Eco-efficient Repair and Rehabilitation of Concrete Infrastructures

Fernando Pacheco-Torgal, Robert E. Melchers, Xianming Shi, Nele de Belie, Kim Van Tittelboom, Andres Saez Perez, Robert Melchers

• Publisher: Woodhead Publishing
• Year: 2017
• Print ISBN: 9780081021811
• eBook ISBN: 9780081021828
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Eco-efficient Repair and Rehabilitation of Concrete Infrastructures provides an updated state-of-the-art review on eco-efficient repair and rehabilitation of concrete infrastructure. The first section focuses on deterioration assessment methods, and includes chapters on stress wave assessment, ground-penetrating radar, monitoring of corrosion, SHM using acoustic emission and optical fiber sensors. Other sections discuss the development and application of several new innovative repair and rehabilitation materials, including geopolymer concrete, sulfoaluminate cement-based concrete, engineered cementitious composites (ECC) based concrete, bacteria-based concrete, concrete with encapsulated polyurethane, and concrete with super absorbent polymer (SAPs), amongst other topics.Final sections focus on crucial design aspects, such as quality control, including lifecycle and cost analysis with several related case studies on repair and rehabilitation. The book will be an essential reference resource for materials scientists, civil and structural engineers, architects, structural designers and contractors working in the construction industry.- Delivers the latest research findings with contributions from leading international experts- Provides fully updated information on the European standard on materials for concrete repair (EN 1504)- Includes an entire sections on the state-of-the-art in NDT, innovative repair and rehabilitation materials, as well as LCC and LCA information

1

Introduction

Fernando Pacheco-Torgal, University of Minho, Guimarães, Portugal

Abstract

This chapter begins with some comments on sustainability challenges followed by an overview on concrete infrastructure deterioration. It addresses deterioration causes and future climate change impact related causes. It also includes some estimates on costs of repair and rehabilitation. A book outline is presented.

Keywords

Concrete deterioration; carbonation; corrosion; climate change; repair and rehabilitation

1.1 Repair and rehabilitation of concrete infrastructures on the context of sustainable development

Rockström et al. (2009) proposed an approach to global sustainability defining nine interdependent planetary boundaries within which they expect that humanity can operate safely. This include:

1. climate change (CO₂ concentration in the atmosphere <350 ppm and/or a maximum change of +1 W/m² in radiative forcing);

2. ocean acidification (mean surface seawater saturation state with respect to aragonite ≥80% of pre-industrial levels);

3. stratospheric ozone (<5% reduction in O₃ concentration from pre-industrial level of 290 Dobson Units);

4. biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N₂ to 35 Tg N/yr) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P);

5. global freshwater use (<4000 km³/yr of consumptive use of runoff resources);

6. land system change (<15% of the ice-free land surface under cropland);

7. the rate at which biological diversity is lost (annual rate of <10 extinctions per million species).

Two additional planetary boundaries for which a boundary level was not yet determined are: chemical pollution and atmospheric aerosol loading. According to the authors, the “transgression one or more planetary boundaries may be deleterious or even catastrophic due to the risk of crossing thresholds that will trigger non-linear, abrupt environmental change within continental- to planetary-scale systems”. These authors estimated that humanity has already transgressed three planetary boundaries for changes to the global nitrogen cycle, the rate of biodiversity loss and, above all, climate change (Hansen et al., 2013, 2016, 2017). Most unfortunately, the repeated fiascos of the so-called Conference of Parties (COPs) in Warsaw (COP-19) in 2013, Lima (COP-20) in 2014, Paris (COP-21) in 2015 and, most recently, Marrakech (COP-22) in November of 2016 to agree on important reductions on greenhouse gas emissions only worsened the climate change scenario. The major problem being the fact that the major emission emitters: China, US and India, do not accept severe cuts. If the position of China and India is understandable from an economic view, the US is not, because it is a well-developed economy, and on a per-capita historical basis, the U.S. is 10 times more accountable than China and 25 times more accountable than India for the increase of atmospheric CO₂ above its preindustrial level (Hansen and Sato, 2016).

As a consequence of this worrying status, it remains crucial to act in order to address those problems in a context in which urban human population is growing exponentially. Each day there are now about 200,000 new inhabitants on planet Earth and in the next decades human population will almost double, increasing from approximately 3.4 billion in 2009 to 6.4 billion in 2050 (WHO, 2014). As a consequence, recent estimates on urban expansion suggests that until 2030 a high probability exists (over 75%) that urban land cover will increase by 1.2 million square kilometer (Seto et al., 2012). This overpopulation will require new infrastructure and will put increase pressure on the existent infrastructures.

Concrete infrastructure encompasses bridges, piers, pipelines, dams, pavements, or buildings that are crucial to services and economic activities of modern civilization. Unfortunately, concrete deteriorates due to several causes including: mechanical deterioration from impact or excessive loading, or deterioration due to physical causes of erosion or shrinkage. More frequently, however, it deteriorates through chemical detrimental reactions when it is exposed to environmental conditions containing chlorides from seawater or from deicing salts, atmospheric carbon dioxide, or other aggressive media (Glasser et al., 2008).

The importance of concrete durability has been emphasized by Mora (2007), when he stated that increasing durability from 50 to 500 years would mean a reduction of its environmental impact by a factor of 10. Concrete infrastructure with low durability requires frequent maintenance and conservation operations and its integral replacement is associated with the consumption of huge amounts of raw materials and energy. Many of the degraded concrete infrastructures were built decades ago when little attention was given to durability issues (Hollaway, 2011). Deficient execution due to poor workmanship is also a relevant cause of premature degradation of concrete infrastructure and reinforcement corrosion (Costa and Appleton, 2002) and this cause is becoming increasingly relevant in recent decades (Elrakib and Arafa, 2012), relevant to the cost increase of workmanship. Additionally, the majority of technical standards and codes that deal with durability design and control of execution do not make any provisions for the assessment of concrete cover depth achieved in structures. This constitutes a serious gap, because failure to comply of the concrete cover depth with the specifications is one of the main causes of premature deterioration of reinforced concrete structures (Monteiro et al., 2015; de Medeiros et al., 2016).

Climate change is also increasingly responsible for the premature deterioration of concrete infrastructure. Not only due to occasional and extreme atmospheric events, but in a more frequent pattern due to concrete carbonation associated with the steady increase on CO₂ concentration (molecules of CO₂ for every one million molecules in the atmosphere) (Fig. 1.1). Its important to mention that 2016 was the first year with atmospheric CO₂ concentrations above 400 ppm all year round (Betts et al., 2016) and even if all the greenhouse gas emissions suddenly ceased, the amount already in the atmosphere would remain there for the next 100 years (Clayton, 2001). Wang et al. (2010) showed that additional carbonation-induced damage risks for the A1FI emission scenario (CO₂ concentrations increasing by more than 160% to 1000 ppm by 2100) are up to 16% higher if there are no changes to how concrete structures are designed or constructed.

Figure 1.1 Predicted estimates of CO₂ concentrations. Actual atmospheric CO₂ concentration has been plotted side by side along with predicted concentrations for 2000–13 and shown in the inset panel. Source: From Saha, M., Eckelman, M., 2014. Urban scale mapping of concrete degradation from projected climate change. Urban Clim. 9, 101–114. Copyright © 2014, with permission from Elsevier (Saha and Eckelman, 2014).

Stewart et al. (2011) found that carbonation-induced corrosion can increase by over 400% by 2100 for inland arid or temperate climates in Australia. Bastidas-Arteaga et al. (2013) noticed that climate change might reduce the time to failure of reinforced concrete structures by up to 31%. Talukdar and Banthia (2013) found that concrete structures that will be constructed in the year 2030, in areas where carbonation induced corrosion would be a concern (moderate humidity, higher temperatures and for a dry exposure class), structures are expected to show a reduction in serviceable lifespan due to climate change of approximately 15–20 years, with signs of damage being apparent within 40–45 years of construction. Since, in urban settings, CO₂ concentrations can be much higher than in nearby rural environments, and that urban areas are subject to increase temperature levels due to urban heat island effects, this means that concrete infrastructure located in urban areas are subject to more intense carbonation-damaging actions. According to Saha and Eckelman (2014), climate change will accelerate corrosion and degradation of concrete structures in Boston. By the year 2055, the chlorination-induced corrosion depth in concrete structures built in year 2000 may exceed the code-recommended protected cover thickness of 38 mm. For carbonation-induced corrosion, the threshold year is 2077. Rehabilitation of concrete infrastructures to address future carbonation-induced corrosion under much-higher CO₂ concentrations, or any other climate change related deterioration action, can be considered in the context of urban adaptation. Fig. 1.2 shows a world map concerning the status of urban adaptation to climate change in areas with over one million inhabitants, each covering a total of 1.3 billion people. Many of the existing infrastructures will still be in use by 2030 and even in 2050 when climate change might have far more substantial impacts than today, meaning that repair and rehabilitation action will be needed to prevent premature degradation (Giordano, 2012). Worldwide concrete infrastructure repair rehabilitation needs are therefore enormous. In US there are more than 60,000 structurally deficient bridges. For China this number exceeds more than 80,000 bridges. In Europe in the next 10 years some 1500 railway bridges are expected to be strengthened, 4500 have to be replaced, and the deck of other additional 3000 bridges has to be replaced (Casas, 2015). Consequently, its costs are staggering. According to OECD, improving the world’s infrastructure will require an estimated $7 trillion/year USD (Kennedy and Corfee-Morlot, 2013).

Figure 1.2 Map of global urban adaptation panel. Source: From Araos, M., Berrang-Ford, L., Ford, J., Austin, S., Biesbroek, R., Lesnikowski, A., 2016. Climate change adaptation planning in large cities: a systematic assessment. Environ. Sci. Policy 66, 375–382. Copyright © 2016, with permission from Elsevier (Araos et al., 2016).

In the US, the corrosion deterioration cost due to deicing and sea salt effects is estimated at over 150 billion dollars and infrastructure repair rehabilitation overall needs are estimated to be over 1.6 trillion dollars over the next years (Davalos, 2012). A climate-change induced acceleration of the corrosion process by only a few percent can result in increased maintenance and repair costs of hundreds of billions of dollars annually (Bastidas-Arteaga and Stewart, 2015). The annual cost of corrosion worldwide is already over 3% of the world’s Gross Domestic Product (GDP) (Bossio et al., 2015). In Europe, bridge maintenance repair and strengthening requires an annual budget of £215M, and that estimate does not include traffic management cost (Yan and Chouw, 2012). In US, costs related to wasted fuel and time loss due to traffic congestion are estimated between 50 and 100 billion dollars (Report, 2012; Schlangen and Sangadji, 2013). In the in city of Hong Kong, more than 580,000 vehicles cross its 900 highway bridges on a daily basis (Pei et al., 2015). This traffic volume is expected to duplicate in the next decades. It can never be overemphasized that Earth’s populations are growing at a very fast pace and as a consequence in 2014 there will be 12,000 million vehicles on the road and by 2035 this number will increase to 2000 million and 2500 million by 2050 (Navigant Research, 2014). This means that concrete highways bridges will be subject to increase use and will reach the end of their service life sooner than expected and repair and rehabilita...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Foreword
• 1. Introduction
• Part I: Deterioration assessment
• Part II: Innovative concrete repair and rehabilitation materials
• Part III: Design, LCC, LCA, and case studies
• Index