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.