Published on: 2026-09-10
Source: Saint Petersburg State University of Architecture and Civil Engineering –
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Senior Lecturer of the Department of Construction Technology Maria Kagan as part of the grant competition for carrying out research work by the scientific and pedagogical staff of SPbGASU in 2026, conducted research work “Development of a technology for arranging technological seams and joints in reinforced concrete structures.”
The relevance of the research topic is determined by the widespread use of monolithic, precast, and precast-monolithic reinforced concrete structures in modern construction. In the area of construction joints, where the newly poured concrete mixture (“new” concrete) is connected to the previously laid (“old” concrete), a reduction in strength and density is often observed, which deteriorates the operational characteristics of structures. Existing regulatory methods for preparing joint surfaces are labor-intensive and do not always ensure the required bonding quality.
The aim of the scientific work was to improve the technology for forming joints and seams to ensure reliable and uniformly strong contact between concretes of different ages. To achieve this goal, the following tasks were addressed:
- technological factors affecting the strength of the concrete contact zone have been identified;
- technological solutions have been proposed to improve the quality of bonding different-age concretes, and a techno-economic assessment of the proposed methods has been carried out;
- Methodological approaches have been developed to justify the technological parameters for creating equal-strength concrete joints.
It has been established that the quality of the joint is significantly influenced by the physicochemical properties of the newly applied mixture, in particular, the type of binder and the pH level of the mixing solution. It has been proven that when slag-alkaline concrete mixtures with a mixing solution pH above 12 come into contact with a concrete base (“old” Portland cement concrete), a strong bond is formed. It was also found that when using such mixtures, there is no need for labor-intensive mechanical cleaning of the joint surface from the cement film, which greatly simplifies the technology.
A method has been proposed that allows the practical construction of monolithic horizontally-oriented reinforced concrete structures with a working concreting joint, while achieving strength and crack resistance indicators close to those of a monolithic structure.
Using modeling of construction processes for the installation of a monolithic floor slab with a technological concreting joint, an assessment of the technical and economic indicators was made for the installation of the technological concreting joint in a reinforced concrete structure using various technologies. Compared to the standard (SP 70.13330.2012 “Load-bearing and enclosing structures”), the use of the proposed technology allows a reduction in the production time by up to 15 percent with a slight increase in labor costs, up to 1 percent. At the same time, the cost of the slag-alkaline mixture compared to the Portland cement analogue is up to 42 percent lower.
The scientific novelty of the work lies in the proposed methodological approaches that allow the selection of technologies for creating concrete joints and monolithic joints of reinforced concrete structures based on the criteria of ensuring the compressive, shear, and pull-off strength of the concrete in the contact zone, as well as setting the technological parameters of the laid concrete mix taking into account the surface treatment methods of the “old” concrete and its age. The scientific novelty also consists in advancing the scientific understanding of the theoretical foundations for selecting technological parameters for the creation of working concrete joints in reinforced concrete structures when using alkali-activated binder-free concrete mixtures.
In connection with the implementation of resource-saving policies – both state and global – developments related to the use of man-made raw materials and secondary material resources are of special importance. This is relevant for all regions of the Russian Federation in accordance with the concept of strategic development of the construction industry and housing and communal services of Russia until 2030 with a forecast until 2035, due to the proposed technological solutions involving the use of alkali-activated clinker-free concretes, which are more energy-efficient and utilize metallurgical industry waste during their production.
The technology has undergone pilot production testing and is recommended for use in construction companies. The results obtained should be used when developing the work production project, process charts for the installation of monolithic horizontally-oriented reinforced concrete structures (floor slabs, foundation slabs), as well as process charts for the installation of butt joints of prefabricated reinforced concrete structures.
The research results are of interest to design and construction organizations, allowing them to incorporate effective and economical solutions at the design stage that ensure high quality and operational reliability of reinforced concrete structures. The research materials will also find application in the educational process at SPbGASU for training specialists in the construction field.
The news is published based on the results of the execution of the SPbGASU 2026 grant.
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