Characterization of the Interface Between Fresh Concrete and Formwork

Bouharoun, Samir

doi:10.3846/13923730.2014.893912

Cited by 7 publications

(3 citation statements)

References 22 publications

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“…The FE model, which is shown in Figure 2 , consists of a single spherical capsule surrounded by three contact surfaces representing the bottom and side edge of the mixer and the concrete atop the capsule. The contact interface between the mixer wall and the capsule outer layer is modeled as surface friction, with a static friction coefficient of 0.34 [ 78 ]. The top contact interface represents the cohesive structure of the fresh concrete atop the capsule.…”

Section: Methodsmentioning

confidence: 99%

Performance Modeling of Spherical Capsules during Mixing of Self-Consolidating Concrete

Chidiac

Reda

2023

Materials

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Autonomous healing is a very promising technique in self-healing concrete systems. For capsules to achieve their anticipated performance, they should be able to survive the harsh mixing conditions of concrete, yet rupture upon concrete cracking. At present, there are no standard test methods, either experimental or analytical, for determining the capsule survival rate during concrete mixing. This study investigates the correlation between the capsules’ shell properties, concrete rheological properties, the capsules’ external forces, and capsule survival rate during concrete mixing. Finite element and statistical modeling techniques were employed to evaluate the capsule performance and predict the survival rate of capsules during concrete mixing, with 68% confidence. The results revealed that the capsules’ survivability during concrete mixing is highly influenced by the capsule’s radius-to-thickness ratio, the rheological properties of the fresh concrete, the average-paste-thickness (APT) of the concrete mix, the aggregate content and angularity, and the speed of the mixer. In brief, capsules with a radius-to-thickness ratio between 30 and 45 are likely to survive concrete mixing and yet still rupture upon concrete cracking.

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Section: Methodsmentioning

confidence: 99%

Performance Modeling of Spherical Capsules during Mixing of Self-Consolidating Concrete

Chidiac

Reda

2023

Materials

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“…A higher SV range is undesirable as it mobilises the concrete particles within the oil-formwork interface, thus softening takes place resulted in concrete sticking on formwork and striping is difficult (Bouharoun et al, 2012, Freedman, 1975. The saponification ability of a vegetable esters in forming soap layers at the formwork interface is an added advantage for surface release lubrication, as oil participates in the formation of interstitial mediums creating a stable emulsion in the vicinity of formwork (Bouharoun, 2016).…”

Section: A R T I C L E I N P R E S Smentioning

confidence: 99%

Palm Olein Lubricates and Removes Freshly Baked Concrete From Its Formwork

Loh¹

2021

JOPR

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Typical use of toxic and flammable petroleum-based mould oil for concrete manufacturing and its everincreasing price have prompted the search for a user-friendlier vegetable oil alternative. This study examines the potential use of a refined palm oil, i.e., palm olein for mould release lubrication. Its use eliminates additional steps required for structural modification and avoids food insecurity conflict due to its abundance and versatility. Blending palm olein (base oil) with a tackifier (specialty additive) was attempted to investigate their mould release characteristics. The concerned lubricating properties, i.e., viscosity index and flash point of the formulated mould oil were comparable to that of petroleum counterpart, while those distinguishable characteristics were saponifiable value, acid number and free fatty acid, which contributed to better mould release ability. The unmodified palm olein-based mould oil exhibited moderate level of oxidative stability with added advantages of non-corrosiveness and biodegradability. The optimised blend (90:10 of oil: additive) on trial could detach the moulded concrete from its formwork smoothly, showing good releasing ability desirable for concrete making.

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“…At present, rare works have been implemented on the distribution of coarse aggregate in the interfacial zone of new-old concrete, but some works about the wall effect in case of casting in formwork have been carried out to study the distribution of coarse aggregate near concrete surface, which is still of good reference for this paper. 25,26 Kreijger 27 conducted an experimental study on the composition and properties of the surface layer of monolithic concrete. In the experiment, the ordinary Portland cement with content of 325 kg/m 3 was used.…”

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confidence: 99%

Modeling coarse aggregate distribution in interfacial zone of new–old concrete in precast concrete structures

Zhao

Chen²

2022

Structural Concrete

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There are a large number of interfacial zones of new-old concrete in precast concrete structures, and the wall effect causes the reduction of coarse aggregate in the interfacial zones, which leads to the weaker physical, mechanical and durability properties of this part. In the present paper, some new-old concrete specimens with different chiseled depths at the interfaces were made to simulate the wet joints of precast concrete structures. The distribution characteristics of the coarse aggregate volume fraction in the interfacial zones of new-old concrete specimens were obtained by DIP (Digital Image Processing) technology. The results show that the distribution of the coarse aggregate volume fraction in the interfacial zones is similar to a positive V-shape (no chiseling) or partial V-shape (chiseled interface), and is generally lower than that of the noumenons of new and old concrete (constant values). With the increase of chiseled depth, the valley point (i.e., the minimum value) of the distribution curve of coarse aggregate volume fraction in the interfacial zone will move upwards and offset toward the old concrete. When the offset reaches 2 mm from the interface, it remains stable. The multiple irregular cone-shape small pits on the actual chiseled surface are abstracted into a single bulging slope pit, and the area ratio of new-old concrete on the cross section within the chiseled range is derived. On this basis, the model of the coarse aggregate volume fraction in the interfacial zone varied with the distance from the interface is proposed.coarse aggregate distribution, interfacial zone, new-old concrete, precast concrete structure | INTRODUCTIONCompared with cast-in-place concrete structures, precast concrete structures have significant advantages in terms of production technology and environmental impact, so they have been widely used all over the world for decades. 1,2 With the extensive promotion of precast concrete structures in China in recent years, its application will be further expanded in the future. 3 Precast concrete structures have two connection modes: dry connection and wet connection, of which the latter is dominant. 4,5 In wet connection system, there are many seams between new and old concrete as well as a large number of steel bars connection nodes, which make the wet joints become the weak parts in physical, mechanical Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.

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Characterization of the Interface Between Fresh Concrete and Formwork

Cited by 7 publications

References 22 publications

Performance Modeling of Spherical Capsules during Mixing of Self-Consolidating Concrete

Performance Modeling of Spherical Capsules during Mixing of Self-Consolidating Concrete

Palm Olein Lubricates and Removes Freshly Baked Concrete From Its Formwork

Modeling coarse aggregate distribution in interfacial zone of new–old concrete in precast concrete structures

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