Microstructural analysis of RPC (Reactive Powder Concrete)

The term Ultra-High Performance Concrete (UHPC) refers to a relatively new class of advanced cementitious composite materials whose mechanical and durability properties far surpass those of conventional concrete. This class of concrete has been demonstrated to facilitate solutions that address specific problems in the United States highway bridge infrastructure. Initial material development research on UHPC began more than two decades ago. First structural deployments began in the late 1990s. First field deployments in the U.S. highway transportation infrastructure began in 2006. For this study, UHPC-class materials are defined as cementitious-based composite materials with discontinuous fiber reinforcement that exhibit compressive strength above 21.7 ksi (150 MPa), pre- and post-cracking tensile strength above 0.72 ksi (5 MPa), and enhanced durability via a discontinuous pore structure. This report documents the state of the art with regard to the research, development, and deployment of UHPC components within the U.S. highway transportation infrastructure. More than 600 technical articles and reports covering research and applications using UHPC have been published in English in the last 20 years, with many more published in other languages. The report includes information about materials and production, mechanical properties, structural design and structural testing, durability and durability testing, and actual and potential applications. The report concludes with recommendations for the future direction for UHPC applications in the United States.

https://rosap.ntl.bts.gov/view/dot/26387/dot_26387_DS1.pdf

Ultra-High Performance Concrete: A State-of-the-Art Report for the Bridge Community

Durability of ultra-high performance concrete – A review

Development of ultra-high-performance concrete using glass powder – Towards ecofriendly concrete

The results of an experimental investigation of UHP-FRC tensile response under a range of low strain rates are presented. The strain rate dependent tests are conducted on dogbone specimens using a hydraulic servo-controlled testing machine. The experimental variables are strain rate, which ranges from 0.0001 1/s to 0.1 1/s, fiber type, and fiber volume fraction. Five different types of fibers are considered including straight and twisted fibers with different geometric properties. The rate sensitivity of the composite material in tension is evaluated in terms of its first cracking strength, post-cracking strength, energy absorption capacity, strain capacity, elastic modulus, fiber tensile stress and number of cracks. The test results show pronounced rate effects on post-cracking strength and energy absorption capacity. Further, post cracking strength varies linearly with the fiber reinforcing index and energy absorption capacity varies linearly with the product of the fiber length and the reinforcing index, as predicted from the theory for fiber reinforced concrete.

Strain rate dependent properties of ultra high performance fiber reinforced concrete (UHP-FRC) under tension

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 factorKIc, and the average fracture energy,\(\bar G_F \), 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.

Mechanical properties of reactive powder concretes

Le programme de recherche presente regroupe les communications suivantes : 1 - les betons de poudres reactives (Richard,P - Cheyrezy,M) ; 2 - Analyse de la microstructure du beton de poudres reactives (BPR) (Cheyrezy,M - Maret,V - Frouin,L) ; 3 - Etude experimentale de la deformation sous contrainte et du comportement a la rupture du beton de poudres reactives (BPR) (Dugat,J - Roux,N - Bernier,G) ; 4 - Definition d'une loi de comportement du BPR (Behloul,M) ; 5 - Mise en oeuvre des betons de poudres reactives dans le BTP (Roux,N - Barranco,M) ; 6 - Etude experimentale sur la durabilite des betons de poudres reactives (Roux,N - Andrade,C - Sanjuan,MA).

Les betons de poudres reactives (bpr) a ultra haute resistance (200 a 800 mpa)

Considerable progress has recently been achieved in strength and ductility of concretes. The use of superplasticizers and large amounts of silica fume led to densified cementitious matrices and improved adherence to the fiber reinforcement. These two properties are obtained with Compact Reinforced Composite (CRC) developed at Aalborg Portland and closely studied during a 3-year EC. The investigations reported in this paper cover the application of ultra high strength-fiber reinforced concrete to enhance performance of beams, columns and beam to column connections. Mechanical tests were performed on full-scale structural elements. Beams of 13 m in length, columns of 2.9 m in compression with and without eccentricity of the load, and beam to column connections were tested. In all cases, concrete strengths of more than 150 MPa were achieved. Due to CRC's high compacity and its extreme resistance to the penetration of aggressive elements, the CRC cover to the reinforcement was typically reduced from 30 mm to at least 12 mm. It has been shown that a reduction in concrete cover to the reinforcement is compatible with the requirements of structural applications. The tests carried out have shown the possibility of using ultra-high strength concrete for large-scale structural concrete elements and opens new fields of applications. This contributes to saving raw materials, weight and volume and to improving ductility and durability.

G Bernier

Papers

Mechanical properties of reactive powder concretes

Les betons de poudres reactives (bpr) a ultra haute resistance (200 a 800 mpa)

Structural applications using ultra high-strength fiber reinforced concrete