International Concrete Abstracts Portal

Strain-hardening cement-based composites (SHCC) are a group of high-performance materials which shows a high non-linear deformation capability and experiences strainhardening behaviour under tensile loading. This behaviour is achieved by a specific material design which uses micro-mechanical effects to enhance the bridging properties of the fibres. In the presented research work, a series of large-scale uniaxial tension tests was performed to investigate the influence of the steel reinforcement on the load-bearing capacity as well as on the deformation and cracking behaviour of slabs made of SHCC. Both the global deformations of the test specimens and local deformations of the reinforcement bars were measured. The experiments showed that the load-bearing behaviour of the structural elements is characterized by multiple cracking of SHCC. This results in a quasi-elastic, tensionstiffening behaviour of the tension element after the initial cracking strength was reached. For a realistic description of this load bearing behaviour, a model for concrete stress-strain relationship is proposed.

A four-year industrial research project led by Polytechnique Montreal was conducted to develop innovative precast bridge barriers made with high-performance fibre-reinforced concretes (HPFRC). The design of a 2-m long precast barrier in HPFRC anchored with Ushape rebar on a bridge slab was optimized using nonlinear finite element calculations. Specimens were produced at full scale in a precast plant and tested in laboratory under various experimental conditions. Phase 1 of the project included application of static and impact loadings on the barrier. Phase 2 concerned the mechanical behaviour of overhang bridge slabs with precast barriers (with or without longitudinal continuity) and cast-in-place barriers. Experimental results demonstrated that the bridge slab and barrier exceed the CSA static design load requirements with all configurations tested, and utilization of precast barriers with longitudinal continuity improve the ultimate load. Numerical models accurately reproduced the various experimental conditions studied; they were then used to provide information on the impact of barrier length.

An experimental campaign on a full-scale steel-fibre-reinforced concrete (SFRC) flat slab of 70kg/m³ was performed in order to investigate the design methods recently published by fib in the Model Code for Concrete Structures 2010 (MC2010). These experiments were based on uniformly distributed loadings as well as concentrated loadings. By using the concrete’s characterization on small specimens, the ultimate flexural load-bearing capacity of the slab was checked according to the relationships given in the MC2010 with a full plastic approach. The tests confirm the ductile behaviour and the redundancy potential of SFRC in flat slabs. Identification of the worst yield lines pattern remains an important task for the designer as it significantly influences the result. Structural design supported by the yield line theory and laboratory characterization based on three-point bending tests provides a rather conservative result for comparison with the observations of the full-scale test.

The concrete precast industry often has to cope with the difficulties concerning the production of structural elements with complex or atypical shapes. This is the case of flat concrete slabs, whose thin geometry involves difficulties in the placement of reinforcement, resulting in a large cost and time consumption during the construction process. This paper presents the results of research project which aims to optimize the geometry and the reinforcement of floor slabs for precast electrical equipment shelters. The results obtained by testing five simply supported full scale steel-fibre-reinforced self-compacting concrete thin slabs, subjected to point loads and continuously supported over the four edges, are reported and discussed. Non-linear finite element simulations are also presented to corroborate the experimental results and propose design solutions for reinforcement optimization.

The results of an experimental campaign, performed on plates in three-point bending, are described and analysed in the present paper. The aim is to tailor, through tests on full-scale structures, a new lightweight cement-based composite having the same mechanical performances as reinforced concrete, but without the presence of steel rebar. Accordingly, with respect to a traditional plain concrete, aggregates made with expanded clay and polymeric fibres were used, respectively, to reduce the weight and increase the ductility. Moreover, the minimum amount of fibres is defined by means of the ductility criteria already adopted for the minimum reinforcement ratio in reinforced concrete beams. The proposed tailor-made concrete was used to rebuild the sidewalks of a bridge in northern Italy.