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The quality and the durability of the concrete structures are affected by lots of degradation processes. In the case of reinforced concrete (RC) structures, the most known degradation process is corrosion of reinforcement. RC members have to fulfil the conditions given in Eurocode (STN EN 1992-1-1, STN EN 1992-2). Horizontal beams are mainly subjected to bending and shear. The paper deals with reinforcement corrosion of stirrups (shear reinforcement) and its influence on the load-carrying capacity of the existing bridge concrete structures. There are considered one type of passive stage calculation and one type of active stage calculation in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Continuous shear connection, using a cut steel strip, is an upcoming solution for composite beams. With the activation of friction on the sides of the steel strip this method has already been used to design and build large durable bridges during the sixties. However direct shear transmission into the steel strip though teeth of the cut is also possible and has been scrutinized with the support of the European Research Fund for Coal and Steel. It is characterized by a high initial stiffness, bearing capacity and ductility. It allows new and economic construction methods, as the PreCoBeams (Prefabricated Composite Beam used as formwork). PreCoBeams are for instance composite beams associating steel T-sections acting as tension member with a concrete top chord acting as compression member. Steel parts are generally obtained from rolled steel profiles that are longitudinally cut in two identical T-sections. The cut is performed with a special shape to allow the shear longitudinal transmission between steel and reinforced concrete. In general, prefabricated, composite, longitudinal PreCoBeam bridge elements are produced in factory. They consist of at least one steel T-section associated to a precast first phase concrete flange. Second phase concrete layer is then completed in-situ after erection of the bridge elements on abutments. These PreCoBeam bridges are very economic in design and construction, though the main market drawback for PreCoBeams is the missing design rules for the shear connection. This paper introduces the static and fatigue design of continuous steel plate shear connections used for PreCoBeams derived from the recent research activities. The CL shape of the cutting has been tested in fatigue, ultimate and service limit states and validated in the scope of a bridge application. This concept aims at developing a competitive solution for small span bridges. The various solutions realized in the last years in many European countries, some of them presented in the paper, show clearly its interest. [Copyright &y& Elsevier]

Abstract: Infrastructures cover a very broad spectrum of different materials. This paper focuses on civil engineering structures, concrete and asphalt in particular. The public demand for such infrastructures is high level of service and performance, high durability and minimum negative ecological impact. New emerging self healing materials science provides solutions to the problem. An overview is given of new developments obtained in research on self healing of cracks in cement based materials and asphalt concrete. At Delft University various projects are running to study self healing mechanisms. The first project that is discussed is Bacterial Concrete, in which bacteria are mixed in concrete, that can precipitate calcite in a crack and with that make concrete structures water tight and enhance durability. In a second project hybrid fibre reinforced cementitious materials are studied that can mechanically repair cracks when they occur. The last project described in this paper is on the ravelling of porous asphalt concrete and how to heal this damage by incorporating embedded microcapsules or steel fibres. The state of the art results in all projects show that self healing is not just a miracle, but materials can be designed for it. [Copyright &y& Elsevier]

It has been years since the resistance of concrete to internal cracking induced by cyclic freezing and thawing was first evaluated according to Polish standard PN-88/B-06250 through checking the so called freeze-thaw resistance level. Concrete is most often classified as F-T resistant when after 150 cycles of freezing and thawing, the relative strength loss ΔR is equal to or lower than 20%, this value being based on average strength values of reference specimens (cubes) and those subjected to freezing, with no scatter taken into account. Previous research has shown that strength loss ΔR is accompanied by mass gain resulting from microcrack formation in concrete – for ΔR=20% the critical mass gain Δm is about 10 g. Knowing the variation history of the specimen mass in relation to the number of F-T cycles, the critical number of cycles leading to structural damage can be determined for each specimen being tested. This can be the basis for determining the parameters of Weibull distribution and developing a damage model for concrete subjected to freezing - the number of freeze-thaw cycles needed to damage the concrete for the assumed level of probability. The paper analyses the results from the tests performed on two concretes with different freeze-thaw durability. [ABSTRACT FROM AUTHOR]

This paper discusses how cover thickness is selected based on values of diffusion coefficients regarding its durability by obtaining the limit concentration of chlorides at its surface, typical for Portland cement CEM I 42.5R and Portland cement with low alkali content CEM I 42.5N/SR3/NA, and considering the example of a beam bridge structure - the impact of cover on load- bearing capacity as a function of span. [ABSTRACT FROM AUTHOR]

Foamed concrete (FC) is promising material in modern building industry because of simple technology and wide range of properties may be achieved. Basic problems of FC are shrinkage and decreased strength, comparing to aerated autoclaved concrete. In the case of wet and cold climate, durability also plays in an important role. The paper discussed the possibilities for creating durable high performance FC by applying intensive mixing technology and using modifying micro admixtures. Characteristics of FC, such as strength, density, water absorption, carbonization and frost resistance, are discussed as the basic components of durability. Properties of different compositions of FC were tested and compared. Technological methods for obtaining high performance concrete are summarized. It is pointed out, that creating of more durable FC makes possible to increase life cycle of material and promote rational use of natural resources. [ABSTRACT FROM AUTHOR]

This paper presents some problems connected with causes of reinforced concrete silos failure. Reinforced concrete silos and other shells were built for decades. Vitality i.e. durability of cracked silo walls are one of the most important parameters during designing process, constructional and exploitation time of these shells. Some reasons of appearance of horizontal and vertical cracks as temperature, pressure of stored material, live loads e.g. wind, dynamic character of wind, moisture, influence of construction joints, thermal insulation, chemistry active environmental etc. reduce the carrying capacity of the walls of the silos and causes lower the state of reliability. Horizontal and vertical cracks can cause corrosion of concrete and steel bars, decreasing stiffness of contraction, bigger deflection, increasing of carbonation of concrete cover and dank of concrete wall. Horizontal and vertical cracks allow condensate water infiltrates into wall. Local and global imperfactions of concrete shells are increasing according to greater number of cracks. Taking into account these facts, reducing of strength parameters reduce the service life of the whole reinforced concrete structure causing failure status. The technology of repairing cracked walls must take into consideration the model of failure, simple one parameter or complex as series or parallel system models. [ABSTRACT FROM AUTHOR]

Designing concrete structures for a very long service life may have considerable economic and societal benefits including minimized material consumption over the long term, thus contribute to more sustainable solutions. However, such long service lives require determination and extrapolation of environmental loadings and material durability performance over a long period, as well as reliable and operational models for service life predictions. Codes and standards give deem-to-satisfied recommendations for intended working (service) life up to about 100 years. However, if higher working lives of 200 and 300 years are specified, as for monumental buildings, bridges and other important infrastructures, more in-depth service life predictions are required. This paper focuses on durability and service life predictions for reinforced concrete structures for working (service) life requirements above 100 years. [ABSTRACT FROM AUTHOR]

An important factor within Europe's development process is the transportation system. “Design and build” projects allow the implementation of efficient, economical and also modern structures. The present paper presents a quick overview of new designed and executed structures: VTR ® modular composite bridges. These bridge solutions combine many important aspects: reduced costs, fast and simple erection, modularity, durability and robustness, low maintenance costs and an appealing aesthetical aspect. [ABSTRACT FROM AUTHOR]

Railway bridges represent the significant parts of the railways due to their key and strategy position in transportation infrastructure. During the years of exploitation, many degradation processes and external influences attack the bridge structures. Due to those effects their durability and reliability is decreasing depending on time. On the other hand, the traffic load remains almost the same or even higher than in the past. But, bridges should not to become the limiting component of communication capacity and traffic reliability passage. In the period of 2013-14 the collective of the Department of structures and bridges has worked up the Guideline “Determination of load-carrying capacities of railway bridges” [1] . The Guideline was prepared for Slovak Railways and it was also published in the Czech Republic as the methodology instruction [2] . Therefore, the paper describes general concept and basic assumptions for evaluations of existing railway bridges and determining their load-carrying capacities based on the principles of Eurocodes. [ABSTRACT FROM AUTHOR]

The green concrete capable for sustainable development is characterized by application of industrial wastes to reduce pollution of the environment. Fly ash processed with nanotechnology developed by Indonesia Center for Ceramics using Polishing Liquid Milling Technology. Nanomaterial concrete is new generation concrete formed of materials of the grain size of nanoscale. The materials used in this research were cement type I, nanosilica 10 - 150 nm, quartz powder in 0.3 - 25.0 μm, fine sand (quartz of sand) size of 50 - 650 μm, coarse aggregate in 5 - 10 mm, and superplasticizer. In this paper, mechanisms are discussed by which the incorporation of nanomaterials in concrete enhances durability to sulfate attack. Application of nanotechnology is an effective way to reduce environment pollution and improve durability of concrete. For countries like Indonesia, this technology can play an important role in meeting the huge demand for infrastructure in a sustainable manner. [ABSTRACT FROM AUTHOR]

Utilization of laterite rock at 20% as partial aggregate replacement in concrete production is seen as one of the alternative to reduce the high dependency of concrete industry on granite aggregate supply and preserve this natural resource for future generation. This paper reports the durability performance of concrete containing laterite aggregate upon sulphate attack. A reference mix, plain concrete consisting 100% granite aggregate and another one mix containing 20% laterite aggregate as partial coarse aggregate replacement were used. All specimens were prepared in cubes of (100×100×100 mm) and subjected to water curing for 28 days. After that, the specimens were immersed in Magnesium Sulphate solution for a period of 50 weeks. The durability of the concrete mixes was determined through measurement of mass change and residual compressive strength. The compressive strength test was conducted following the procedures in BSEN 12390 – 3. Upon exposure in sulphate environment, reaction between sulphate ions and portlandite which formed gypsum contributes to concrete expansion and disintegration causing strength reduction in both specimens. Owing to the small difference in total mass loss and residual compressive strength between the two mixes, it is concluded that the sulphate resistance of laterite concrete is comparable to plain concrete. [ABSTRACT FROM AUTHOR]

This paper reports an experimental study of the influence of marble powder used as partial substitute for Portland cement (PC) on the mechanical properties and durability of high performance concretes. The analysis of the experimental results on concrete at 15% content of marble powder with a fineness modulus of 11500 cm 2 /g, in a chloride environment, showed that it contributes positively to the perfection of its mechanical characteristics, its durability with respect to migration of chloride ions and oxygen permeability. On the basis of the experiments performed, it can be concluded that the marble powder is suitable for formulation of high performance concretes (HPC) and their properties are significantly better compared to the reference concrete (RC). [ABSTRACT FROM AUTHOR]

Sulfate attack and its effects are important from both scientific and industrial viewpoints. It is perceived that cements containing pozzolan have better performance in sulfatesolutions,since the pozzolanic reactions reduce the quantity of calcium hydroxide and increase calcium silicate hydrate. This paper investigates the physical and mechanical properties ofconcretes made by blended cement containing Algerian natural pozzolan of volcanic origin, and Portland cement. inorder to better determine the pozzolanic effect of the pozzolan addition in the concrete, the analysis of the experimental results of the effect of the partial replacement of the cement by the natural pozzolana showed that it contributes positively to the improvement of its mechanical characteristics, its durability with respect to theultrasonic pulse velocity as well as the sulphate resistance. The present study confirms the pozzolanic reactivityof the natural pozzolans used. [ABSTRACT FROM AUTHOR]

The precast concrete structures are very popular for many construction designers. The appropriate design and performance of structural joints are essential preconditions for durability and effectiveness of this type of structures. Headed fastenings made of rebar steel appertain currently to the attractive solution for creating compact structural joints. The resistance of this type of anchors can be increased by using supplementary steel reinforcement. Our research and studies, focused on headed fastening and supplementary reinforcement, are briefly described. The experimental research is then discussed in the paper. [ABSTRACT FROM AUTHOR]

Some dolomite aggregates exposed to a wet environment may decompose. The presence of sodium, magnesium, calcium and sulfate ions in the corrosive medium and the higher temperature can increase the rate of aggregate decomposition. The results of a study on the impact of defined environmental exposition to a H 2 O, Mg(OH) 2 , MgSO 4 , Na 2 SO 4 solutions in various temperature conditions on the susceptibility to dedolomitisation processes of cement concrete made with selected dolomite aggregate are presented in the paper. The observation of linear extension as well as changes in compressive strength and surface alteration due to corrosive exposition conditions were the key diagnostic features adopted for this examination. [ABSTRACT FROM AUTHOR]

The paper deals with corrosion resistance of cement mortars with various amounts of ground granulated blast-furnace slag (GGBS). The mortars were tested in the environment containing acids and sulphates corresponding to the aggressive factors acting on concrete in agricultural areas. The strength development of the composites with GGBS is slower; however, the losses in their strength and mass, as well as linear changes, after storing in the aggressive environment, are lesser than for those containing only Portland cement. This can be attributed, most likely, to the favourable changes in the hardened paste microstructure, caused by GGBS presence. The addition makes the structure of the hardened cement paste more compacted, diminishing the porosity and improving the tightness The long-term tests confirm that cement composites containing GGBS can be rational substitutes for ordinary cement concrete in the aforementioned field. However, the subject of the presented research were mortars; the conclusion shall be verified by concrete testing, planned as the next step of the project. [ABSTRACT FROM AUTHOR]

In EN 13670:2009 standard: Execution of concrete structures there are general rules of moisture curing of concrete in structures. In the standard 4 classes of concrete curing are described. Determination of curing class depends on required level of compressive strength immediately after curing (percentage of required characteristic strength after 28 days). Time of curing depends on rate of strength development and concrete surface temperature. In the standard there is a lack of information about influence of curing class on concrete durability characteristics. The main condition to obtain durable concrete is proper curing regime. Not cured on improperly cured concrete has weakened surface layer. Extremely faults in curing process could lead to defects visible on the concrete surface. More often defects are latent inside the concrete and could be revealed during exploitation, leading to durability reduction. The main effect is increase of surface layer porosity (reinforcement cover) and decrease of its protective properties and tightness. Consequently worsening of mechanical properties could be observed as well as water-tightness, frost resistance, chemical aggression resistance, carbonation resistance and diffusivity of chloride. The analysis shown in the paper are the result of 3-yers long investigation conducted by authors, which main goal was to determine appropriateness and way to include durability requirements in designing of curing class according to EN 13670:2009. Thawing-freezing resistance, scaling with salts resistance, depth of water penetration under pressure and absorptivity were adopted as the basic durability factors. Concretes with different cement types, different rate of compressive strength development, air-entrained and non-air-entrained were tested. Time of curing was differentiated in the range of classes 1,3,4 following standard EN 13670:2009 requirements. Practical conclusions were formulated which allows to consider durability presumptions in technological requirements contained in concrete works specifications. [ABSTRACT FROM AUTHOR]

Some dolomite aggregates exposed to a wet environment may decompose. The presence of sodium, magnesium, calcium and sulfate ions in the corrosive medium and the higher temperature can increase the rate of aggregate decomposition. The results of a study on the impact of defined environmental exposition to a H2O, Mg(OH)2, MgSO4, Na2SO4 solutions in various temperature conditions on the susceptibility to dedolomitisation processes of cement concrete made with selected dolomite aggregate are presented in the paper. The observation of linear extension as well as changes in compressive strength and surface alteration due to corrosive exposition conditions were the key diagnostic features adopted for this examination. [ABSTRACT FROM AUTHOR]

The paper presents an assessment of durability of an acrylic coating weathered both under natural and artificial conditions. The effect of various degradation factors on service life of the material has been presented. The material in question is used to protect concrete against carbonation. Some diagnostic instruments, such as FTIR analysis, Scanning Electron Microscopy (SEM) and examination of barrier properties and adherence to the concrete substrate, have been used to determine the weathering rate of the material. [ABSTRACT FROM AUTHOR]

In EN 13670:2009 standard: Execution of concrete structures there are general rules of moisture curing of concrete in structures. In the standard 4 classes of concrete curing are described. Determination of curing class depends on required level of compressive strength immediately after curing (percentage of required characteristic strength after 28 days). Time of curing depends on rate of strength development and concrete surface temperature. In the standard there is a lack of information about influence of curing class on concrete durability characteristics. The main condition to obtain durable concrete is proper curing regime. Not cured on improperly cured concrete has weakened surface layer. Extremely faults in curing process could lead to defects visible on the concrete surface. More often defects are latent inside the concrete and could be revealed during exploitation, leading to durability reduction. The main effect is increase of surface layer porosity (reinforcement cover) and decrease of its protective properties and tightness. Consequently worsening of mechanical properties could be observed as well as water-tightness, frost resistance, chemical aggression resistance, carbonation resistance and diffusivity of chloride. The analysis shown in the paper are the result of 3-yers long investigation conducted by authors, which main goal was to determine appropriateness and way to include durability requirements in designing of curing class according to EN 13670:2009. Thawing-freezing resistance, scaling with salts resistance, depth of water penetration under pressure and absorptivity were adopted as the basic durability factors. Concretes with different cement types, different rate of compressive strength development, air-entrained and non-air-entrained were tested. Time of curing was differentiated in the range of classes 1,3,4 following standard EN 13670:2009 requirements. Practical conclusions were formulated which allows to consider durability presumptions in technological requirements contained in concrete works specifications. [ABSTRACT FROM AUTHOR]

Ladle furnace slag (LFS) is a by-product of the steel making process. In this paper ladle furnace slag was used as filler material for the production of self-compacting concrete mixtures of different strength classes. Different contents of ladle furnace slag filler, ranging from 45 to 92.5 kg/m³ were incorporated. The produced concretes were tested in the fresh state for fluidity, passing ability and resistance to segregation and in the hardened state for compressive strength, carbonation and chloride penetration resistance. The test results showed that ladle furnace slag can be used as filler for producing self-compacting concretes with enhanced durability characteristics resulting this way to lower cost environmentally friendly durable concrete mixtures. [ABSTRACT FROM AUTHOR]

The paper deals with experimental results of combined sulphate expansion and freeze-thaw attack on air entrained (AE) and non-air entrained (nAE) ordinary portland cement mortars. After prior freezing and thawing of the 4x4x16 cm mortar bars the part of them was subjected to sulphate attack of the 5% Na2SO4 solution. Another part of mortar bars was immersed in the sulphate solution for 110 days and then these bars were frozen and thawed. The resistance of nAE and AE mortars to regular sulphate and freeze-thaw attacks alone was tested as well. In order to compare damage degree of mortars in all environments, there were investigated long term linear strains (expansion), and compressive strength of mortars. Also the SEM and XRD analyses of mortars were carried out. Compared to the individual sulphate attack alone, prior freeze-thaw and following it sulphate attack affected significant acceleration of sulphate expansion of nAE and AE mortars as well, despite much better resistance of AE mortars to freezing and thawing. However, the prior sulphate attack significantly reduced AE mortars resistance to freezing and thawing. The SEM analysis showed that air voids in AE mortars were partially filled with ettringite. Its precipitation in air voids of AE mortars caused that the volume of air was diminished and freeze-thaw resistance of AE mortars was significantly decreased and it was as low as resistance of nAE mortars was. The complete destruction of AE mortars subjected to sulphate attack alone occurred earlier than that of nAE mortars did. Based on SEM analysis results it is suggested that lower sulphate resistance of AE mortars was due to higher porosity of the air void-paste interface and its higher initial w/c ratio compared to 'bulk paste' farther away from. [ABSTRACT FROM AUTHOR]

The paper deals with corrosion resistance of cement mortars with various amounts of ground granulated blast-furnace slag (GGBS). The mortars were tested in the environment containing acids and sulphates corresponding to the aggressive factors acting on concrete in agricultural areas. The strength development of the composites with GGBS is slower; however, the losses in their strength and mass, as well as linear changes, after storing in the aggressive environment, are lesser than for those containing only Portland cement. This can be attributed, most likely, to the favourable changes in the hardened paste microstructure, caused by GGBS presence. The addition makes the structure of the hardened cement paste more compacted, diminishing the porosity and improving the tightness The long-term tests confirm that cement composites containing GGBS can be rational substitutes for ordinary cement concrete in the aforementioned field. However, the subject of the presented research were mortars; the conclusion shall be verified by concrete testing, planned as the next step of the project. [ABSTRACT FROM AUTHOR]

Abstract: The paper describes a development and use of lightweight concrete and lightweight self-compacting concrete using artificial lightweight aggregate based on expanded clay for ready mix concrete and precast elements. The objective of this research was to evaluate the lightweight concrete on durability of concretes placed in chemically aggressive liquid and gaseous environments (high concentrations of sulphate, chloride ions, automotive gas, oil and gaseous CO2 and SO2 environments). [Copyright &y& Elsevier]

Abstract: Under normal circumstances, reinforced concrete structures (RCS) show excellent performance in terms of durability and structural behaviour except for the zones that are subjected to severe mechanical or cyclic loading and aggressive environmental conditions. Therefore the methods of rehabilitation or strengthening of these zones should be reliable, effective and economical. Today, many scientists, academics and engineers understood the extremely low porosity and low permeability characteristics of ultra high performance fibre concrete (UHPFC) giving its enhanced durability over high performance concrete (HPC), thus making it potentially suitable for rehabilitation and retrofitting problematic RCS. The advantages of utilising the technology of UHPFC in repairing works includes (i) decrease the working time needed for the rehabilitation works; and (ii) increase the serviceability and durability to an extent where the repaired structures can meet the expected design life of the structures, with minor preventative measure. This paper discusses and reviewing some of the most recent issues and findings using UHPFC as a repair material. The results of the findings will also be presented to prove that the UHPFC displays excellent repair and retrofit potentials in compressive and flexure strengthening and possesses high bonding strength and bond durability as compared with other types concrete. [Copyright &y& Elsevier]