著者

荒巻 卓見 中田 善久 大塚 秀三 宮田 敦典

出版者

一般社団法人 日本建築学会

雑誌

日本建築学会技術報告集 (ISSN:13419463)

巻号頁・発行日

vol.27, no.65, pp.58-63, 2021-02-20 (Released:2021-02-20)

参考文献数

11

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The purpose of study was to clarify the quality of plywood for concrete formwork with reuse of forms and the finish of concrete surface using reused plywood. In this study, an experiment on influence of reuse (up to 4 times) of plywood for conventional formwork at building construction site was carried out. Regarding the influence of reuse on the quality of plywood, bending strength, bending Young’s modulus, and surface roughness were investigated. In addition, the influence of reused plywood on gloss, color unevenness, and water absorption of the concrete surface was investigated. Moreover, in order to confirm the influence of reuse of plywood at construction site, the results of this experiment at building construction site were compared with the results of laboratory experiment conducted so far.

著者

荒巻 卓見 中田 善久 大塚 秀三 手島 基 宮田 敦典

出版者

一般社団法人 日本建築学会

雑誌

日本建築学会技術報告集 (ISSN:13419463)

巻号頁・発行日

vol.20, no.44, pp.13-18, 2014-02-20 (Released:2014-02-20)

参考文献数

14

被引用文献数

2 3

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This study purposed for prehension about the actual situation of work from the viewpoint of formwork contractors. In this paper, we conducted a questionnaire survey about concrete form plywood, strength and rigidity of form, and formwork based on the experience of formwork carpenters in Kanto region. As a result, it elucidated the actual situation of work, concrete form plywood, strength and rigidity of form, and formwork in the construction site.

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 西 祐宜

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.762, pp.1021-1031, 2019 (Released:2019-08-30)

参考文献数

23

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Experimental research was conducted to clarify fundamental characters of high-strength concrete plasticized by air-entraining and high-range water-reducing admixture. Plasticized high-strength concrete was water cement ratio of 28 to 48%, and target slump-flow was fluidized to 50cm using air-entraining and high-range water-reducing admixture. Investigated items are adsorption characteristics of air-entraining and high-range water-reducing admixture and influence of the difference of various conditions of water cement ratio, unit water amount, slump before plasticization, environmental temperature, fluidization time on properties of plasticized high-strength concrete. As a result, air-entraining and high-range water-reducing admixture showed different adsorption characteristics during mixing and plasticization, and at plasticization, fluidity could be increased with less use than at mixing. Considering the adsorption characteristics of air-entraining and high-range water-reducing admixture, the agglomeration characteristics of cement is thought to change markedly within 180 minutes from 120 minutes after mixing. The decrease in slump-flow amount after plasticization of plasticized high-strength concrete is larger than that of standard high-strength concrete. Also, slower the plasticization time, larger the decrease in slump-flow amount. The setting time of plasticized high-strength concrete tends to be faster than standard high-strength concrete, and the difference increases as environmental temperature to colder. Among properties of hardened concrete, effect of plasticizing by air-entraining and high-range water-reducing admixture on compressive strength, Young's modulus and drying shrinkage ratio was small. From the above results, high-strength concrete plasticized by air-entraining and high-range water-reducing admixture has same points to be noted as conventional plasticized concrete, such as decrease in slump-flow amount after plasticization is larger and setting time faster. However, it is possible to obtain hardened concrete comparable to standard high-strength concrete while reliably obtaining necessary slump-flow.

著者

宮田 敦典 中田 善久 大塚 秀三

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.751, pp.1217-1227, 2018 (Released:2018-09-30)

参考文献数

38

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It is significant to accurately grasp the pressure loss per unit length of pipeline in calculating total pressure of pipeline. The standard value of pressure loss per unit length of pipeline is shown in recommendation for practice of placing concrete by pumping methods. The standard value of pressure loss per unit length of pipeline were obtained from pumping experiment conducted around 1970. But, mix-proportion and concrete materials has changed compared to the 1970s. Especially, design strength has risen compared to the 1970s, and high-range AE water reducing agent was developed and has spread. Therefore, concrete that has been used recently can't apply the standard value of pressure loss per unit length of pipeline. So this study aimed to reveal influence of mix-proportions on the pressure loss per unit length of pipeline by literature survey and pumping experiment. In the first, we studied the influence of water-cement ratio on the pressure loss per unit length of pipeline. Pressure loss per unit length of a pipe tended to be roughly proportional to the square of cement-water ratio. Next, we examined pressure loss per unit length of pipeline for each slump of concrete that more than W/C 45%, and we examined pressure loss per unit length of pipeline for each unit water content of concrete that less than or equal to W/C 45%. As a result, pressure loss per unit length of pipeline tended to increase when slump decrease and unit water content is low. And we derived the relational expression between pressure loss per unit length of pipeline and true output capacity. In additions, this paper proposed standard value of pressure loss per unit length of pipeline of concrete that more than W/C 45% on the basis of literature survey results. Finally, we confirmed the validity of the relational equation obtained from literature survey by pumping experiment. This paper shows a result of pressure loss per unit length of pipeline of concrete with normal portland cement. Therefore, we should does experiment of test pumping with reference to result of this paper when we use concrete with cement and materials other than normal portland cement.

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.