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International Concrete Abstracts Portal

Showing 1-5 of 48 Abstracts search results

Document: 

SP200-31

Date: 

June 1, 2001

Author(s):

B. C. Han, H. D. Yun, and S. Y. Chung

Publication:

Symposium Papers

Volume:

200

Abstract:

The use of recycled-aggregate concrete is increasing faster than the development of appropriate design recommendations. This paper reports limited experimental data on the shear capacity of reinforced concrete beams recycled-aggregate. Twelve beams were tested to determine their diagonal cracking and ultimate shear capacities. The variables in the test program were shear-span/depth ratio a/d =1.5, 2.0, 3.0, and 4.0; aggregate types; and shear reinforcement ratio ps = 0, 0.089, 0.244, 0.507, and 0.823 percent. Six of the test beams had no web reinforcement and the other six had web reinforcement along the entire length of the beam. Test results indicate that the ACI Building Code predictions of Eq. (1 l-3) and (1 l-5) for recycled aggregate concretes are unconservative for beams with a tensile steel ratio of 1 .11 percent, and a ld ratios greater than 3.0.

DOI:

10.14359/10598


Document: 

SP200-05

Date: 

June 1, 2001

Author(s):

B. te Dorsthorst, A. Fraaij, T. Kowalczyk, and G. Sluimer

Publication:

Symposium Papers

Volume:

200

Abstract:

One of the main problems of sustainable building is that the existing systems don’t lead to clean and direct reusable secondary building materials after demolition. In constructions in the Netherlands many different building materials are being used. When a building has reached its end of life, it will be demolished and it becomes demolition waste. Because a lot of different building materials will be mixed together during the demolition process, much effort must be taken before the Demolition and Construction Waste can be re-used. To solve this problem, two steps need to be taken. Firstly a building should be designed for recycling and secondly all buildings should be dismantled into elements or reduce to in clean secondary materials. The approach here is twofold. Firstly, research into the demolition/dismantling-process in order to find the bottlenecks in closing of the material cycle (at either element or material level). Secondly, as a spin-off of solving these problems, recommendations for future building-systems: design for recycling. This paper describes how certain demolition and dismantling techniques can be used in achieving the goals of sustainable design and construction.

DOI:

10.14359/10572


Document: 

SP200-07

Date: 

June 1, 2001

Author(s):

J. J. Brooks and M. A. Megat Johari

Publication:

Symposium Papers

Volume:

200

Abstract:

The effects of metakaolin and silica fume on the creep and shrinkage of concrete were investigated. Compared with the control concrete, the concrete containing the mineral admixtures had lower early age autogenous shrinkage measured from the time of initial set, but the long-term autogenous shrinkage measured from the age of 24 hours was increased. The total shrinkage (autogenous plus drying shrinkage) measured from 24 hours was reduced. Drying shrinkage was less than for the control concrete. The basic creep of sealed concrete and total creep of drying concrete were significantly reduced due to metakaolin and silica fume particularly at higher replacement levels.

DOI:

10.14359/10574


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: 

SP200-16

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


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