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 51 Abstracts search results

Document: 

SP234

Date: 

March 22, 2006

Author(s):

Editor: V.M. Malhotra

Publication:

Symposium Papers

Volume:

234

Abstract:

SP-234 The Canada Centre for Mineral and Energy Technology (CANMET) of Natural Resources, Ottawa, Canada, has played a significant role in Canada for over 40 years in the area of durability of concrete. CANMET, in association with the American Concrete Institute and the Institute for Research in Construction/National Research Council, Ottawa, sponsored the First CANMET/ACI International Conference on Concrete Durability held in Atlanta, Georgia, April 27-May 1, 1987. The refereed proceedings of the Atlanta conference and Montreal conference (the Second CANMET/ACI International Conference on Concrete Durability, held August 4-9, 1991) were published as ACI SP-100 and ACI SP-126, respectively. Unlike the first conference, this second conference was not named after any individual(s), and the future conferences in this series would follow this precedent. In 2006, CANMET, in association with several other organizations in Canada and the U.S., sponsored the Seventh CANMET/ACI International Conference on Durability of Concrete. The conference was held in Montreal, Canada, on May 28-June 3, 2006. More than 75 papers were peer reviewed in accordance with the policies of the American Concrete Institute. The proceedings of the conference, consisting of 50 refereed papers, were published by the American Concrete Institute as ACI SP-234. In addition to the papers that have been published in the refereed proceedings, more than 50 other papers were presented at the conference. A number of these were published as supplementary papers in a special volume. During the conference, special sessions were held on subjects with sulfate attack on concrete and high-performance lightweight concrete. Some of the papers related to these subjects were published in the supplementary volume. Thanks are extended to more than 15 review panel members who met in Budapest, Hungary, in 2002 to review the papers. Without the dedicated efforts of the reviewers, it would not have been possible to have the proceedings ready for distribution at the conference. The cooperation of the authors in accepting reviewers’ suggestions and in revising their manuscripts accordingly is greatly appreciated. The authors are also to be commended for their prompt return of their finalized manuscripts. The assistance of A. Bilodeau, Chair of the audio-visual review panel, is gratefully acknowledged. Thanks are also extended to P. Gupta and C. Mansfield-Joiner for their help in processing the manuscripts. The contributions of the ACI staff for their help in publishing the proceedings on time is also recognized. As an integral part of the conference, a special symposium was held to honor Professor K. Sakata of Japan for his outstanding contributions in the broad area of concrete design and technology over the past 20 years. The proceedings of the symposium were published as a separate volume.

DOI:

10.14359/15727


Document: 

SP234-35

Date: 

March 22, 2006

Author(s):

T. Schmidt, J. Neuenschwander, M. Romer, and T. Luthi

Publication:

Symposium Papers

Volume:

234

Abstract:

Deterioration processes on concrete structures are a result of an interaction between the concrete and its environment. In this project the mechanisms of deterioration due to chemical interaction of sulfate containing aqueous solutions are being investigated by a non destructive test method. It uses ultrasonic surface waves to investigate the topmost layer of mortar samples. A pitch and catch arrangement in immersion technique is used to generate the so-called leaky Rayleigh wave. A reduction of the measured sound velocity is proposed to be an indicator of the degradation of the surface region of the mortar sample. First measurements have been performed for reference mortar and for mortar samples exposed to aggressive conditions. A reduction of the velocity of the leaky Rayleigh wave of more than 5% could be detected. This physical alteration was compared and correlated with microscopical findings of the surface layer.

DOI:

10.14359/15959


Document: 

SP234-31

Date: 

March 22, 2006

Author(s):

F.P. Glasser and K.L. Scrivener

Publication:

Symposium Papers

Volume:

234

Abstract:

The degradation of concrete exposed to environments containing sulfate ions is a complex phenomenon. The increasing complexity of cementitious materials through the incorporation of supplementary cementing materials coupled with the demand for structures with longer service life, require a better understanding of the process of sulfate attack. This paper discusses the issues involved and presents the approach of the NANOCEM consortium to the research needs.

DOI:

10.14359/15955


Document: 

SP234-32

Date: 

March 22, 2006

Author(s):

K. Yamada, M. Ichikawa, K. Honma, H. Hirao, and D. Mori

Publication:

Symposium Papers

Volume:

234

Abstract:

In order to examine the possibility of thaumasite formation in concrete containing limestone powder and exposed to marine environments, immersion tests in artificial seawater, chloride and sulfate solutions at 5 & 20 °C were carried out as well as an exposure test in cold marine environments around 2.6 °C. From laboratory tests of 6 months compressive strength of mortar was found to decrease when immersed in chloride bearing solution. This was caused by an increase in porosity by the dissolution of Ca(OH)2. Although in sulfate solution no compressive strength decrease was observed even at 5 °C, thaumasite formation was detected in mortar containing limestone. However, after exposure in cold marine environment for 1.5 years, no degradation and no thaumasite formation was observed in seawater exposure. It is suggested that chloride ions suppress the formation of thaumasite to some degree.

DOI:

10.14359/15956


Document: 

SP234-33

Date: 

March 22, 2006

Author(s):

H. Justnes and E. Rodum

Publication:

Symposium Papers

Volume:

234

Abstract:

Condition survey of cementitious composites serving under three widely different environments revealed that thaumasite; Ca3Si(OH)6(SO4)(CO3) 12H2O, had contributed to the general degradation of the material. The first case was a concrete beam from a manure cellar at a farm. There was severe degradation of the outer parts due to sulfate attack under conditions of high degree of water saturation. The binder was cracked and substantial amounts of thaumasite were identified. The source of carbonate for the thaumasite formation may be carbonation or urea-cement interaction, while the required sulfate comes from the manure as such or oxidized sulfides. The second case was a bridge where seagulls have nested on the lower I-beam for a few years. It was heavily polluted by guano from the birds containing chlorides, phosphates, sulfates and nitrogen compounds (urea, nitrates etc). Degradation of the microstructure started in the outer layers with deposition of a number of odd compounds along with thaumasite. The third case was a cooling water pipe made of asbestos reinforced cementitious binder (no aggregate). The cooling water was seawater and the 30 years old tubes had started to break occasionally when pumps were started. About 15 mm of the totally 36 mm wall thickness was affected chemically by seawater from both sides. Thaumasite layers were found parallel with the tube length along with cracks. The sulfate source is likely to be seawater.

DOI:

10.14359/15957


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