Environmental influence in construction materials

Concrete as one of the most widely used construction material in building industry, has considerable implementing in bridge engineering due to its extensive number of effective technical characteristics. However, according to exploitation environment, there are substantial factors such as aggressive liquids (e.g. deiced salts, sulfates, etc), rapid temperature alterations and the increasing rate of CO2 to take into account predicting actual retained service life of concrete structure and the need of repairmen to increase the lifespan of the bridge. According to several measuring, concentration of atmospheric CO2 is reported linearly increasing and is modeled to appear as exponential increase in the next decade. This environmental influence leads to accelerated carbonation process of concrete and brings up the importance of its potential untimely degradation mechanism. Hence, the main aim of this research is to give an analyzed overview of the carbonation depths of selection of 11 concrete bridges in Estonia built in the period of 1976-2007 and their relation with compressive strength of concrete. In addition to in situ tests, laboratory research was performed to understand natural carbonation rate and compressive strength relations of concrete.

This paper deals with the roof structural system using prestressed girders made of ultra-high performance concrete (UHPC). One of the aims of this study is to verify whether the option of the UHPC girders could be under certain boundary conditions competitive with the commonly used construction materials. Due to its high strength, UHPC enables the design of the structural elements with the high load bearing capacity and with smaller slenderness compared to normal strength concrete elements. The price of UHPC is currently still very high compared to the normal strength concretes or steel. Therefore, its use for the usual designed structures does not recently seem too economically attractive. The effect of material savings is nonnegligible in the case, that a self-weight of the structure forms dominant component of the total load. In addition to the high strength, UHPC has very high resistance to environmental influences. It is therefore likely, that UHPC could be advantageously applied e.g. for the roofing of industrial buildings of chemical plants with high aggressive environments, because there are high demands on the life cycle of the structure.

- The issue of global warming strongly encourages architects to use sustainable materials to preserve nature. Bamboo material is an ecological and sustainable material. Bamboo is also predicted as a future material. The strengths and advantages of bamboo are very likely to be used as a building construction material. Unfortunately, it is not uncommon for bamboo material to be used inappropriately so that it does not optimize the ecological and sustainable properties of bamboo. The object of study chosen was the Bumi Pemuda Rahayu bamboo hall. This object is close to the concept of sustainability as seen from the function of the building, which is a co-creating space that prioritizes sustainability-related activities. This research uses qualitative-quantitative methods that will compare the theory regarding the concept of sustainability of materials related to the building material life cycle with the data obtained. The concept will be divided into three aspects, namely design aspects, construction aspects, and maintenance and renovation aspects. These three aspects can be examined by knowing the object data related to these aspects. The results of the study will answer whether the use of bamboo material in the object of study is in accordance with the concept of sustainability of the bamboo material. The analysis of the design stage pays attention to material selection, material preservation, how to optimize the age of bamboo and the selection of a structural system. The construction stage is analyzed by considering the type of connection used. The maintenance and renovation phases are analyzed by paying attention to how to renovate the bamboo structure and post-construction maintenance of the building. This building is appropriate in choosing the type of material, applying preservation of bamboo materials, and successfully preventing bamboo from environmental influences in order to reach its optimal age. In terms of structural system selection, this building is also appropriate by applying the arc rod structural system. Bolted joints are appropriate for complex structural systems, it's just that there must be special treatment at the base of the arc structure that receives the greatest load due to cracks. Renovation and maintenance aspects must be considered again because this building will have difficulty if you have to do renovations, especially on the arc structure. Maintenance that is rarely performed can also reduce the life of the building. Key Words: bamboo, sustainable materials, Bumi Pemuda Rahayu

Damage assessment of reinforced concrete structures using a model-based nonlinear approach – A comprehensive review

Concrete and reinforced concrete are the main structural materials in modern construction. The area and volumes of application of these materials continues to expand. In recent years, in the practice of construction, there is a tendency to the use of structures that combine load-bearing and enclosing functions, as well as the functions of technological equipment. At the same time, their working conditions are becoming more complicated and harsh. In addition to the usual force effects (loads), structures are exposed to all kinds of environmental influences (actions) in the form of substances, energy, or a combination thereof. According to current design standards in reinforced concrete structures designed to work in aggressive environments corrosion of materials is not allowed. However, there is a large amount of structures that have received corrosion damage at the operation stage. The standards do not contain any guidelines for designing a parameters of the primary protection and repair system for reinforced concrete structures and their elements (durability forecast, repair period, determination of structural and technological parameters of the primary protection or repair systems). Thus, there are tasks of designing the protection of reinforced concrete structures both at the design stage and at the operation stage. At the design stage, it is necessary to determine the structural and technological parameters of the primary protection that ensure the service life of structures or the period between repairs. At the stage of operation, it is necessary to determine the parameters of repair systems which provide the residual service life until the next repair or liquidation of reinforced concrete structures. Our research shows the economic feasibility of designing reinforced concrete structures interacting with aggressive environment, taking into account the kinetics of concrete corrosion. The optimal design methods can be used to obtain the most economical solutions. We have developed quantitative methodology for the design of primary protection of reinforced concrete structures.

Настоящая работа посвящена исследованию влияния на механические свойства бетона материалов, доступных на местных рынках Вьетнама, а именно: тонкомолотого кварцевого песка (кварцевая мука-Км), суперпластификатора (СП) и промышленных отходов, таких как зола-унос (ЗУ) и микрокремнезём (МК). Основной целью исследования было получение высокоэффективного бетона с использованием преимущественно местных материалов для достижения предела прочности при сжатии более 80 МПа. Материалы и методы. В исследованиях использовались следующие материалы: сульфатостойкий портландцемент PC40 (тип V) компании Luks Cement Limited (Вьетнам); ультрадисперсный микрокремнезем (МК) фирмы Sikacrete® PP1 - Sika Limited (Вьетнам); золаунос (ЗУ) тепловой электростанции PhaLai (Вьетнам); крупный и мелкий заполнители. В ходе работы реализованы методы, с помощью которых были определены прочность бетона на сжатие, прочность на осевое растяжение и прочность на растяжение при изгибе. Результаты. Для получения бетонов более плотной и однородной структуры с высокой прочностью оптимальные дозировки минеральных добавок, частично замещающих цемент в бетонной смеси, составляют 30 % золы-уноса и 10 % микрокремнезема, а также 20 % кварцевой муки вместо части мелкого заполнителя. Выводы. На основе результатов исследований был сделан вывод, что высокопрочный бетон, содержащий в своём составе минеральные добавки – микрокремнезём и золууноса, а также тонкомолотый кварцевый порошок и суперпластификатор, обладает высокой прочностью за счёт снижения пористости цементного камня и улучшения сцепления между ним и заполнителем. Полученные высокопрочные бетоны могут быть использованы при строительстве высотных зданий, мостов, транспортных туннелей и других подземных сооружений благодаря достижению высокой ранней прочности и обеспечению требуемой долговечности в условиях воздействия агрессивных сред, а также из-за сокращения стоимости и сроков строительства. The research examines the effect of the construction materials available on the Vietnamese market on the mechanical characteristics of concrete. The research particularly focuses on fineground quartz sand (quartz flour-Km), superplasticizing agent (SA) and industrial waste such as furnace dust (FD) and silica fume (SF). The main research objective was to obtain high-efficiency concrete using mainly local materials to achieve compression strength of more than 80 mPa. Materials and methods. The following materials were used in the research: sulphate-resisting portland cement PC40 (type V) by Luks Cement Limited (Vietnam); ultra-disperse silica fume (CF) by Sikacrete® PP1; Sika Limited (Vietnam); furnace dust (FD) by PhaLai thermal electric power station (Vietnam); coarse and fine aggregate. As part of the research, the relevant methods were used to determine the compression strength of concrete, direct tensile strength and bending tensile strength. Results. In order to produce a denser and more homogeneous structure with a high strength, the optimum dosing of mineral additives that partially replace cement in a concrete mixture was used: 30 % of furnace dust and 10 % of silica fume, as well as 20 % quartz flour instead of fine aggregate. Findings. Based on the results of the research, it was concluded that high-performance concrete with mineral additives such as silica fume and furnace dust; and fine quartz powder and superplasticizing agent, has high strength by reducing the porosity of the cement stone and improving the adhesion between the aggregate. The obtained high-strength concrete can be used in constructing high-rise buildings, bridges, transport tunnels and other underground installations by achieving high early strength and the required durability under the influence of corrosive environment, as well as due to the cost and construction period reduction.

The term corrosion originates from the Latin word “corrosio”, meaning erosion or degradation. Metal corrosion refers to their deterioration and becoming unserviceable as a result of chemical, electrochemical, or biochemical effects. Due to the reduction of the free energy of a construction material, metals exhibit thermodynamic instability. In essence, corrosion can be defined as the destruction of metals and alloys under the influence of the external environment. In some metals, the degradation process occurs not only on the surface but also within the material. This leads to the disruption of the crystal lattice structure and results in the loss of intrinsic properties. When impurities are abundant within the metal, galvanic couples may form on the surface, leading to localized points of attack and the development of pitting corrosion, which accelerates metal degradation. The economic damage caused by corrosion across different countries can be illustrated by several examples. According to Le Metayer, in 1953 the economic loss to Norway due to corrosion amounted to 180 million marks. In 1964, damages to France’s marine structures reached 80 million francs. Every year, biological corrosion results in a loss of 25 million dollars in Australia and 5 million dollars in New Zealand. In the United States, biofouling in the shipping industry causes an annual loss of 10 million dollars, while sulfate-reducing bacteria in underground pipelines cause damages estimated between 500–2000 million dollars annually. To protect the famous Eiffel Tower from corrosion, 70 tons of special paint and varnish are applied every three years. Generally, the surfaces of metals in their normal state and after corrosion differ significantly. However, certain types of corrosion are invisible to the naked eye. This phenomenon, known as intergranular corrosion (metal embrittlement), occurs due to the disruption of the crystal lattice structure of metals. Corrosion of metals is observed under various environmental conditions such as water, atmosphere, soil, acidic, and alkaline media. The electrochemical corrosion process occurs as a result of the formation of a double electric layer at the metal–environment interface. In some cases, chemical effects are accompanied by physical degradation, which is termed erosion–corrosion or fretting–corrosion. In the case of iron and its alloys, rusting occurs as hydrated corrosion products are formed from oxides. Non-ferrous metals also corrode, although they do not form rust. During the design and construction of pipelines, the protection of pipeline structures and foundations of pipes from environmental impacts must be ensured. Keywords: pipeline, metal, environment, protective coating, corrosion

Modern concretes are characterised not only by rising demands on properties but also by increasingly complex compositions. With sophisticated formworks and dense reinforcements, the trend in concrete technology continues towards to self-compacting and easily-compacting concretes. The use of highly effective superplasticizers makes these concretes not only more efficient but also more susceptible to environmental factors and influences. Compliance with desirable fresh and hardened concrete properties is becoming increasingly problematic. In this case, there are no methods for testing today’s concretes, especially the easily-compacting and self-compacting concretes, which are suitable for construction sites. Because of their sensitivity, however, these should be examined separately for their tendency to segregation and, in this context, for their sedimentation stability. For this reason, a test method is currently being developed at the Institute of Construction Materials at the University of Stuttgart, which is intended to examine concretes in particular for this problem. First preliminary test in a simplified procedure have already confirmed the basic idea of testing.

ABSTRACTEnvironmentally assisted cracking (EAC) is a potential threat to the safety and integrity of water-wetted components in operating water-cooled nuclear power plants. Two forms of EAC are commonly distinguished, depending on the form of loading contributing to damage: stress corrosion cracking (SCC) and corrosion fatigue. A number of instances of in-service degradation due to EAC have occurred in operating plants worldwide, often leading to unplanned plant outages. Understanding the causes of EAC is essential to minimise the loss of plant availability due to its occurrence and to avoid the possibility of catastrophic failure, for example, if a crack grew to a critical size in a major pressure boundary component. This paper will describe some examples of these phenomena in the main materials of construction of pressure boundary and other critical components in pressurised and boiling water reactors (BWRs). Over the last several decades, substantial research programmes have been carried out in a number of laboratories worldwide, aimed at further understanding of the processes leading to EAC to manage occurrences in plant and minimise future failures. Selected areas of research on EAC in light water reactor environments are discussed. Corrosion fatigue in low-alloy pressure vessel steels was the subject of considerable attention in the 1980s and early 1990s because of its potential threat to pressure vessel integrity and the publication of data, suggesting that there is a major influence of environment on fatigue crack growth in some laboratory tests. The author’s research provided insight into the conditions under which the major environmental effects occur and contributed to the development of an ASME Code Case for pressurised water reactor (PWR) conditions which provided a means of screening based on steel sulphur content and loading conditions. More recently, the research focus in this area has moved to austenitic stainless steels, again providing support to Code Case development and furthering mechanistic understanding. A recent review of knowledge gaps for EPRI provides a basis for future research on environmentally assisted fatigue and will inform the development of new assessment methodologies. A key area of the current study concerns differences in loading conditions between specimens in laboratory tests and plant components subject to transient loading. In the case of SCC, stainless steels have shown the greatest propensity to cracking in BWRs, while Alloy 600 has been a major cause of in-service failures in PWRs, both on the primary side, as recognised by Coriou in the early 1960s, and in secondary environments where a number of different corrosion-related failure processes have been identified. High-strength alloys, such as Alloy X-750 used for fastener applications, have also caused failures in both reactor types. For austenitic materials, SCC susceptibility is enhanced by irradiation, resulting in failures in core internals components. Ferritic stainless steels also undergo SCC under some specific circumstances but are generally more resistant than the lower chromium austenitic materials.

For centuries timber has been the most popular construction material. However, over the last few decades, it gave way to man-invented structural materials, it is still willingly used in civil engineering, commonly for roof constructions, ceilings but also small bridges, lookout towers. Sometimes, as a result of environmental deterioration or changes in load conditions, timber structure requires to be strengthened. Flexural or tensile performance could be simply increased by using external fiber reinforced plastic (FRP) composite sheets or strips. Such type of reinforcement almost does not change the geometry, but uncovered may be exposed to environmental influences including sunrise heating. Its temperature can exceed 70°C, while commonly as save is considered temperature below 45°C. Paper describes the bending tests of timber beams externally strengthened with three types of composites: unidirectional CFRP sheet, CFRP strip and SRP tape. Beams were heated in the various ranges of temperatures and tested in flexure. Among nine tested beams only one, heated to 95°C failed by delamination of composite overlay, the remaining beams reinforced with CFRP strips and SRP tapes could not be destroyed due to deflection outside the press cylinder range, while beams strengthened with CFRP sheets failed after rupture of carbon fibers. Experiment results show that independently of the type of reinforcement danger temperatures can be recognized over 90°C. Under that temperature behaviour of heated beams is only slightly worse than tested in room temperature and differences are visible in deflections. As a result of slippage in the adhesive layer weakened by temperature measured deformation growths. This trend applies to both CFRP strip and sheet strengthened specimens. It should be emphasized that the obtained results are much better than in the case of commonly tested reinforced concrete beams, which were subjected to delamination failure just a little above 65°C.

This article is devoted to improving heat utilization systems for industrial and municipal heat supply. It outlines methods for enhancing the cooling systems of kilns used in the firing of construction materials, identifies ways to stabilize the thermal regime, and establishes the conditions for developing functional layouts for furnace units. Rotary kilns, operating under varying environmental influences such as air temperature, wind speed, solar radiation, and atmospheric precipitation, lose up to 30% of their heat through the lateral surface into the surrounding environment. These external factors negatively affect the thermal condition of the furnace unit, leading to overheating during warm periods and overcooling in cold seasons, which in turn decreases the durability of the lining and the quality of the produced materials. Typically, natural cooling of the kiln side surface is assumed in order to maintain the necessary internal surface temperature and extend the lining’s lifespan. However, this is an uncontrolled process with the aforementioned disadvantages. One approach to increasing the efficiency of fuel combustion heat utilization is the implementation of a regulated cooling system for rotary kilns. One possible solution is a recirculating channel design, which relies on the repeated use of the heat carrier flow. The share of recirculated flow increases as outdoor temperature decreases. Under summer design conditions, the system operates as a direct-flow type, delivering the entire stream to end users. In winter conditions, air is supplied from the bypass line. Based on these considerations, formulas are derived for determining the main parameters of the stabilizing cooling system for rotary kilns, intended for residential and municipal heat supply applications.