Concrete Research and Technology

Aging Characteristics and Quantification of Internal Water in Concrete under Drying

Doyeon Kwak, Katsuro Kokubu, Kimitaka Uji

2005 Volume 16 Issue 3 Pages 1-10
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_1

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Internal water in concrete has a significant relation on the pore structure.Except for chemically combined water, all water exists in pore and its aging characteristics change with pore.For the purpose of quantification and classification of internal water in concrete, this study is conducted by long-term drying test.Results suggest that internal water can be classified with combined water, evaporated water, hydrated water under drying and remained water. Furthermore, water rate in each type under different water-cement ratio and curing time can be estimated from its quantification, respectively.

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Effects of the Solid Content of Coarse Aggregate on Compactability

Jun Liaing, Kimitaka Uji, Katsuro Kokubu, Atsushi Ueno

2005 Volume 16 Issue 3 Pages 11-19
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_11

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When the shape of particle and the grading of the coarse aggregate are not adequate, the deformation resistance of concrete become large in accordance with the interaction of coarse aggregate, and the compactability may be affected greatly. In this study, the effect of the solid content on the compactability of concrete was investigated fundamentally under the condition that the solid content varied with the crushed limestone of several shapes and grading. The compaction completion energies were measured by the compaction test machine, which was developed by authors. From the test results, it was clarified that the compaction completion energy decreased with the increase of solid content. Also, we discussed the relationship between the sand-total aggregate ratio for the maximum solid content of fine-coarse blended aggregate and that for the minimum compaction completion energy based on the experiments.

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Calculation of LCC and Selection System of Repairing Method for Reinforced Concrete Members Exposed to Sea Environments

Toshiaki Takahashi, Michitaka Sakai, Hiroshi Seki, Manabu Matsushima

2005 Volume 16 Issue 3 Pages 21-29
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_21

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In recent years, the necessity and importance of maintenance management of RC structure have been recognized.Under such situation, reduction of maintenance management cost has been strongly required and life cycle cost (LCC) has been paid attention to. However, at the present stage, the calculation method and the evaluation technique of LCC have not been fully established. Moreover, LCC will be greatly influenced with social and economical conditions. The paper discussed LCC of RC members which were exposed to sea environments. Those members might be damaged due to corrosion of reinforcing bars and might be obliged to repair. Calculation method and evaluation of LCC were scrutinized especially in consideration of the price increase rate and the interest rate of capital which might be influential factors of LCC for the repairing methods. Finally, the adequate maintenance system of LCC regarding repairing method and repairing time was proposed.

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Steel Corrosion Induced by Chloride or Carbonation at Bending Crack in High Performance Fiber Reinforced Cementitious Composites

Youichi Hiraishi, Takamitsu Honma, Muneyuki Hakoyama, Shinichi Miyazat ...

2005 Volume 16 Issue 3 Pages 31-38
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_31

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High Performance Fiber Reinforced Cementitious Composites (HPFRCC) have some micro cracks under the bending load. In this study, the durability for the steel corrosion in HPFRCC is clarified. Therefore, the corrosion cell formation pattern and the rate are compared between HPFRCC and plain mortar. Especially, the multiple cracks at HPFRCC are focused. As a result; 1) The corrosion cell formation pattern of HPFRCC is microcell, while that of plain mortar is macrocell. 2) The corrosion rate of HPFRCC is lower than that of plain mortar. 3) From the above results, it can be confirmed that the durability for chloride or carbonation corrosion of HPFRCC is higher than that of plain mortar.

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Flexural Crack Behaviour of Reinforced Concrete Members Using Molten Slag from Industrial Waste

Takeju Matsuka, Koji Sakai, Kenya Watanabe, Satoshi Kusanagi

2005 Volume 16 Issue 3 Pages 39-48
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_39

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The melting treatment of the illegally dumped industrial waste and polluted soil in Teshima Island, Kagawa, has begun in Naoshima Island. At present, the molten slag is being used in precast concrete products and non-reinforced concrete structures as a fine aggregate.
This paper describes flexural behaviour of reinforced concrete beams using the Teshima molten slag. The experimental results showed that load carrying behaviour of reinforced concrete beams using the molten slag can be evaluated by conventional methods and the crack widths of reinforced concrete beams are influenced by the presence of molten slag and the compressive strength of concrete.

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Shear Destruction of PC Beam by Cussioned Impact Being Given Near Support

Shingo Hatano, Ichiro Kuroda, Nobuaki Furuya, Sachio Nakamura

2005 Volume 16 Issue 3 Pages 49-58
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_49

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This research has an intention to reveal shear destruction behavior of PC beams which are given impact load through sand or gravel cushion to a near point of a support. The first step of the experiment is weight falling test onto a buffer sand box placed on a PC beam, and then the residual bearing capacity of damaged beams are statically measured. With these experiments, buffer effect of sand or gravel on shear destruction of PC beams is quantitatively understood to some degree.

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Compression Failure in Reinforced Concrete Shear Wall with Ultra-high-Strength Materials

Hitoshi Kumagai, Masami Tozawa, Yukinobu Kurose

2005 Volume 16 Issue 3 Pages 59-68
Published: September 25, 2005
Released on J-STAGE: November 13, 2012

DOIhttps://doi.org/10.3151/crt1990.16.3_59

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A structural system using reinforced concrete core wall makes architectural free planning possible since the core wall can bear most of seismic force and relieve the load of columns. In this study, lateral loading tests on the reinforced concrete shear wall with 120N/mm² compressive strength concrete and uni-axial compression tests on the model extracted from the shear wall have been conducted. The test results reveal that its structural performance is greatly affected by axial compression behavior of the compression zone in the shear wall. Scale effect and lateral confinement effect should be considered appropriately in applying this structural system.

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