There are a lot of monolithic and precast-monolithic reinforced concrete structures in construction. The relevance of the issue of ensuring reliable contact of concrete in the seams and joints in the contact zone of newly laid (""new"") concrete with already gained a certain strength (""old"") concrete is increasing. In the work, the influence of the pH of the medium on the adhesion strength of ""new"" and ""old"" concrete, which occurs when making joints in prefabricated monolithic structures and organizing technological seams of concreting in monolithic construction, was considered. Standard methods were used. Experimental data have been obtained that indicate the influence of the pH of the ""new"" medium on the adhesion strength of the ""new"" concrete with the base of the ""old"" concrete. The analysis and comparison of the received results with the data of the researches conducted earlier is carried out. Recommendations are formulated to improve the strength of concrete contact in seams and joints during the construction of monolithic and precast-monolithic reinforced concrete structures.

Keywords: new-to-old concrete bonding, technological concreting joint, monolithic reinforced concrete structures, precast-monolithic reinforced concrete structures