Influence of technological factors on the strength of concrete in the contact zone of a new-to-old concrete bonding

Currently, monolithic and precast-monolithic structures made of reinforced concrete are being widely used. So, the matter of ensuring reliable contact between concretes: newly laid (new) and the one which already gained certain strength (old), is relevant. In this paper, the issue of ensuring the necessary strength of the connection of new-to-old concrete has been viewed, which arises when organizing technological seams of concreting and making joints in precast-monolithic structures. The existing proposals in Russian and foreign sources on improving the contact strength of new-to-old concrete have been considered. The analysis and comparison of the obtained results of experimental research conducted by the authors of this article earlier has been given. Conclusions that contribute to improving the contact strength of concrete in monolithic and precast-monolithic reinforced concrete structures have been worded. A new method for arranging technological seams has been proposed, which is organized according to the technology of embedding the joints of precast reinforced concrete structures using a concrete mixture based on a slag binder with a basicity factor(Mo) more than 1.0, mixed with an alkaline solution with a pH level above 12.0. The economic substantiation of the advantages of the developed technology in comparison with the classical version of the working seam of concreting has been presented.