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International Concrete Abstracts Portal

Showing 1-5 of 34 Abstracts search results

Document: 

SP65-07

Date: 

August 1, 1980

Author(s):

Katharine Mather

Publication:

Symposium Papers

Volume:

65

Abstract:

Subsequent to the investigation of the correlation between laboratory accelerated freezing and thawing and weathering at Treat Island, Maine, reported in 1953 (1) there have been some developments especially in the field of sulfate resistance of concrete that serve to further elucidate the findings then reported. There have also been many contributions to improve understanding of the causes and nature of the many different kinds of chemical reactions that can and do occur between aggregates of all kinds and the surrounding cement paste, so long as the exposure of the concrete is such as to keep it moist--as is the case at Treat Island, Maine. This paper suggests that there is a complex series of interactions among the constituents of cements, aggregates, and seawater not previously appreciated. Sulfate susceptibility of blended cements is becoming better understood and the use of certain blended cements promises to provide a useful alternative to moderately or highly sulfate-resisting portland cements. It also now is clear that no aggregate particle in portland-cement concrete long stored in an environment of moistness and moisture movement can be regarded as completely inert. What is becoming clear is that aggregates differ greatly in the nature, degree, and consequences of their chemical activity.

DOI:

10.14359/6349


Document: 

SP65-25

Date: 

August 1, 1980

Author(s):

M. Makita, Y. Mori, and K. Katawaki

Publication:

Symposium Papers

Volume:

65

Abstract:

This report describes laboratory and field tests on the corrosion preventive effects of resin coating, galvanizing, cathodic protection, concrete surface coating and commercial inhibitors used as a protection measures for steel in concrete. The following conclusions were drawn from the test results: (1) The best in protective performance among the epoxy coatings is the powder epoxy. For protective performance, a coating thickness of 150um or greater is required, but for good bond to concrete, the thickness is preferably less than 150um. Thus the coating thickness of 150um is considered to be optimum. The liquid type tar epoxy coating is not satisfactory in its protective performance or for bond to concrete. (2) Galvanization gives good protective performance but is not always satisfactory at the splash zone. (3) Cathodic protection has an excellent protective effect in the tidal area and in seawater. The voltage to be applied is preferably -1000 to -1200mV. When it is higher than -800mV, the effect is not satisfactory, and when lower than -1500 mV, over-protection may result. (4) Urethane coating over the concrete surface failed to give a satisfactory cutoff effect in the tests and proved to be of no protective value. (5) Sodium sulfite series inhibitors had no protective effect.

DOI:

10.14359/6367


Document: 

SP65-27

Date: 

August 1, 1980

Author(s):

V. D. Vanden Bosch

Publication:

Symposium Papers

Volume:

65

Abstract:

Different types of blast furnace slag cement with increasing amounts of slag were tested for sulfate resistance according to the ASTM C 452, the Koch and Steinegger test and the Mehta test; the results were compared with the performances of portland cement under same conditions. The evolution of the strengths as a function of time and of composition of the liquid phase (sea water or salt solution of 5% Na2S04 - 5% MgS04 and 5% MgC12 ) was investigated on mortar bars. The conclusions are that the chemical resistance of the blast furnace slag cement improves with the slag content; a high fineness of grinding improves both the chemical resistance and the mechanical strength. Exemples of marine structures made with blast furnace slag cements in the Netherlands are given. Some of these structures are more than 50 years old and still in an excellent condition. The best chemical resistance is obtained when the slag content of the cement is higher than 65-70%. This is imputable to the fact that, in these conditions, the formation of ettringite is impossible, due to the low content of free calcium hydroxide in the cement paste. A magnesia content of the slag higher than 5% is harmless, because Mg0 is entirely in the glass phase and not present as the expanding periclase variety.

DOI:

10.14359/6369


Document: 

SP65-20

Date: 

August 1, 1980

Author(s):

Shinzo Nishibayashi, Kiyoshi Yamura, and Shoichi Inoue

Publication:

Symposium Papers

Volume:

65

Abstract:

The seawater resistance of concrete must be considered when it is used for construction on the sea-shore or in the ocean. This paper describes an accelerated test method for assessing durability by subjecting the concrete to repeated cycles of seawater immersion and oven-drying. Test were carried out to evaluate the procedure in which, in addition to visual observation, reduction in dynamic modulus and length changes of the concrete up to 200 cycles were measured. Resistance indicators are proposed which combine these factors. Among the variables included in the test specimens it was found that seawater resistance of concrete is mainly affected by the type of cement, the water-cement ratio, the mixing water (fresh or seawater) and the age at immersion (period of pre-curing) .

DOI:

10.14359/6362


Document: 

SP65-03

Date: 

August 1, 1980

Author(s):

M. L. Conjeaud

Publication:

Symposium Papers

Volume:

65

Abstract:

Five kinds of commercial Portland cements and one C3S sample were used for the study. The test prisms were made of mortar with a cement-sand ratio of 1 : 3 and a water-cement ratio chosen in order to give an ASTM flow of 110 +_ 5 %. After 28 days water curing, the test prisms were immersed in seawater, then, at fixed periods, up to 3 years, they were investigated by means of strength tests, chemical analysis, X-ray diffraction and scanning electron microanalysis. Results obtained show that SO3 and especially Cl diffuse rapidly in the cement mortars, but their penetration is soon slowed down by the formation of an almost impermeable Mg(OH)2 and/or aragonite layer on the mortar. It is postulated that this formation of a protective layer which occur with all the cements investigated is the main reason why immersed cement mortars are little attacked by seawater, even when the cement is C3A-rich whereas attack is greater at tide level where the Mg(OH)2 and/or aragonite layer is subject to cracking.

DOI:

10.14359/6345


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