Injection Technologies for the Repair of Damaged Concrete Structures

This book presents the main physical and mechanical characteristics of concrete and reinforced concrete materials as well as evaluation methods and typical damage that can be expected over long-term use.

The authors pay special attention to the description and use of up-to-date injection technologies for strengthening the damaged structural elements of a long-term operation; they present recommendations for choice of materials for the implementation of such technologies. The book contains criteria for injection materials and examples of compliant polymer materials.

The methods and means for technical diagnostics of damaged concrete and reinforced concrete constructions of long-term operation are given a significant place. Damage mechanisms are considered. The information presented includes data concerning equipment and appliances used in injection renewal works. The case studies provided illustrate the removal of damage and the extension of service life for certain renewed objects of long-term operation.

The intended audience is comprised of building engineers, scientists, lecturers, and high school students specializing in construction.

This book contains 192 illustrations, 26 tables, and 211 references.

The Chapter presents general characteristics of concretes and reinforced concretes, their classification, grading and designations. Definition of structure inhomogeneity in these materials and its effect on service characteristics are given. The Chapter contains typical diagrams of concrete deformation and fracture as well as nominal strength values for different concrete grades in tables. Besides strength, other important mechanical characteristics, such as fracture toughness, are of no less importance in concretes. The authors provide a summary of existing fracture toughness criteria and methods for experimental fracture toughness determination. At present, concrete science can formulate only individual aspects of a concrete strength and deformation theory. Considering concrete as a composite material with hierarchical structure (at micro, meso, and macro levels) and analyzing these structure levels, the authors propose a mathematical model enabling the establishment of quantitative relations between breaking (tensile) and compressive strength values for a porous material such as concrete.

The Chapter contains classification and mechanical properties of concrete reinforcement as well.

The subject of this chapter is the effect of main corrosive air and/or water environment factors on strength of structural concrete and reinforced concrete during long-term operation. Specific destructive action of static and/or cyclic loads and induced complex deformations on processes of concrete damage and fracture is considered. Included case studies characterize decrease in concrete strength and load-carrying capability due to intense corrosion processes occurring on its surface and/or bulk. The specific effect of aggressive gas environments causing discontinuity of concrete’s heterogeneous structure and nucleation of defects such as cracks, laminations, cavities or others is characterized. Outline and characterization of principal biological and microbiological factors affecting the concrete injury in practice are given. Basic kinds of stress corrosion degradation causing thinning and load-bearing capacity diminishment of steel reinforcing wires in concrete are covered. The authors present analysis of combined effects of static/cyclic mechanical loads and corrosive air and/or water environment on injury and fracturing of concrete structures and constructions over long-term operation.

General description of injection technologies suitable for practical application in strength and serviceability restoration of concrete and reinforced concrete structures of long-term operation in the construction practice and municipal services is given. Technical requirements for injection technologies are determined. Key technical aspects of preparation of concrete and reinforced concrete structures damaged by cracks or other dangerous defects for implementation of injection technologies are considered. The chapter contains a description of disadvantages of feeding aqueous cement or cement/polymer suspensions into cracks or damaged zones of concrete structures and buildings.The authors substantiate a technical feasibility of implementation of technological processes for repair and restoration of degraded building structures using fluent dual-component injection polymer materials.

General principles of implementation of technological processes based on reactive polymer composition injection into cracks or defects in concrete and reinforced concrete take place in the chapter. The technologies based on the most effective polyurethane injection material application get detailed description here. The list and specifications of injection technologies suitable for practical application in strength and serviceability restoration of concrete and reinforced concrete structures are given. Processes of injection and/or waterproofing repair of inner surfaces in sewage collectors or pipelines get detailed consideration in this chapter. Technical parameters and operational principle of the mobile diagnostic-restoration complex mounted in the truck van are characterized as well as constituting particular diagnostic or processing devices, appliances and instruments.

Chapter 5 describes analytical models of and solutions to specific problems concerning strength of deformed bodies with defects filled with injection materials. Obtained solutions are the theoretical basis for service life estimations for structural elements after renewal by injection technologies. For this purpose, a mathematical model of a cracked material healed with injection technologies was developed. The authors analyzed the model in both 2D and 3D formulations. This chapter presents applicability limits of results obtained in two-dimensional approximation. Investigation of crack wedging effects by injection mixtures shows that such effects are significant since they can lead to the growing of the initial crack-like defects under certain conditions.

The extent of filling of defects with an injection material is the important parameter of the technology under consideration. Complete defect filling, in practice, is often hardly attainable, due to various reasons. Therefore, it is important to develop approaches for evaluation of the influence of incomplete defect filling on the effectiveness of damaged structural element renewal.

The problem of injection into a damaged body containing a system of mutually interacting cracks is also considered. The authors consider in detail injection into a system of two cracks. They study the effectiveness of strength restoration for the case of cylindrical structural elements. The solution for transverse compression of a cylindrical element along the planar defect is included.Such specimen configuration is widely used for strength at the testing of brittle materials for strength and fracture toughness. The convenience of such a configuration is in that it requires no special equipment for experiments except for a compression machine. The basic experimental investigations necessary for optimization of injection technologies have been performed using this scheme alone.

Chapter 6 describes analytical models of and solutions to specific problems concerning strength of deformed bodies with defects filled with injection materials. Obtained solutions are the theoretical basis for service life estimations for structural elements after renewal by injection technologies.

For this purpose, a mathematical model of a cracked material healed with injection technologies was developed. The authors analyzed the model in both 2D and 3D formulations. This chapter presents applicability limits of results obtained in two-dimensional approximation. Investigation of crack wedging effects by injection mixtures shows that such effects are significant since they can lead to the growing of the initial crack-like defects under certain conditions.

The extent of filling of defects with an injection material is the important parameter of the technology under consideration. Complete defect filling, in practice, is often hardly attainable, due to various reasons. Therefore, it is important to develop approaches for evaluation of the influence of incomplete defect filling on the effectiveness of damaged structural element renewal.

The problem of injection into a damaged body containing a system of mutually interacting cracks is also considered. The authors consider in detail injection into a system of two cracks. They study the effectiveness of strength restoration for the case of cylindrical structural elements. The solution for transverse compression of a cylindrical element along the planar defect is included. Such specimen configuration is widely used for strength at the testing of brittle materials for strength and fracture toughness. The convenience of such a configuration is in that it requires no special equipment for experiments except for a compression machine. The basic experimental investigations necessary for optimization of injection technologies have been performed using this scheme alone.

The analysis of available publications and patents related to methods and means (devices) for non-destructive testing and quantitative status estimation of long-term concrete and reinforced concrete structures damaged by cracks and/or other dangerous defects is given. The authors provide and characterize a classification scheme for non-destructive testing methods used to determine initial mechanical parameters of concrete and reinforced concrete building structures and those degraded during operation. They consider and evaluate the conventional in building practice techniques and monitoring devices for technical diagnostics of damaged concrete structures. They also analyze the main physical and mechanical methods for laboratory testing of concrete and reinforced concrete specimens as well as methods for technical diagnostics of the status of structures of long-term service. The presented methods include visual inspection, optical, acoustic (or ultrasound), and radiation techniques and devices for crack and/or defect detection and sizing. Description of electrochemical techniques and devices for measuring the extent of degradation in steel concrete reinforcing elements with the aim of making decisions as to the possibility of further reliable use of the concrete and reinforced concrete structures damaged by cracks and/or other defects is provided. Case studies of use of up-to-date technical diagnostic devices for such purposes are considered. The design of a computerized truck-mounted mobile diagnostic-restoration complex for major repair of the sewage collectors and main pipelines is developed. Operational parameters of diagnostic or processing devices, appliances and systems of the complex are included. Practical implementation of the complex in industrial and municipal building structures is illustrated.

This chapter presents results of wide practical implementation of injection materials and technologies for renewal of concrete and reinforced concrete structures in industrial and municipal building structures of Ukraine damaged by cracks and/or other defects. Case studies of combined injection and waterproofing works in overground, underground, and underwater structures of stationary atomic power plants, as well as river hydroelectric pumped storage power stations, are illustrated. Descriptions of blockage technologies of water leakage through cracks or seepage through defect zones using injection materials in dams, turbine rooms, or adjoining working rooms of hydraulic works are represented. The process specific features and practical results on renewal of inner surfaces in concrete and reinforced concrete sewage collectors and water main pipelines 1400...3000 mm in diameter in the city of Lviv are given. Case studies of injection strengthening and surface protective waterproofing of injured tunnels, bridges, and traffic interchanges for rail and motor transport, as well as foundations, walls, and vaults of houses, churches, and other historical relics in antique city districts, are presented. Renewal with modern cement materials and surface protective waterproofing of reinforced concrete berths and other structures in seaports that have undergone long-term exposure to sea slaps and active humid air corrosion is illustrated.