Impact of Delays During Concreting of Reinforced High-performance Concrete Beams

Increasing application of HPC commit to analysis its concreting process - the article raises the issue of impact of delays during concreting of reinforced high-performance concrete beams. It is difficult to cast the whole structure monolithically if the concrete elements are large size; there are some limitations to the availability of formwork, concrete workers or supply of the fresh concrete. In such cases, it becomes necessary to perform structure elements in two or more stages, which leads to formation joints - plane of weakness or discontinuity formed when a batch of concrete hardens before the next batch is placed. Correctly located and properly executed construction joints provide limits for successive concrete placements, without adversely affecting on structure. There is many available guidance as to the location and performance of joints in case of ordinary concretes - some special requirements for HPC have not been found. The main purpose of the research was detailed analysis of the Ultimate Limit State as well as Serviceability Limit State (deflection and cracks) on full-size HPC beams, with different positioning of joints. Both the network of cracks as well as deflection, shaped differently for beams made of HPC in relation to pattern made of ordinary concrete. The obtained results allowed to determine best technology of shaping joints in the beam elements made of HPC, providing obtain an element comparable to the beams which was cast the whole.