Dissertations / Theses on the topic 'Protective Concrete Structures'

The analysis of penetration of warheads in concrete protective structures is an important part of the study of weapon effects on protective structures. This type of analysis requires that the design load in the form of a warhead is determined, and its characteristic and performance within a protective structure is known. Constitutive equations for concrete subjected to weapon effects have been a major area of interest for a long time, and several material models for concrete behaviour are developed. However, it is not until recent years that it has been possible to use finite element (FE) analyses to simulate the behaviour of concrete targets during projectile penetration with acceptable results. The reason for this is a combination of several factors, e.g. development of suitable material models for concrete, enhancement of numerical methodology and affordable high capacity computer systems. Furthermore, warhead penetration has primary been of interest for the armed forces and military industry, with a large part of the conducted research being classified during considerable time. The theoretical bases for concrete material behaviour and modelling with respect to FE analyses of projectile penetration are treated in the thesis. The development of weapons and fortifications are briefly discussed in the thesis. Warheads may be delivered onto a protective structure by several means, e.g. artillery, missiles or aerial bombing, and two typical warhead types were used within the study. These warhead types were artillery shells and unitary penetration bombs for the use against hardened targets, with penetration data for the later warhead type almost non-existing in the literature. The penetration of warheads in concrete protective structures was therefore studied through a combination of experimental work, empirical penetration modelling and FE analyses to enhance the understanding of the penetration phenomenon. The experimental data was used for evaluation of empirical equations for concrete penetration and FE analyses of concrete penetration, and the use of these methods to predict warhead penetration in protective structures are discussed within the thesis. The use of high performance concrete increased the penetration resistance of concrete targets, and the formation of front and back face craters were prevented with the use of heavily reinforced normal strength concrete (NSC) for the targets. In addition, the penetration depths were reduced in the heavily reinforced NSC. The evaluated existing empirical penetration models did not predict the behaviour of the model scaled hardened buried target penetrators in concrete structures with acceptable accuracy. One of the empirical penetration models was modified to better describe the performance of these penetrators in concrete protective structures. The FE analyses of NSC gave reasonable results for all simulation cases, with the best results obtained for normal impact conditions of the penetrators.<br>Analyser avseende stridsdelars penetration i skyddskonstruktioner av betong viktigt för studier av vapenverkan mot skyddskonstruktioner. Dessa analyser förutsätter att dimensionerande last i form av stridsdel bestäms, samt att dess karakteristik och verkan mot skyddskonstruktioner är kända. Konstitutiva modeller för betong utsatta för vapenverkan har varit av stort intresse under en lång tid och ett flertal materialmodeller har utvecklats. Det är emellertid först på senare år som det varit möjligt att använda finita element (FE) analyser for att simulera beteendet för betongmål vid projektilpenetration med acceptabla resultat. Anledningen till detta kan tillskrivas kombinationen av ett flertal faktorer, t ex utvecklingen av lämpliga materialmodeller, förbättringar av numerisk metodik och utvecklingen av kostnadseffektiva beräkningsdatorer. Penetration av stridsdelar har dessutom i huvudsak varit av intresse för militären och försvarsindustrin, vilket har resulterat i att en stor del av den bedrivna forskningen har varit hemligstämplad under lång tid. Grunderna avseende betongs materialbeteende och beskrivning av detta med avseende på FE-analyser av projektilpenetration behandlas i denna licentiatuppsats. Den fortifikatoriska utvecklingen och utvecklingen av vapen diskuteras kortfattad i uppsatsen. Ett flertal olika typer av stridsdelar är av intresse avseende verkan mot skyddskonstruktioner, t ex artillerigranater, missiler eller flygbomber. I denna studie beaktades två typiska stridsdelar, artillerigranater och penetrerande bomber. De senare är specifikt konstruerade för användande mot skyddskonstruktioner och företrädesvis mot betongkonstruktioner. Det visade sig dessutom att data avseende penetration i betong för denna typ av penetrerande stridsdelar i stort sett inte var publicerade. Penetration av stridsdelar i betong studerades därför med en kombination av experimentella metoder, empiriska penetrationsmodeller och FE-analyser för att öka förståelsen för problemställningen. De experimentella modellresultaten användes för att utvärdera både de empiriska penetrationsmodellerna och FE-analyserna avseende betongpenetration, med båda metodernas användande diskuterat i uppsatsen. Användandet av högpresterande betong ökade penetrationsmotståndet för betongmålen i jämförelse med standardbetongmålen. Det var även möjligt att förhindra kraterbildningen på fram- och baksidan av de kraftigt armerande standardbetongmålen, detta medförde även en reducerad penetration för projektilerna i målen. De existerande empiriska penetrationsmodellerna kunde inte förutsäga penetrationen av modellprojektilerna i betongmålen med godtagbara resultat. Istället vidareutvecklades en av dessa modeller för att bättre beskriva denna typ av penetrerande stridsdelar i skyddskonstruktioner av betong. Finita elementanalyserna av standardbetongmålen visade sig ge ett rimligt beteende för alla analyserade modeller, med de bästa resultaten erhållna för vinkelrätt anslag för de modellprojektilerna av de penetrerande stridsdelarna.<br>QC 20111116

INTRODUCTION The main objective of this dissertation is to compile a comprehensive literature review of surface protection systems, including their historical development, specification and use, and to conduct an industry review from the South African market. With a vast amount of deteriorating reinforced concrete structures and fast developing technology of surface treatments, it is important that engineers have a good working understanding of concrete deterioration, repair and the use of surface protection systems. Additionally, engineers need to have a good understanding of the pore structure of concrete and its transport properties as this is important to understanding the applicability and use of surface treatments (Breysse and Gérard, 1997; Leeming et al., 1997; Ballim, Alexander and Beushausen, 2009). TRANSPORT PROPERTIES The movement of ions or fluids in concrete occurs due to four basic mechanism; diffusion, permeation, absorption and migration, as briefly outlined below. The kinetics of movement is broadly governed by the size and nature of the concrete pore structure and its exposure environment (Ballim, Alexander and Beushausen, 2009; Basheer and Barbhuiya, 2010). Process Description Diffusion: Movement of ions, gas or liquid under a concentration gradient Permeation: Movement of a fluid through a concrete matrix under an externally applied pressure gradient when saturated with that fluid Absorption: Where a fluid is drawn into the pores of concrete through capillary suction Migration: Movement of ions due to an electrical potential gradient Combined transport mechanisms and long-term changes in transport behaviour may need to be considered, Additionally, the size, nature and degree of cracking is an especially important consideration (Ballim, Alexander and Beushausen, 2009). DETERIORATION OF CONCRETE Rebar corrosion is the biggest threat to the durability of reinforced concrete structures, and is influenced mainly by the quality of the concrete, its cover depth to the reinforcement and the environmental exposure conditions. The primary causes of rebar corrosion are carbonation and chloride ingress. Chemical and acid attack may be of concern in certain environments. When using reactive aggregates, alkali-aggregate reaction may also be of concern to unreinforced and reinforced concrete. Surface protection systems can assist in reducing the effects due to the influence of the above penetration processes. Additionally,in harsh environmental conditions, such as in marine areas, additional protection measures are oftenrequired to ensure that concrete (existing or new) will not prematurely deteriorate during its service life (Beckett et al., 1987; Technical Committee 60-CSC RILEM, 1988; ACI Committee 201, 2008; Larsen, 2008; Ballim, Alexander and Beushausen, 2009; Gjørv, 2011). Typically, the following repair techniques may be considered in the repair and service life extension of concrete structures (Mackechnie and Alexander, 2001): • Crack Repairs • Patch Repairs • Surface Coatings • Migrating Corrosion Inhibitors (MCI’s) • Electrochemical Techniques • Cathodic Protection • Demolition and Reconstruction REPAIR STANDARDS To ensure that a concrete repair project is successful, a systematic approach to the inspection and repair strategy development needs to be followed (Building Research Establishment, 2000b). The European standard EN 1504 and the Concrete Repair Manual from the American Concrete Institute provides such an approach. South Africa does not have such a standard, but is in the process of adopting the European standards for concrete (South African Bureau of Standards, 2017), EN 206 and EN 1992 - it would thus be highly beneficial for South Africa to move towards the adoption of the EN 1504 code as well. EN 1504-9 is a very important part of the code, as it provides a structured approach to the investigation of the cause of deterioration and outlines the “Principles of protection and repair.” EN 1504-2 covers the use of surface treatment systems, and its provisions are intended to be used as “Methods” in order to cover the “Principles” outlined in EN 1504-9 (Atkins et al., 2009; Raupach and Büttner, 2014). SURFACE PROTECTION SYSTEMS Modern technological advances have given rise to numerous surface treatment systems available on the market with various sub-categories that can assist in achieving the durability requirements of a concrete structure, from silanes, siloxanes, many types of polyurethanes and modified cementitious coatings as well as hybrid systems. Each product and system has its use, advantages and disadvantages and the selection of a system and decision on whether to apply a surface treatment or not can be a complicated matter. This decision is often left to the discretion of the engineer, and therefore engineers need to have a good working understanding of surface treatment systems (Leeming et al., 1997; Beushausen and Alexander, 2011; ACI Committee 546, 2014a). Surface protection systems can be classified according to the way in which the protective action is provided. This is the classification system used by EN 1504 and is divided as follows: HYDROPHOBIC IMPREGNATION These are low viscosity fluids which penetrate several millimetres into the concrete and considerably increase the water penetration resistance of concrete, whilst still allowing the passage of water vapour and gases. Typical examples are silanes and siloxanes. They are also referred to as pore lining penetrants (Beckett et al., 1987; Leeming et al., 1997; Bijen, 2003; ACI Committee 546, 2014b). IMPREGNATION These are low viscosity solutions that penetrate 1 - 3 mm into the concrete and effectively block pores. They differ from Hydrophobic Impregnations in that they are more restrictive to the passage of water vapour and gases. Typical examples are silicates and silicoflourides as well as certain types of polyurethanes (Beckett et al., 1987; Leeming et al., 1997). COATINGS These are treatments that form a continuous protective layer on the surface of the concrete. They are typically 0.1 mm - 5 mm thick, but may be thicker than 5 mm for certain applications. Typical examples are polymer-modified cementitious systems and polyurethanes (Beckett et al., 1987; BS EN 1504-2, 2004). Surface treatment systems need to meet specified performance criteria. In terms of the concrete durability, these are typically (Beckett et al., 1987): • Ingress protection • Moisture control • Physical resistance / Surface improvement • Resistance to chemicals • Increasing resistivity • Cathodic control Treatment systems may also be required to bridge cracks, be applied to moist concrete or operate in harsh exposure and weather conditions. Therefore, the selection of a system needs to consider these factors and testing may be required for certain critical properties on-site to determine its suitability. Engineers, owners and suppliers need to collaborate in order to achieve a good solution. EN 1504-2 (2004) provides a detailed list of performance criteria for each of the various types of treatments along with the relevant code of practice for testing. In general, suppliers recommended application guidelines should be followed in the application of the system. INDUSTRY REVIEW A review of products and recent applications from Sika and A.B.E. Construction Chemicals is provided in this work. It was found that polymer-modified systems are still the most commonly used system. Siloxanes are often used for hydrophobic impregnation treatments, as the pure silanes are intended for high-performance usage and are only used in special circumstances. Each of the suppliers provides detailed application guidelines for each of their products as well as generalised expected performance criteria. Many of the products available have been formulated such that they are applicable to a wide range of applications, and it appears that some known problems with certain products have been improved on. DISCUSSION &amp; CONCLUSIONS Findings of this report are listed below. • The selection of a treatment system is a complex issue and therefore requires engineers to have a good appreciation of various surface treatments systems. A proper framework and set of guidelines is needed. Notwithstanding the above, collaboration between the owner, engineer and supplier will go a long way to a successful application. • South Africa is lacking in the availability of detailed information for engineers to assess, design, specify and monitor treatment systems. South Africa is also in the process of adopting the Eurocodes for concrete design. The EN 1504 repair code contains specific provisions for surface treatments systems and should now be considered for implementation in South Africa. In the interim, EN 1504 can be used to assist in ensuring a standardised approach has been followed in a repair project. • The current EN 1504 surface treatment classification divides systems into Hydrophobic Impregnation, Impregnation and Coatings. Whilst these are generally acceptable it may be worthwhile to reconsider Coatings as two types i.e. 'coatings’ for thinner coatings and 'overlays’ for thicker coatings, as these treatments may function in a very different manner - overlays function by their thickness providing protection and may not be especially complex treatments. They may also simply be applied for levelling and have a treatment or coating applied over them. • Hydrophobic Impregnation is commonly achieved by the use of silanes or siloxanes or silanesiloxane blends. In particular, silane-siloxane blends are most commonly used. This is due to cost, difficulties in application of silanes, and environmental concerns with the volatile organic compound content of silanes. • There are conflicting reports on the effectiveness in the use of silicate systems for improving concrete durability. This appears to be in-part due to the lack of agreement on the exact nature of the protection mechanism. Further research is required to reconcile differences in reporting. • Polyurethanes are very versatile and are available in various forms. Many differences were found in literature on the effectiveness of polyurethanes for improving durability, and sometimes within the same generic type. One of the problems appears to be that researchers often don’t describe precisely enough the exact nature of the polyurethane that was used in their works. A standardised reporting approach is needed. However, polyurethanes have been shown to positively effect many durability issues in concrete such as water absorption, chloride diffusion and carbonation - depending on the specific polyurethane used. • Polymer-modified cementitious coatings are the most commonly available and used surface treatments, and can be used for a wide range of applications. Their exact properties depend on their formulation, type of polymer and polymer-cement ratio. However, they are generally very versatile and most commercially available products can be used to achieve a wide range of properties, including improving the durability of existing concrete surfaces. They are sensitive to weather conditions during curing and special precautions may be required.

Cathodic protection (CP) has been increasingly used on reinforced concrete structures to protect steel reinforcement from corrosion. However, due to the complexity of environmental conditions, the specifications in national and international standards are still open to discussion in engineering practices for their accurate suitability. To some extent, the design aspects are still based on practical experience. It implies a great deal of estimations and assumptions. The research conducted in the thesis aims to address some of these challenges. To obtain reliable experimental results, the present study at first investigated the influence of experimental methods on the measurement of concrete electrical resistivity. It studied the effect of alternative current (AC) frequency, electrode materials and electrode configuration. Based on the results, an optimised method was decided for all the series of the experimental tests in this study. The CP study consists of two major works. The first one was to investigate the chloride contaminated concrete exposed to atmospheric condition. Impressed constant current method was adopted for the operation of CP. A series of electrical and electrochemical measurements were conducted for concrete resistivity, corrosion potential, corrosion rate, degree of polarization, instant-off potential and four-hour potential decay. An evaluation on the current adopted criterion in standards has been carried out on the experimental results. The second work was to investigate the corrosion of rebar in concrete specimens submerged (fully and partially) in salty water. For such more corrosive environment, a comparison between the impressed CP operation using constant current and that using constant potential has been conducted. The experiments evaluated the effects of the two major environmental factors, i.e. water and chloride contents, on reinforced concrete durability. The work provided a deep understanding on the electrochemical behaviour of the reinforced concrete system and effectiveness of CP implementation under severe conditions. The research work has an important contribution to fundamental science of corrosion and reinforced concrete deterioration, and the technology and practical application of CP for reinforced concrete structures. The main results of this work indicate the important influence of the frequency and electrode configuration on the electrical resistance measurement. For the reliability of electrical resistivity measurement, a high frequency of 10,000 Hz and an internal carbon fibre electrode method are recommended. Regarding the CP for the chloride contaminated reinforced concrete exposed to the atmosphere, it is suggested that adopting an instant-off potential of -500 mV with respect to Ag/AgCl/0.5KCl reference electrode can provide sufficient protection for the reinforced concrete of up to 0.59 % total chloride by weight of concrete, or concrete resistivity is greater than 6.7 kΩ.cm. Furthermore, it was found that the 100 mV depolarization criterion for the evaluation of CP performance gives an overestimated protection. A depolarization of 50 mV is therefore proposed. In terms of the submerged specimens, the results showed that the water content and chloride content should be explicitly related to the corrosion state rather than through a single parameter of the concrete resistivity for the complicated situations because the water content will affect the oxygen transportation in concrete, and the oxygen availability at the rebar surface will play an important role in the corrosion process, and this is unassessable by concrete resistivity. Moreover, 4 or 24 hours for the 100 mV depolarisation criterion in standards is not applicable for CP assessment where concrete structures are fully submerged due to the low availability of oxygen. On the other hand, the depolarization criterion can be used if the specimens are partially submerged, but different parameters affect the depolarization value such as the magnitude of the applied protection current or potential, chloride concentration, oxygen availability and time of depolarization.

Hydrophobic impregnations often referred to as water repellent agents, today mainly consisting of alkylalkoxysilanes, are often used on concrete to prolong the service life of the structure. This is accomplished by protecting the reinforcement bars from chlorides or by changing the moisture content inside. When the concrete is treated with a water repellent agent the properties of the surface layer becomes hydrophobic and thereby water droplets are stopped from entering, still allowing water vapour to pass through. This change can reduce chloride ingress and stop heavy rain from penetrating through the surface layer. This thesis presents results concerning how the properties of concrete are affected by a hydrophobic impregnation. Moisture transport and fixation in the surface layer of the concrete are studied as well as the secondary effects of more practical use such as the effect on chloride ingress, water absorption and humidity level. It also presents results on how the penetration depth and concentration of the water repellent agent (i) depend on a number of parameters, and (ii) affect the outcome of the treatment. Water repellent treatments on a number of different concrete structures in Stockholm, ranging from tunnel to high-rice building, are evaluated as well. The three most important factors for the penetration of any water repellent agent into concrete are time, porosity and degree of saturation. A semi-empirical equation is derived that gives an idea on how much these factors affect the efficient penetration depth of the water repellent agent. The depth and concentration have a major effect on the performance of the treatment. The moisture diffusion coefficient for a water repellent treated concrete is close to constant and not nearly as dependent on the relative humidity (RH) as for untreated concrete. Unlike untreated concrete, where capillary suction plays an important role for the moisture transport at high RH, the vapour transport is the dominant transport mechanism even at high RH for water repellent treated concrete. The moisture fixation is affected by a water repellent treatment and the effect is clearest at high moisture levels. The main reason for this is that the capillary porosity is affected by the treatment to a relatively high degree while the gel porosity to a large extent remains unaffected. A hypothesis is presented which suggests that the RH inside the concrete at the time of the treatment affects not only the depth and concentration but also in which range of pore radii the water repellent agent is present and active. The durability of hydrophobic impregnations can be divided into surface effects and in depth effects. The first is sensitive to the environmental and mechanical loadings and normally disappears within a year while the later can be long lasting if a sufficient depth is reached. Hydrophobic impregnations are not the answer to all problems in concrete related to moisture, but if correctly used it can prolong the service life of the structure which will lead to savings of natural resources and thus both economical and environmental savings for the community.<br>Vattenavvisande impregneringsmedel, som i dagsläget till största del består av alkylalkoxysilaner, används ofta på betong för att förlänga livslängden på konstruktionen. Detta syfte uppnås genom att armeringen skyddas mot klorider eller att fukthalten inuti betongen sänks. När betongen impregneras ändras ytskiktets fuktmekaniska egenskaper från hydrofila till hydrofoba vilket gör att vattendroppar kan stoppas medan vattenånga tillåts passera. Dessa förändrade egenskaper kan medföra att kloridinträngningen minskar och att kraftiga regn inte tränger genom det impregnerade skiktet. Denna avhandling presenterar resultat om hur betongen påverkas av en vattenavvisande impregnering. Fukttransport och fuktfixering i betongens ytskikt har undersökts men även sekundära effekter som kloridinträngning, vattenabsorption och förändring i fuktinnehåll vilka alla är av större praktisk nytta. Avhandlingen presenterar också resultat om vilka faktorer som påverkar impregneringens inträngningsdjup och koncentration samt vilken betydelse dessa har för funktionen. För att utvärdera impregneringars effekt i olika miljöer har ett stort antal objekt i Stockholm undersökts, innefattande olika konstruktioner från en tunnel till höghus. Impregneringens inträngningsdjup och koncentration har en avgörande betydelse för dess funktion. De tre viktigaste faktorerna för alla impregneringsmedels inträngning i betong är tid, porositet och fuktnivå. En semiempirisk ekvation har tagits fram där det framgår hur dessa tre faktorer påverkar det slutliga inträngningsdjupet för impregneringen. Till skillnad från obehandlad betong är transportkoefficienten för en impregnerad betong nästan oberoende av den relativa fuktigheten (RF) i omgivningen. Vid höga RF, där största delen av fukttransporten i obehandlad betong sker på grund av kapillärkrafter, är ångtransporten fortfarande den dominerande transportmekanismen i impregnerad betong. Fuktfixeringen i betong påverkas av en impregnering och effekten är störst vid höga RF. Det är dock tydligt att en viss mängd fukt finns inuti den impregnerade betongen. Detta kan förklaras med att största delen av kapillärporerna påverkas av impregneringen medan gelporerna förblir obehandlade. Resultaten indikerar också att fuktnivån vid impregneringstillfället avgör vilken del av porsystemet som kan behandlas och inte bara koncentrationen och inträngningsdjupet. Långtidsegenskaperna hos impregneringen kan delas upp i yt- och djupeffekt. Effekten på ytan avtar normalt sett inom ett år på grund av damm och partiklar, UV-ljus, slitage mm. Djupeffekten påverkas däremot inte av dessa faktorer och kan finnas kvar i decennier. Vattenavvisande impregneringar är inte lösningen på alla fuktrelaterade problem i betong, men om de används på rätt sätt så kan det förlänga livslängden på många konstruktioner. Detta leder till ett bättre hushållande med naturresurser och därmed både ekonomiska och miljömässiga besparingar för samhället.<br>QC20100715

This investigation determined that severe corrosion of steel can occur in the submerged portions of reinforced concrete structures in marine environments. Field studies of decommissioned pilings from actual bridges revealed multiple instances of strong corrosion localization, showing appreciable local loss of steel cross-section. Quantitative understanding of the phenomenon and its causes was developed and articulated in the form of a predictive model. The predictive model output was consistent with both the corrosion rate estimates and the extent of corrosion localization observed in the field observations. The most likely explanation for the observed phenomena that emerged from the understanding and modeling is that cathodic reaction rates under oxygen diffusional limitation that are negligible in cases of uniform corrosion can nevertheless support substantial corrosion rates if the corrosion becomes localized. A dynamic evolution form of the model was created based on the proposition that much of the steel in the submerged concrete zone remained in the passive condition given cathodic prevention that resulted from favorable macrocell coupling with regions of the steel that had experienced corrosion first. The model output also matched observations from the field, supporting the plausibility of the proposed scenario. The modeling also projected that corrosion in the submerged zone could be virtually eliminated via the use of sacrificial anode cathodic protection; the rate of corrosion damage progression in the low elevation zone above water could also be significantly reduced. Continuation work should be conducted to define an alternative to the prevalent limit-state i.e., visible external cracks and spalls, for submerged reinforced concrete structures. Work should also be conducted to determine the possible structural consequences of this form of corrosion and to assess the technical feasibility and cost/benefit aspects of incorporating protective anodes in new pile construction.

The durability of concrete structures is affected by a number of factors such as environmental exposure, electrochemical reactions, mechanical loading, impact damage and others. Of all of these, corrosion of the reinforcement is probably the main cause for the deterioration of steel reinforced concrete (RC) structures. Corrosion management is becoming increasingly necessary as a result of the growing number of ageing infrastructure assets (e.g. bridges, tunnels etc.) and the increased requirement for unplanned maintenance in order to keep these structures operational throughout their design life (and commonly, beyond). The main RC repair, refurbishment and rehabilitation approaches generally employed can be broadly categorised under a) conventional, b) surface treatments, c) electrochemical treatments and d) design solutions. The overarching aim of this research was to identify the key corrosion management techniques and undertake empirical investigations focused on full-scale RC structures to investigate their long-term performance. To achieve this, individual research packages were identified from the above broad five approaches for repair, replacement and rehabilitation. These were 1) Patch repairs and incipient anodes, 2) Impressed Current Cathodic Protection, 3) Galvanic Cathodic Protection and 4) Hydrophobic treatments. The selection of the above research packages was based on past and present use by the construction industry to repair, refurbish and rehabilitate RC structures. Their contributions may be broadly categorised as i) Investigations on how specific treatments and materials perform, ii) Investigations on the effectiveness of existing methods of measurements and developing alternatives, iii) Changes to the existing theory of corrosion initiation and arrest and iv) Changes to management framework strategies. The key findings from each research package can be summarised as follows: Macrocell activity appears to be a consequence rather than a cause of incipient anode formation in repaired concrete structures, as has previously been presented; ICCP has persistent protective effects even after interruption of the protective current; Discrete galvanic anodes installed in the parent concrete surrounding the patch repair are a feasible alternative to galvanic anodes embedded within the patch repairs of RC structures; Silanes may have a residual hydrophobic effect even after 20 years of service.

Thin layered systems can be considered as a solution to the repair and protection of concrete structures. This subject was studied in the current investigation. Some common uses of these systems include protection, upgrading and rehabilitation of the floor slabs,restoration of appearance of the structures, impermeability, skid resistance, wear resistance, and protection of the reinforcing steel of concrete structures against atmospheric or chemical attack. However it can be said that protection, upgrading and rehabilitation of floor slabs are the main uses for the design of modem thin layered systems. For example a thin layer of a polymer concrete with a thickness of less than 3 nun can resist a very highly concentrated load resulting from a steel wheel rolling load of 5000 N without any sign of defect. Thin layer systems therefore include traditional screeds, externally bonded steel plates, plasters and coatings as well as the more recent hi - tech. systems. Like any other structure, a thin layered system may break down as the result of many causes. Among other types of failures, delamination defect is the most common mode of failure and particularly relevant to a thin layered system. This phenomenon which mostly occur between the upper layer directly subjectedto the load and the subsequent layer, is due to debonding or slippage at the interface of the two layers. A delamination may occur at the interface of a thin layered system even without any sign of failure in other parts of the structure. Steel wheeled trolleys and fork - lift trucks are among the most anticipated types of loading and causes of failures in the thin layered systems. Different combinations of thin layered systems were prepared using some special flooring materials, both in small and large scales. Despite the lack of any standard test, the action of a steel wheel rolling load on the ready made and purpose made specimens of thin layered systems was well simulated using the Steel Wheel Rolling Load Rig. The NUROLF, Newcastle University Rolling Load Facility, was also used for simulating the action of a tyred vehicle wheel rolling load on the thin layered systems of large scale. Some simple ways for detecting any possible delamination at the interface of the thin layered systems were examined. In addition to the available material characteristics tests, a relatively new simple shear box test was proposed for defming the relationship between normal stress and the correspondings hear strength for each combination of the materials at each age of the test. The results were then used as the basis for the subsequent structural analysis. The structural analysis of the systems was carried out for both of the experiments using the finite element method and the interface technique. In spite of the simplifications made in the solution, the analytical results were consistent with the experimental results to a considerable extent. Based on the results of this investigation, a relatively constitutive procedure was concluded for predicting the behaviour of a thin layered system under the action of a wheel rolling load with regard to the delamination defect.

Since mid-80‟s cathodic protection (CP) has been recognised as the „‟only technique known to stop corrosion regardless of the levels of chloride contamination in concrete‟‟ (FHWA, 1982) and is proved to be the most cost effective means to extend the useful life of the structure. Cathodic protection is an electrochemical technique to stop/mitigate corrosion by supplying „current‟ from an external source in order to suppress the „internally generated‟ current flow due to corrosion processes. The „external‟ current source could be obtained simply by coupling the steel to another electrochemically more active metal, e.g. zinc; alternatively the „external‟ current may be derived from a mains operated low voltage DC power source, viz. transformer/rectifier unit. These two different approaches to supply „external‟ current to stop corrosion are generically termed as: „Sacrificial Anode Cathodic Protection (SACP)‟ system and „Impressed Current Cathodic Protection (ICCP)‟ system, respectively. Both approaches have proved to be feasible, but the impressed current CP system offers greater flexibility with regard to its ability to provide the necessary current in situations where concrete resistivity is relatively high and variable. The sacrificial anode system is most effective if the concrete resistivity is very low or the anode is placed in a very low resistivity environment such as soil with low resistivity, as the inherent driving voltage is low e.g. the potential difference between zinc and corroding steel in concrete is limited to approximately 0.7 volts. Other contra-distinction between the two approaches are that the design life of the sacrificial anode systems are usually range between 10 -15 years; on the other hand the design life of the ICCP systems could be well in excess of 60+ years ( depending on the type of anode system). Page 2 Following the successful application of first CP system, based on impressed current CP (ICCP), on a bridge deck in California, USA 1973, the technology has advanced significantly, particularly the anode systems (which is the main arbiter of a CP system) to deliver the protection current efficiently providing adequate protection (i.e. meeting the criteria recommended in BS EN ISO 12696: 2012 and other International Standards). Most of the CP installations worldwide are operating in ICCP mode. However, due to the escalating cost of anode systems and associated external power supply as well as monitoring/control units for ICCP installation has led researchers to actively pursue different means of developing low cost anode systems. Researchers have mainly focused on sacrificial anode CP (SACP) systems, as SACP does not require an external power supply and control units, but the drawback to this anode system is that it has a shorter life span (usually 10 -15 years compared to 60+ years for ICCP anodes). This work describes the development of an ICCP anode system design utilising commercially available zinc rich paint (ZRP) as a primary anode material offering an innovative but considerably low cost alternative to currently used materials for ICCP anode systems. It also describes the development of a simple and low cost „multifunctional‟ probe for monitoring the performance of the installed CP system, among other functions, such as LPR measurements, macrocell corrosion current measurement, E-log I tests for assessing the current requirements for CP design. For these functions both laboratory investigations and field trial on real life structure were employed.

La réaction sulfatique interne (RSI) est une réaction de gonflement interne des matériaux cimentaires générant des contraintes importantes qui conduisent progressivement à la fissuration, à la perte de cohésion et à la ruine des structures de génie civil. Par ailleurs, les échanges hydriques entre le matériau et la lixiviation des alcalins du béton constituent des facteurs favorisant la réaction. Afin d'interrompre ces échanges, des approches par revêtement sont en cours de déploiement depuis quelques dizaines d'années. Cependant, des obstacles à la définition d'une procédure de traitement claire et pertinente des ouvrages de génie civil atteints de RSI par revêtement sont d'une part, la complexité des mécanismes et des phases d'évolution de la RSI et d'autre part le manque de recul sur l'efficacité et la durabilité de ces revêtements. Ce travail de thèse a donc ciblé ces deux problématiques. Pour cela, des expérimentations débutées d'une part, il y a une décennie ont été poursuivies, respectivement sur l'influence sur le long terme de l'humidité relative et sur l'efficacité d'un système de revêtement polymère multicouche pour la protection de bétons atteints de la RSI. D'autre part, l'étude de la durabilité de ces revêtements a été effectuée en condition de vieillissement libre sur ouvrage et en conditions de vieillissements contrôlés en laboratoire. Une campagne expérimentale de grande envergure a également été conduite afin d'étudier la RSI sur des corps d'épreuve de l'échelle de la structure et sur des carottes exposées à différentes conditions de limitation de la RSI. Ces travaux ont ainsi permis d'identifier des facteurs de vieillissement et les dégradations de revêtements de protection multicouches en polymère utilisés comme barrières étanches pour des bétons atteints de RSI. Aussi, pour adapter la stratégie de traitement des ouvrages atteints de RSI, la campagne sur des corps d'épreuve de grande dimension a permis de mettre en lumière les problématiques d'effet d'échelle et de différence de cinétique qui peuvent exister entre l'échelle du laboratoire et l'échelle de la structure. Ces corps d'épreuves représentent également un support pour des futures études expérimentales et des modélisations pour traiter les questions relatives à la RSI dans les ouvrages<br>Delayed Ettringite Formation (DEF) is an internal swelling reaction in cementitious materials, generating significant stresses that progressively lead to cracking, loss of cohesion and the ruin of civil engineering structures. In addition, water exchanges between the material and the leaching of alkalis from the concrete are factors that encourage the reaction. To interrupt these exchanges, coating approaches have been deployed for several decades. However, the obstacles to defining a clear and relevant procedure for treating civil engineering structures suffering from DEF by coating are, on the one hand, the complexity of the mechanisms and evolution phases of DEF and, on the other hand, the lack of hindsight on the effectiveness and durability of these coatings. This thesis therefore focused on these two issues. To this end, experiments begun a decade ago were continued on the long-term influence of humidity and on the effectiveness of a multi-layer coating system for protecting concrete affected by DEF. In addition, the durability of these coatings was studied under free on-site aging conditions and controlled aging conditions in the laboratory. A large-scale experimental campaign was also carried out to study DEF on structural-scale test bodies and on cores exposed to different DEF-limiting conditions.This work made it possible to identify aging factors and the degradations of multilayer polymer protective coatings used as impermeable barriers for concrete suffering from DEF. Also, to adapt the treatment strategy for structures suffering from DEF, the campaign on large-scale test bodies highlighted the problems of scale effect and the difference in kinetics that can exist between the laboratory scale and the scale of the structure. These test bodies also provide a basis for future experimental studies and modelling to address issues relating to DEF in structures

En zone de montagne, les avalanches de neige menacent les personnes et également les structures de génie civil. Ce travail de thèse se focalise sur une structure de protection en BA (Béton Armé) de type mur en L. L'objectif est de caler et valider un modèle EF (Elément Fini) 2D afin d'étudier le comportement de tels ouvrages sous l'effet de champs de pression induits par des avalanches de neige dense et d'évaluer leur vulnérabilité face à cet aléa naturel. Quatre lois de comportement décrivant la rhéologie du béton ont été testées en vue de reproduire le plus précisément possible la ruine du mur en BA. Un modèle physique de la structure à échelle 1/6 a permis, via un test pushover, d'obtenir des données expérimentales utiles pour le calage des modèles EF proposés. Seulement deux des lois de comportement ont permis de converger vers un mode de ruine pertinent et en accord avec les observations expérimentales. Le modèle EF une fois calé a ensuite été utilisé afin d'investiguer la réponse mécanique de l'ouvrage sous sollicitation avalancheuse. En fonction de l'impulsion du signal de chargement, trois régimes peuvent être obtenus (quasi-statique, dynamique et impulsionnel). Dans le cas d'une avalanche de neige dense, les résultats montrent que la réponse mécanique de la structure en question peut être considérée comme quasi-statique. Toutefois, les signaux avalancheux dépendant de nombreux facteurs (type d'avalanche, densité, température, etc.), différents types de réponses peuvent potentiellement se développer. Pour finir, la vulnérabilité et la fiabilité du mur en BA ont été étudiées afin de préciser l'influence d'une part de la géométrie et d'autre part des caractéristiques des matériaux sur la capacité de protection qu'offre ce type d'ouvrage. In fine, ces résultats pourront être utilisés dans un cadre de gestion intégrée du risque<br>Snow avalanches threaten people and also different types of civil engineering structures in mountainous areas. This PhD thesis focuses on a protective RC (Reinforced Concrete) structure consisting of an L-shaped wall. The objective of this study is to calibrate and validate a 2D FE (Finite Element) model in order to explore the mechanical behavior of such RC structures loaded by snow avalanche pressure fields and to assess their vulnerability when exposed to this kind of natural hazard. Four constitutive laws describing the concrete rheology were tested to describe the collapse of the RC wall. A physical 1/6-scale model permitted obtaining, via a pushover test, useful experimental data for the calibration of the proposed FE models. Two concrete models allowed converging to a relevant collapse of the structure in agreement with the experimental observations. Then, the calibrated FE model was used to investigate the mechanical response of the wall under avalanche loading. According to the impulse of the loading signal, three regimes can occur (quasi-static, dynamic or impulsive). In the case of dense-snow avalanches, the results show that the mechanical response of this structure can be described as quasi-static. However, avalanche signals depend on many factors (type of avalanche, density, temperature, etc.) and several types of responses can potentially develop. Finally, the vulnerability and the reliability of the RC wall were studied to show the influence of the geometry and the material properties on the capacity of the protective structure. In fine, these results will be used in an integrated risk framework in order to help decision makers

This master´s thesis deals with the suppression of algal growth on concrete structures. The subject of the work is to design and coatings their own structural concretes containing protective element in order to inhibit the growth of algae. As the coating are tested commercially avaiable and newly created systems. Testing systems are based on the portland cement and chelates of metal (Cu, Ni, Co, Mn, Zn, Al).

Epoxy intumescent coatings are fire protection systems for steel structural elements that are widely used in applications that protection from severe hydrocarbon fires is required, such as oil and gas facilities. These polymer coatings react upon heating and expand into a thick porous char layer that insulates the protected steel element. In the typical fire scenarios for these applications, the intumescent coatings must resist very high heat fluxes and highly erosive forces from ignited pressurised gases. Hence, continuous fibre reinforcement is embedded in the thick epoxy coating during installation, so as to ensure the integrity of the weak intumesced char during fire exposure. This reinforcement is typically in the form of a bidirectional carbon and/or glass fibre mesh, thus under normal service conditions a fibre-reinforced intumescent coating (FRIC) is essentially a lightly fibre-reinforced polymer (FRP) composite material. This thesis examines the impacts of embedded high strength fibres on the tensile behaviour of epoxy intumescent materials in their unreacted state prior to fire exposure, and the potential enhancements that arise in the structural performance of elements protected with FRICs. An experimental programme is presented comprising tensile coupon tests of unreacted intumescent epoxies, reinforced with different fibre meshes at various fibre volume fractions. It is demonstrated that the tensile properties of FRICs can be enhanced considerably by including increasing amounts of carbon fibre reinforcement aligned in the principal loading direction, which can be tailored in the desired orientation on the coated structural members to enhance their load carrying capacity and/or deformability. An experimental study is presented on coated intact and artificially damaged I-beams (simulating steel losses from corrosion) tested in bending, demonstrating that FRICs can enhance the flexural response of the beams after yielding of steel, until the tensile rupture of the coatings. An analytical procedure for predicting the flexural behaviour of the coated beams is discussed and validated against the obtained test results, whereas a parametric analysis is performed based on this analytical model to assess the effect of various parameters on the strengthening efficiency of FRICs. The results of this analysis demonstrate that it is feasible to increase the flexural load capacity of thin sections considerably utilising the flexural strength gains from FRICs. Finally, a novel application is proposed in this thesis for FRICs as a potential system for structural strengthening or retrofitting reinforced concrete and concrete-encased steel columns by lateral confinement. An experimental study is presented on the axial compressive behaviour of short, plain concrete and concrete-encased structural steel columns that are wrapped in the hoop direction with FRICs. The results clearly show that epoxy intumescent coatings reinforced with a carbon fibre mesh of suitable weight can provide lateral confinement to the concrete core resisting its lateral dilation, thus resulting in considerable enhancements of the axial strength and deformability of concrete. The observed strengthening performance of the composite protective coatings is found to be at least as good as that of FRP wraps consisting of the same fibre reinforcement mesh and a conventional, non-intumescent epoxy resin. The predictive ability of existing design-oriented FRP confinement models is compared against the experimental results, and is found to be reasonably precise in predicting the peak strength of the tested columns, hence existing models appear to be suitable for design and analysis of column strengthening schemes with the proposed novel FRIC system. The research presented herein shows clearly that FRICs have a strong potential as alternative systems for consideration in the field of structural strengthening and rehabilitation, since they can provide substantial enhancements in the load carrying capacity for both applications considered. At the same time FRICs can thermally protect the underlying structural elements in the event of a fire, by intumescing and charring, thus potentially eliminating the need for additional passive fire protection that is common with conventional fire-rated FRP wrapping systems. Although this thesis provides a proof-of-concept for use of the proposed novel FRICs as structural strengthening materials, considerable additional research is particularly required to study their fire protection performance when applied to concrete substrates, to make use of the proposed hybrid functionality with confidence.

The main subject of this diploma thesis is elaboration of construction and technological preparation for the main structure of the Smart Light shop in Bratislava. For main structure has been processed time schedule of the construction, single item budget, machine configuration design, drawing of building site, coordination situation of the building with connection to the infrastructure, safety and health protection during work on building site. Part of the thesis is processing study of main construction technological parts. Diploma thesis in technological prescript focuses on implementation of floor structure with cast epoxy walking surface. There has been elaborated testing and quality plan of this technological part. Additional chapter approximates built-in technology – cooling ceiling structure. For elaboration of this diploma thesis were used programs AutoCAD, CONTEC, BuildPowerS, Microsoft Excel, Microsoft Word.

Dans le cadre de la mise à niveau sismique des bâtiments existants, la technique de renforcement par placage et enrobage de polymères renforcés de fibres (FRP) offre une réponse pertinente. L’objectif de cette thèse est de proposer une modélisation fiable pour la détermination de la réponse quasi-statique et dynamique d’une grande variété d’éléments de structure et d’identifier les apports possibles d’une telle modélisation à la conception. Les stratégies de modélisation s’appuient sur l’utilisation d’éléments finis massifs ou basés sur une cinématique simplifiée (coques multicouches et poutres multifibres), associés à des modèles locaux d’endommagement et de plasticité pour les matériaux en présence (béton, armatures et FRP). L’hypothèse d’adhérence parfaite, d’une part, entre les armatures et le béton, et d’autre part, entre les bandes de FRP et le béton, permet de calculer efficacement les cas des poteaux courants, des poteaux courts, des voiles longs et courts, dans les régimes quasi-statique (pushover) et dynamique. Le renforcement par placage et enrobage FRP pour des structures en béton armé, est reproduit au sein de la modélisation par un apport de matière (éléments de type barre avec les caractéristiques propres des FRP) et des modifications des paramètres de la loi de comportement du béton, justifiées par l’expérimentation et la littérature. La pertinence de l’approche est finalement démontrée en confrontant la réponse temporelle de structures à l’échelle 1, de type ossature ou de type contreventé par des voiles, aux résultats expérimentaux issus de benchmarks internationaux<br>In the context of the building’s protection against seismic risk, the strengthening technique by FRP (Fiber Reinforced Polymers) plating and wrapping provides a relevant solution. The objective of this thesis is to propose a reliable modeling for determining the quasi-static and dynamic responses of a wide variety of structural elements and to draw advantage in design. The modeling strategies make use of 3D elements or finite elements based on simplified kinematics (multilayer shells or multifiber beams), associated with local damage and plasticity laws for the constitutive materials (concrete, rebar and FRP). The perfect bond assumption between steel-concrete and FRP-concrete allows efficiently calculating the quasi-static and dynamic behaviors of short and slender columns, as well as short and slender walls. The mechanical contribution of FRP plating and wrapping is reproduced in the modeling by adding material (bar type elements with FRP characteristics) and by changing the parameters of the concrete model on the basis of the experience and analytical formula issued from the literature. The relevance of the approach is finally highlighted by comparing the time-history response of real braced frame or wall structures with the experimental results

The subject of this thesis is the construction and technological project of a residential building Hlavackova. The work is mainly focused on the stage of construction. The work includes technical report building equipment, wider transport relations, design of mechanical assemblies, technological prescription monolithic structures and related inspection and test plans, safety, environmental protection, work contract, draft securing material resources for rough substructure and special use of roads, financing construction costs and schedule of construction.

In my master's thesis I deal with constructive technological project of medical faculty of Charles Univerisity. The aim is to solve the structure in terms of financial, time and technology. Constructive technological project of my thesis contains site equipment, time and financial schedule, design of mechanization, technological prescription, inspection and test plan, health and safety, etc.

Master´s thesis deals with construction technology project of Sewerage and wastewater treatment plants. The old building objects will be demolished and there will be built new objects on the same place as before. The target of the reconstruction is reducing the amount of energy and increase technological and technology level of wastewater treatment. One of the part of the reconstruction is build new filling station and the sanitation of pipelines on the other side of the river.

Main goal of this thesis is effective design and comprehensible description of the assembly of reinforced concrete skeleton warehouse in Šakvice. In several chapters of this thesis is for preparing of this investor´s plan solved supplies prefabricated components. As well as their assembly into construction, equipment of construction site, used technologies, quality control and safety of performed works. There is great emphasis on the construction budget and its chronology. The aim was to use the rapid progress of construction of the supporting skeleton, taking into account the financial coast of the proposed technology.

The aim of this final thesis was static protection for castle in Miroslavské Knínice. It was necessary to explore several respects and find signs of violation. Next analyze and propose suitable assurance of individual parts. Separe into the stages of construction and to consider the proposal in terms of ensuring the resistance of materials. Finally create a detailed documentation in the range suitable for performance. Based on engineering geology and visual survey was designed horizontal bracing prestressing cables at three levels. The first level "A" consists of a closed circuit of prestressed reinforced concrete passports, supplemented by the cross and construction of prestressed reinforced concrete passports. Next level "B,C" is used to secure the top of the building. Levels “B,C” are proposed using prestressed cable in spare cable channels.

This thesis deals with the construction process of the apartment house Ponavia Park located in Brno. The thesis solves the individual realization phases of the main building phase. Building site equipment is designed for the projected construction process in three different variations. A technical report is also included in the building site. Critical points within the transport of materials and machines are also verified. A financial plan for the whole building is made as an summarizing time schedule for the apartment building. The sources for the financial plan are the figures taken from the Czech building objects classifications (JKSO). The summarizing time schedule is made in MS Projekt software and it’s designed as a Gantt diagram. A design of the main building machines and mechanisms was also made for the projected construction process. All of the machines were assessed for their respective required function on the building site. Also included in this thesis is a construction method for the reinforced concrete structures. The construction method deals with the realization process of waterproof concrete, reinforcement binding, formwork of the vertical and horizontal structures and also the process of concrete curing. The construction method is followed up by quality control and test plans for reinforced concrete structures, and a construction site safety plan that is made in the form of predicted main safety risks at the building site. For the noise load on the surrounding buildings a noise study is made. The study examines the intensity of noise in the protected outdoor space. This study was made in the Hluk+ software. The thesis also includes an item budget for the apartment house that was made in Build Power S software.

A numerical model for the cathodic protection of steel in reinforced concrete is developed. Parameters are set to represent a three-dimensional section of a bridge beam exposed to the atmosphere and coated with a thermally sprayed zinc anode. Both diffusion of oxygen and conduction of charge within the concrete are considered explicitly through a two-dimensional finite element model. The diffusivity and conductivity are represented as functions of concrete moisture content. Electrochemical reactions considered at the rebar-concrete interface are reduction of oxygen, oxidation of iron, and evolution of hydrogen in a constant-potential cathodic protection circuit. Reaction-kinetic parameters for actively corroding steel (not passivated steel) are used. Reactions at the zinc-concrete interface are not considered explicitly. The effectiveness of protection is found to vary significantly with both concrete moisture content and position on the rebar. For spatially uniform pore saturation, the drier the concrete is, the greater the corrosion current and the greater the non-uniformity. Protection is significantly more effective at the "front" of the rebar (closest to the zinc anode) than at the "back" (closest to the center of the beam). Corrosion current is greater under drying conditions than under wetting conditions. The numerical model is applied towards interpretation of the "100-mV polarization decay criterion" that is often used to assess the effectiveness of cathodic protection. It is found that the polarization decay predicted from relaxation of oxygen concentration gradients was comparable in magnitude to that observed experimentally, but depends on location on the rebar. A numerical model for the transport of ions in porous concrete under cathodic protection is presented. In this initial model, transport of the ions zinc, calcium, chloride and hydroxide is described by a one-dimensional Nernst-Planck equation at constant current density with generation of zinc ions at the anodic interface, generation of hydroxide ions at the cathodic interface, and no chemical reactions in the bulk of the concrete. The equations are solved numerically by two methods: the point method, in which concentrations and electric potentials are solved for directly through finite-difference approximations of the differential equations and the box method, in which the domain is divided into discrete volume elements with flux balances for each chemical component and for charge. A base grid of 41 nodes is used. Results for the system after 96 and 9600 days of cathodic protection are discussed. Both numerical methods yielded concentration profiles that are virtually indistinguishable. Numerical noise in the box method leads to values in the first and second derivatives of the electric potential that tend to oscillate around the central values represented by the same smooth curve of the point method. In contrast, the point method shows greater apparent numerical deviation from electroneutrality which is largest near the boundaries and decays towards the center in damped oscillations. The deviations decrease with smaller size of grid elements and higher order difference approximations. The magnitude of the charge density in the bulk of the concrete calculated from the second derivative of the electric potential through Poisson's equation is shown to be negligible compared to the overall electroneutrality calculated from the concentrations of ions. At 96 days, the relative contributions of migration and diffusion to the overall flux are shown to vary widely with position and species; migration can neither be neglected nor can a "corrected" Fick's law approach be used. Zinc ions are found to have moved approximately 15 mm into the bulk of the concrete at 96 days.<br>Graduation date: 2006

With the increasing threat of explosions on infrastructures across the world, the protective techniques against blast loading on existing structures have become more and more significant. As an energy absorptive material, aluminium foam has been introduced to be a sacrificial cladding on structures. This thesis aims to discover the protective effect of aluminium foam on reinforced concrete (RC) structural members which has been a common structural type for existing buildings. Homogeneous aluminium foam was firstly studied both numerically and theoretically. Based on the investigations of homogeneous foam, graded density aluminium foam was introduced to improve the protective effectiveness and efficiency. Blast experiment and analytical model were involved in the study of graded density aluminium foam on RC slabs.<br>Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2017

Chloride ion migration was studied under accelerated cathodic protection conditions using 6" x 6" x 6" mortar blocks of varying initial chloride content and water to cement ratios. An iron mesh embedded parallel to one face in the blocks acted as the cathode and zinc was thermally sprayed on the opposite face to form an anode. First, the potential response of two blocks was studied at a current density of 3 mA/ft��. One block was outfitted with a heat sink and moisture barrier while the other block was periodically wetted. Second, eight blocks were polarized at various current densities for a period of one year. In both sets of experiments, the blocks were maintained in controlled humidity and temperature. The potential across the blocks was recorded at periodic intervals and mortar samples were drilled to measure the chloride content as a function of aging. Based on observations of the first study a theoretical model was constructed which indicates that zinc based electrochemical products form at the zinc-concrete interface. The effect of the electrochemical product on raising the resistance across a cathodic protection set-up may be of consequence and should be further studied. Blocks polarized at 6 mA/ft�� exhibited similar behavior as the blocks polarized at 3 mA/ft��, but the response was twice as fast. This result indicates that studying cathodic protection under accelerated conditions is valid. The chloride content of samples obtained from one set of blocks over the course of the experiment was normalized against the initial chloride profile. The normalized profiles were calculated as a function of aging and they supported the hypothesis that chloride ions would move away from the rebar and towards the sprayed zinc anode under cathodic protection.<br>Graduation date: 2001

碩士<br>國立成功大學<br>土木工程學系專班<br>91<br>Corrosion of steel caused reinforced concrete structures damaged and collapsed in marine environment Chloride could be considered as one of the major important corrosion factor. Therefore, preventing and eliminating chlorides in concrete should be an effective way to prevent steel corrosion. Recent studies pointed out that corrosion theory, deterioration of concrete、polarization and desalinization treatment .In the study, four topics were discussed .They were included steel corrosion improvement, concrete quality, electrolyte variation and chloride removal efficient analysis .The test results showed that chloride removal from concrete is a effective and feasible way .it could remove up to 60% chloride .and steel corrosion is reduced, The durability of reinforced concrete structure is improved . In field of harbor environment ,the test results about sheet-pile、coping-wall etc. showed that anti-corrosion was effective way ,the life of structures is improved.

Terrorism pose a serious threat nowadays and many countries have the concern of protecting his people and most important buildings. This concern is an opportunity to strengthen the research of the behaviour of buildings under blast in order to reduce the magnitude of the effects of these catastrophic events. The present thesis aims to create a functional system to improve the security of critical buildings, either new or adapting old buildings to receive this new system. This system also tries to be cost efficient, so this can be used in most buildings. This thesis was centred in one system with two variations. The systems had the same lower reinforced concrete slab with 2,60 x 2,00 m and 0,12 m of thickness. The first system consisted in using 32 steel tubes of 76,1 mm outer diameter arranged uniformly and eight concrete panels, each one with 1,00 x 0,65 m and 0,07 m of thickness, on top of these tubes. The second system was the same concrete panels on top of 32 steel tubes with 48,3 mm outer diameter. To test these systems four blast trials were prepared: the first is the reference specimen and the other two using the two mentioned variations of the system. These slabs were tested simply supported in two parallel edges, with a span of 2,30 m. In all tests 6,00 Kg of the explosive Eurodyn 2000 were used at a distance of 1,85 m from the top of the slab to the centre of the explosive. The results show an improvement in the residual deformation and on the opening of the visible cracks of the base reinforced concrete slab.

Tese de Doutoramento em Engenharia de Segurança ao Incêndio, apresentada ao Departamento de Engenharia Civil da Faculdade de Ciências e Tecnologia da Universidade de Coimbra<br>The use of carbon fibre reinforced polymer (CFRP) laminates on strengthening and rehabilitation of reinforced concrete (RC), steel and timber structures has been widely used in the past few years due to the excellent mechanical performance, lightness, ease of application and corrosion resistance at ambient temperature of this composite material. However, it is well known that CFRP strengthening systems are very vulnerable to high thermal exposure as well as the ones developed in a fire scenario. These systems can rapidly lose the effectiveness of their service conditions and (in some cases) lead the structure to collapse. In these systems, the bond between the CFRP and concrete is the most critical element. When exposed to high temperatures, the bond loses its mechanical properties and consequently the strengthening system collapses. The increasing use of these systems on the strengthening of concrete structures, the possibility of fires in buildings, their thermal vulnerability and the gap in current fire design standards, have generated many concerns for the fire safety engineering society. Therefore, a better understanding of the thermomechanical response of CFRP-strengthened structures, especially RC beams, under thermal conditions is crucial, enabling a reliable safety design of those structures in fire situations. This PhD thesis and the consequent research intends to be an important contribution in this regard. The main purpose of this research was to assess the flexural behaviour of RC beams externally strengthened with CFRP laminates under fire conditions. Other important goal of this investigation was to evaluate the effectiveness/influence of the different and new fire protection systems varying its thickness and to verify their practical applicability in strengthening systems in a fire situation. In order to achieve the objectives of this research, an experimental and numerical program have been carried out at the Department of Civil Engineering (DEC) of the University of Coimbra (UC), in Portugal. In the experimental part, a great number of fire resistance (FR) tests were carried out on CFRP-strengthened RC beams thermally insulated with passive fire protection systems of vermiculite-perlite (VP), expanded clay (EC) aggregates and ordinary Portland (OP) cement-based mortars, in a fire scenario as real as possible. These tests were intended to study several parameters that might influence the structural response of these members in fire situations, such as, the critical temperature-time of debonding of the EBR strengthening system, collapse of the fire protection system and of the beam failure. The FR tests have been performed under transient state conditions with the specimens subjected to a serviceability loading. In addition, flexural tests at ambient temperature have been performed as reference. To complement the experimental program, Single lap Shear Tests (SST) at elevated temperatures on concrete blocks strengthened with CFRP laminates were performed. The SST tests were carried out to investigate the behaviour of the bond between concrete and CFRP at elevated temperatures in terms of bond strength, displacements and axial strains. The response of the bond was analysed under steady state conditions. First, the specimens were heated to the setpoint temperature and then they were loaded up to failure. The CFRP laminate was in both type of tests assembled using the externally bonded reinforcement (EBR) technique. Reference tests at ambient temperature were also carried out. Regarding the numerical phase, a large number of numerical simulations using a three-dimensional (3D) commercial finite element (FE) software package was performed. The numerical analyses made it possible to verify the results of the experimental tests and allow to enlarge the research to other situations not tested experimentally in a future parametric study. A series of different parameters that have influence on the behaviour of RC beams strengthened with CFRP in a fire situation were simulated. The experiments confirmed the limited fire behaviour of the CFRP-concrete bond in these systems and the need for their fire protection, which in turn is a critical zone. The results showed that the passive fire protection materials provided the integrity of strengthening for long periods of fire exposure. The results of SST tests also showed that approximately 40% of the bond strength was lost to temperatures near to the glass transition temperature (Tg) of the adhesive. However, despite the loss of bond strength with the increasing temperatures, a significant residual strength retention was still noticed for temperatures higher than the Tg. Similar tendency was noticed on the fire tested CFRP-strengthened RC beams, where the debonding of the strengthening system also occurred for temperatures above Tg of the adhesive. Finally, the FE models developed were successfully validated and presented an excellent agreement with the experimental results, being able to reproduce the thermomechanical response of the tested beams with fairly good accuracy.<br>O uso de laminados de polímero reforçado com fibra de carbono (CFRP) no reforço e reabilitação de estruturas de betão armado, aço e madeira tem sido amplamente utilizado nos últimos anos devido ao seu excelente desempenho mecânico, leveza, facilidade de aplicação e resistência à corrosão sob condições de temperatura ambiente. No entanto, é bem sabido que os sistemas de fortalecimento CFRP são muito vulneráveis à elevada exposição térmica, como aquelas desenvolvidas em um cenário real de incêndio. Esses sistemas podem rapidamente perder a eficácia de suas condições de serviço e (em alguns casos) levar a estrutura ao colapso. Nestes sistemas, a ligação entre o CFRP e o betão é a área mais crítico. Quando exposto a altas temperaturas, a ligação perde suas capacidades mecânicas e, consequentemente, o sistema de fortalecimento colapsa. O uso crescente desses sistemas no reforço de estruturas de betão, a possibilidade de incêndios em edifícios, sua vulnerabilidade térmica e a lacuna nas normas atuais de projeto de incêndio têm gerado muitas preocupações para a sociedade de engenharia de segurança contra incêndios. Portanto, um melhor entendimento da resposta termomecânica de estruturas reforçadas com CFRP, especialmente vigas de betão armado, sob condições térmicas é crucial, permitindo projetar essas estruturas de forma segura para situações de incêndio. Essa tese de doutorado e a consequente pesquisa pretendem ser uma importante contribuição nesse sentido. O principal objetivo desta pesquisa foi avaliar o comportamento à flexão de vigas de betão armado reforçadas externamente com laminados CFRP sob condições de incêndio. Outro objetivo importante desta investigação foi avaliar a eficácia/influência de diferentes e novos sistemas de proteção contra incêndio, variando sua espessura, e verificar sua aplicabilidade nos sistemas de reforço para uma situação de incêndio. Para atingir os objetivos desta pesquisa, um programa experimental e numérico foi desenvolvido no Departamento de Engenharia Civil (DEC) da Universidade de Coimbra (UC), em Portugal. Na parte experimental, um grande número de ensaios de resistência ao fogo foram realizados em vigas reforçadas com CFRP, termicamente protegidas com sistemas passivos contra incêndio compostos por argamassas de vermiculita-perlita (VP), agregados de argila expandida (EC) e cimento Portland comum (OP ) em uma configuração de ensaios que representasse um cenário de incêndio da forma mais fiel possível. Pretendeu-se com estes ensaios estudar vários parâmetros que pudessem influenciar a resposta estrutural destes elementos em situações de incêndio, como a temperatura crítica vs. tempo do colapso do sistema de reforço EBR, o colapso do sistema de proteção contra incêndio e a falha da viga. Os ensaios de resistência ao fogo foram realizados em condições de estado transitório com os provetes sujeitos a uma carga de serviço. Além disso, ensaios de flexão à temperatura ambiente foram realizados como referência. Para complementar o programa experimental, ensaios de cisalhamento único (SST) em blocos de betão reforçados com laminados de CFRP à temperaturas elevadas foram realizados. Os ensaios SST foram realizados para investigar o comportamento ao fogo da ligação entre o betão e o CFRP em termos de resistência à tração, deslocamentos e deformações axiais. A resposta da ligação foi analisada em condições de estado estacionário. Primeiro, as amostras foram aquecidas até a temperatura nominal e, em seguida, foram carregadas até a falha. O laminado de CFRP foi em ambos os tipos de ensaios colado usando a técnica de ligação externa (EBR). Ensaios de referência à temperatura ambiente também foram realizados. Em relação à fase numérica, foi realizado um grande número de simulações numéricas utilizando um software comercial de elementos finitos tridimensionais (3D). As análises numéricas permitiram verificar os resultados dos ensaios experimentais e tornou possível a ampliação da pesquisa para outras situações não testadas experimentalmente em um futuro estudo paramétrico. Uma série de diferentes parâmetros que influenciam no comportamento das vigas de betão armado reforçadas com CFRP em situação de incêndio foram simulados. Os experimentos confirmaram o comportamento limitado ao fogo da ligação CFRP-betão e a necessidade de sua proteção contra incêndio, que por sua vez é uma zona crítica. Os resultados mostraram que os materiais passivos de proteção contra incêndio proporcionaram a integridade do reforço por longos períodos de exposição ao fogo. Os resultados dos ensaios SST também mostraram que aproximadamente 40% da resistência mecânica da ligação foi perdida para temperaturas próximas à temperatura de transição vítrea (Tg) do adesivo. No entanto, apesar da perda da resistência mecânica da ligação com o aumento de temperatura, uma significativa retenção mecânica residual ainda foi notada para temperaturas superiores a Tg. Tendência semelhante foi notada nas vigas reforçadas com CFRP ensaiadas ao fogo, onde a falha do sistema de reforço também ocorreu para temperaturas superiores a Tg do adesivo. Por fim, os modelos de elementos finitos desenvolvidos foram validados com sucesso e apresentaram excelente compatibilidade com os resultados experimentais, sendo capazes de reproduzir a resposta termomecânica das vigas testadas com boa precisão.