High-temperature behaviour of HPC with polypropylene fibres

Kalifa, P.; Chêne, Grégoire; Gallé, C.

doi:10.1016/s0008-8846(01)00596-8

Cited by 635 publications

(388 citation statements)

References 19 publications

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“…Figure 6b shows that the decrease of pore pressure is consistent with the increase of vapor permeability at 20 • C only for plain mixes (Mixes 70-S and 95-S), while for fiber-reinforced mixes (Mixes 70-Pm1 and 70-Pm2) the vapor permeability at 20 • C does not seem to be a proper parameter to describe the decrease of the peak pressure in the pores as a function of the concrete type. This fact can be ascribed to the much more significant increase of the permeability with the temperature in fiber-reinforced concrete compared to plain concrete (due to the melting and degradation of the fibers -above 165 • C -and to the formation of new microcracks starting from the voids left by the fibers [4]). Unfortunately, vapor permeability in heated specimens has not been measured so far in this project, but tests have been planned and will be performed shortly.…”

Section: Porosity Vapor Permeability and Pore Pressurementioning

confidence: 99%

“…This is possible because pp fibers melt and degrade above 165 • C [3], and generate not only new voids (corresponding to their volume), but create a network of micropores connecting the already-existing pores. In such a way, continuous channels are formed, that allow the vapor to migrate inside the material, towards cooler and lower-pressure zones, and the risk of explosive spalling is reduced [4][5][6]. On the other hand, it is well known that adding steel fibers (sf) increases concrete toughness in the post-peak range, and reduces spalling sensitivity too, even if less efficiently than pp fibers [7].…”

Section: Introductionmentioning

confidence: 99%

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Concrete spalling sensitivity versus microstructure: Preliminary results on the effect of polypropylene fibers

Rossino

Monte

Cangiano

et al. 2013

MATEC Web of Conferences

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Abstract. The phisyco-mechanical processes triggering concrete explosive spalling are related to the heat-induced micro-and meso-structural changes. To have new information on concrete properties at the microstructural level, as well as on how concrete spalling sensitivity is affected by polypropylene and steel fibers, and by aggregate type, ordinary and high-performance concretes are investigated in this research project, after being heated to different temperatures. The focus is on the relationship among porosity, vapor permeability, pore pressure and microcracking inside the cementitious matrix. Polypropylene fibers are shown to increase the total porosity, to favor microcracking and to reduce significantly pore pressure, to the advantage of concrete resistance to explosive spalling, whose risk is markedly reduced -or even zeroed.

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Section: Porosity Vapor Permeability and Pore Pressurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Concrete spalling sensitivity versus microstructure: Preliminary results on the effect of polypropylene fibers

Rossino

Monte

Cangiano

et al. 2013

MATEC Web of Conferences

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“…O mecanismo de atuação das fibras poliméricas está associado principalmente ao aumento controlado da permeabilidade do concreto após a fusão e degradação das fibras [29][30][31][32]. Como o pó de alumínio, as fibras podem ser misturadas a seco com as outras matérias primas que compõe a formulação e durante a moldagem e enrijecimento do concreto, formam uma rede tridimensional.…”

Section: Fibras Poliméricasunclassified

“…Elevados níveis de permeabilidade podem ser atingidos aumentando-se a quantidade de fibras adicionadas à formulação [30,34,38] ou considerando-se uma fração volumétrica fixa, otimizando sua geometria (Fig. 7a) [36][37][38].…”

Section: Fibras Poliméricasunclassified

Aditivos de secagem para concretos refratários: pó de alumínio e fibras poliméricas

Salomão

Bittencourt²,

Pandolfelli

2008

Cerâmica

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Evolução histórica do procEsso dE sEcagEm dE concrEtos rEfratáriosEmbora existam registros anteriores à era cristã da utilização de concretos e argamassas em construções (Êxodo, 5:7), seu uso em aplicações voltadas à indústria de refratários tornou-se comercialmente viável e se popularizou a partir da segunda metade do século XX [1]. Nas primeiras formulações descritas em trabalhos científicos, foram utilizados agregados de sílica, aluminas e hidróxidos de alumino de baixa pureza, argilas refratárias e cimentos de baixa refratariedade (principalmente, pelo elevado teor de silicato de cálcio) [2,3]. Sem as atuais tecnologias de agentes dispersantes e modelos de empacotamento de partículas, teores de água da ordem de 20-25%peso eram necessários para misturar e transportar essas formulações. Adicionalmente, grandes quantidades de cimento eram empregadas para garantir propriedades mecânicas mínimas após a desmoldagem.Por volta de 1964, vários trabalhos identificaram questões importantes referentes ao processo de secagem desses materiais [4,5]. Devido à baixa qualidade e granulometria grosseira das matérias primas utilizadas, ao elevado volume de água empregado na mistura e ao aquecimento gerado pela hidratação parcial das grandes quantidades de cimento empregadas, as estruturas geradas nessas condições eram muito porosas e permeáveis. Como conseqüência, freqüentemente, a secagem ocorria tão rapidamente que os ligantes hidráulicos utilizados não tinham tempo de reagir com a água e fornecer resistência mecânica suficiente para a desmoldagem. Além disso, após a secagem, também se verificava a ocorrência de trincas e vazios causados pela má compactação das partículas. A combinação desses fatores gerava materiais com propriedades termomecânicas e aditivos de secagem para concretos refratários: pó de alumínio e fibras poliméricas

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“…A lot of research has been carried out in order to model the spalling tendency of HPC and to propose some alternative solutions such as different mixture proportions or use of materials that provide a passive or active protection against spalling. Among the solutions proposed, the addition of polypropylene fibres seems to be an effective one (15)(16)(17)(18)(19)(20). It was reported (21) that polypropylene melts at 160-168 • C whereas HPC spalls when the air temperature ranges between 190-250 • C.…”

Section: Introductionmentioning

confidence: 99%

Influence of length and dosage of polypropylene fibres on the spalling tendency and the residual properties of self-compacting concrete after heated at elevated temperatures

Sideris

Manita

2013

MATEC Web of Conferences

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Abstract. The objective of this paper was to study the influence of different length and dosage of polypropylene fibres on the properties of self-compacting concretes at elevated temperatures. A total of five self compacting concretes and one normally vibrated concrete were produced. The poypropylene fibres were of different length (12 mm, 6 mm and 3 mm) and were added at dosages of 1.0 Kg/m 3 and 0.5 Kg/m 3 . The properties measured after fire exposure were the compressive strength, splitting tensile strength and water capillary absorption. The best overall performance was observed on the fibre reinforced self compacting concrete produced with the 6 mm HPR fibres at a dosage of 0.5 Kg/m 3 .

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High-temperature behaviour of HPC with polypropylene fibres

Cited by 635 publications

References 19 publications

Concrete spalling sensitivity versus microstructure: Preliminary results on the effect of polypropylene fibers

Concrete spalling sensitivity versus microstructure: Preliminary results on the effect of polypropylene fibers

Aditivos de secagem para concretos refratários: pó de alumínio e fibras poliméricas

Influence of length and dosage of polypropylene fibres on the spalling tendency and the residual properties of self-compacting concrete after heated at elevated temperatures

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