External Links: FCT, FEUP
Producing structures that would function more efficiently over time, through the enhancement of durability is one of the ways by which the construction industry can become a part of the solution to the problem of sustainable development. The recent advances in the field of high-performance fibre reinforced concretes (HPFRC) have been a significant step to produce a material with longer life cycles. HPFRC is a cementitious material that can be seen as an extension of ordinary fibre concretes and high performance concretes. The main feature of these materials is the optimum combination of strength and toughness, with structural steel being its closest competitor, but also substantially higher durability. HPFRC also can offer the advantage of belonging to the family of Self Compacting Concretes, thus allowing a simple placement of the material in forms, even in complicated shapes. Its high unit cost makes it difficult to apply HPFRC in ordinary structures; but these high-tech concretes can be competitive solutions for structures that have special needs in terms of low self-weight, speed of erection and resistance to aggressive environments. Nevertheless, there is a lack of experience with the material in terms of design, practical application and actual performance of structures.
The present research project will focus in the study and development of tailor-made, robust and eco-efficient HPFRC mixtures to demonstrate the applicability and advantages of these materials for use in light and thin precast elements and in repair/rehabilitation applications. By using HPFRC in precast elements, the use of ordinary reinforcement can be avoided entirely thanks to the tensile capacity offered by the fibres, which leads to very slender and lightweight elements. This is very relevant, for instance, in the case of precast ring segments for construction of wind towers to facilitate storage, transport, lifting and placing operations in construction sites of difficult access. Concerning repair/rehabilitation applications, HPFRC applied in thin layers (with or without reinforcement) can also be advantageous to replace an existing, carbonated and cracked concrete surface with a new watertight and strong layer. Focusing on these two different target applications, this research project considers HPFRC as a construction material, investigating its performance at the level of the material itself and at the level of structural elements. Scientific mix-design methods will be used dealing with constituent materials specific properties, supported by non-destructive testing, to come up with an optimized concrete mixture, for defined performance requirements. Synergies between cements and various supplementary cementitious materials and new types of fibres produced by Portuguese companies will be explored to improve concrete properties, in the fresh and hardened states, and to make HPFRC more economical and eco-efficient. Both experimental testing and numerical modeling covering the several relevant aspects of material performance will be carried out.
Due to high failure rate often observed with the industrial implementation of new technologies and materials, it is apparent that quality assurance of HPFRC is absolutely necessary, both on the materials research level, as well as in the later production in field. Therefore, focussing on early–age development of concrete properties; crack detection, damage evaluation and fibres distribution in concrete elements; and interface phenomena between old and new concretes in repairing interventions, within the current project acoustic emission and electrical resistivity non-destructive techniques will be selected and evaluated on practicability and applicability. Besides, new innovative experimental set-ups will be developed to facilitate the linking of laboratory and field data, providing a better estimate of real performance.
HPFRC can be considered “the building material of the future” since it increases the sustainability of a structure by meeting technical requirements to lengthen its life-cycle and reduce the CO2 emissions related with its construction. Moreover, it can be applied for repair/retrofitting of existing structures.
Project cofinanced by: