ABOUT THE 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.

International Concrete Abstracts Portal

Showing 1-5 of 25 Abstracts search results

Document: 

SP163-19

Date: 

August 1, 1996

Author(s):

Michel Pigeon, Ann Lamontagn, and Caroline Talbot

Publication:

Symposium Papers

Volume:

163

Abstract:

The use of dry-mix shotcrete for the repair of structures in a marine environment was the subject of an investigation carried out for the Canadian Coast Guard. In addition to the control mixture, four different mixtures using two aluminate-based accelerating admixtures at two different dosages were prepared. All mixtures contained steel fibers and silica fume and were air- entrained. For each mixture, a panel of approximately 1.0 m x 1.0 m was shot on a wharf (in the St. Lawrence River north of Quebec City) to study the influence of freezing and thawing cycles in the presence of salt water, the influence of wetting and drying cycles, and the abrasion due to ice packs. Three panels were also shot with each mixture for laboratory testing purposes (mechanical strength, durability, and microstructure). The accelerating admixtures that were used were not found to have any adverse effects on any of the properties of the hardened shotcretes. The initial setting time was reduced to values below six minutes. For all five mixtures, the resistance to scaling due to freezing in the presence of deicer salts (ASTM C672) was found to be not very good. This confirms the results of previous tests which have also shown a negative influence of silica fume on the scaling resistance of dry-mix shotcrete measured in the laboratory.

DOI:

10.14359/1368


Document: 

SP163-22

Date: 

August 1, 1996

Author(s):

Vute Sirvivatnanon, P. Marsh, and P. Nelson

Publication:

Symposium Papers

Volume:

163

Abstract:

The concrete lining the outfall canal of Munmorah Power Station, built by the Electricity Commission of New South Wales (now operating as Pacific Power) in the mid-1960s, has been subjected to flowing seawater for 30 years. Two types of concrete, a portland cement concrete and a fly ash concrete, were used for the construction of the canal. This presented an ideal opportunity for a comparison to be made of the performance of the two binders in concretes which were subjected to the same aggressive environment. Limited information was available on the concretes from trial mixture records. A recent field investigation revealed similar chloride ingress into the two concretes in the tidal zone. This was so despite the fact that the fly ash concrete had a lower binder content than the portland cement concrete. As such, a lower strength grade and, hence, a fly ash concrete with higher water permeability can perform as well as a portland cement concrete. In the dry area above the high tide mark, the carbonation depth of the fly ash concrete was greater than the portland cement concrete. No corrosion was found in any reinforcing steel, as there was sufficient cover in both concretes to prevent the chloride ions or carbonation front reaching the steel. The effectiveness of a number of investigative techniques was evaluated during the investigation. It was found that the apparent chloride diffusion coefficients, determined from short-term immersion, the water permeability coefficients, and copper to copper sulfate half-cell potential measurements were poor indicators of the real long- term performance.

DOI:

10.14359/1371


Document: 

SP163-17

Date: 

August 1, 1996

Author(s):

Adnan Sharafi, Abdulghafoor QasimiI, and S. M. K. Chetty

Publication:

Symposium Papers

Volume:

163

Abstract:

Long-term research studies on the effectiveness of corrosion protection systems for reinforced concrete exposed to aggressive environmental conditions of the United Arab Emirates have been in progress at the exposure site adjacent to Dubai Creek since December 1991. These studies cover reinforcing bar coating systems and different products comprising pore blocking admixtures and a penetrating surface sealer. The parameters included in the studies are two water-cement ratios of 0.44 and 0.6, two types of curing regimes (laboratory conditions and actual construction practices), two concrete reinforcing bar covers (10 mm and 30 mm), and three site exposure conditions above ground, below ground, and in the tidal zone). The effectiveness is assessed through accelerated laboratory tests and site exposure tests. The tests performed at different ages include compressive strength, water absorption, water penetration, capillary rise and chloride ingress, crack appling, and measurements. Also conducted were electrochemical testing comprising half-cell potential, resistivity, linear polarization, corrosion current, and AC impedance. One-year and two-year results have been previously published; the present paper updates the findings, emphasizing the electrochemical testing results. The results to date show that the performance of the epoxy coated reinforcing bar is encouraging, while the performance of the most of the products studied is not satisfactory.

DOI:

10.14359/1366


Document: 

SP163-11

Date: 

August 1, 1996

Author(s):

Paul Sandberg, Karin Pettersson, and Oddny Jorgenson

Publication:

Symposium Papers

Volume:

163

Abstract:

High-performance concrete slabs have been field exposed at the Traslovslage marine field station at the Swedish west coast since April 1992 as a part of the Cementa/Euroc sponsored project, "Durability of Marine Concrete Structures." The concrete slabs mounted on a floating pontoon are exposed in three exposure zones: submerged, splash, and upper splash zones. The results after two years of exposure confirmed the expected inverse relationship between chloride ingress and water-to-binder ratio. The use of five to 10 percent silica fume in the binder had a very positive effect on reducing the chloride ingress, but no benefit at all was found for concrete with fly ash in the binder as compared to the use of five percent silica fume. Generally, the results indicated that high-performance concrete may be regarded as extremely resistant to degradation by reinforcement corrosion, as long as effects of cracks are not considered. The extremely low levels of chloride ingress in the high-performance concrete indicated that the service life in practice will be decided by the properties of defects in the concrete microstructure. As a consequence, it was recommended that durability research on high-performance concrete should address the effects of cracks, of voids at the steel surface, and of other defects in the microstructure on the long-term performance. Such studies are currently being undertaken in Sweden, Norway, and Denmark.

DOI:

10.14359/1361


Document: 

SP163-13

Date: 

August 1, 1996

Author(s):

Shin Tanikawa, R. Narayan Swamy, and Tony Laiw

Publication:

Symposium Papers

Volume:

163

Abstract:

Concrete structures exposed to a salt-laden environment often suffer from both carbonation and chloride contamination. This paper presents test data on the ability of a highly elastic acrylic rubber coating to resist the penetration of both chloride ions and carbon dioxide. In addition, the bond strength of the coating to the concrete substrate when subjected to repeated cyclic wetting by chloride solution and drying is also reported. The chloride ion penetration resistance of the coating and its bond strength to concrete were studied by exposing reinforced concrete slabs, some fully coated and others half-coated, made with three water-cement ratios, to cycles of wetting with four percent sodium chloride solution and drying. The tests were carried out for 50 cycles extending over a period of over 500 days. The carbonation resistance of the coating was established through tests on cores taken from four structures exposed to aggressive marine conditions and subsequently repaired with the acrylic rubber coating. The results show that this acrylic rubber coating has excellent resistance to both chloride ion penetration and carbonation. No chloride ions were found in slabs fully protected with the acrylic coating. The migration of chlorides from the uncoated into the coated parts was confined to the immediate boundary between the two and was small and slow. Chloride penetration occurred by a time-dependent diffusion process, but largely in the direction of gravity. In a carbonating environment, coated concrete showed significant reduction in carbonation depth; there was evidence of realkalization of the carbonated concrete.

DOI:

10.14359/1363


12345

Results Per Page