ŽPSV (Czechia)

Concrete is the most popular building composite material (CM). Its long-term aging properties depend on the mixture, the setting and the curing. When concrete is produced and used in the place where we want it to be for the whole of its life, it is very sensitive and easily ruined. Curing is one of the things that we do to keep concrete protected during the first week or so of its life: we maintain proper temperature (neither too hot nor too cold) and dampness. The acoustic-emission method and the electrical-property measurement technique are applied to monitor early-age concrete. The relationships between the acousticemission activity, the temperature and the electrical properties, e.g., the resistivity and the capacity of concrete at an early age were studied in this research. W. Chen et al. studied the microstructure development of hydrating cement pastes during early ages using non-destructive methods including the ultrasound P-wave propagation-velocity measurement and non-contact electrical-resistivity tests. Nevertheless, there are not many references about the continuous study of the properties of concrete during an early age. A long-time monitoring of concrete properties is necessary to determine its lifetime and quality. The acoustic-emission method was proven to be a very advantageous tool for a non-destructive monitoring of structural microchanges during the lifetime of concrete. The differences between hardened concrete mixtures detected with acoustic emission can partly determine their properties at the age of 28 d. The basic concrete property is its compressive strength after 28 d; nevertheless, this can change over a long time period, thus a continuous measuring needs to be applied.

Paper presents some results of long-term research of a new optimized subtle precast construction system based on high performance silicate composites. The system is particularly aimed for building construction in passive or zero-energy standard. Subtle structural elements from high performance concrete (HPC) can be integrated into building envelope of energy efficient buildings with significant reduction of envelope structure and avoiding risk of thermal bridges. Significant advantages of subtle elements are material and energy savings during production, transport, manipulation and construction on building site.Paper presents experimental verification of connection between columns and beams ensured by Peikko ́s PCs corbels. Moreover, production of two prototypes of high performance fibre reinforced columns over two floors is presented. Prototypes were casted in ŽPSV a.s. plant, Litice nad Orlicí in June 2014. Complex LCA analysis of three various reinforced concrete columns was performed. Analysis covers construction life phase. Consequently, environmental impacts of assessed variants were compared and evaluated. Results show that it is possible to reduce some impacts on the environment from 16 up to 65% in comparison with common solution of reinforced concrete columns due to the utilization of excellent mechanical properties of high performance concrete that enables the design of subtle structural elements.