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International Concrete Abstracts Portal

Showing 1-5 of 34 Abstracts search results

Document: 

SP65-10

Date: 

August 1, 1980

Author(s):

V. M. Malhotra, G. G. Carette, and T. W. Bremner

Publication:

Symposium Papers

Volume:

65

Abstract:

This progress report describes the CANMET research project for the determination of durability of portland cement/ granulated blast-furnace slag/fly ash concretes in marine environment. The research project has been divided into three phases. Experimental work associated with Phases I and II is :partly complete and the experimental work for Phase III will commence in May-June, 1980. The work entails making mixtures of 0.1 m3 size with water to cementitious materials ratios ranging from 0.40 to 0.60. The cementitious materials used employed various replacements of portland cement with fly ash and granulated blast-furnace slag. The prisms and cylinders have been installed at a natural weathering station at Treat Island, Maine, where they are exposed to the effects of the alternating conditions of immersion of the specimens in sea water, then exposure to cold air and the effects of more than 100 cycles of freezing andthawing per winter. The test specimens at Treat Island are being monitored at yearly intervals for visual deterioration, and measurements are being taken to determine changes in pulse velocity and fundamental resonant frequency. The specimens from Phase I have nou been exposed for one year and the results of first yearly inspection indicate no significant deterioration of any specimens except for some surface scaling on those made with high water-cement ratios and incorporating high percentages of slag.

DOI:

10.14359/6352


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: 

SP65-28

Date: 

August 1, 1980

Author(s):

Joseph I. Heneghan

Publication:

Symposium Papers

Volume:

65

Abstract:

This paper presents data, based on extensive rehabilitation of the underside of concrete pier in the harbor of Portland, Maine, of the compressive strengths of shotcrete used as the sole repair material. This paper reviews the principal causes of damage to concrete in a marine environment, including erosion by "scour action," alternate wetting and drying in the "splash zone" and the problems resulting from intrusion of the salts contained in sea water into the concrete. Recommendations as to proper proportioning and mix designs for shotcrete to be used as the repair material for such structures is presented as well as criteria for the use of accelerating admixtures in the shotcrete material. A discussion of the use of both latex modified and calcium aluminate cement shotcrete for rehabilitating deteriorated concrete in an aquatic environment is offered. This paper also considers the proper preparation of the surfaces to be repaired as well as the special problems associated with the placement of shotcrete while working in areas subjected to tidal and wave action.

DOI:

10.14359/6370


Document: 

SP65-21

Date: 

August 1, 1980

Author(s):

Yoshio Kasai and Noboru Nakamura

Publication:

Symposium Papers

Volume:

65

Abstract:

This paper describes the use of an accelerated test method for durability of mortars using various cements exposed under the combined wetting and drying cycle conditions to seawater, simulating the concrete structures in marine environment. The mortar specimens were prepared using 12 types of cement and various water-cement ratios. The specimens were dried at 30, 60 and 80°C for 6 hours and subjected to wetting at 30°C in substitute seawater with salt concentrations of 0, 3.27 and 6.54 percent. Damage to the specimens exposed to such conditions is classed according to the following three types : scaling, cracking and sound due to attack by seawater and thermal shock.

DOI:

10.14359/6363


Document: 

SP65-15

Date: 

August 1, 1980

Author(s):

C. Y. Lin

Publication:

Symposium Papers

Volume:

65

Abstract:

Electrolysis has been used to investigate the deterioration of flexural bond in reinforced concrete structures under combined effects of exposure to marine environment and heavy sustained loads. Beams were loaded to develop specific crack widths, and loadings were then maintained to simulate the service condition. Direct current was impressed on the beams to accelerate corrosion of reinforcement so that the crack of concrete could be observed within the time limit of this investigation. The effects of impressed current on the reinforced concrete in relation to the crack width, sustained load and overload are described. Beams designed with tension reinforcement overlapped at midspan were subjected to impressed current until the concrete cracked. The average ultimate bond stress of the cracked beams was calculated based on the tension force developed in the reinforcement. A reduction in average ultimate bond stress due to corrosion of reinforcement is reported.

DOI:

10.14359/6357


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