Monolithic reinforced concrete structures are widely used in construction practice. When concreting massive structures, technological and organizational difficulties may arise in ensuring the continuity of the concrete mix, which leads to the need to organize working joints. Studies conducted earlier show a decrease in strength characteristics in this area and the bearing capacity of the entire structure. Known and practical solutions to the problem cause additional labor, material and time costs. In this paper, we propose a method for installing a technological seam caused by unplanned interruptions in concreting for technological and organizational reasons, based on previously conducted experimental and pilot studies by the author of this article. The proposed method consists in the fact that, when a break occurs, subsequent concreting is carried out with a break from the previously concreted section, while a stepped profile is formed with the help of fasteners, as a result of which a space is organized bounded by the surface of the first and second concreted sections and a formwork of a shape close to pyramidal, similar to the run-in fines, during the construction of brickwork. After holding the concrete of both sections and dismantling the cut-offs, a concrete mixture of the same class on Portland cement is laid within the free space of the applied slag-alkali solution with the characteristics: slag with a basicity modulus of more than 1.0; an alkaline solution with a hydrogen index level above 12.0. The technological features of performing forced seam concreting according to the proposed method are given.

Keywords: concrete contact zone, technological concreting joint, unplanned concreting working joint, monolithic reinforced concrete structures

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