Slipform Construction Research Articles

Experimental investigation on reducing the interface adhesion of concrete and formwork via electroosmosis approach

Slipform construction is widely used for building deep-buried vertical and inclined shaft concrete linings due to its efficiency and cost advantages. The adhesion of the interface during demoulding is crucial for the efficiency and quality of slip form construction. In this paper, a novel approach is proposed to reduce the adhesion between concrete and formwork based on electroosmotic technology. A self-designed concrete electroosmotic demoulding device was developed to simulate the electroosmotic slip-form construction of the shaft lining. The variations in parameters such as current and permeability during electroosmosis were analyzed, and the impact of electroosmotic parameters on the adhesion and demoulding quality of concrete was investigated. The results indicate that the electroosmotic method can significantly reduce the adhesion. Concrete demoulding defects are significantly reduced and smoother after electroosmotic treatment. This study provides a scientific basis and technical support for optimizing concrete construction demoulding technology.

Application of Hydraulic Slipform Construction Technology of Thin Wall Hollow Pier in Highway and Bridge Engineering

Application of Hydraulic Slipform Construction Technology of Thin Wall Hollow Pier in Highway and Bridge Engineering

Progress and Key Technical Control Points of Side Slip-form Construction Technology

Slip-form pavement of road surface construction is an efficient mechanical construction method, compared to the traditional construction method of erection of template for cast in situs or backcourt prefabrication while hoisting in the front court, slip-form construction technology dispenses with the prefabrication site and a lot of prefabrication dies, meanwhile, it reduces the process of handling and lifting, and can improve the flatness of the structure to obtain beautiful line type and unified color. Moreover, it can achieve “low-carbon” construction by reducing the energy consumption. In this paper, introduction was given for key technology of the construction technology and the current foreign development situation, to provide a reference for engineering technicians.

Mechanical properties of GFRP slip-form for in-situ application

In this paper, a more effective construction method is introduced, wherein the mechanical advantages of Glass Fiber Reinforced Polymer (GFRP) are applied to the slip-form method. The slip-form method, which is a typical moving form method, has advantages such as reduced construction duration and simple components because it enables continuous forming work of concrete in a single construction. However, it is vulnerable to corrosion, quality control is difficult, and the form plate cannot be reused. In this study, a tensile test was carried out on a GFRP plate by using a new method to apply the steel form to the GFRP plate. Effective GFRP slip-form shape and the application method were proposed by conducting finite element analysis and parametric analysis based on the results of the GFRP plate tensile test; performance was verified through a structural test. From the test results, the GFRP slip-form showed better structural performance than the steel form, and the GFRP slip-form construction method may reduce costs because of its reusability, easy quality control, and reduced construction duration.

Development of Self-compacting Concrete with Good Shape Stability for Slipform Construction

Abstract The aim of this research project was to modify a conventional self-compacting concrete (SCC) for use in a slip-form paver. For this purpose, two alternatives were investigated: (1) thixotroping agents (concept A) that were added to the original concrete mix and (2) viscosity-increasing additives (concept B) that were intermixed shortly before the concrete was finally placed to reduce the concrete’s flowability. The investigations were performed preliminarily on pastes and mortars and only subsequently on concretes. For the modification of pastes and mortars, thixotroping additives mainly based on modified starches and modified polymers were used. For modification of the viscosity, superabsorbent polymers and naphthalene sulfonates in combination with polycarboxylate ether (PCE) were considered. The conducted investigations indicated that it is quite difficult to create slip-form SCC using thixotroping additives because the thixotropic effect is reversible and results in a low “green strength” when the concrete is mixed for a second time (e.g., during the delivery and placement process). When superabsorbent polymers and naphthalene sulfonate were added during the concrete placement, the stiffening effect was irreversible.

콘크리트 교량 방호벽의 균열원인 및 패턴 분석에 대한 연구

콘크리트 방호벽 및 중앙분리대는 교량의 부속시설이지만, 슬립폼 시공과 넓은 비표면적으로 인해 초기재령 균열이 발생하기 쉽다. 본 연구에서는 대형 교량의 방호벽과 중앙분리대 콘크리트의 외관조사 및 비파괴실험을 수행하여 균열의 원인과 발생 균열의 패턴을 분석하였다. 이를 위해 시공기간을 고려하여, 건조수축, 수화열 해석이 수행되었으며, 현장의 환경조건을 고려하여 소성수축 특성을 평가하였다. 평가결과 대상구조물의 균열 원인은 철근위치에 따른 소성침하균열, 소성수축 및 건조수축에 의한 복부균열, 재료분리에 따른 상부균열로 추정할 수 있었다. 또한 균열원인과 발생 패턴을 도식화하였으며, 시공 및 재료분야에서 균열제어대책을 제안하였다. 해상위 교량에 설치하는 중앙분리대 및 방호벽 콘크리트는 환경조건 (풍속, 온도, 습도)에 매우 민감하여 초기재령균열이 쉽게 발생하므로 재료선택 및 시공방법에 신중을 기해야 한다. Concrete guide rail and median barrier are an attached RC member, however they are vulnerable to cracking due to slip form construction and large surface of member. In this study, causes and pattern of cracking are analyzed through assessment and NDT (Non-Destructive Technique) evaluation for concrete guide rail and median barrier on highway structure. For this work, analysis on drying shrinkage and hydration heat are performed considering installation period, and plastic shrinkage is also analyzed considering their environmental conditions. From the evaluation, plastic settlement around steel location, drying/ plastic shrinkage, and aggregate segregation are inferred to be the main causes of cracking in the structures. The crack causes and patterns are schematized and techniques of crack-control are suggested. Furthermore concrete guide rail/ median barrier in the bridge on the sea are vulnerable to cracking at early age so that special attentions should be paid at the stages of material selection and construction.

Study on Vibrational Liquefaction Behavior of Air-Entrained Concrete

With respect to the liquefaction behavior of cement concrete material in a vibrational condition, the varying patterns of the vibrational viscosity coefficients, vibrational energy transfer and rheological mechanical behavior of air-entrained concrete and non-air-entrained concrete in a vibrational shear condition were compared by analyzing the vibrational liquefaction processes of concrete. The study has found that the vibrational viscosity coefficient of concrete with air entraining agent added increased notably so that air-entrained concrete can maintain good shuttering behavior during slip-form construction; presence of a large number of tiny bubbles in air-entrained concrete allowed more even transfer of vibrational energy in concrete; and the rheological mechanical behavior of concrete was improved after air entraining agents were added so that it became easier to liquefy by vibration and had better shaping effect upon completion of vibration. Keywords: air-entrained concrete, slip-form construction, cement concrete pavement, vibrational liquefaction

Vibration Characteristics of Air-Entrained Concrete Based on Slipform Construction

Vibration characteristics of air-entrained concrete was analyzed by vibration slump loss, formwork ability and vibration viscosity coefficient through comparative testing. The results showed that: air-entrained concrete has a characteristic that high slump in vibrating and low after. It was significance to construction with slipform paver. Air-entraining agent improved the concrete structural viscosity under high-frequency vibration was the reason for this characteristics.

東京スカイツリー<sup>®</sup>におけるスリップフォーム工法による心柱の構築

自立式電波塔としては世界一の高さとなる東京スカイツリーの中心部には，直径8m，高さ375mのプレストレスト鉄筋コンクリート造の円筒「心柱」が設置されている。心柱は天望デッキの上まで貫いており，タワー本体の揺れを軽減する制振システムの機能をもつ。心柱は直径約10mの狭い空間と限られた期間で造る必要があり，「スリップフォーム工法」を採用した。本稿ではスリップフォーム工法による心柱の構築の状況について報告する。

지진모의실험을 위한 10층 R.C. 공동주택의 1:5 축소모델 설계 및 시공

본 연구의 목적은 지진모의실험을 위한 1:5 축소 10층 R.C. 공동주택 모델의 제작과정을 통하여, 실험체의 효율적인 설계 및 제작 과정을 개발하는 것이다. 실험체의 축소율은 가용한 진동대의 크기(<TEX>$5m{\times}5m$</TEX>)와 최대 허용무게(600kN)및 모델 철근(D3 볼트, <TEX>${\phi}2$</TEX> 강선)의 경제성과 상용성을 고려하여 결정하였다. 모델 철근은 현장에 바로 설치하기 어렵기 때문에 철망을 제작한 후 현장에서 조립하였다. 벽체와 슬래브를 동시에 타설할 경우 거푸집의 탈형이 매우 어렵기 때문에, 벽체를 먼저 타설하고 양생 후 탈형한 뒤 슬래브 거푸집을 설치하였다. 벽체 거푸집은 반복 사용이 가능한 Slip form 형태로 한쪽은 합판, 다른 한쪽은 아크릴로 제작하여 타설시 밀실도를 확인할 수 있도록 하였다. 1:5 축소 10층 R.C. 공동주택모델을 제작하기 위해 총 제작 기간은 약 6개월이 소요되었으며, 전임 연구원 5명, 작업보조원 612명 일의 인원이 투입되었다. The purpose of this study was to develop an efficient process in the design and construction of a 1:5 scale 10-story R.C. apartment building model for an earthquake simulation test. The reduction ratio of the specimen was determined by the size (<TEX>$5m{\times}5m$</TEX>) and pay load (600kN) of the available shaking table and the availability of model reinforcements. For efficiency and quality control of the reinforcement work, prefabrication was used. Construction was conducted in two steps, the wall in one step, and another step for the slab, because it was impossible to remove the formwork of a wall if the walls and slabs in a story were constructed in one step. The slip form construction method was used repetitively for walls. The formwork of a wall was made with veneer and acryl plate on each side, so it was possible to check the quality of the concrete placing. To construct this model, it took roughly six months with five full-time research assistants, for a total of 602 man days of labor in construction.

Slipforming with fibre-reinforced concrete for efficient crack control

The paper presents the results of slipforming field trials carried out to investigate the potential of polypropylene fibre reinforced concrete in reducing the need for anti-cracking conventional reinforcement in slipform construction. Three trials are reported in which polypropylene fibre reinforced concrete of different strengths ranging between 43 and 54 N mm−2 was used to replace conventional reinforcement in normal concretes. In addition steel fibre (melt-extract) reinforced concrete of strength 60 N mm−2 was also used in one of the trials. In order to achieve optimum mix design, use was made of pulverized fuel ash, silica fume and admixtures such as superplasticizer, retarder and air entrainer as required. The results of the field trials confirm the promising potential of fibre-reinforced concrete in eliminating the need for conventional anti-cracking reinforcement in slipform construction.

Slipforming of Reinforced Concrete Shield Building

The unique design and construction features of slipforming the heavily reinforced concrete cylindrical shield walls at the Satsop nuclear plant site are presented. It proved that, with proper planning, design, and coordination, the slipform construction technique can be successfully applied to large and heavily reinforced concrete structures. The shield walls were designed in compliance with seismic requirements which resulted in the need for reinforcing steel averaging 550 pounds per cubic yard (326 kg/m3). A 25 ft (7.6 m) high, three-deck moving platform was designed to permit easy installation of the reinforcing steel, embedments, and blockouts, and to facilitate concrete placement and finishing. Two circular box trusses, one on each side of the shield wall, were used in combination with a spider truss to meet both the tolerance and strength requirements for the slipform assembly. Use of preassembled, lifted-in-place sleeve tower racks that combined diagonal and vertical bars for the openings with two vertically aligned pipe sleeves greatly eased the installation. Specific recommendations for future slipforming are also presented.

Horizontal slipform construction with low slump concrete : Hsia, F T Ph D thesis, Michigan State Univ, 1977, 234P

Horizontal slipform construction with low slump concrete : Hsia, F T Ph D thesis, Michigan State Univ, 1977, 234P

Horizontal Slip-Form Construction—Section Stability

Horizontal slip-form construction with low slump concrete is adaptable to geometrical cross sections with large longitudinal dimensions. Section heights of 5 ft (1.5 m) or more have been readily constructed. A limitation of the method has been the lack of a simple method for evaluating the section stability. To provide the needed information, an experimental slip-form constructed wall section was analyzed by the finite element method using mechanical properties from laboratory tests converted to field mix conditions. Results showed that section stability can be determined by a comparison of the maximum shear stress with the undrained shear strength from unconfined compression tests on fresh concrete. Using results from the finite element method, a simplified analysis uses the relationship between a shape factor and stress ratio to determine the maximum shear stress. Comparison of this stress with the available undrained shear strength gives a measure of the factor of safety for the slip-form constructed section.

Horizontal Sup-Form Construction-Low Slump Concrete

Low slump (less than 25 mm) concrete when properly proportioned can be used for horizontal slip-form construction of elongated concrete structures 5 ft (1.5 m) or more in height. Elimination of conventional forms saves time, labor, and material costs thereby making this construction method relatively economical. A limitation of the method has been the lack of information on the mechanical behavior of low slump concrete in its fresh state. The mortar-voids mix design method provided an effective means for control of test variables including the water-cement ratio, cement content, and mortar content. Other variables included temperature, air content, and particle shape. Using 6-in. x 12-in. (152-mm x 305-mm) cylindrical samples of fresh concrete, the unconfined compression test was used for evaluation of the yield stress, ultimate strength and elastic and plastic moduli. Experimental data are summarized showing these mechanical properties plotted versus the test variables.

Slip Form Construction of Cement Storage Silos

Slip Form Construction of Cement Storage Silos

Novel Structural Frame Combined With Slip-Form Construction Results in Record Breaking Construciton Time

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