Proceedings of the 7th International Conference on Concrete Repair, Rehabilitation and Retrofitting

Table of Contents

1. Frontmatter

2. Keynote Papers

   1. Frontmatter

   2. Enhancing Maintenance and Sustainability of Concrete Sewers Using a Predictive Service Life Approach

      Alice T. Bakera, Mark G. Alexander

      Abstract

      The service life of a sewer is often set at around 100 years, regarded as a sufficient operational period without significant repairs being required. However, sewer concrete may experience severe deterioration, leading to structural and functional failures. 40% of failures can be attributed to biogenic acid corrosion, a chemical reaction between biologically produced sulfuric acid and concrete, leading to a loss of structural integrity and performance. Consequently, service life prediction models are needed for sewer management. Numerous models have been developed, but most remain ineffective and complex. The most common and widely used model is the Life Factor Method (LFM), but this model is limited when concrete with modern, high-performance binder systems and various reactive aggregates are used in different sewer environments. This paper presents further development of the LFM and applies it to predict the performance of different concrete mixes used for sewers in practice. The enhanced LFM model comprises sewer environment and material resistance factors, in which the environment factor evaluates the amount of acid produced on the exposed concrete surface in a sewer system, and the material resistance factor evaluates the amount of acid to be neutralised by the exposed concrete, considering the influence of binders and aggregates. Evaluating these two factors allows prediction of the corrosion rate of concrete with different binder/aggregate combinations when exposed to different sewer environments.

   3. Life Cycle Strategy Optimization: A Methodological Framework for Concrete Structures Rehabilitation Decision Making Through LC(C)A

      Bart Craeye, Lydia Wittocx, Oskar Seuntjens, Neel Renne, Robin Debaene, Hanne Bielen, Ben Moins, Amaryllis Audenaert, Matthias Buyle

      Abstract

      The need for sustainable rehabilitation (maintenance and repair) of existing structures is urgent and due to the expected deterioration of buildings and civil structures, there will be a great need for preventive and/ or curative interventions in the near future. More than 70% of the damage to reinforced concrete (RC), structures is linked to reinforcement corrosion, which can affect the durability of the structure and the residual load-bearing capacity. With the European transition towards a circular economy and the sustainable development goals in mind, it is important to deviate from considering only the technical requirements and initial costs during the design. Priority should be given to preserving products by extending their service life and prioritizing service life thinking. Therefore, the environmental impact and financial costs over the entire life cycle and the intended service life (SL) extension need to be considered. To assess the durability of RC structures and interventions throughout their life cycle, life cycle assessment (LCA) and life cycle cost analysis (LCCA) can be applied. For this reason, it is favourable to economically and environmentally optimize the intervention strategy for preventive maintenance and curative repair of corrosion-damaged RC structures (M&R strategies), based on a multi-criteria framework with the incorporation of LC(C) A. A residential building with damaged RC balconies in a Belgian coastal environment is chosen as case study. The objective is to assess five commonly used repair techniques environmentally and economically, i.e. patch repair, conventional repair, galvanic cathodic protection, impressed current cathodic protection, and total replacement. For a brief extension of the buildings’ SL (up to 5 years), patch repair emerges as the most favourable option, maintaining the existing condition with minimal intervention. However, to reach a longer SL extension (up to 40 years), conventional repair or cathodic protection emerge as competitive options where the entire renewal of concrete elements exhibits the highest overall environmental and financial impact.

   4. Concrete Resistivity Revisited: Experience with Testing on Existing Structures

      Rob Polder, Karla Hornbostel, Bart Craeye, Bjorn Van Belleghem

      Abstract

      The resistivity of concrete expresses its ability to conduct electrical current, which is carried by ions dissolved in the pore liquid. This is relevant for depassivation of embedded reinforcement by chloride transport, corrosion propagation and the application of electrochemical protection methods. Testing resistivity on existing structures may (i) reveal zones where corrosion initiation could occur early, due to high cover permeability and/or increased wetness, (ii) provide an indication of corrosion rate after depassivation, (iii) give information for defining zones in cathodic protection systems and (iv) help specify repair materials for matching resistivity with the parent concrete, as is required for cathodic protection. Several methods can be applied on site, for example non-destructive testing by means of a four-point electrode probe (Wenner probe), or destructive testing a.o. using a two electrode method on extracted cores.

      A set of RILEM Technical Recommendations published about 20 years ago is now under revision by the RILEM TC-OCM and the authors are members of the working group revising the Recommendation for On-site Resistivity Testing. This paper provides background, describes execution of on-site measurements using the four-point method and reports on experience in the field based on several cases in different countries, including measurement variability and the influences of exposure and concrete composition.

   5. Challenges in Implementation of Durability Design in Concrete Construction in India

      Manu Santhanam

      Abstract

      The use of performance-based design for achieving durable concrete structures is gaining traction across the world. The emphasis on linking concrete performance to the specific deterioration mechanisms has led to the incorporation of relevant durability testing in construction projects. However, there are several challenges in implementation of durability design strategies in the field, especially from the perspective of emerging economies like India. The objective of this paper is to highlight the important factors that come in the way of implementing durability design practices. There is a clear need for focused research that can help sort out such issues.

   6. Survival Analysis for Concrete Pavement Service Life Assessment

      Daniel King, Peter Taylor

      Abstract

      Operators and owners of roadways and airfields around the world spend a great deal of resources monitoring the condition of their pavements. Collection and analysis of these data are critical to predicting remaining service life, which is needed to plan future maintenance and rehabilitation activities. Understanding typical pavement service life is also important to the decision-making process for new pavement design and construction, including for activities such as life cycle cost analysis and life cycle assessment. Survival analysis is a statistical technique to analyze and model the expected amount of time before an event occurs. Widely-used in fields such as clinical medicine, epidemiology, and finance, researchers have also used survival analysis to study the performance of pavements and rehabilitation treatments. The survival life of a pavement may be defined in terms of time from construction until major rehabilitation or reconstruction, or time until various measures of pavement condition reach a critical performance threshold. This study provides a review of the literature of survival analysis applied to different types of concrete pavements and concrete pavement rehabilitation treatments, including concrete overlays. These analyses have used a variety of estimators to model concrete pavement service life, to investigate the sensitivity of concrete pavement performance to different design and construction parameters, and to compare the relative performance of different types of designs and rehabilitation treatments. The outcomes of these studies indicate that survival analysis is a useful tool for probabilistic estimation of concrete pavement service life and can provide useful insight into important factors in concrete pavement performance.

3. Condition Assessment and NDT

   1. Frontmatter

   2. Residual Service Life Assessment of an Offshore Concrete Structure in the North Sea

      Gro Markeset, Rolf Magne Larssen

      Abstract

      This paper presents a residual service life assessment of an offshore concrete structure for oil and gas production in the North Sea. After 15 years in operation, plans were initiated for a service life extension from 30 to 50 years, and a condition assessment of the concrete structure above the sea level was carried out. A probabilistic service life model based on Fick’s 2nd law of diffusion was used in the documentation of the residual service life of the concrete structure. The model parameters were adapted the actual structure, where the statistical data for the apparent diffusion coefficients and the surface concentrations were determined from concrete cores drilled out from the concrete above sea level. Using an acceptance limit of 10% probability for corrosion initiation, a service life of 50 years was obtained for the homogeneous, good quality concrete and a concrete cover in accordance with specified requirement of 50 mm + 20/− 0. Further, an updated service life analysis, based on chloride profiles determined 13 years later, indicated an even longer service life.

   3. Damage Assessment of the Carinus Bridge (B2918) Over the Berg River in Velddrif, South Africa

      Wandie Olivier, Philip D. Ronné

      Abstract

      The Carinus Bridge is located at km 140.49 on Trunk Road 77/1 (R27) and crosses the Berg River estuary immediately south of Velddrif in the Western Cape, South Africa. Bridge inspections conducted principally by visual means, identified certain elements of the bridge that had deteriorated and has resulted in the bridge being classified as a highly critical structure. The most prominent defects relate to the half-joints in the central span (span 6) that has a drop-in element and is the longest span over the main river channel. Highways England’s CS 466 Risk Management and Structural Assessment of Concrete Half-joint Deck Structures was used to assess the primary risk. From this assessment, the half-joints on three corners were deemed a very high risk with the northwest corner being classified as immediate risk. This paper presents the findings from diagnostic tests performed at the existing bridge, with emphasis placed on the assessment of the exposure environment and reporting of environmental rate parameters that can be used for new reinforced concrete construction in the vicinity of the Berg River Estuary.

   4. Demolition of Refinery Interchange Bridge B4247: Condition of a 58-Year Old Prestressed Concrete Bridge After Demolition

      Kinte van Breda, Wandie Olivier, Anton Faure

      Abstract

      The reconstruction and upgrading of Trunk Road 11/1 (TR11/1, better known as the National Route N7) in Cape Town in the Western Cape necessitated the demolition of the Refinery Overpass Bridge B4247. This bridge had both insufficient vertical and horizontal clearance for the proposed widening of the N7. Furthermore, the existing precast beam-and-slab deck suffered from continuous vehicular impact damage over the years, resulting in continued costly repairs. This paper describes the condition of this bridge after a 58-year service life. The primary objective is to report and comment on the condition of this bridge in order for other engineers who have to rehabilitate, raise or widen similar bridges built during the same time, to have an indication of the quality of materials, workmanship, condition and behaviour. During and after the demolition operation, a visual inspection of the rubble was undertaken to evaluate the condition of this bridge which was constructed in 1965. Concrete cores taken before the demolition revealed higher concrete strengths of 50% and more, except for the precast beams concrete strengths which were well below the expected design strength after 58 years. Carbonation and durability tests done on concrete fragments indicated a robust and durable structure which would easily reach its intended 100-year design life.

   5. Assessment of SFRC Slab-on-Piles Through In-Situ Load Testing

      Cosmin Popescu, Björn Täljsten

      Abstract

      Demonstrating the performance of a structural component is typically accomplished through calculations based on engineering models. However, advancements in material science have enabled the use of new materials in the construction industry. One example is fibre-reinforced concrete, which consists of concrete with short, discontinuous fibres dispersed throughout its volume to enhance performance under service limit states. The absence of conventional reinforcement can affect ductility and load capacity, making calculations alone insufficient to demonstrate the performance of these elements. Therefore, load-testing programs need to be developed. This paper reports and discusses the results of a full-scale test on a fibre-reinforced concrete multi-span slab-on-piles. The development of the test program, including the loading setup to achieve failure loads, is presented. The slab's performance is evaluated in terms of deflections and crack widths at various loading intervals corresponding to both service limit states and ultimate limit states.

   6. Non-destructive Testing of a Post-tensioned Concrete Road Bridge in Norway

      Björn Täljsten, Cosmin Popescu, Mats Holmqvist

      Abstract

      The Herøysunds bridge on the west-coast in Nordland Fylke in Norway had undergone concrete repair works with focus on reinforcement corrosion. During these actions, it was discovered that the tendon ducts had loss of injection.

      To ensure the safety of the bridge it was decided to map voids and defects in the ducts. Several risk areas were pointed out by the contractor and a non-destructive test (NDT) was carried out. The scope of the NDT inspection was to determine voids in the cable ducts at the areas which had been pointed out by the designer. In the project we followed a strict procedure. Based on this we used a combination of different methods such as GPR (Ground Penetrating Radar), UPE (Ultra Pulse Echo) and IE (Impact Echo). It should be mentioned that considerable experience is needed when these methods are combined to investigate voids and defects in tendon ducts. In addition, it is difficult to determine the degree of grouting in the duct and the NDT methods often need to be combined with partly destructive testing, i.e. a hole needs to be drilled into the duct and closer investigation with for example endoscope might be needed. The results from the NDT investigate shows that the suggested approach was successful and it was possible with high accuracy to detect voids in the ducts. The methodology forms a basis for the procedure recommended by the Norwegian Public Roads Administration.

   7. Assessing the Seismic Performance of Existing Reinforced Concrete Buildings in New Zealand

      Lusa Tuleasca, Wei Loo

      Abstract

      The 2011 Canterbury earthquake in New Zealand motivated a revision and enhanced standardization of protocols for the assessment of the earthquake risk of existing buildings across the country. The resulting document arising after significant consultation and discussion is the 2017 publication “The Seismic Assessment of Existing Buildings Technical Guidelines for Engineering Assessments”. The document provides guidelines on determining whether a building should be rehabilitated after an earthquake. This article is written primarily with the objective of providing a notion of how seismic assessment practice has changed in New Zealand since the Canterbury earthquakes in the context of these new technical guidelines. The procedures within the ISA (Initial Seismic assessment) and DSA (Detailed Seismic Assessment) are discussed. Two cases of the assessments being applied are then presented, the first example being that of a four-story reinforced concrete building in Auckland, an area of relative low seismicity, and the second example which is a four-story reinforced concrete building in Wellington, an area of very high seismicity.

   8. Correlation Between Damage Parameters and Mechanical Properties of Concrete Affected by ASR

      E. Baret, M. Kaleghi, B. Fournier, B. Bissonnette, L. Courard

      Abstract

      To investigate the potential correlation between damage parameters used to assess the level of alkali silica reaction (ASR) in concrete and the mechanical properties of the material is a promising approach. Currently, ASR damage evaluation of concrete is done following FHWA protocol [1]. The actual level of damage (diagnosis) is evaluated using the Stiffness Damage Test (SDT) and the Damage Rating Index (DRI). Both methods provide parameters correlated to the concrete's expansion level. In addition, future potential of damage (prognosis) is assessed using residual expansion tests in specific climatic conditions (R.H. > 95% and T = 38 ±°C) and alkaline solution (NaOH 1N, 38 ±°C). Expansion is thus currently used to assess the damage and predict future deterioration. However, only expansion measurements are insufficient for infrastructure managers who need to understand the structural impact of ASR on concrete structures. Therefore, this research aims to identify new correlations between the actual test results and structural parameters of the concrete, providing more relevant information for infrastructure management. In this project, cores from ASR-affected bridges were extracted, cut into samples and subjected to both prognosis and diagnosis tests, as well as compressive tests, directly after extraction and after expansion tests, respectively. A linear trend was identified for compressive strength, correlating with DRI values in cores tested after extraction, indirectly linking to the concrete's expansion level. Young's modulus also decreased with additional expansion during the tests, but no significant trendline was identified.

   9. Condition Assessment of Concrete Railway Sleepers: Residual Risk of Assessment Methods

      A. Lambrechs, H. Beushausen

      Abstract

      The condition assessment of concrete sleepers poses a challenge for the South African rail network for two primary reasons: the scale at which measurements need to be conducted and the presence of ballast stone, which obstructs direct access to the sleepers for visual and non-destructive assessment. Literature related to common concrete sleeper defects and methods of condition assessment was reviewed. Literature was used to assess which of the concrete sleeper functional requirements a specific defect will inhibit or prohibit. A Failure Mode and Effect Analysis (FMEA) showed the severity of the concrete sleeper defects, their frequency of occurrence, and the quality of information provided by each of the condition assessment methods. The Residual Profile Number (RPN) from the FMEA showed which defects presented the highest unmitigated risks to continued rail operations. The top two most critical sleeper defects, longitudinal cracking and vertical cracks at the rail seat, are related to assessment methods that allow for maintenance planning requirements. Sleeper body abrasion was found to be the only defect that is currently not related to a method for detecting the condition well enough to sufficiently mitigate the residual risk to continued network operations. Methods that assess sleeper body abrasion need to be improved to meet maintenance planning requirements.

   10. An Analysis of the Impact of Chloride-Induced Corrosion on Reinforced Concrete Structures in the Port of Cape Town

       Mishka Prinsloo, Hans Beushausen

       Abstract

       Corrosion of steel reinforcement is a main deterioration mechanism for reinforced concrete structures in the marine environment, where chloride ingress may cause severe and widespread damage. For infrastructure owners, an improved understanding of the particular environment can lead to the design of more durable structures, or the improved maintenance of existing structures, both leading to more effective investment decisions. The objective of this research were to perform as-built data collection, visual condition assessments and cover measurements on various reinforced concrete structures in the port of Cape Town, with the aim of drawing correlations between the parameters of marine exposure, cover depth, and age of structure to the damage rating related to chloride-induced corrosion.

   11. Establishment of Technology to Automatically Determine the Presence or Absence of Steel Wires by Magnetic Data of Pre-tensioned Girder PC Steel Using Non-destructive Testing Device

       Katsunori Teshima, Atsushi Yamada, Shinichiro Okazaki

       Abstract

       Sensing technology using magnetism and IoT technology ‘SenrigaN’ is a non-destructive testing technology currently under development. SenrigaN is a solution that visualizes fracture of internal PC steel wires in concrete structures in real time. By analyzing magnetic data using magnetic sensing and IoT, it is possible to instantly find fracture locations on-site bridges. At the same time, it is necessary to appropriately find whether PC steel wires are fractured. In this study, we used Magnetic Flux Leakage method and using a 3-axis magnetic measurement device to automatically capture the characteristics of changes in the magnetic flux waveform when steel inside concrete breaks and built a model that finds the presence or absence of a break.

   12. Assessment for Fire Damage in Concrete Structures with Electrical Resistance Measurement

       Toru Kinose, Kei-ichi Imamoto, Natsuki Yoshida, Daiki Atarashi

       Abstract

       When devising plans for repairing and reinforcing concrete structures after a fire, one must evaluate the effects of heat on concrete. When a fire occurs in a concrete structure, the moisture contained within it evaporates owing to high temperatures. The authors investigated methods to assess the effect of heat by correlating the drying process during a fire with the heating temperature. In this study, a method for evaluating the drying degree of concrete after fire exposure was examined by measuring the electrical resistance, which is closely related to the moisture content of concrete. Initially, a method was investigated to measure the electrical resistance in the depth direction from the surface of fire-damaged concrete. Subsequently, the electrical resistance of the specimens heated to simulate fire conditions was measured, and the relationships among the electrical resistance, moisture content, and heating temperature were compared. Measuring the electrical resistance of the surface of concrete damaged by fire and then comparing it to the resistance of unheated concrete allows one to identify the area that had been heated to 150 ℃ or more and became almost completely dry.