Article

Reinforced reactive powder concrete plate under cyclic loading

Journal of the Chinese Institute of Engineers 03/2007; 30:299-310. DOI: 10.1080/02533839.2007.9671256
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    ABSTRACT: Reactive Powder Concretes (RPC) are a set of ultrahigh-strength concretes reinforced with steel fibers. Their compressive strength is between 200 and 800MPa, and their flexural strength can reach 140MPa.RPC200 has been studied with respect to compressive strength and two-point loading strength to define its mechanical behavior.RPC800, which has been mostly studied from the point of view of compressive strength, displays hardening elastic non-linear behavior at low stress. This behavior is similar to that of some natural rocks. The critical stress intensity factorK Ic , and the average fracture energy, [`(G)]F\bar G_F , ofRPC200 andRPC800 have been studied experimentally by applying the theory of linear fracture mechanics (compliance method). The fracture energy, which is a measurement of ductility, can reach 40,000 J/m2 forRPC200, as compared to 100 to 150 J/m2 for ordinary concretes. Fracture energy depends on the volume of fibers added to the concrete. The optimum content is between 2 and 3% by volume. Les Bétons de Poudres Réactives (BPR) constituent une famille de bétons à ultra hautes performances renforcés de fibres métalliques. Leur résistance en compression se situe entre 200 et 800 MPa et leur résistance en flexion peut atteindre 140 MPa. Le BPR200 a été étudié en compression et en flexion 4-points pour définir son comportement mécanique. Le BPR800, étudié principalement en compression, présente un comportement non linéaire élastique à faible contrainte. Ce comportement s'apparente à celui de certaines roches naturelles. Le facteur d'intensité de contrainte KIc et l'énergie moyenne de fracturation [`(G)]F\bar G_F du BPR20 et du BPR800 ont été étudiés expérimentalement en appliquant la théorie de la mécanique linéaire de la rupture (méthode de la complaisance). L'énergie de fracturation qui caractérise la ductilité peut atteindre 40 000 J/m2 pour le BPR200 à comparer à des valeurs de 100 à 150 J/m2 pour les bétons traditionnels. L'énergie de fracturation dépend du volume de fibres ajouté au béton. Le dosage optimal se situe entre 2 et 3 vol-%.
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    ABSTRACT: Two reactive powder concretes (RPC) were produced on an industrial scale at the Université de Sherbrooke and in a nearby precast plant. A 2.6 m3 mix was prepared in a ready mix truck while a 1.35 m3 mix was prepared in the central mixer of the precast plant. The ready mix RPC was sampled before and after the addition of steel fibers while the one produced at the precast plant was sampled only at the end of the mixing process. These RPCs were tested for compressive strength, modulus of elasticity, freezing and thawing cycling resistance, scaling resistance to deicing salts, and resistance to chloride ion penetration. Large samples were also cast allowing core samples to be taken. The results show that a 200 MPa compressive strength could be achieved in both cases: after curing in hot water at 90 deg C or in the low pressure steam chambers at the precast plant. Confinement of the RPC in a steel tube greatly increases its compressive strength and its ductility. The two mixes were found to he freeze-thaw resistant and presented a very low mass loss under the scaling test. Chloride ion permeability was below 10 Coulombs even for the specimens containing steel fibers; this extremely low value translates to the quasi-impermeability of the two RPCs.
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    ABSTRACT: In this paper, the effect of silica fume on the bond characteristics of steel fiber in matrix of reactive powder concrete (RPC), including bond strength, pullout energy, etc., are presented. The experimental results on steel fiber pullout test of different conditions are reported. Various silica fume contents ranging from 0% to 40% are used in the mix proportions. Fiber pullout tests are conducted to measure the bond characteristics of steel fiber from RPC matrix. It is found that the incorporation of silica fume can effectively enhance the fiber–matrix interfacial properties, especially in fiber pullout energy. It is also concluded that in terms of the bond characteristics, the optimal silica fume content is between 20% and 30%, given the conditions of the experimental program. The microstructural observation confirms the findings on the interfacial-toughening mechanism drawn from the fiber pullout test results.
    Cement and Concrete Research. 01/2004;

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