Corrosion Of Infrastructure Research Articles

Severe Corrosion of Carbon Steel in Oil Field Produced Water Can Be Linked to Methanogenic Archaea Containing a Special Type of [NiFe] Hydrogenase.

Methanogenic archaea have long been implicated in microbially influenced corrosion (MIC) of oil and gas infrastructure, yet a first understanding of the underlying molecular mechanisms has only recently emerged. We surveyed pipeline-associated microbiomes from geographically distinct oil field facilities and found methanogens to account for 0.2 to 9.3% of the 16S rRNA gene sequencing reads. Neither the type nor the abundance of the detected methanogens was correlated with the perceived severity of MIC in these pipelines. Using fluids from one pipeline, MIC was reproduced in the laboratory, both under stagnant conditions and in customized corrosion reactors simulating pipeline flow. High corrosion rates (up to 2.43 mm Fe0 · yr-1) with macroscopic, localized corrosion features were attributed to lithotrophic, mesophilic microbial activity. Other laboratory tests with the same waters yielded negligible corrosion rates (<0.08 mm Fe0 · yr-1). Recently, a novel [NiFe] hydrogenase from Methanococcus maripaludis strain OS7 was demonstrated to accelerate corrosion. We developed a specific quantitative PCR (qPCR) assay and detected the gene encoding the large subunit of this hydrogenase (labeled micH) in corrosive (>0.15 mm Fe0 · yr-1) biofilms. The micH gene, on the other hand, was absent in noncorrosive biofilms, despite an abundance of methanogens. Reconstruction of a nearly complete Methanococcus maripaludis genome from a highly corrosive mixed biofilm revealed micH and associated genes in nearly identical genetic configuration to that in strain OS7, thereby supporting our hypothesis that the encoded molecular mechanism contributed to corrosion. Lastly, the proposed MIC biomarker was detected in multiple oil fields, indicating a geographically widespread involvement of this [NiFe] hydrogenase in MIC.IMPORTANCE Microorganisms can deteriorate built environments, which is particularly problematic in the case of pipelines transporting hydrocarbons to industrial end users. MIC is notoriously difficult to detect and monitor and, as a consequence, is a particularly difficult corrosion mechanism to manage. Despite the advent of molecular tools and improved microbial monitoring strategies for oil and gas operations, specific underlying MIC mechanisms in pipelines remain largely enigmatic. Emerging mechanistic understanding of methanogenic MIC derived from pure culture work allowed us to develop a qPCR assay that distinguishes technically problematic from benign methanogens in a West African oil field. Detection of the same gene in geographically diverse samples from North America hints at the widespread applicability of this assay. The research presented here offers a step toward a mechanistic understanding of biocorrosion in oil fields and introduces a binary marker for (methanogenic) MIC that can find application in corrosion management programs in industrial settings.

Assessing the impacts of scale residues from offshore oil and gas decommissioning on marine organisms

Successful decommissioning of offshore oil and gas infrastructure requires an effective and safe approach to assessing and managing chemical and radiological residues. Scale frequently accumulates on the interior surfaces of pipes and other structures and may persist long after extraction operations have ceased. Scale materials can contain a range of metal contaminants (including mercury), as well as naturally occurring radioactive materials. In newer or more accessible infrastructure, the scale is routinely removed, and becomes a waste product. The persistent nature of scale contaminants can result in a radiological dose to the organisms living on, or near an intact pipeline. Eventually, infrastructure corrosion following insitu decommissioning (abandonment) could lead to metal and radionuclide contaminants being accessible to the surrounding seafloor environment, where bioaccumulation and subsequent ecotoxicological effects from the chemical and radiological properties of the scale could occur. The paper describes a tiered approach to assess the ecological impacts of pipeline scale in order to assist operators with their plans for decommissioning offshore infrastructure, especially when considering ‘leave in place’ options.

Properties and Performance of Novel Mg(OH)2-Based Coatings for Corrosion Mitigation in Concrete Sewer Pipes.

The biological activity occurring in urban sewerage systems usually leads to the (biogenic) corrosion of pipe infrastructure. Anti-corrosion coating technology was developed in an effort to protect sewer pipes from degradation. This study evaluates a new class of relatively low-cost magnesium hydroxide-based coatings, regarding their ability to adhere efficiently onto the concrete surface, and offer efficient corrosion protection. Six magnesium hydroxide-based coatings were prepared with the addition of two different types of cellulose, used as adhesion additives, and these were applied on concrete specimens. Pull-off measurements showed that the addition of higher amounts of cellulose could improve the coating adhesion onto the concrete surface. An accelerated sulfuric acid spraying test was used to evaluate the consumption time of the applied coatings and their efficiency in maintaining over time slightly alkaline pH values (above 8) on the coated/protected surfaces. At the end of spraying test, a mineralogical analysis of surface samples was performed, indicating that the formation of corrosion by-products (mainly gypsum) was increased when the added amount of cellulose was lower. Hardness and roughness measurements were also conducted on the concrete surfaces, revealing that the coatings helped the concrete surface to preserve its initial surface properties, in comparison to the uncoated specimens. A SEM/microstructure analysis showed that aggregates were formed (possibly consisting of Mg(OH)2), affecting the reactivity of the protected surface against sulfuric acid attack.

Bridge deck assessment using infrastructure corrosion assessment magnetic method (iCAMM™) technology, a case study of a culvert in Markham city, Ontario, Canada

Steel reinforcement corrosion can result in disastrous bridge failures over time. To manage the human and financial risks associated with such unexpected functional bridge failures, the reinforcements' condition should be quantified using Non-Destructive Testing (NDT) methods. In this case history, the condition of culvert C072's reinforced concrete (RC) bridge structure (located in the north of Markham, Ontario, Canada) is inspected. The inspection, carried out under the supervision of the Corporation of the City of Markham, used a passive magnetic-based NDT technology, the Infrastructure Corrosion Assessment Magnetic Method (iCAMM™). The inspection outcomes demonstrate that the sections close to the south and north ends of the bridge display the most-severe reinforcement anomalies: roughly, a maximum of 20% and 14% of the reinforcement's cross-sectional area loss are detected close to the bridging structure's south and north ends. Additionally, an area in the middle of the bridge is found to have a noticeable anomaly in the reinforcement. The results generated from the magnetic data, collected using an iCAMM™ scanner, are in good agreement with visual-investigation results and the culvert's historical information, such as the concrete's chloride content and compressive strength values, as well as information from a half-cell potential survey. Culvert C072's condition is considered moderately deteriorated and corrective actions are recommended.

Evaluation of corrosion inhibition and self healing capabilities of nanoclay and tung oil microencapsulated epoxy coatings on rebars in concrete

Corrosion of civil infrastructure is the biggest challenge faced by the construction industry worldwide and billions of dollars are spent for its repair and rehabilitation. One of the methods to mitigate the effects of corrosion is the use of Epoxy Coated Rebars (ECR) in concrete. But epoxy coatings are inherently brittle and susceptible to crack initiation and propagation. Thus, to further improve their efficiency in inhibiting corrosion, modifications in the epoxy coatings have to be done. In the present study, it is suggested to modify epoxy coatings by adding nano-clay and tung oil microcapsules. To measure the effectiveness of these coatings to corrosion inhibition, non-destructive monitoring has been done using electrochemical current measurements and ultrasonic guided wave propagation characteristics while the coated rebars are subjected to impressed current accelerated corrosion. The corrosion introduces non-uniform and localized pits in the rebars and disturbs the path of the propagating guided waves through it by mode conversions and scattering which results in drop in transmitted guided wave signal strengths. Nano dispersion of clay in epoxy not only increase of toughness, tensile and flexural properties of the epoxy but leads to torturing of the path for moisture progression. Lastly, the hydrophobic nature of modified clays will aid in reducing progression of water molecules. This was successfully illustrated by very small corrosion current values and small rate of drop in ultrasonic guided wave voltage signals as compared to plain epoxy coated rebars. On the other hand, tung oil microcapsules in Urea-formaldehyde (UF) shells prepared by in-situ polymerization improves the self-healing ability and adhesion strength of capsule embedded coatings and act as self-healing agents. Tung-oil micro-encapsulated coatings perform the best in terms to corrosion resistance as well as bonding with surrounding concrete. The drop in voltage amplitudes as well as the rate of voltage drop with increasing corrosion exposure is very nominal and insignificant. It points towards remarkable inhibition of corrosion offered by self-healing tung oil microcapsules to corrosion damage.

Experimental on thermal performance of bridge deck with hydronic heating system

Hydronic heating systems with geothermal heat exchangers are one of the innovative methods for bridge deck deicing in winter, which avoids infrastructure corrosion and environmental pollution caused by chemical methods. This paper focused on field tests of the thermal performance of a bridge deck with a hydronic heating system under heating conditions. The inlet fluid temperatures were kept constant to study the transient heat flux through outlet fluid temperatures under different ambient temperature conditions. Three different inlet fluid temperatures of 30.5 °C, 35.5 °C, and 41.0 °C were considered in the field test. The objective of this paper is to study the influences of the air temperature, slab temperature, and inlet fluid temperature on the heat exchange flux and the thermally induced stresses due to heating. The results indicate that the inlet fluid temperature should be controlled above 2.3 times the absolute value of the air temperature to keep the slab surface temperature above 0 °C when the air temperature is below 0 °C. The thermally induced stresses caused by operating the system are smaller than 5% of the strength of the concrete, which are negligible.

Oil reservoir simulating bioreactors: tools for understanding petroleum microbiology.

Various aspects of the oil fields in terms of microbial activity (souring, biocorrosion, etc.) and oil production (polymer flooding, etc.) have been evaluated through a variety of experiments. The primary step to study these properties in the laboratory requires the construction and operation of up-flow oil reservoir simulating bioreactors (ORSBs) in real time. Souring by reduction of sulfate to sulfide is a major contributor in enhancing corrosion of metal infrastructure used for oil production and processing. Whether the injection of biocides prevents or remediates reservoir souring can be addressed by flooding up-flow ORSBs. The potential of biopolymers/biosurfactants produced by different microbial strains have also been investigated for the role in maintaining additional oil recovery using ORSB. Additionally, key issues of polymer behavior during flooding of reservoirs could be understood during laboratory studies by monitoring the in situ porous medium rheology. Besides, the change in various ORSB parameters helps in adjudging the effect of different biosurfactants/biopolymers in enhancing oil recovery. Parameters such as permeability reduction, adsorption, interaction with porous matrix, and formation damage can be evaluated using ORSB. The analysis of earlier studies indicated that running bioreactors for longer duration of time can help in drawing conclusion with sharpness and less ambiguity. The current review discusses the construction and application of various types of ORSBs including the experimental studies employing ORSBs.

Conceptual hydrogeological and numerical groundwater flow modelling around the Moab Khutsong deep gold mine, South Africa.

Prediction of response to fissure water pumping from a shaft on the surrounding areas is conducted with a numerical model, which was refined using environmental stable isotope (ESI), Tritium and hydrochemical datasets. The numerical model domain covers the local carbonate rock units mainly because it is known to be the main source of groundwater.Based on the hydrochemical dataset of the fissure water pumped at the shaft, strong signature of Na–Cl type water originating from the seepage of a waste rock dump as well as polluted water from mine offices, loading/unloading and parking lot areas, is evident. The environmental isotope data demonstrated that fissure water intercepted at the shaft has strong footprint of surface water and polluted groundwater from nearby areas. The 30-year numerical model prediction indicates that pumping at a rate of 2500 m3/day or more would cause the radius of influence to expand to areas where the central tailings storage facility is located and could possibly draw highly acidic water. Interception of acid rock drainage could cause sever corrosion of pump infrastructure, enhance dolomite dissolution and local ground subsidence as well as possibly compromise the structural integrity of the central tailings dam.It is recommended that the current groundwater monitoring network be revised for taking proactive action. The study highlights the relevance of integrating various sets of data to improve understanding of the conceptual flow before any numerical modelling is attempted.

Atmospheric Corrosion Assessment of Structural Steel Exposed in The Environment of Palm Oil Processing (PKS) Industry Around Coastal Zone

Corrosion is the main cause of mature failures for infrastructure such as residential, public facilities, and also industries. Regarding of industry which having a rapid growth in the province of Aceh, especially Palm Oil Processing (PKS), the existence must be noticed in line with the environmental impact that caused by operations such as industrial gases which can be polluted the atmosphere. This condition can transform the infrastructure especially steel which is located around PKS becomes more vulnerable to the corrosion attacks. This study aims to investigate the corrosion atmospheric of structural steel in the PKS area and operational impacts for the infrastructure of PKS at PT. Ensem Sawita and PKS PT Anugerah Fajar Rejeki(AFR). Infrastructure corrosion is focused on measuring atmospheric corrosion rate of structural steel surrounding PKS area. Several types of steels will be selected as a specimen. The corrosion rate is calculated with mass-loss method referring to ASTM G50 standard. The location of selected PKS is around ± 5kmfrom the coast. The results are obtained after exposure during 4 months, the corrosion rate that occurs for 5 types of structural steel was in normal level. It is classified in the outstanding level of relative corrosion resistance (<1mpy). So, the usage of 5 types structural steel is relatively safe on palm industries and related areas.

Deep-Subsurface Pressure Stimulates Metabolic Plasticity in Shale-Colonizing Halanaerobium spp.

Bacterial Halanaerobium strains become the dominant persisting microbial community member in produced fluids across geographically distinct hydraulically fractured shales. Halanaerobium is believed to be inadvertently introduced into this environment during the drilling and fracturing process and must therefore tolerate large changes in pressure, temperature, and salinity. Here, we used a Halanaerobium strain isolated from a natural gas well in the Utica Point Pleasant formation to investigate metabolic and physiological responses to growth under high-pressure subsurface conditions. Laboratory incubations confirmed the ability of Halanaerobium congolense strain WG8 to grow under pressures representative of deep shale formations (21 to 48 MPa). Under these conditions, broad metabolic and physiological shifts were identified, including higher abundances of proteins associated with the production of extracellular polymeric substances. Confocal laser scanning microscopy indicated that extracellular polymeric substance (EPS) production was associated with greater cell aggregation when biomass was cultured at high pressure. Changes in Halanaerobium central carbon metabolism under the same conditions were inferred from nuclear magnetic resonance (NMR) and gas chromatography measurements, revealing large per-cell increases in production of ethanol, acetate, and propanol and cessation of hydrogen production. These metabolic shifts were associated with carbon flux through 1,2-propanediol in response to slower fluxes of carbon through stage 3 of glycolysis. Together, these results reveal the potential for bioclogging and corrosion (via organic acid fermentation products) associated with persistent Halanaerobium growth in deep, hydraulically fractured shale ecosystems, and offer new insights into cellular mechanisms that enable these strains to dominate deep-shale microbiomes.IMPORTANCE The hydraulic fracturing of deep-shale formations for hydrocarbon recovery accounts for approximately 60% of U.S. natural gas production. Microbial activity associated with this process is generally considered deleterious due to issues associated with sulfide production, microbially induced corrosion, and bioclogging in the subsurface. Here we demonstrate that a representative Halanaerobium species, frequently the dominant microbial taxon in hydraulically fractured shales, responds to pressures characteristic of the deep subsurface by shifting its metabolism to generate more corrosive organic acids and produce more polymeric substances that cause "clumping" of biomass. While the potential for increased corrosion of steel infrastructure and clogging of pores and fractures in the subsurface may significantly impact hydrocarbon recovery, these data also offer new insights for microbial control in these ecosystems.

Sustainable Green Construction Chemicals in Infrastructure Development

Sustainability is one of the most important steps towards reducing the carbon footprint all over the world and also for the balanced growth of each country. The construction sector delivers the infrastructure and buildings to society by consuming a large amount of non-renewable energy. This paper discusses the construction chemical industry and particularly construction chemical companies specially focused on polycarboxylate ether based green admixtures, underground structure protection with green and sustainable materials, overall building protection, thermal insulation, cool roof treatment and similar other futuristic technologies which have been developed recently will play a vital role towards sustainability. The construction chemicals referred above can be considered as key drivers of sustainable construction and hence research and engineering fraternity will have to make an elaborate technological benefit of it. It is also necessary to ensure that treatments like thermal insulation, solar reflective coatings are to be used with appropriate application technologies. With the development of smart cities project in India, such green construction chemicals could improve the quality and sustainability of the project. India loses INR 2 trillion (USD 40 billion) which is roughly about 4% of our national GDP every year due to corrosion of infrastructure, industrial equipment, and other vital installations, according to last estimates from CII [1]. Laboratory and practical work done by the manufacturer of green construction materials and discussion thereof will put forth the importance of this.

Going Viral: Emerging Opportunities for Phage-Based Bacterial Control in Water Treatment and Reuse.

Water security to protect human lives and support sustainable development is one of the greatest global challenges of this century. While a myriad of water pollutants can impact public health, the greatest threat arises from pathogenic bacteria that can be harbored in different components of water treatment, distribution, and reuse systems. Bacterial biofilms can also promote water infrastructure corrosion and biofouling, which substantially increase the cost and complexity of many critical operations. Conventional disinfection and microbial control approaches are often insufficient to keep up with the increasing complexity and renewed relevance of this pressing challenge. For example, common disinfectants cannot easily penetrate and eradicate biofilms, and are also relatively ineffective against resistant microorganisms. The use of chemical disinfectants is also curtailed by regulations aimed at minimizing the formation of harmful disinfection byproducts. Furthermore, disinfectants cannot be used to kill problematic bacteria in biological treatment processes without upsetting system performance. This underscores the need for novel, more precise, and more sustainable microbial control technologies. Bacteriophages (phages), which are viruses that exclusively infect bacteria, are the most abundant (and perhaps the most underutilized) biological resource on Earth, and hold great promise for targeting problematic bacteria. Although phages should not replace broad-spectrum disinfectants in drinking water treatment, they offer great potential for applications where selective targeting of problematic bacteria is warranted and antimicrobial chemicals are either relatively ineffective or their use would result in unintended detrimental consequences. Promising applications for phage-based biocontrol include selectively suppressing bulking and foaming bacteria that hinder activated sludge clarification, mitigating proliferation of antibiotic resistant strains in biological wastewater treatment systems where broad-spectrum antimicrobials would impair pollutant biodegradation, and complementing biofilm eradication efforts to delay corrosion and biofouling. Phages could also mitigate harmful cyanobacteria blooms that produce toxins in source waters, and could also serve as substitutes for the prophylactic use of antibiotics and biocides in animal agriculture to reduce their discharge to source waters and the associated selective pressure for resistant bacteria. Here, we consider the phage life cycle and its implications for bacterial control, and elaborate on the biochemical basis of such potential application niches in the water supply and reuse cycle. We also discuss potential technological barriers for phage-based bacterial control and suggest strategies and research needs to overcome them.

Long‐Term Performance and Deicing Effect of Sustained‐Release Snow Melting Asphalt Mixture

To accelerate snow and ice melting, traditional chloride‐based salts are spreaded on asphalt pavement surface, causing serious environmental pollution and infrastructure corrosion. For sustained‐release snow melting asphalt mixture, the snow melting agent of Mafilon is directly added to asphalt mixture by replacing partial mineral powder to develop a new type of functional asphalt mixture. In this paper, through the Marshall test, immersion Marshall test, rutting test, trabecular bending test, and Cantabro test, the effects of Mafilon addition on asphalt pavement performance is systematically analysed. Meanwhile, salt precipitation rate is measured by conductimetry to estimate effective deicing period of the pavement. Finally, a new experimental device is designed to quantitatively evaluate snow melting effect of sustained‐release snow melting asphalt pavement. The experimental results show that replacing 70% of the mineral powder with Mafilon by volume can achieve satisfactory snow melting effect without affecting usability of asphalt pavement.

Understanding the effect of ventilation, intermittent pumping and seasonality in hydrogen sulfide and methane concentrations in a coastal sewerage system.

Gas pollutants emitted during wastewater transport contribute to atmospheric pollution, aggravated risks for utility workers, infrastructure corrosion, and odour nuisance. Field studies have shown that is difficult to effectively obtain reliable correlations between in-sewer air movement and gas pollutant concentrations. This study aimed at investigating the influence of different ventilation and operating conditions in H2S and CH4 horizontal and vertical movement in a section of a gravity sewer, downstream of a pumping station. Relevant liquid and gas phase quality parameters were monitored, and significant H2S concentrations were measured (with lower contents of CH4). Results evidenced that headspace temperature and ventilation played a key effect when analysing H2S and CH4 dynamics. Setups with a similar content of sulfide and chemical oxygen demand resulted in different H2S and CH4 headspace concentrations. It was also observed that an increase in ventilation resulted in a decrease of average headspace relative humidity of over 70%, with clear implications in corrosion potential estimates. Another interesting observation was that the wastewater drag induced by intermittent pumping, in absence of ingassing, originated pressure differences of up to 0.2Pam-1 between studied manholes. This differential originated a wave pattern of gas moving upstream and downstream, thus resulting in several gas peaks per pumping event, at the same sections. In addition, in confined setups, full mixing was not observed along the manholes.

Novel 'chemical cocktails' in inland waters are a consequence of the freshwater salinization syndrome.

Widespread changes in water temperatures, salinity, alkalinity and pH have been documented in inland waters in North America, which influence ion exchange, weathering rates, chemical solubility and contaminant toxicity. Increasing major ion concentrations from pollution, human-accelerated weathering and saltwater intrusion contribute to multiple ecological stressors such as changing ionic strength and pH and mobilization of chemical mixtures resulting in the freshwater salinization syndrome (FSS). Here, we explore novel combinations of elements, which are transported together as chemical mixtures containing salts, nutrients and metals as a consequence of FSS. First, we show that base cation concentrations have increased in regions primarily in North America and Europe over 100 years. Second, we show interactions between specific conductance, pH, nitrate and metals using data from greater than 20 streams located in different regions of the USA. Finally, salinization experiments and routine monitoring demonstrate mobilization of chemical mixtures of cations, metals and nutrients in 10 streams draining the Washington, DC-Baltimore, MD metropolitan regions. Freshwater salinization mobilizes diverse chemical mixtures influencing drinking water quality, infrastructure corrosion, freshwater CO2 concentrations and biodiversity. Most regulations currently target individual contaminants, but FSS requires managing mobilization of multiple chemical mixtures and interacting ecological stressors as consequences of freshwater salinization.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Impact of Road Salt on Drinking Water Quality and Infrastructure Corrosion in Private Wells.

Increased road salt use and resulting source water contamination has widespread implications for corrosion of drinking water infrastructure, including chloride acceleration of galvanic corrosion and other premature plumbing failures. In this study, we utilized citizen science sampling, bench-scale corrosion studies, and state-level spatial modeling to examine the potential extent of chloride concentrations in groundwater and the resulting impact on private wells in New York. Across the sampled community, chloride levels varied spatially, with the highest levels in private wells downgradient of a road salt storage facility followed by wells within 30 m of a major roadway. Most well users surveyed (70%) had stopped drinking their well water for aesthetic and safety reasons. In the bench-scale experiment, increasing chloride concentration in water increased galvanic corrosion and dezincification of plumbing materials, resulting in increased metal leaching and pipe wall thinning. Our simple spatial analysis suggests that 2% of private wellusers in New York could potentially be impacted by road salt storage facilities and 24% could potentially be impacted by road salt application. Our research underscores the need to include the damage to public and privately owned drinking water infrastructure in future discussion of road salt management.

Microbial Sulfate Reduction and Perchlorate Inhibition in a Novel Mesoscale Tank Experiment

Microbial sulfate reduction occurs ubiquitously in natural environments. In oil and gas reservoirs, the generation of sulfide (also known as souring) can result in the corrosion of steel infrastructure and downgrading of oil quality, among other environmental and health-related concerns. The complex interplay between hydrological, geochemical, and biological processes during souring is poorly understood, preventing effective treatment and mitigation especially in naturally heterogeneous subsurfaces. In this work, three-dimensional flow tank experiments are utilized as a mesoscale experiment that links well-constrained batch and column experiments to field measurements. The mesoscale tank experiment investigating perchlorate treatment of souring is coupled with reactive transport modeling to understand the effects of heterogeneity on souring and effectiveness of perchlorate treatment. Tracer experiments were conducted at the start and end of the experiment to constrain flow pathways and heterogeneities. Is...

Hydration of Concrete: The First Steps.

Concrete is the most important construction material used by mankind and, at the same time, one of the most complex substances known in materials science. Since this mineral compound is highly porous, a better understanding of its surface chemistry, and in particular the reaction with water, is urgently required to understand and avoid corrosion of infrastructure like buildings and bridges. We have gained insight into proton transfer from concrete upon contact with water by applying the so-called Surface Science approach to a well-defined mineral, Wollastonite. Data from IR (infrared) spectroscopy reveal that exposure of this calcium-silicate (CS) substrate to H2 O leads to dissociation and the formation of OH-species. This proton transfer is a chemical reaction of key importance, since on the one hand it triggers the conversion of cement into concrete (a calcium-silicate-hydrate phase), but on the other hand also governs the corrosion of concrete. Interestingly, we find that no proton transfer takes place when the same surface is exposed to methanol. In order to understand this unexpected difference, the analysis of the spectroscopic data obtained was aided by a detailed, first-principles computational study employing density functional theory (DFT). The combined experimental and theoretical effort allows derivation of a consistent picture of proton transfer reactions occurring in CS and CSH phases. Implications for strategies to protect this backbone of urban infrastructure from corrosion in harsh, aqueous environments will be discussed.

Challenges and opportunities in corrosion of steel in concrete

This paper summarizes the grand societal, economic, technological, and educational challenges related to corrosion of steel in concrete, and presents the state-of-the-art of the most relevant issues in the field. The enormous financial impact of infrastructure corrosion seems to be inadequately balanced by educational and research activities. This presents a unique opportunity in many countries for maintaining or improving their competitiveness, given the major technological challenges can be solved. The main technological challenges are (1) the ever-increasing need to cost-effectively maintain existing, ageing reinforced concrete structures, and (2) designing durable, thus sustainable new structures. The first challenge arises mainly in industrialized countries, where there is a need to abandon conservative, experience-based decision taking and instead move to innovative, knowledge-based strategies. The second challenge regards mainly emerging countries expanding their infrastructures and where thus a major beneficial environmental impact can still be made by providing long-lasting solutions. This means to be able to reliably predict the long-term corrosion performance of reinforced concrete structures in their actual environments, particularly for modern materials and in the absence of long-term experience. During the second half of the last century, civil engineers, materials scientists, and chemists have in many countries made considerable attempts towards understanding corrosion of steel in concrete, but many of the approaches got bogged down in empiricism. From reviewing the state-of-the-art one can conclude that transport modeling in concrete is relatively well-advanced, at least in comparison with understanding corrosion initiation and corrosion propagation, where many questions are still open. This presents a number of opportunities in scientific research and technological development that are discussed in this paper.

Sulfur flows and biosolids processing: Using Material Flux Analysis (MFA) principles at wastewater treatment plants

High flows of sulfur through wastewater treatment plants (WWTPs) may cause noxious gaseous emissions, corrosion of infrastructure, inhibit wastewater microbial communities, or contribute to acid rain if the biosolids or biogas is combusted. Yet, sulfur is an important agricultural nutrient and the direct application of biosolids to soils enables its beneficial re-use. Flows of sulfur throughout the biosolids processing of six WWTPs were investigated to identify how they were affected by biosolids processing configurations. The process of tracking sulfur flows through the sites also identified limitations in data availability and quality, highlighting future requirements for tracking substance flows. One site was investigated in more detail showing sulfur speciation throughout the plant and tracking sulfur flows in odour control systems in order to quantify outflows to air, land and ocean sinks. While the majority of sulfur from WWTPs is removed as sulfate in the secondary effluent, the sulfur content of biosolids is valuable as it can be directly returned to soils to combat the potential sulfur deficiencies. Biosolids processing configurations, which focus on maximising solids recovery, through high efficiency separation techniques in primary sedimentation tanks, thickeners and dewatering centrifuges retain more sulfur in the biosolids. However, variations in sulfur loads and concentrations entering the WWTPs affect sulfur recovery in the biosolids, suggesting industrial emitters, and chemical dosing of iron salts are responsible for differences in recovery between sites.