Shuzo Otsuka

QUESTIONNAIRE SURVEY FOR COMPONENT MATERIALS AND ERECTION OF CONVENTIONAL FORMWORK BY FORMWORK CONTRACTORS

荒巻卓見ー ーーーー * 1 中田善久ー ーーーー* 2 大塚秀三ー ーーーー * 3 宮田敦典ー ーーーー* 4 キーワード: アンケート調査,型枠工事業者,在来型枠工法,内端太, セパレータ

INVESTIGATION OF REVIBRATING CONDITIONS WHEN DEFORMED BARS ARE IN CONTACT WITH INTERNAL VIBRATOR: –Influence of difference in diameter of steel bar–@@@－鉄筋径の違いによる影響－

In this study, influence of revibrating conditions on bond strength by changing diameter of steel bar were investigated. Parameters included diameter of steel bar, timing of revibration, duration of revibration and duration of contact between steel bar and internal vibrator. As a result, bond strength showed a decrease when diameter of steel bar is larger. And the influence of revibration and contact between steel bar and internal vibrator showed an increase when diameter of steel bar is smaller. This paper also proposed an appropriate method of revibration including difference diameter of steel bar.

INFLUENCE OF LENGTH OF TIP HORSE AND POSTURE ON OVERLOAD OF BOOM DEVICE IN BOOM OPERATION OF PLACING CONCRETE BY PUMPING METHOD

This paper deals with consideration in boom operation changed length of tip horse to boom and posture of boom in placing concrete by pumping method. Therefore, Quality variation of concrete after pumping show a tendency to almost equal in length pipe for boom. Pressure line for boom should be consideration that length extended pipe line is longer. In addition, Posture of boom should be consideration that take measures to prevent overload for boom as much as type M keep.

QUESTIONNAIRE SURVEY TARGETED TO SUBCONTRACTORS ON THE ACTUAL STATE OF DEMOLITION WORK

Until now, demolition work has been upgraded about technical matters and qualification system. However, actual state of demolition work from Engineer and skilled worker’s standpoint has not been fully elucidated. Therefore, the purpose of this study is to investigate the actual state of demolition work by the questionnaire survey targeted to subcontractors. As a result, this paper showed the actual state of demolition work about preliminary survey, calculation, consciousness of accepting order and contract system, construction scheme, construction control and human materials.

IMPROVEMENT IN CONCRETE SURFACE PROTECTION ABILITY USING BOTH SILANE AND SILANE-SILOXANE LAYERS

In order to improve in concrete surface protection ability with retaining its low gloss, two types of silane penetrant (silane-1 and silane-2), one type of silane-siloxane surface coating material and the standard commercial penetrant were examined. The silane penetrants having different reaction speeds were individually coated on the concrete surface. The silane-1 deeply penetrated than the silane-2. However, the silane-2 which reacts faster than the silane-1 showed the excellent properties of preventing water permeability, carbonation and chloride-ion penetration. This is supposed that it generated steadier and thicker siloxane-bond network in the inner side of the pores of the treated concrete than the other. Treatment with both silane and silane-siloxane layers showed much better properties than a single treatment of them. The combination of the silane-2 and silane-siloxane layers gave the best durability to the concrete surface among the surface treatment materials. The gloss measurement showed that the specimens coated with the silanes had low glosses as same as the untreated one. On the other hand, the specimens with the silane-siloxane resulted having high glosses because of its own high gloss.

EFFECTS OF SAMPLING DEPTH FOR DISTRIBUTION OF COMPRESSIVE STRENGTH AND STRENGTH DEVELOPMENT OF CORE SPECIMENS IN FULL SCALE MODEL OF HIGH-STRENGTH CONCRETE COLUMN USING VARIOUS CEMENTS

The purpose of this paper is to clarify effect of sampling depth for distribution of compressive strength and strength development of core specimens in full scale model of high-strength concrete column using various cements. As a result, the following conclusions are obtained: 1) Compressive strength ratio difference between uppermost and lowermost part of core specimens is reduced in proportion to core strength. 2) Coefficient of variation of core strength is reduced in proportion to core strength. 3) Apparent density ratio difference between uppermost and lowermost part of core specimens is reduced in proportion to core strength.

Application of Molten Slag Fine Aggregate Concrete Using Superplasticizer

With increasing number of melting-solidification plants for the domestic wastes and incineration ashes, the resulting molten slag is now expected as a recycled aggregate for concrete in Japan, while application examples until now are limited to non-loadbearing pre-cast concrete and concrete secondary products. This study deals with a full-scale application of molten slag recycled fine aggregate. Starting with the inspection of monthly variations in quality of molten slag fine aggregate in a plant, construction of a full-scale structure was attempted using the recycled aggregate concrete with a superplasticizer. During construction, pumpability of the recycled concrete was examined and the quality of hardened concrete in the structure was evaluated. It was shown that quality variation of the molten slag fine aggregate during eight months was sufficiently small, and pumpability as well as concrete quality in structure showed no significant difference with those of the ordinary concrete.