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International Concrete Abstracts Portal

Showing 1-5 of 48 Abstracts search results

Document: 

SP200-16

Date: 

June 1, 2001

Author(s):

M. K. H. Patoary and P. Nimityongskul

Publication:

Symposium Papers

Volume:

200

Abstract:

The investigation presented in this study shows an example of the improvements of fly ash fineness achieved by a physical process, air-classification and a mechanical process, grinding. To make high-performance concrete, three different types of fly ash namely, original, air-classified, and ground fly ash, with different finenesses was used as cement replacement. The percentage replacement of cement by each type of fly ash was used as 0, 10, 15 and 20% by weight of cementing materials. Finally, the results were compared with silica fume concrete. The results showed that substitution of part of the cement with original or classified fly ash produces concrete mixtures with greater workability than the control as measured by slump and slump-flow. On the contrary, it was found that the ground fly ash, having more or less the same degree of fineness as classified fly ash resulted in a lower workability due to the loss of its spherical shape and lubricant effect. The inclusion of original fly ash reduced the early strength and this reduction was more significant with the increase of percentage replacements. Classified and ground fly ash improved the early strength. The long-term strength development of classified and ground fly ash concrete was found to be considerably higher than that of control concrete for all the percentage replacements.

DOI:

10.14359/10583


Document: 

SP200-35

Date: 

June 1, 2001

Author(s):

J. Beslac and K. Mavar

Publication:

Symposium Papers

Volume:

200

Abstract:

The results of laboratory and in situ tests of a number of different types of coatings commercially available in Croatia (polymer-cement, epoxy, acrylic, epoxy-acrylic and epoxy-polyurethane), used for reinforced concrete protection of the KRK bridge, are presented. The tests have been carried on throughout the last ten years. Some coatings like epoxy and polymer-cement were found completely unacceptable for the technical reasons. However, epoxy-polyurethane coatings applied on the concrete finished with the thin layer of epoxy-cement mortar are estimated rather effective. They had high adhesion strength (above 2,0 MPa), very low gas permeability, low capillary absorption, satisfactory water vapour diffusion and satisfactory ageing resistance.

DOI:

10.14359/10602


Document: 

SP200-42

Date: 

June 1, 2001

Author(s):

S. K. Mandal and M. A. Mansur

Publication:

Symposium Papers

Volume:

200

Abstract:

Unlike circular columns, jacketing of oblong or wall-type columns produces only marginal improvement in strength and ductility because of inadequate confinement and premature debonding of the wrap. Some possible ways to overcome this problem, at least partially, are to round the corners, to add a semi-circular segment at each of its shorter sides or to produce an elliptical shape enclosing the oblong column. A total of 13 specimens of these cross sectional shapes were tested in direct compression to assess the enhancement afforded by external fiber wraps. It has been found that the modification of a rectangular section by including a semi-circular segment on each of its shorter side or transforming the section to an ellipse before applying fiber wrap leads to a substantial improvement in strength as well as ductility. Of the two fibers used, the glass fiber composite proved to be more cost effective in terms of strength and ductility enhancement.

DOI:

10.14359/10609


Document: 

SP200-44

Date: 

June 1, 2001

Author(s):

P. Stroeven, Z. Shui, C. Qian, and Y. Cheng

Publication:

Symposium Papers

Volume:

200

Abstract:

This paper deals with trial testing on concrete reinforced by different combinations of carbon-steel, polypropylene-steel or steel-steel hybrid fibres in the low volume content range to ensure high electrical resistivity of the fibre concrete. Optimum reinforcement composition is obtained for (compression, splitting tension, and flexural) strength testing conditions and for post-peak behaviour. The effect of various measures adopted to promote uniform fibre distribution are assessed by impedance measurements. During the testing program, fibre distribution is checked by microscopy and SEM.

DOI:

10.14359/10611


Document: 

SP200-26

Date: 

June 1, 2001

Author(s):

V. Matte, M. Cheyrezy, M. Moranville, C. Richet, and J-M Torrenti

Publication:

Symposium Papers

Volume:

200

Abstract:

The Reactive Powder Concretes (RPC) are well known for their high strength, but they also present good performances regarding durability aspect due to their very dense microstructure. Studies were made to evaluate the durability of RPC to : freeze-thaw scaling, carbonation, chloride ions diffusion, abrasion coefficient and shrinkage. Their very good performance characteristics have led to a specific research programme to evaluate the long-term durability of RPC for nuclear waste containment. Several kinds of potential degradation are studied, but here only the attack by de-ionised water, a very severe leaching test, will be presented. After pre-determined periods, the material was analysed regarding its microstructure (altered depth, composition and mineralogical changes), porosity and ion transport properties. The results of SEM, X-Ray diffraction, mercury intrusion porosimetry, BET pore-size and tritium diffusion coefficient analyses are presented.

DOI:

10.14359/10593


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