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International Concrete Abstracts Portal

Showing 1-5 of 13 Abstracts search results

Document: 

SP220

Date: 

March 1, 2004

Author(s):

Editors: Ole Mejlhede Jensen, Dale P. Bentx and Pietro Lura / Sponsored by: ACI Committee 236

Publication:

Symposium Papers

Volume:

220

Abstract:

Autogenous deformation of concrete is the free deformation of sealed concrete at a constant temperature. A number of observed problems with early-age cracking of high-performance concrete can be attributed to this phenomenon. During the last 10 years, this has led to an increased focus on autogenous deformation within both concrete practice and concrete research. The papers in this publication were presented at the American Concrete Institute’s Fall Convention in Phoenix, Arizona, October 2002, and will help readers understand the complexity of the autogenous deformation of concrete. The 12 papers from eight different countries indicate the broad, global research efforts dealing with autogenous deformation, and illustrate that interest in autogenous deformation is shared throughout the worldwide concrete community. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP220

DOI:

10.14359/14028


Document: 

SP220-11

Date: 

March 1, 2004

Author(s):

B.S.M. Persson

Publication:

Symposium Papers

Volume:

220

Abstract:

An experimental investigation of HPSCC, is outlined. Optimizations were performed on a laboratory scale according to an ideal grading of the particles in the fresh concrete for SCC, with high strength, high durability in marine environment or with fire spoiling safety. SCC was introduced in the full-scale production of beams and piles. The results showed high slump flow and robustness that allowed for a reasonable variation of the water-cement ratio, w/c, keeping the fresh concrete properties within the limits of the full-scale production even at elevated temperature. Creep, shrinkage, salt frost scaling and sulphate resistance did not differ much from the corresponding properties of vibrated concrete, NC. Internal frost resistance was improved for SCC compared with NC but the chloride migration was larger in SCC with limestone powder than in NC. Spoiling of the concrete during fire, especially in low-w/c concrete, was avoided by use of polypropylene fibers.

DOI:

10.14359/13156


Document: 

SP220-03

Date: 

March 1, 2004

Author(s):

K. S. Douglas and K. C. Hover

Publication:

Symposium Papers

Volume:

220

Abstract:

This paper evaluates a test method for measuring bulk, autogenous volume changes in cement paste and mortar. In this test method, paste and mortar were sealed in latex membranes and submerged in water. The weight of the specimens was recorded periodically, both in air and submerged in water, and their volume change was calculated using Archimedes' principle. Several sources of error in the test method were identified, and measures were taken to account for some of this error. It was concluded that the experimental error for this test may be quite substantial as the test duration increases, and therefore this test method is most suited for measuring the early age volume changes of cement paste and mortar.

DOI:

10.14359/13148


Document: 

SP220-05

Date: 

March 1, 2004

Author(s):

P.-C. Aitcin, G. Haddad, and R. Morin

Publication:

Symposium Papers

Volume:

220

Abstract:

High-performance concrete is very vulnerable to early cracking because it does not bleed and it develops within the first 24 hours a significant autogenous shrinkage when it still has a very weak tensile strength. Plastic shrinkage cannot always be fought with curing membrane: fog spraying is much more appropriate. Among the different means already available to fight early autogenous shrinkage external water curing is a very efficient one. Water curing must be extended for 7 days. At the present state of the technology concretes having a water/cement ratio of 0.36 are the more robust against early cracking when an external water curing is used. The cost of water curing can represent from 0.1 to 1.5% of the total construction cost of concrete structures, a good investment in a sustainable development perspective.

DOI:

10.14359/13150


Document: 

SP220-04

Date: 

March 1, 2004

Author(s):

P. Lura, Y. E. Guang, and K. van Breugel

Publication:

Symposium Papers

Volume:

220

Abstract:

In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure.

DOI:

10.14359/13149


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