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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 60 Abstracts search results
Document:
SP178
Date:
June 1, 1998
Author(s):
Editor: V.M. Malhotra
Publication:
Symposium Papers
Volume:
178
Abstract:
SP-178 This Symposium Publication contains the proceedings of the Fourth CANMET/ACI/JCI International Conference held in Tokushima, Japan, in June 1998. Sixty-two refereed papers were accepted for presentation at this conference and for this publication.
DOI:
10.14359/14171
SP178-08
I.D. MacGregor
Elasticity, shrinkage, and creep to one year were measured on 150 mm diameter by 300 mm cylinders made from concrete with crushing strengths of 40 and 70 MPa and slumps of approximately 80 mm. Within each strength grade a 25% fly ash replacement concrete was designed to match the normal portland cement (NPC) slump and 28 day strength. Creep samples were loaded at 3, 7, 14 and 28 days after water curing at 27°C and then tested in air at 25 o C and 65% relative humidity to approximately match Hong Kong’s sub-tropical climate. The maximum interval between readings was 14 days. Interface creep cylinder surfaces were ground. Hong Kong materials were used. The ash has a cementing efficiency that varies from 74 to 114% and typically has a silica content of 52% and an alkali oxide content of 3%. The admixtures used were a lignosulphonate/carbohydrate retarding water reducer/plasticiser, and a napthalene sulphonate and modified lignosulphonate superplasticizer. Hong Kong elasticities can be low due to the aggregates used; a granite in this study. There was little difference between the NPC and fly ash pairs of concrete samples at the end of one year. The similarity is considered to be due to the high fly ash cementing efficiency and the relatively high humidity testing regime. There was little variation in the 12-month elasticities and shrinkages between the four curing ages but big decreases in the 12-month load induced specific creeps.
10.14359/5976
SP178-09
M. Kurita and T. Nomura
This paper presents the development of a new type of high-performance concrete, a highly-flowable steel fiber-reinforced concrete. This concrete has superior characteristics, such as high flowability and adequate segregation resistance, retention of high flowability, and high-strength at an early age. In order to obtain such properties, it is necessary to use high early-strength portland cement, fly ash, a viscosity agent, an air entraining and a high-range water reducing admixture. Moreover, partially replacing cement with fly ash is found to be an effective method to improve the retention of slump flow. Pumpability of highly-flowable steel fiber-reinforced concrete containing fly ash has also been evaluated from the results of the experimental pumping tests.
10.14359/5977
SP178-10
K. Kohno, Y. Mitsuiwa and K. lshimaru
The effects of steam curing conditions such as the presteaming period and the maximum curing temperature on the compressive strength of fly ash concrete were investigated and compared with those of plain concrete in order to use fly ash for precast concrete products. The replacement ratios of cement by fly ash were 0, 20 and 40 percent. The presteaming period ( 2, 4 and 6 hours ) and maximum temperature during steam curing ( 65°C and 80°C ) were varied in this test. The compressive strength of 100 X 200 mm cylinder specimens were determined at the ages of 1, 7 and 28 days. As a result of this investigation, the adoption of a longer presteaming period of 4 to 6 hours and a maximum curing temperature from 65°C to 80°C is recommended for the steam curing of fly ash concrete to obtain higher strength at various ages.
10.14359/5978
SP178-11
H. Justnes,B. Ardoullie, E. Hendrix, E.J. Sellevold and D. Van Gemert
The total chemical shrinkage of silica fume and Class F fly ash, both as pozzolanic materials reacting with lime and as mineral additives replacing portland cement, was studied. The external chemical shrinkage of cement paste with silica fume and fly ash replacement was studied as well. By increasing pH the rate related to the pozzolanic reaction decreased for sitica fume and increased for fly ash. Although the presence of alkalis are catalytically necessary for a rapid pozzolanic reaction of silica fume, the pH increase reduces the solubihty of calcium hydroxide (CH) due to the common ion effect. This may explain why the reaction rate decreases if dissolution of CH, followed by precipitation of CSH, is the rate-limiting step. The increased reactivity of fly ash, caused by a pH increase, indicates that the dissolution of the glassy aluminosilicate phase by alkalis was determining the overall rate of the process. The total chemical shrinkage was crudely estimated to be 8.8 ml/l00 g of reacted silica fume and 10.0 ml/l00 g of reacted fly ash, as compared with 6.3 ml/l00 g of portland cement. The measured shrinkage for silica fume could be higher than the above value since minor amounts of silicon metal in the silica fume could produce an expansion due to evolved hydrogen gas.
10.14359/5979
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