maslehuddin

Publication:

Symposium Papers

Volume:

132

Abstract:

There is an increasing tendency worldwide toward using cements blended with fly ash, silica fume, blast furnace slag, and natural pozzolans. Incorporation of these materials in concrete makes it dense and impermeable. While the effect of chloride and sulfate ions on the durability of blended cements is well documented, meager data are available on the synergistic effect of high concentrations of these salts on the durability performance of these cements. Since the structural components, especially foundations in the coastal areas in some parts of the world, are subjected to high concentrations of these salts, it is imperative to investigate the performance of blended cements in such environments. In this investigation, mortar and concrete specimens made with Type I cement blended with fly ash, silica fume, and blast furnace slag were exposed to a highly concentrated chloride-sulfate (2.1 percent SO4-- and 15 percent Cl- solution for a period of 540 days. The performance of these cements in resisting reinforcement corrosion was evaluated by monitoring half-cell potentials and measuring corrosion rates at periodic intervals. Deterioration due to sulfate ions was evaluated by visual survey, and measuring loss in compressive strength. Results indicate that surface deterioration and loss in strength was greater in blast furnace slag and silica-fume cement specimens compared to fly ash and plain cement specimens. Severe surface scaling and considerable reduction in strength (55 to 75 percent) was observed in the former cements. Moderate surface deterioration and loss in strength of about 25 percent was observed in fly ash and Type I cements. Corrosion of steel in silica fume and blast furnace slag was, however, much lower than in fly ash blended and Type I cements.

DOI:

10.14359/2433


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