Service Life of Concrete Repairs

European standards for concrete repair PETER ROBERY

The concrete repair industry has come a long way since 1954 when Concrete Repairs Ltd (CRL) was established as a contractor. Until the early 1980s the majority of repairs were to buildings and marine structures. The work consisted of breakout using hand pneumatic tools and reinstatement using site batched repair mortars and concretes with waterproof additives, such as styrene butadiene rubber (SBR) polymers, to enhance durability.In the 1980s pre-bagged repair materials using freeze-dried polymers started to become available which improved the quality control for the repairs, and complete repair systems were marketed by suppliers. These consisted of steel and concrete primers, repair concretes and mortars, and finish coating systems.For the first time clients could specify with some confidence a complete repair system from one supplier. But specifiers were still struggling to quantify the works in this growing industry due to lack of experience and no acknowledged method of measurement. It was very common for concrete repair projects to go way over budget due to poorly constructed bills of quantities and underestimates in quantifying the work.The market for concrete repair in the UK has grown in the last 20 years as the concrete structures of the 1950s and 60s have matured and it was realised that chlorides from de-icing salts and admixtures such as calcium chloride have initiated rapid corrosion of the reinforcement.There has been a great deal of research into concrete deterioration and in particular corrosion of the reinforcement. This has led to the development of corrosion control techniques and improved repair systems which have brought about a step change in the way we deal with concrete repair and produced harmonised European Standards.This chapter will look at how concrete repair is quantified, specified, procured and executed but first of all it will address the importance of safety.

Much of Australia’s concrete bridge infrastructure is in coastal areas exposed to saline environments and, consequently, at risk of chloride-induced steel reinforcement corrosion. Carbonation-induced corrosion of reinforcing and prestressing steel in concrete is a risk to inland bridges. These threats are common throughout the world. Concrete repair and protection of such structures remains as necessary today as ever. This article presents some observations regarding conventional concrete patch repair.

Concrete repair and rehabilitation are vital disciplines in structural and civil engineering, given the age of concrete infrastructure and the need to extend its service life. Most repair projects involve removing deteriorated or damaged concrete, followed by applying a patch repair mortar or bonded overlay. These repairs are typically done with proprietary repair materials of very high strength exceeding 40 MPa, which is related to the general misconception that the high strength of cementitious materials correlates with high quality and structural contribution. However, the performance of concrete repairs deteriorates with the increasing strength of the repair material, which is related to an increasing tendency to crack and debond. Furthermore, repair patches commonly do not contribute to the load-bearing behaviour of the structure, mainly because of creep and shrinkage of the repair mortar. This paper discusses common misconceptions around the ‘structural repair’ of concrete members and the related adverse effects regarding sustainability costs. Recommendations for rational and more sustainable repair approaches are presented.

This paper comprehensively summarizes and discusses the latest research progress in the underwater concrete structure damage repair technology of infrastructures. The prompt application of underwater concrete structure repair technology can effectively deal with the damaged parts of underwater concrete structures, and it can ensure the safe and stable operation of infrastructure and extend its service life. Firstly, this study uses bibliometric methods to analyze the characteristics of the literature on research into underwater concrete repair in the past 30 years (1993–2023), and expounds the research status and hotspots of this field. Then, we conduct a comprehensive classification and discussion of the underwater concrete structure damage repair technologies at the current stage. This technology can be divided into two major types: direct underwater type and dry environment type. Further, the development history of these technologies is systematically sorted out and, combined with practical engineering application cases, the operation processes, applicability, limitations, and economy of these technologies are analyzed. Finally, the challenges and future development trends of the current underwater concrete structure damage repair technology are pointed out, which provides a direction for future research on the intelligent maintenance of underwater concrete structures.

Near-to-surface properties affecting bond strength in concrete repair

Civil engineers must assure that buildings have long and durable lives, and therefore structural assessment and repair are routinely required and must be performed with the utmost accuracy and professionalism. Assessment, Evaluation, and Repair of Concrete, Steel, and Offshore Structures presents the typical causes of structural failure and their mechanisms, discusses the most up-to-date methods for evaluation and structural assessment, and explains the best project management strategies from the feasibility stage through operations and maintenance. Numerous types of structures are examined and are further illustrated by relevant case studies. Features: Examines the probability of several types of structural failure and includes reliability analysis. Presents best practices for predicting the structural lifetime for both onshore and offshore structures and reviews the most advanced methods for repair. Includes numerous practical case studies of structural failure and offers mitigation strategies depending of type of structure.

Concrete structures are susceptible to cracking, which can compromise their integrity and durability. Repairing them with ordinary Portland cement (OPC) paste causes shrinkage cracks to appear in the repaired surface. Alkali-activated binders offer a promising solution for repairing such cracks. This study aims to develop an alkali-activated paste (AAP) and investigate its effectiveness in repairing concrete cracks. AAPs, featuring varying percentages (0.5%, 0.75%, 1%, 1.25%, 1.5%, and 1.75%) of polyethylene (PE) fibers, are found to exhibit characteristics such as strain hardening, multiple plane cracking in tension and flexure tests, and stress-strain softening in compression tests. AAP without PE fibers experienced catastrophic failure in tension and flexure, preventing the determination of its stress-strain relationship. Notably, AAPs with 1.25% PE fibers demonstrated the highest tensile and flexural strength, exceeding that of 0.5% PE fiber reinforced AAP by 100% in tension and 70% in flexure. While 1% PE fibers resulted in the highest compressive strength, surpassing AAP without fibers by 17%. To evaluate the repair performance of AAP, OPC cubes were cast with pre-formed cracks. These cracks were induced by placing steel plates during casting and were designed to be full and half-length with widths of 1.5 mm and 3 mm. AAP both with and without PE fibers led to a substantial improvement in compressive strength, reducing the initial strength loss of 30%-50% before repair to a diminished range of 2%-20% post-repair. The impact of PE fiber content on the compressive strength of repaired OPC cube is marginal, providing more flexibility in using AAP with any fiber percentage while still achieving effective concrete crack repair. Considering economic and environmental factors, along with observed mechanical enhancements, AAPs show promising potential for widespread use in concrete repair and related applications, contributing valuable insights to the field of sustainable construction materials.

One of the major degradation problems in concrete structures is chloride initiated reinforcement corrosion resulting in cracked, spalled and delaminated concrete. Thesedamages are repaired for large amounts of money and because of high repair costs it is important to perform durable repairs. This thesis work has included interviews, laboratory and field studies in the area of concrete repairs. The interviews were held mainly with bridge engineers at the Swedish Road Administration and Banverket (the Swedish Railway Administration). The questions asked tothese people were about their experience in the field of concrete repairs. The objective withthe interview study was to collect knowledge and experience about concrete repair at these two governmental authorities. The main objective of the laboratory study was to investigate chloride transport in the transition zone between a chloride contaminated substrate concrete and an initially chloride free repair concrete by establishing chloride profiles. The second objective was to detect any reinforcement corrosion in relation to the transition zone. The reinforced laboratory specimens with premixed chlorides (1 or 4 wt % per cement) in the substrate concrete have been exposed during 13 years either outdoors or in a climate chamber with relative humidity of 80 %. The main results show that reinforcement corrosion occurred in and near the transition zone in local active areas with passive areas between, macrocell corrosion, and that the chlorides are transported from the contaminated substrate concrete into the repair concrete. Three different repaired concrete structures, one road bridge, one pedestrian bridge and one parking structure, were investigated in the field study. All three structures are treated with deicing agents in the winter time. The objective with the field study was to investigate if the same phenomenon can be observed as in the laboratory study. The main conclusions, from the investigation on drilled cores from each structure, are that chlorides in contaminated substrate concrete can be transported into a repair concrete and reinforcement corrosion may occur in the transition zone between the two different materials. The results are in accordance with the results in the laboratory study. It was also seen that a repair concrete with relative low w/cratio may reduce the ingress of external chlorides. Finally, the results in this thesis indicate that there is a risk for reinforcement corrosion in the vicinity of the transition zone between repair concrete and a substrate concrete which must be considered in concrete repair work. For example the chloride content around a repair must not exceed a certain level when a repair is performed. The chloride transport into the repair concrete can be useful to transport chlorides and reduce the content of chlorides in the substrate concrete. The advantages with this are that the amount of removed contaminated substrate concrete can be minimized and the risk for corrosion in the substrate concrete is lower. If the repair concrete is reinforced with conventional black steel there may on the other hand be a risk for corrosion in the repair concrete instead if high levels of chlorides are transported. Also external exposure of chlorides must be considered for the risk of corrosion in the repair material. Further research is needed about when different corrosion mechanisms and chloride diffusion mechanisms occur in reinforced concrete repairs. The experience from the used analyzing methods in the laboratory investigations are possible to use in coming research projects in the field of concrete repair. The next step after this thesis work should be in order to increase the understanding of the repaired concrete system including the important compatibility issues, the author believes that the most fruitful way consists of further laboratory investigations, field studies and optimisation of the repair material.

The paper presents the results of developing paint and varnish coatings for protecting metal bridge structures, featuring high durability under operating conditions. The focus is on preparing metal surfaces for painting, specifically developing a formulation for a pre-treatment composition prior to paint and varnish application. The composition is a solution based on mixed solvents, one of which is an ester and the other an aromatic hydrocarbon, containing nanomaterials. The specific solvents used in the composition, as well as the types and amounts of nanomaterials, depend on the type of film-forming agent in the applied paint and varnish. The conducted studies on a specific example of a composition formulation, including a solution based on mixed solvents (butyl acetate (52-55 wt.%) and toluene (45-48 wt.%), containing a concentrate with carbon nanotubes and silicon dioxide, in an amount of 0.01-0.2 wt.%, including 10 wt.% single-wall carbon nanotubes and silicon dioxide nanoparticles and 90 wt.% mixture of triethylene glycol dimethacrylate and alkylammonium salt of high-molecular copolymers showed that acrylic paint and varnish coatings acquire increased physical and mechanical properties (adhesive strength, abrasion resistance, resistance to deformation effects, etc.). At the same time, there is an increase in the dielectric constant of the coating (from 16.45 to 18.39), which characterizes its increased conductivity, as well as a decrease in the dielectric loss tangent (from 0.017 to 0.008), which indicates the production of antistatic coatings. The chemical resistance of the coatings increases, which characterizes their resistance to aggressive environments, expressed in better preservation of properties according to the criteria: change in gloss (hue), whitening, blistering, peeling, wrinkling. When considering the formation of interaction on the metal surface during its contact with the coating during surface treatment with nanomaterials, the following mechanisms of action of nanomaterials with a metal surface were revealed, which are consistent with the provisions of the electrical theory of adhesion and the theory of the physical chemistry of polymers: interaction of nanomaterials with surface atoms of the metal with the formation of electrovalent interaction by the donor-acceptor mechanism; Chemical interaction (chemisorption) of the active sites on the surface of carbon nanotubes with the metal surface layer. Industrial testing of the resulting solution yielded a positive result: after 28 months of operation, the coating obtained by surface treatment with the nanomaterial composition, compared to the untreated coating, performs its functions and exhibits superior decorative and protective properties. The technical and economic efficiency of the developed approach is ensured by improved adhesive-cohesive interaction of paint and varnish coatings, which creates conditions for extending their service life and periods between repairs; and by reducing resource and energy costs without compromising coating quality due to the use of a small amount of binary nanomaterials in the developed composition.

Observations by engineers throughout Florida revealed that traditional materials used for the repair of concrete pavements and structures often succumb to premature failure after relatively short service lives. A previously existing standard specification for repair materials was based solely on hardened physical properties, specifically compressive strength and length change. A more rigorous testing program was needed, in which the qualification process for repair materials evaluated both physical and durability properties. A testing regimen was devised to evaluate the capacity of each material for use in the repair of structural concrete. The objective of this analysis was to determine the performance of each material type and to properly assign it a repair application category. The testing regimen also evaluated the tests themselves to determine their applicability to evaluate specific material properties, and the potential usage for product acceptance. The sampling, testing, and evaluation procedures are discussed and resultant specification changes are described.

Innovative Solutions for the Construction and the Repair of Hydraulic Structures

This book serves as a comprehensive resource for professionals, students, and researchers in civil engineering, offering insights into advanced structural maintenance and repair techniques. The content is organized into eight units, covering a wide range of topics related to the preservation and improvement of concrete and steel structures. The book begins with an introduction to the key concepts in structural maintenance and repair, emphasizing the importance of concrete quality, damage assessment, and overall structural deterioration. It highlights the multifaceted nature of maintenance, including inspection, repair methods, and the conservation of heritage structures. Subsequent units delve into various aspects of structural maintenance and repair, including concrete quality assurance, durability, and the impact of design and construction errors. The use of specialized materials such as polymer concrete, sulphur infiltrated concrete, and fibre-reinforced concrete is explored, along with practical techniques for repair and demolition. The book also covers damage assessment, offering guidance on evaluating structural decay and monitoring distress in concrete structures. It provides insights into understanding different types of cracks and methods for measuring and monitoring them. Concrete structure repair techniques are thoroughly examined, including fracture repair, crack routing, stitching, prestressing, drilling, and the use of advanced materials to mitigate corrosion. The book concludes with a focus on steel structures, discussing repair types, preventive measures, and addressing common issues such as defects in welded joints. Additionally, the book addresses seismic retrofitting and the maintenance of heritage structures, highlighting their vulnerability to earthquakes and the importance of preserving historic buildings through retrofitting and restoration. Overall, this book provides a valuable and practical resource for those involved in civil engineering, offering a comprehensive understanding of advanced structural maintenance and repair techniques across various construction materials and methodologies.

One of the most common deterioration mechanisms in concrete structures is reinforcement corrosion caused by chlorides. An often used repair strategy is to remove the damaged concrete and sometimes also undamaged concrete and replace with a repair concrete. The chloride contaminated undamaged concrete and the repair concrete have to be compatible in order to achieve a durable system. This laboratory study has investigated 13-year-old reinforced concrete specimens with both substrate concrete with mixed-in chlorides and an initially chloride free repair concrete. The main objective was to study chloride transport from the contaminated substrate concrete into the repair concrete and establish chloride profiles across the interfacial region and interfacial zone between the two materials. Another objective was to evaluate the location of reinforcement corrosion in the interfacial zone, in the substrate concrete and in the repair concrete. The main results from this laboratory investigation show that reinforcement corrosion occurs in and near the interfacial zone between chloride contaminated and repair concrete. It was found that the corrosion occurs in local areas with passive steel areas between, i.e. macrocell corrosion. The chlorides are transported from the contaminated substrate concrete into the repair concrete. This investigation indicates that there is a risk for reinforcement corrosion around a patch repair when the substrate concrete has chloride contents exceeding 1.0 wt% by weight of cement.

Characterization of Substrate-to-Overlay Interface Bond in Concrete Repairs: A Review