International Concrete Abstracts Portal

Concrete tubes are usually produced by a centrifugation method using steel bar reinforcements. The reinforcement of concrete with steel bars is expensive, susceptible to corrosion and leads to rather thick and heavy structural elements. The application of short fiber reinforced cement (FRC) or mortar is a suitable alternative. The paper presents the development and evaluation of a suitable FRC for this particular application. First, the cement matrix was optimized for use in a conventional casting forming process. A mixture of ultra-fine cement and ordinary Portland cement improves the rheological properties of the fresh mixture and results in a very dense cement matrix with excellent mechanical properties. This optimized cement matrix was then reinforced with different kinds of carbon and polymeric fibers such as PVA and PP. Hereby, the carbon fibers primarily increase the flexural and tensile strength of the material, whereas the polymer fibers tend to improve the ductility of the cement matrix. Furthermore, the influence of water-reducing agents, of different constituents (microsilica, filler, sand), and the mixing process on the mechanical properties were studied. The mechanical properties were found to depend also on the curing conditions of the hydrated samples. The microstructure and the fiber-matrix interface were investigated by ESEM (Environmental Scanning electron microscope). In a further test series, the mixtures were optimized with regard to the flow properties needed for the centrifugation process. The mechanical properties and the microstructure were investigated. As a result, this work shows the possibility to apply the FRC for industrial production of centrifuged tubes.

Ductal® is a new material technology offering a unique combination of superior characteristics including ductility, strength, and durability, while providing highly moldable products with a quality surface. The technology provides compressive strengths up to 200 MPa (30,000 psi), and flexural strengths up to 50 MPa (7,200 psi). The material’s unique combination of superior properties enables the designer to create thinner sections, longer spans, and higher structures that are lighter, more graceful and innovative in geometry and form while providing superior durability and impermeability against corrosion, abrasion, and impact. This material provides the precast industry with opportunities to improve many existing products and manufacture new products that will compete with other materials such as stainless steel, cast iron, ceramics, and others. This paper presents properties of the material, design assumptions for project solutions and the manufacture, installation and assembly procedures for specific projects including roof panels, 5 sided-boxes and anchor plates. Many economies gained from this new technology are a result of engineering new solutions for old problems. By utilizing the unique combination of superior properties, designs can eliminate passive reinforcing steel and experience reduced global construction costs, form works, labour and maintenance. Additionally, this relates to benefits such as improved construction safety, speed of construction, extended usage life and others.

This paper first proposes a reviewing and a critical analysis of the different UHPFRC which exist, and secondly presents a new cement composite, the CEMTECmultiscale®, patented by the Laboratoire Central des Ponts et Chaussées (Paris, France). This cement composite has been tested under static bending and asymmetric fatigue bending From this experimental study, the following comments can be made : - The characteristic strength and ultimate strain in compression are respectively equal to 205 MPa, and 4 10-3. - the Young modulus is equal to 55 GPa and the Poisson coefficient is equal to 0.21. - The average modulus of rupture (MOR) is equal to 61.5 MPa; - The average strain related to the average MOR is equal to 9.2 10-3. - A critical initial static strain threshold exists. Before this threshold a specimen in CEMTECmultiscale® does not fail during a bending fatigue loading and beyond this threshold the failure fatigue cycles number linearly depends of the initial static strain. The strain threshold determined in this study is between 1.24 x 10-3 and 1.44 x 10-3. - Below a loading ratio R = 0.65, failure during bending fatigue test never appears with a specimen of CEMTECmultiscale ®.

Even though the knowledge about the load bearing behavior of Textile Reinforced Concrete (TRC) is still limited, there are already applications of TRC such as cladding panels and integrated framework systems. Up to the present, the design and dimensioning of TRC members is mainly based on extensive test series targeted to the particular application. Certainly, this approach is very goal-oriented. However, because design rules are not supported by mechanical models, high safety factors are incorporated. Within the scope of the collaborative research center “TRC: foundations for the development of a new technology” (SFB 532) at the Technical University of Aachen, Germany, the missing consistent description of the load bearing behavior of TRC is being developed. Thereby, experiments and numerical simulations at different levels, i.e., micro-, meso- and macro-levels, are performed. In this paper, the main results of the research program are presented.

This paper presents engineering use of textile reinforced concrete (TRC) for integrated formwork applications. The integrated formwork are very light compared to the normal precast elemets owing to their small thickness, typically around 10 mm. The cross-section of the integrated formwork can be chosen as dictated by the specific application, and the composite can be designed to have a high load-bearing capacity. The young concrete is protected against moisture loss by the integrated formwork that remains in place. Hence, neither demoulding nor curing of TRC integrated formork is required. The integrated formwork also possess a high quality surface appearance. In this contribution, a compilation of results from testing performed on the textile reinforced concrete integrated formwork is presented.