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Showing 1-5 of 62 Abstracts search results

Document: 

SP179-07

Date: 

June 1, 1998

Author(s):

T. Yamato, Y. Emoto and M. Soeda

Publication:

Symposium Papers

Volume:

179

Abstract:

This paper presents the results of an investigation to determine the performance characteristics of concrete made with recycled coarse aggregate from a plant. Slump and air content of fresh recycled aggregate concrete are studied. The compressive strength, drying shrinkage and resistance to freezing and thawing were investigated experimentally when the types and combinations of coarse aggregate, admixture, air content and so on were varied. It was found that the recycled aggregate concrete decreased the compressive strength at 7 to 28 days as compared with those properties of the control concrete. The decrease in strength can be suppressed low by partial use of recycled coarse aggregate. Drying shrinkage of recycled aggregate concrete showed larger value than conventional crushed aggregate concrete. The use of shrinkage reducing agent can reduce the drying shrinkage of recycled aggregate concrete. The resistance to freezing and thawing of recycled aggregate concrete was lower than that of control concrete of similar composition. The decrease in resistance to freezing and thawing can be suppressed low by partial use of recycled aggregate, reducing W/C and increasing entraining air.

DOI:

10.14359/6034


Document: 

SP179-16

Date: 

June 1, 1998

Author(s):

Y. Kubo, A. Hattori, T. Miyagawa and K. Hori

Publication:

Symposium Papers

Volume:

179

Abstract:

This paper deals with various types of silanes (alcohol or water sol-vent, polymerization degree) and silane systems, which are typical hydrophobic agent as repair materials. From the viewpoint of the deterioration mechanism, water control in concrete structures is one of the most important repair strategies. Therefore, various types of surface treatments which can control water content in concrete structures are applied for repair work. Silanes and silane systems were one of the most important for hydrophobic treatment. In this study, the effect of various types of silanes and silane treatment systems on the hydrophobicity of treated concrete is investigated. Furthermore, water control property in concrete treated with silane system is discussed.`

DOI:

10.14359/6043


Document: 

SP179-17

Date: 

June 1, 1998

Author(s):

L. Coppola, R. Troli, P. Zaffaroni and M. Collepardi

Publication:

Symposium Papers

Volume:

179

Abstract:

Portland cement contains sulfur compounds from the clinker phase and from added calcium sulfate (e.g. gypsum) which acts as a set regulator. The purpose of this investigation was to study the influence of the sulfate content in the clinker phase on the performance of superplasticized concrete mixtures in terms of initial slump level at a given water-cement ratio (0.49, slump-loss rate, and compressive strength at early and later ages. Two batches (A and B) of clinker from the same kiln source were studied, the main difference being the content of sulfate (SOs) in the clinker (0.72% and 1.40% respectively). Different percentages of natural gypsum, as set regulator, were interground in a laboratory mill to manufacture portland cements: A1 , A2 , A3 from clinker A, and B1 , B2 , B3 from clinker B. Three levels of total sulfate content in terms of SOs were set: 3.0% in portland cements A1 and B1 , 3.5% in portland cements A2 and B2 ; 4.0% in portland cements A3 and B3. At a given sulfate content in portland cement, the lower the clinker sulfate content, the more effective is the slump increase of the concrete caused by the superplasticizer addition. Moreover, the lower is the clinker sulfate content, the lower is the slump-loss rate of the superplasticized concrete mixture. Finally, at a given water-cement ratio, there is a reduction in the compressive strength at early ages (< 3 days) when the low sulfate clinker is used to manufacture portland cements. These results are related to the effect of the clinker sulfate content on the degree of cement hydration: the lower the clinker sulfate content, the lower the early cement hydration in terms of gypsum consumption, ettringite formation, and tricalcium silicate (alite) hydration.

DOI:

10.14359/6044


Document: 

SP179-53

Date: 

June 1, 1998

Author(s):

Y. Kasai, M. Kawamura and J.D. Zhou

Publication:

Symposium Papers

Volume:

179

Abstract:

About 20 million cubic meters used-timbers are discharged every year from demolished buildings, mainly wooden houses in Japan. The authors have carried out a study on recycling used timber as wood-chip concrete. The experiment was carried out as follows. First, the wood-chips were filled into a steel mold to achieve the desired packing ratio with a compressive stress of 0.5-l .OMPa. Then, the fresh cement paste was injected into the mold to make the specimens. The densities of the wood-chip concrete in this case generally fall into the range of 920kg/m3 to 1250kg/m3. To evaluate the performance of the wood-chip concrete, bending strength, compressive strength, drying weight loss and shrinkage, thermal conductivity, and thermal expansion were tested. Furthermore, two types of artificial light-weight aggregate were added to the wood-chips mold and cement paste simultaneously to reduce the densities of the concrete, and the compression of the wood-chips for packing was not needed in the production process. The densities of the wood-chip concrete with the light weight aggregates were about 780kg/m’ to 92Okglm’. After these tests, it became clear that the wood-chip concrete will be suitable for use as a building material, for partition walls, floor joists, floor boards, etc.

DOI:

10.14359/6079


Document: 

SP179-06

Date: 

June 1, 1998

Author(s):

B.K. Van, D.G. Montgomery, I. Hinczak and K. Turner

Publication:

Symposium Papers

Volume:

179

Abstract:

This paper describes rapid testing methods for determining blocking behaviour, deformability and segregation resistance of self-compacting concrete. Laboratory test results have shown that the proposed methods can reduce the required extent of laboratory testing and enable the tests to be carried out in less time. A simple apparatus for segregation resistance testing is also proposed. This apparatus and modified L-box apparatus are considered useful for rapid testing of segregation resistance, deformability and blocking behaviour of fresh self-compacting concrete.

DOI:

10.14359/6033


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