著者

梅本 宗宏 森田 武 梶田 秀幸 平島 岳夫

出版者

公益社団法人 日本コンクリート工学会

雑誌

コンクリート工学 (ISSN:03871061)

巻号頁・発行日

vol.55, no.10, pp.869-873, 2017 (Released:2018-10-01)

参考文献数

2

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日本建築学会では,各種構造材料の火災時を想定した高温性状に関する情報を体系的に整理・取りまとめた「構造材料の耐火性ガイドブック 2017」(第3版)を2017年2月に刊行した。本ガイドブックでは,建築で用いられる構造材料を,コンクリート材料・鋼材・木質系材料・アルミニウム合金および新材料(FRP,ガラス,膜材料等)の5つに大分類し,火災時および火災後を想定した材料の高温性状に関する文献調査ならびに系統的な整理を行っている。本稿は,本ガイドブックの概要を報告する。

著者

南 浩輔 太田 健司 舟橋 政司 梶田 秀幸

出版者

公益社団法人 日本コンクリート工学会

雑誌

コンクリート工学 (ISSN:03871061)

巻号頁・発行日

vol.57, no.1, pp.91-93, 2019 (Released:2020-01-01)

参考文献数

11

被引用文献数

1

著者

中田 善久 斉藤 丈士 梶田 秀幸 大塚 秀三 春山 信人

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.82, no.738, pp.1145-1154, 2017 (Released:2017-08-30)

参考文献数

17

被引用文献数

3 4

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The authors have carried out the experiments to identify the effects on fluidity, resistance to segregation, strength, Young's modulus, dry shrinkage and durability of high-strength concrete when unit water content was varied in high-strength concrete while unit bulk volume of coarse aggregate was fixed, or the volumetric ratios of cement paste and fine aggregate were varied. Three types of cement, ordinary Portland cement, moderate-heat Portland cement and low-heat Portland cement, were used. Limestones were adopted as coarse aggregate. Water-cement ratio was varied with 45, 35 and 25%. Analysis were carried out in concern with properties of fresh concrete, properties of concrete hardening, and properties of hardened concrete where unit water content was varied. When water-cement ratio was 35%, changes in the properties of high-strength concrete with hard sandstones used as coarse aggregate owing to the increase of unit water content were also examined. As a result of the experiments, it was found that increasing of the water content caused no segregation of materials, facilitation of handling, reducing of changes in the retention of slump and slump flow, increasing of flow velocity in L-box tests and increasing of bleeding only slightly. Few effects were observed on the initial properties and on the properties of hardened concrete. Based on the above, it is assumed that slightly increased unit water content in the range between 5 to 10 kg/m3 in high-strength concrete with fixed unit bulk volume of coarse aggregate will improve construction performance without great affection of the quality parameters while the deterioration of the parameters has been afraid when unit water content was increased.

著者

中田 善久 斉藤 丈士 梶田 秀幸 大塚 秀三 春山 信人

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.83, no.748, pp.751-761, 2018 (Released:2018-06-30)

参考文献数

14

被引用文献数

3

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The authors have carried out experiments to identify the effects on fluidity, separation resistance, strength, Young's modulus, drying shrinkage and durability of high-strength concrete when sand-total aggregate ratio was varied. In high-strength concrete while water-cement ratio and cement-paste volume was fixed, that is, volumetric ratios of coarse aggregate and fine aggregate were varied. Three types of cement, normal portland cement, moderate-heat portland cement and low-heat portland cement, were used. Limestones and sandstones were adopted as coarse aggregate. Water-cement ratio was fixed as 35%. Unit water content was fixed as 170kg/m3. Analysis were carried out in concern with properties of fresh concrete, properties of concrete hardening, and tendency of properties of concrete where sand-total aggregate ratio was varied. As a result of the experiments, If sand-total aggregate ratio is smaller than general range, impression of state of fresh concrete tends to be somewhat impaired, but even if sand-total aggregate ratio is somewhat larger than general range, impression of state of fresh concrete is it was not compromised. However, when sand-total aggregate ratio is large as addition rate of high-performance AE water-reducing agent is significantly large, impression of state is impaired due to separation of fresh concrete in addition to increase in bleeding and delay of settling-time. In hardened concrete, influence of sand-total aggregate ratio on compressive strength is small, As sand-total aggregate ratio is larger, tendency of young's modulus to slightly decrease, tendency of length change by drying to slightly increase, tendency of carbonation depth to slightly increase. Based on the above, high-strength concrete may possibly obtain hardened concrete of required quality even if sand-total aggregate ratio is increased somewhat within range where separation resistance is not impaired in consideration properties of fresh concrete.

著者

梶田 秀幸 中田 善久 桝田 佳寛 笹倉 博行

出版者

日本建築学会

雑誌

日本建築学会構造系論文集 (ISSN:13404202)

巻号頁・発行日

vol.84, no.761, pp.905-915, 2019 (Released:2019-07-30)

参考文献数

19

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In this study, with high strength concrete ranging from slump 21 cm up to slump flow 60 cm as the applicable range; in order to shed light on the steady-state flow of fresh concrete in inclined flow test apparatus, we compared and examined the velocity at the tip of the flow determined the vicinity of the gate and the velocity at the tip of the flow of the inclined portion determined from near the end of the test apparatus. Then, based on the relationship between the apparent shear strain rate and the apparent shear stress determined from the velocity at the tip of the flow of near the end of the test apparatus in the inclined portion, we calculated the apparent yield value and the apparent plastic viscosity, and we examined it appropriateness by comparing with the yield value and the plastic viscosity calculated by Terada et al. In addition, we carried out a pumping experiment with an actual pipe length of about 35m, and in addition to confirming the appropriateness of the apparent yield value and the apparent plastic viscosity from the change in the quality of concrete before and after pumping, with regard to evaluation of pumpability of concrete from the relation of pressure loss inside the pipe, we compared and examined with the outcome of the studies conducted by Wami et al. and Terauchi et al. As a result, the following findings were obtained. (1) By measuring the velocity at the tip of the flow of near the end of the test apparatus in the flow portion of the inclined flow test apparatus, we measure the velocity at the tip of the flow where deformation and flow due to the weight of the concrete is close to the steady-state flow, and we could obtain appropriate apparent yield value and apparent plastic viscosity. (2) We proposed the test method of apparent rheological constants determined from the velocity at the tip of the flow of near the end of the test apparatus in the flow part of the inclined flow test apparatus. (3) As a result of investigating the changes in the quality of concrete before and after pumping, values of the apparent yield value and the apparent plastic viscosity obtained from the inclined flow test were appropriate, and the apparent plastic viscosity may evaluate the viscosity of the concrete. (4) As a result of investigating the relationship with pressure loss inside the pipe, it was found that the apparent plastic viscosity obtained from the inclined flow test shows the plastic viscosity of concrete, and it suggested that it may be possible to evaluate the pressure loss inside the pipe from the product of apparent plastic viscosity and actual discharge amount.