Estudio experimental de juntas de hormigonado en estructuras de edificios

Experimental study of joints in concrete structures of buildings

The Instructions and Standards of different countries deal with joints in concrete structuers, either those of work or those of shinkage, but in a very brief and in general nor very clear way. In the present research, it has been materialised a part of a continuous lintel of a building which has been tested by means of rupture in laboraory with 18 beams of 20 x 40 cm of section and 5,00 m of span. This has been carried out with the joint situated in different positions, different surface treatments, states of humididty of the koint and various compactation systems of it as well as different compactation systems of the concrete. It has been studied as well the influence of the time passed between the two concretes joined in the joint. The research has allowed to establish that there are several procedures and possible positions for the execution of a joint, without changing either the strength, or the stiffness or the durability of the structure. Nevertheless, out of all of them, the best result has been achieved with the joint situated at a 45º angle at the point of approximately zero moments, with natural rugosity or using a wire mesh as formwork and being he concrete hardened, saturated and superifically dry. Compaction by mechanical vibrating has not shown much difference in results to those obtained by a careful hand vibrating with a bar. The joints of the first concrete that are 2 and 155 days of age haven't shown much difference in the centre of the span, fornworked with a wire mesh have had as well a good performance.