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Home > Publications > 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 62 Abstracts search results
Document:
SP179-36
Date:
June 1, 1998
Author(s):
H. Takenaka, M. Kakizaki, Y. Abe and M . Okada
Publication:
Symposium Papers
Volume:
179
Abstract:
A new method is proposed for the preparation of specimens of high fluidity concrete with excellent flowability and segregation resistance that can not be fully controlled by the current Japanese Industrial Standard. Procedures recommended are: (1) Slump cone should be filled in three equally divided volumes followed by rodding of 5 strokes at each layer; (2) Flow time recommended for quality control should be in 5 to 10 seconds; (3) Cylinder mold of $10 x 20 cm for the compressive strength test should be filled in two equally divided volumes followed by a rodding of five strokes at each layer, considering coarse aggregate content and stability of mechanical properties.
DOI:
10.14359/6063
SP179-37
A. Nishio, H. Tamura and M. Ohashi
Dry crushed rock fines (CRF) which is a nuisance waste at crushed rock aggregate plants has been investigated for its use as a mineral addition in concrete. According to the research conducted so far, both methylene-blue test and sand equivalent test can be applied for the screening test on the quality of CRF Furthermore, CRF is useful not only as supplemental fines in fine particle lacking aggregates such as sea-dredged sand, but also for high-volune fines in self-compacting concrete. This paper presents the test results of a prototype reinforced concrete column and wall structure cast with self-compacting concrete (SCC) containing high-volume of CRF (CRFSCC). Judging from the test results of concrete cores obtained from the column and wall of the structure, the following conclusions were obtained. 1) The greater the distance the concrete flowed through reinforcing steel bars, the greater the segregation of the CRFSCC. 2) Both the front part of the CRFSCC flow and upper part of the CRFSCC structure contained less amount of coarse aggregate, and showed both low values for modulus of elasticity and high values for drying shrinkage. 3) In order to get more homogeneous quality in the structure with CRFSCC, special care is needed for concrete casting procedures. It is suggested that a reverse casting flow direction technique may be effective. 4) Drying shrinkage of CRFSCC did not result in deleterious cracking on the structure.
10.14359/6064
SP179-38
T. Ogasawara, H. Naito, T. Miura, T. Abe and R. Ohmura
Recently, application of super-workable concrete with high flowability, has been increasing in tbe construction of steel-concrete composite structures of sandwich systems, concrete-filled steel tubes, and structures with congested reinforcing bar arrangements since compacting of concrete is difficult in those kinds of structures. In such cases, it is necessary to avoid impairing integrities of the structures as a result of gaps formed between steel and concrete due (0 subsidence and shrinkage of concrete and cracks formed due to restraint by steel. In this study, the influences of the kinds of cement and admixtures, and differences of addition rates on autogenous shrinkage, drying shrinkage, and subsidence of super-workable concrete are examined, as are the influences on gaps formed under diaphragms in concrete as well. As a result, it is found that shrinkage and subsidence behaviors differ considerably depending on the kinds of concrete and admixtures.
10.14359/6065
SP179-39
A. Yasumoto, Y. Edamatsu, M. Mizukoshi and S. Nagaoka
in conjunction with Self-Compacting Concrete and the varying resistance levels to shrinkage crack due to autogenous and drying shrinkage. Resistance was estimated by comparing the cracking-ages of the concrete under restrained conditions. The powdered materials used were normal portland cement, low-heat portland cement, portland blast-furnace slag cement, two blends of normal portland cement and limestone powder (the blending volume ratios of limestone powder were 30% and 55%). From the results of the experiments, it became clear that the resistance level of Self-Compacting Concrete to shrinkage crack was quite different depending on the type of powdered materials used.
10.14359/6066
SP179-40
S. Hiraishi, K. Yokoyama and Y. Kasai
Flowing concrete is a highly flowable and segregation resistant concrete. Shrinkage of the concrete at early ages up to 24 hours under a constant air flow of 8 m/s starting at the age of 2 hours, and crack propagation of the concrete in a restricted form with a thickness of 50 mm have been studied. The experiments were done by controlling the following four mixture parameters, (I) Water - cement ratio: 0.60, 0.45, 0.35, 0.30 and 0.27, (2) Unit amount of water: 185, 175 and 170 kg/m3, (3) Type of cement: normal, high early strength and belite portland cement, (4) Type of inorganic admixture: a ground granulated blast furnace slag and a fly ash and their respective mixture proportions. Effects of the above parameters on crack propagation at early ages were investigated on the basis of authors’ crack evaluation criteria.
10.14359/6067
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