Durability of Concrete Research Papers (original) (raw)

This paper shows the best behaviour of Na2SO4 among other activators of portland blast furnace slag cement. Sodium silicate, extensively used in alkali activated slag, has a poorer performance than Na2SO4 in the presence of Ca(OH)2. Depending on the characteristics of cement and activator, Na2SO4 can increase the early strength gain of blast furnace slag cements without significantly affecting long term compressive strength. A use of sodium sulfate - rich waste could be an environmental solution for waste disposal but further studies will be necessary

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- Durability of Concrete
- by Maryiam Osama
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- Concrete, Durability of Concrete, Alkali Carbonates

Concrete is a porous material. The size and distribution of pores in concrete varies, depending upon the quality of compaction, the materials, the water-to-cement ratio and the degree of hydration. Many of these pores are inter-connected creating larger and more complex pore systems. Water can penetrate this network and cause deterioration of the concrete structure. Silanes have been generally used in the past to help protect reinforced concrete exposed to an aggressive environment. The treatment works as a pore liner, thus ...

- by Simon Austin
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- Corrosion Science, Recycling, Durability of Concrete, Cement and Concrete Materials

Laboratory tests were carried out to investigate the effect of steel fibres and recycled aggregate on the drying shrinkage and creep deformations of concrete. Steel fibres (Dramix 3D 65/35BG) were added to the mixes and washed construction and demolition wastes (CDW size 20mm) were used as a coarse recycled aggregate. The main variables of this study are the steel fibre contents; Vf = 0, 0.5 and 1.0% and the recycled aggregate replacement percentages; RP= 0, 50 and 100%. Small prisms (75×75×200mm) and bobbins (75×365mm) were cast (for 9 mixes), cured (for 28 days) and tested (for up to 90 days). A fine natural aggregate was used in all mixes and the amount of cement and the water-to-cement ratio was kept constant. The results showed that there are significant increments in drying shrinkage, compressive creep and tensile creep by 18%, 15% and 8% were recorded respectively when 50% of the recycled aggregate was used. However, when 100% of the recycled aggregate was replaced, the following results were achieved 38%, 29% and 15% respectively. In contrast, the effect of adding 0.5% of steel fibres content recorded reductions in these deformations (drying shrinkage, compressive creep and tensile creep) by 7%, 3% and 10% respectively. However, further reductions with percentages of 15%, 5% and 20% respectively were seen when 1.0% of fibre content was added. Interestingly, steel fibres had a significant effect on tensile creep and shrinkage, but little effect on compressive creep.

- by Lamen Sryh and +1
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- Concrete, Concrete Technology, Durability of Concrete, Concrete structures

The objective of this study is to develop a new generation of alkali-silica reaction (ASR) inhibiting powder additives or liquid chemical admixtures for concrete. Throughout the paper, the word additive primarily refers to a powder while admixture primarily refers to liquid (pre-dissolved powder); otherwise, the two terms are used interchangeably. These additives are cheaper and more abundant than lithium admixtures, yet provide more consistency in terms of quality, supply, and performance in comparison with supplementary cementitious materials (SCMs). A methodical approach was developed to identify such additives that primarily mitigate ASR by reducing the pH of concrete pore solution. The mechanism of pH reduction was identified and the set of criteria that a potential additive must meet were developed. The suitable additives were screened using ASTM C1293 as well as mortar tests to estimate their impact on the performance of concrete. A final list of seven promising additives was identified.

- by Tiffany Szeles
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- Concrete Admixtures, Durability of Concrete, Alkali Silica Reaction

Smelting and processing of hazardous air-cooled FeMn slag to recover FeMn-alloy of suitable composition for export was found to be feasible and economically viable. The slag resulting from the smelting was water-granulated and produced... more

- by Rupert E Oberholster
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- Durability of Concrete, Alkali Silica Reaction

In the present paper, a numerical and experimental study about creep and shrinkage behavior of a high strength self-compacting concrete is performed. Two new creep and shrinkage prediction models based on the comprehensive analysis on the available models of both conventional concrete and self-compacting concrete are proposed for high strength self-compacting concrete structures. In order to evaluate the predictability of the proposed models, an experimental program was carried out. A concrete which develops 60 MPa within 24 h was used to obtain experimental results. Several specimens were loaded: (i) at different ages and (ii) with different stress-to-strength ratios. Deformation in non-loaded specimens was also measured to assess shrinkage. All specimens were kept under constant stress during at least 600 days in a climatic chamber with temperature and relative humidity of 208C and 50%, respectively. Results showed that the new models were able to predict deformations with good ac...

- by Lino Maia
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- Civil Engineering, Concrete, Concrete Technology, Precast Concrete

This paper presents an overview of research activities carried out by the authors and aiming to investigate the possibility of using recycled concrete aggregates in the production of concrete mixes. It evaluates the effect of these aggregates on the physical, mechanical and durability properties of concrete, as well as the applications of the recycled aggregate concretes.
Статья представляет собой обзор исследовательской деятельности, проведенной авторами для изучения возможности использования заполнителей из рециклированного бетонного лома при производстве бетонных смесей. Исследуется влияние этих заполнителей на физические, механические свойства и долговечность бетона, а также области применения бетонов с утилизированными заполнителями.

In this experimental study, the impact of Portland cement replacement by ground granulated blast furnace slag (GGBFS) and micronized rubber powder (MRP) on the compressive, flexural, tensile strengths, and rapid chloride migration test (RCMT) of concrete were assessed. In this study, samples with different binder content and water to binder ratios, including the MRP with the substitution levels of 0%, 2.5% and 5%, and the GGBFS with the substitution ratios of 0%, 20% and 40% by weight of Portland cement were made. According to the results, in the samples containing slag and rubber powder in the early ages, on average, a 12.2% decrease in the mechanical characteristics of concrete was observed, nonetheless with raising the age of the samples, the impact of slag on reducing the porosity of concrete lowered the negative impact of rubber powder. Regarding durability characteristics, the RCMT results of the samples were enhanced by using rubber powder because of its insulation impact. Moreover, adding slag into the MRP-included mixtures results in a 23% reduction in the migration rate of the chloride ion averagely. At last, four mathematical statements were derived for the mechanical and durability of concrete containing the MRP and GGBFS utilizing the genetic programming method. KEYWORDS Micronized rubber powder; ground granulated blast furnace slag; waste materials; mechanical properties; durability Ground granulated blast furnace slag is one of the by-products of the steel plant that does not react if water is added to it. Unlike pozzolans, which react with and consume calcium hydroxide from cement This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Durability of concrete has been at the forefront of concrete technology and worldwide attention for over three decades due to the premature deterioration of many concrete structures resulting in reduced service life and expensive maintenance and rehabilitation. Despite this emphasis on durability of concrete, however, a significant number of stakeholders are still under the misconception that strength alone is the only specified criterion which can ensure quality, durability and final acceptance of concrete. It is recognised that most concrete requires a minimum level of strength for structural design purposes irrespective of the application. However, this misplaced emphasis on strength alone, and the false thinking that durability of concrete materials and concrete structures is a by-product of compressive strength is fundamentally flawed and unacceptable and not consistent with specified requirements. It must be emphasised that concrete structures very rarely fail due to lack of built-in strength. On the other hand, deterioration processes and built in maintenance from the birth of a structure do occur due to reduced durability which can adversely affect the required service life of concrete structures and put unnecessary strain on maintenance budgets. To address the importance of durability and the misplaced emphasis on strength alone, the durability provisions of AS 5100 Part 5 (2017) were further enhanced and additional parameters and requirements have been introduced since the 2004 edition, to reflect current knowledge and practice, knowledge of applied research, and many years of application and monitoring of these durability provisions on bridges and other structures for major infrastructure, constructed over at least the past 25 years. This paper discusses some of these durability provisions and provides a technical basis for their importance to the delivery of durable concrete bridges and related structures for major infrastructure. Durability issues discussed include the specification of minimum cementitious material content, delayed ettringite formation (DEF) expansion, temperature differential not to exceed 20 ºC, the suggested use of maturity testing to govern curing periods for major infrastructure and supplementary cementitious materials cement replacement levels.

Addressing the use of reinforced concrete for restoration at archaeological sites, Paola Pesaresi, the conservation architect with the Herculaneum Conservation Project, reviews how concrete was employed at Herculaneum during the first half of the twentieth century, and how the subsequent deterioration of the concrete elements incorporated into the site is now being handled by authorities there.

- by Konstantin Kovler and +1
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- Civil Engineering, Construction Materials, Concrete, Recycling
- by Chrysanthos Maraveas
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- Engineering, Structural Engineering, Concrete, Fire Protection

أجريت هذه الدراسة لغرض الوصول إلى نتائج معملية واضحة عن تأثر خواص الخرسانة المتمثلة في مقاومتها للضغط والخواص التي لها علاقة مباشرة بديمومتها مثل: المسامية، نسبة الامتصاص والنفاذية وذلك عند إضافة نسب مختلفة من ألياف البولي بروبالين إلى الخلطة الخرسانية. حيث تم في هذه الدراسة استخدام نسب إضافة للبولي بروبالين ضمن الحدود المسموح بها في المواصفات (0.05 – 0.2%) من حجم الخرسانة وأكثر منها بنسبة إضافة (0.4%) لمقارنتها مع نتائج العينات المرجعية للخرسانة المصنعة بدون ألياف.
أثبتت النتائج النهائية لهذه الدراسة أن إضافة ألياف البولي بروبالين للخرسانة بنسبة (0.1%) من حجم الخرسانة (والتي تعادل 0.9 كجم/م3) يعمل على تقليل مساميتها ونسبة امتصاصها وكذلك نفاذيتها إلي أقل ما يمكن بالمقارنة مع بقية العينات، وإن زيادة استخدام هذه الألياف بنسب إضافة أعلى يجعل من الخرسانة أكثر مسامية وشراهة على امتصاص الماء وأكثر نفاذية. كذلك بينت نتائج مقارنة تأثير إضافة ألياف البولي بروبالين على عينات مصنعة من خرسانة ذات مقاومات ضغط مختلفة ازدياداً واضحاً في قيم المسامية ونسب الامتصاص والنفاذية للعينات ذات مقاومة الضغط الأعلى بالمقارنة مع نظيرتها من العينات ذات المقاومة الأقل. كما أظهرت النتائج أيضا عدم جودة استخدام ألياف البولي بروبالين في تحسين مقاومة الخرسانة للضغط وذلك عند إضافتها بأي نسبة، لذلك يجب أن يراعى هذا التأثير في الاعتبارات التصميمية للعناصر الانشائية المصنعة من هذا النوع من الخرسانة.

- by Igino Giordani
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- Concrete, Non Destructive Testing, Digital Radiography, Durability of Concrete

The review article investigated failure, design issues, repair and strengthening of reinforced concrete (RC) silos, primarily in agricultural set-ups. The durability of RC structures was influenced by the nature of the bulk solids, materials used in the reinforcement of the structures. Traditionally, high-grade steel has been used in silo wall reinforcement because it is affordable and readily available. However, it is susceptible to corrosion. In contrast, fiber-reinforced polymers (FRP) have better mechanical properties (tensile strength, elastic modulus, and Poisson’s ratio) and are not corroded. Additionally, there are limited scalable and facile methods for commercial production. The low ductility elevates the risk of brittle fracture in external pre-stressing concrete repair/strengthening. Beyond the material factors, the existing silo design codes such as BS EN 1991-4:2006, Australian Standard AS 3774-1996, and American Society of Agricultural Engineers ANSI/ASAE EP433 DEC198...

- by Amirreza Talaiekhozani and +1
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- Civil Engineering, Concrete, Concrete Technology, Self-healing
- by Anand Bhattad and +2
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- Concrete Technology, Concrete Admixtures, Durability of Concrete
- by mouna boumaaza
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- Durability of Concrete, Carbonation of Concrete

Crack formation and progression under tensile stress is a major weakness of concrete. These cracks also make concrete vulnerable to deleterious environment due to ingress of harmful compounds. Crack healing in concrete can be helpful in mitigation of development and propagation of cracks in concrete. This paper presents the process of crack healing phenomenon in concrete by microbial activity of bacteria, Bacillus subtilis. Bacteria were introduced in concrete by direct incorporation, and thorough various carrier compounds namely light weight aggregate and graphite nano platelets. In all the techniques, calcium lactate was used as an organic precursor. Specimens were made for each mix to quantify crack healing and to compare changes in compressive strength of concrete. Results showed that bacteria immobilized in graphite nano platelets gave better results in specimens pre-cracked at 3 and 7 days while bacteria immobilized in light weight aggregates were more effective in samples pre-cracked at 14 and 28 days. In addition, concrete incorporated with bacteria immobilized in light weight aggregate, also exhibited significant enhancement in compressive strength of concrete.

- by Wasim Khaliq and +1
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- Concrete, Concrete Technology, Durability of Concrete, Cement and Concrete Materials

Concrete is one of the most important building materials worldwide. One problem with its properties is the low ductility. This brittle behavior allows easy initiation of
natural cracks in the structure, where the cracks introduce water into the concrete matrix which will promote corrosion of the rebar system. To prevent such deterioration, regular
inspection of cracks in concrete structures and their repair are usually carried out by means of some kind of human intervention. On the other hand, for example, a small cut on our body can be healed by a simple treatment even though it takes a couple of days. To solve this problem and reduce maintenance and repair, the cracks should be closed. When these cracks are closed by the parent material itself, this phenomenon is called self-healing. In order to
initiate self-healing in concrete, preconditions have to be fulfilled, i.e. sufficient unhydrated cement in the matrix, a small and stable crack width, and sufficient water for hydration.
Concrete can now be engineered to have a small and stable crack width, combined with an sufficient amount of unhydrated cement. These factors will only support self-healing if water is available. To ensure this water is available inside the crack after cracking of the matrix, water should be encapsulated with a sealing material and embedded inside the matrix. There have been many recent developments in the production of more durable concrete, namely that of self-healing concrete. In this paper different types of self healing methods for concrete are discussed, including self healing with the help of bacteria, popularly known as microbial concrete. From the study, it is concluded that Crack healing of early age cracks does occur and complete recovery of strength is possible when certain conditions are fulfilled.

- by Umer Farooq and +1
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- Concrete Technology, Crack propagation, Durability of Concrete, Concrete cracks

The use of cement and concrete is becoming increasingly widespread all over the world. However, the high energy consumption required for the production of clinker and the greenhouse gas emissions generated during production negatively affect both the economy and the environment. In the studies conducted for many years, researchers have found that the substitution of various pozzolans with cement provides both technical advantages and environmental benefits. The use of pozzolans in cementitious composites provides advantages such as the improvement of the physical and mechanical properties of the material, the conservation of the environment and the economy in terms of the evaluation of industrial wastes. In recent years, studies on the use of nanoparticles in cementitious composites are positively. In this study, it was aimed to investigate the properties of fresh and hardened cement mortars using micro silica as pozzolan and nano silica as nanoparticle. For this purpose, four different cement pastes and mortars mixtures were prepared by substituting 0%, 1%, 2%, 3% nano SiO2 (silica) cement in mortar mixtures containing 5% micro silica. The effects of the nano silica on the micro silica-containing cement paste on the consistency and setting time were investigated. The mortar mixtures produced were subjected to flexural and compressive strength tests on days 7, 28 and 90 th. SEM images of mortar mixtures were taken. As a result, it was found that 2% nano silica ad-mixture of 5% micro silica containing cement admixture affects the flexural and com-pressive strength positively, whereas 2% nano silica admixture increased the flex-ural strength by 13% and compressive strength by 7%.

- by Ilknur Bekem
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- Concrete Technology, Durability of Concrete, Cement, Cement and Concrete Materials

Polimer esaslı üretilen betonlar ve özellikleri

Comprehensive study was made of compressive and flexural strengths by different
types of portland cement used in concretes mixed, placed, and cured at various
temperatures, and includes tests indicate that there is a temperature during the early
life of concrete which is considered optimum with regard to strength at later ages.
This objective provides an overview of the effects of temperature on the behavior of
concrete materials and structures. In meeting this objective the effects of temperatures
as it elevates and depresses from ambient temperature, are worked out.
This paper also deals with the procedure and precautions to be observed while
concreting in extreme weather conditions- hot and cold weather so as to minimize the
detrimental effects of weather on concreting in general types of construction, such as
buildings, bridges, highways, pavements and other similar structures.

The health diagnosis of agricultural structures is critical to detecting damages such as cracks in concrete, corrosion, spalling, and delamination. Agricultural structures are susceptible to environmental degradation due to frequent exposure to water, organic effluent, farm chemicals, structural loading, and unloading. Various sensors have been employed for accurate and real-time monitoring of agricultural building structures, including electrochemical, ultrasonic, fiber-optic, piezoelectric, wireless, fiber Bragg grating sensors, and self-sensing concrete. The cost–benefits of each type of sensor and utility in a farm environment are explored in the review. Current literature suggests that the functionality of sensors has improved with progress in technology. Notable improvements made with the progress in technology include better accuracy of the measurements, reduction of signal-to-noise ratio, and transmission speed, and the deployment of machine learning, deep learning, and arti...

The objective of this paper is to enhance the reduction of corn cob wastes and reduce the cost of concrete production by using locally available materials. Physical and mechanical properties of varying percentage of CCA cement concrete and 100% cement concrete of mix 1:2:4 and 0.5 water-cement ratios were examined and compared. A total of 72 concrete cubes of size 150 A? 150 A? 150 mm3 and 12 concrete cylinders of size 100mm (diameter) x 200mm (height) with different percentages by volume of CCA to Portland cement in the order 0:100, 10:90 and 20:80 were cast, tested and their physical and mechanical properties determined. A high strength (35MPa) concrete was further designed using CCA as a partial replacement for cement with a total of 32 concrete cubes (16 samples each for 0% and 10% partial replacements) and 8 concrete cylinders (4 samples each of 0% and 10% partial replacements). The specific gravity of the CCA was 1.15, while the mechanical properties which included compressive...

- by Oladipupo Olafusi
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- Materials Science, Concrete, Concrete Technology, Durability of Concrete

This paper presents the effects of silica fume on compressive strength, splitting tensile strength, resistance against chloride penetration and water absorption of concrete. Results indicated that the use of silica fume in concrete increased the compressive strength of concrete. Increase in water-binder ratio reduced the compressive strength of concrete irrespective of the use of silica fume. Silica fume had no noticeable effect on the splitting tensile strength of concrete. The resistance against chloride ion penetration increased with the increase in the contents of silica fume in concrete. A reduction in water-binder ratio (from 0.35 to 0.30) increased the ability of the concrete to resist chloride ion's penetration. The introduction of silica fume in concrete reduced the water absorption capacity of concrete. A change in water-binder ratio also dramatically reduced the water absorption of concrete.

- by Muneeb Qureshi
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- Civil Engineering, Structural Engineering, Concrete, Concrete Technology

Português:
O incêndio sempre representou um risco às edificações, comprometendo a segurança estrutural e humana. É de interesse da engenharia civil a análise de edifícios em situação de incêndio, para que se possa prevenir o colapso prematuro da estrutura.Este trabalho tem como objetivo analisar, numericamente, a variação de temperatura nas seções transversais de vigas de concreto armado em situação de incêndio, levando em consideração a compartimentação do ambiente em chamas e material celulóstico como combustível. O estudo utiliza o software ANSYS 16 com verificação do transiente do gradiente térmico na peça. Foram utilizados modelos tridimensionais para a obtenção dos gradientes e determinação da envoltória de 500ºC. Os resultados foram comparados com a ISO 834, NBR 14323 e EUROCODE 1-2,os quais apresentam ábacos com as máximas temperaturas das seções transversais das vigas e linhas isotermas pré-estabelecidas. Encontrou-se uma pequena divergência na angulação das isotermas em comparação com os ábacos analisados, espera-se que em decorrência da discrepância de fatores utilizados nas simulações e no ábaco.
English:
Fire has always represented risk to buildings, compromising structural and human safety. It is an interest of structural engineering the analysis of buildings under fire conditions to prevent the premature collapse of the structure. This paper has the objective to numerically analyze the temperature range in transversal sections of reinforced concrete beans under fire circumstances, considering ambient divisions and cellulosic fuel. The study uses the software ANSYS 16 within verification of the transient thermal gradient in the beam. There was used three dimensional models to obtain the gradients and determine the 932 Fahrenheit envelopment, including thermal structural analysis. The results were compared to ISO 834, NBR 14323 and EUROCODE 1, which shows graphs with the maximum temperatures of the beams sections, and some pre-established isothermal lines. There was found a little divergence in the angulation of isothermals in comparison with the analyzed graphs, it is thought to be caused by the discrepancy of the simulation and the graph used data.

- by Daniel Blanco Lombardi and +2
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- Structures and Fire Engineering, Structural Fire Safety, Durability of Concrete, Segurança Contra Incêndios

High Performance Concrete (HPC) is now a days used widely in the construction industry worldwide. To produce HPC with normal ingredients one use mineral admixtures like silica fume, fly ash and metakoline. In addition admixtures including Superplasticisers are also used. This paper investigates the effect of silica fume (SF), added in varying percentages (0, 3, 5, 7.5, 10, 12.5%), on concrete strength. Superplasticiser-(Viscocrete Tempo 12)-was added to the concrete mixtures as well. Compressive strength, shear strength and tensile strength tests were conducted, and the results were discussed. Results showed that the compressive strength changes with the varying percentage addition of silica fume. The highest compressive strength (88 MPa) was obtained when the percentage of silica fume was 7.5 % of the cement weight. Beyond 7.5 % silica fume, the compressive strength started descending. Tensile and shear strength were found to vary in an inverse relationship with the increasing percentage of silica fume. A significant reduction in tensile strength and shear strength were recorded when the silica fume percentage is increased. However, the 10% ratio between tensile and compressive strength for normal concrete, was not found to be, relevant for HPC with SF.

The objective of this research is to investigate the effectiveness of using waste plastic as fine aggregate replacement in concrete mixtures. The compressive and tensile strengths of various concrete specimens were tested to determine how the incorporation of recycled plastic as a replacement fine aggregate would affect the development of strength in the mixes. Six mixes were compared at replacement increments of 0%, 10%, 20%, 30% and 50%. All stages of plastic replacement showed a noticeable decrease in compressive strength. The 10% replacement level only showed a 15% loss of compressive strength at 21 days compared to the control. Despite being much weaker in compression, the tensile strength test showed that the 10%, 20% and 30% replacement increments were stronger in tension compared to the control.

- by M.R.V.S.G. Guptha, CIVIL, DIET and +1
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- Civil Engineering, Concrete Technology, Durability of Concrete, Concrete Durability

L’idée de recycler les bétons est apparue dans le but principal de préserver l’environnement et de s’intégrer ainsi au concept de développement durable. En effet, la réutilisation des bétons en tant que granulats dans des nouvelles compositions de béton permet de réduire les dépenses sur la gestion des déchets de démolition et, surtout, de protéger les gisements et les montagnes contre l’ouverture de nouvelles carrières. Les granulats provenant du recyclage de bétons peuvent remplacer une partie de granulats naturels lors de la fabrication de nouveaux mélanges de béton. Les taux de substitution des granulats naturels dans cette recherche sont 10, 20 et 30 %.
Le but de cette recherche est d’étudier expérimentalement l’influence des granulats recyclés sur les propriétés du béton telles que sa résistance à la compression, son ouvrabilité et sa porosité, ainsi que sa durabilité.

- by Pierre Matar
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- Concrete, Recycling, Recycled Construction Materials, Recycled Materials

Some countries started to recycle concrete material in order to reuse it in structural or other issues. Some of them, like Germany, Australia and Canada have established their own recommendation guide for recycling concrete. This recycling consists of crushing old concrete into aggregates, and then processing it into new mixture using the recycled aggregates with specified sizes. The aim of this recycling is to save nature from deforestation and dryness, by reducing the need to gravel and so the quarries work, and also to economize the waste management.
The present research work consists of an experimental study treating the impact of using recycled aggregates on the concrete behavior and on the country’s economy. We are especially interested in determining the best composition for the new mixture of concrete resulting from reusing different types of recycled aggregates. Different types of tests have been done depending on the aggregates sizes, their origin and their state (burned or safe). The analysis is based on the comparison between compressive strength, water-cement ratio, slump, porosity and durability. Otherwise, the impact on economy is analyzed, a priori, by studying the effect of reducing the price of the resulting concrete on construction spending. The resulted recommendations indicate the sizes of aggregates which may constitute the best composition for recycling and processing concrete, and the best use for each type of concrete depending on behavior and economy effect.

- by Pierre Matar and +1
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- Concrete, Recycling, Recycled Construction Materials, Recycled Materials

Drugi tom kompleksowego podręcznika poświęconego diagnostyce konstrukcji żelbetowych obejmuje problemy badania zagrożenia trwałości budowli z betonu pod wpływem oddziaływania środowiska. Mając na względzie najnowsze przepisy projektowania zawarte w Eurokodzie 2 (PN-EN 1992-1-1:2008) przedstawiono kolejno: oddziaływanie środowiska na żelbet, korozję zbrojenia, badania właściwości ochronnych betonu, elektrochemiczne pomiary zagrożenia korozją zbrojenia w konstrukcji oraz elektrochemiczne badania laboratoryjne próbek pobranych z konstrukcji.
Podano również przykłady przeprowadzonych badań zawierające opis metody pomiaru, sposobu analizy i interpretacji wyników. Szczegółowo omówiono urządzenia badawcze dostępne w kraju i na świecie. Książkę zilustrowano rysunkami, schematami badań i fotografiami urządzeń. Podręcznik jest przeznaczony dla studentów wydziałów budownictwa, inżynierii lądowej i architektury oraz inżynierów praktyków i rzeczoznawców budowlanych.

RESUMO: Túnel é definido como uma passagem subterrânea que pode, ou não, ter sido moldado pela ação humana. Quando inserido em um sistema de transporte, o túnel atrai parte do tráfego e integra o percurso diário da população. As condições de utilização das estruturas garantem a segurança dos motoristas e pedestres, evitando desconfortos e acidentes. Na cidade do Recife, existem cinco túneis semienterrados, e todos apresentam sinais de deterioração. Grande parte desssas manifestações patológicas presentes nas estruturas são causadas pela influência da água da chuva e do lençól freático sobre a mesma, pois se comportam como agentes de degradação física, química e biológica. O presente artigo científico tem como objetivo caracterizar as manifestações patológicas mais recorrentes nas estruturas dos túneis da cidade do Recife e analisar como as águas influênciam na evolução dos citados processos de degração. Para ter uma melhor visão dessa influência, as inspeções foram realizadas no período compreendido entre os meses de maio e junho de 2017, período tradicional de precipitações intensas no Recife. Após as inspeções ficou evidente que as estruturas inadequadamente protegidas ou originalmente projetadas para condições menos agressivas, quando em contato prolongado com as águas de precipitações e ou do lençol freático apresentam sinais de degradações mais intensas. Os túneis recentemente construídos, que têm o histórico de algamentos e percolação constante de águas, se igualam aos mais antigos no desenvolvimento de manifestações patológicas. Falhas de projeto e execução, ausência de manutenção e impermeabilização precária são os outros fatores contribuintes para a situação atual de degradação acelarada das estruturas, pois o convívio da água com obras subterrâneas é tecnicamente possível, desde que estejam previstas no projeto, sejam adequadamente executadas e preventivamente mantidas.
ABSTRACT: Tunnel is defined as an underpass that may or may not have been shaped by human action. When inserted in a transport system, the tunnel attracts part of the traffic and integrates the daily route of the population. The conditions of use of the structures guarantee the safety of the drivers and pedestrians, avoiding discomforts and accidents. In the city of Recife, there are five tunnels half-buried, and all show signs of deterioration. Most of these pathological manifestations present in the structures are caused by the influence of rainwater and the water table on them, since they behave as agents of physical, chemical and biological degradation. The present scientific article aims to characterize the most recurrent pathological manifestations in the tunnels structures of the city of Recife and to analyze how the water influences the evolution of the aforementioned degration processes. In order to have a better view of this influence, the inspections were carried out in the period between May and June 2017, a traditional period of intense rainfall in Recife. After the inspections it was evident that structures inadequately protected or originally designed for less aggressive conditions, when in prolonged contact with the precipitation waters and or the water table show signs of more intense degradations. The newly constructed tunnels, which have a history of gouges and constant percolation of water, are similar to the older ones in the development of pathological manifestations. Failures of design and execution, lack of maintenance and poor waterproofing are the other contributing factors to the current situation of accelerated degradation of the structures, since the water conviviality with underground works is

- by Ramon Duque
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- Concrete, Durability of Concrete, Tunnel Engineering, Degradation of Concrete

The purpose of this experiment is to obtain the tensile, known as “Modulus of Rupture”, strength of the concrete material and the wood material using flexural tests performed on concrete beams. Tests specimen: • two beams one with steel... more

The purpose of this experiment is to obtain the tensile, known as “Modulus of Rupture”, strength of the concrete material and the wood material using flexural tests performed on concrete beams.
Tests specimen:
• two beams one with steel reinforcement and one without • two timber beams

- by Ermand Mani
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- Concrete, Concrete Technology, Reinforced Concrete Structures, Durability of Concrete
- by Ashok Reddy A.
- •
- Civil Engineering, Structural Engineering, Concrete, Concrete Technology

The present study investigates the performance of self-compacting concrete (SCC) and self-compacting sand concrete (SCSC) incorporating recycled concrete fines and aggregate under different sulphate environments. Similar mixtures incorporating natural aggregates and natural pozzolana were also tested for comparison. Different sulphate attack regimes (i.e. fully submerged and immersion-drying cycles) were applied. Compressive strength development/degradation under sulphate attack was monitored for all tested mixtures. Results indicate that the use of recycled materials did not significantly affect the strength development with respect to mixtures with natural materials. Moreover, mixtures incorporating recycled concrete aggregate and fine recycled concrete exhibited a better sulphate resistance behaviour than those with natural aggregates and natural pozzolana. In conclusion, the quality of the used recycled materials is a key factor in producing green and sustainable self-compacting...

Nel presente lavoro di tesi, dopo una breve introduzione storica sulla nascita del calcestruzzo armato e sulle sue proprietà, si illustreranno i meccanismi con cui si può produrre il degrado nelle strutture realizzate con questo materiale, analizzando i fattori ambientali e di progetto che maggiormente influiscono sulla funzionalità e la sicurezza di tali opere, trattando poi alcuni metodi di prevenzione del degrado e tecniche di ispezione. Tali argomenti risultano utili per affrontare il caso di studio del viadotto sul Polcevera, detto anche ponte Morandi in riferimento all'ingegnere che l’ha progettato, vittima di un ambiente fortemente aggressivo, posto nelle vicinanze del mare e di un complesso industriale, ma anche di una scarsa attenzione alla manutenzione, fattori che ne hanno determinato il collasso strutturale.

For getting the benifit of small crossection and maximum strength of the structures, The use of High
Strength Concrete (HSC) is increased. It is observed that HSC is relatively brittle material. Fibres are added to improve its
ductility. Experimental investigation is carried out to assess behaviour of high strength fibre reinforced concrete
(HSFRC) of grade M70. In addition to normal materials, silica fume, fly Ash and three types of fibres viz., Hooked end
steel Fibre, Flat steel fibre and waving steel fiber are used. The content of silica fume and fly ash is 5% and 10%
respectively by weight of cement. Water to cementitious material ratio was 0.27. Mixes are produced by varying types of
fibres and for each type of fibre its volume fraction is varied from 0.5% to 4.0 % with an increment of 0.5% by weight of
cementitious materials. 75 specimens each of cubes (150×150×150mm), cylinders (150×300mm) and prisms
(150×150×700mm) are tested to study the effect type and volume fraction of fibres on compressive strength, split tensile
strength and flexural strength of HSFRC. The results indicated significant improvement in mechanical properties of
HSFRC.

- by Mohamed Karim
- •
- Environmental Engineering, Malaysia, Highway engineering, Fluids

The matrix mixture of concrete can be made to have high compressive strength. In the present paper, statistical model was built-up to predict the compressive strength of concrete containing different matrix mixtures at fixed age or at different age of 1, 3, 7, 28, 56, 90 and 180 days. The model examines eight different parameters for the matrix mixture that includes: time, water, cement, metakaolin (MK), silica fume (SF), sand (S), aggregate (A)
and superplasticizer (SP). This research addresses the effect of the matrix mixture of concrete on the compressive strength, where this information will help the cement industry in producing the required concrete strength. The results from the predicted model have high correlation to the experimental results for the concrete compressive strength.

- by Mahmoud SAYED AHMED
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- Structural Engineering, Construction Technology, Concrete, Recycling

Bu kitabın amacı; İstanbul ve çevresi taş-doğal agrega ocaklarını böyle bir kitapcıkta toplamak ve genelde sağlam, dayanıklı ve ekonomik yapıların inşaasında kullanılması zorunluluğu olan bu taş ve kum ocaklarının özelliklerini göz önüne kayarak, inşaaat sahibine, kullanıcıya, yapımcıya ve kontrol edenlere bir ışık tutmaktır. Kullanım alanlarının çok geniş olması ayrı özenle seçilmelerini gerektirmektedir.
Kitapta taş ve kum hakkında genel bilgiler verilmiştir. Ayrıca İstanbul civarı taşocakları Anadolu ve Rumeli taşocakları olarak iki ayrı grupta ele alınmıştır. Bu ocaklardan elde edilecek agregaların fiziki, mekanik ve petrografik özellikleri verilmiştir.
Günümüz yasaları göz önünde bulundurularak yeni bir taş ocağı açılımı sırasında takip edilecek yolun seçimi ve işletilmesinde lüzümlu tavsiyeler de bu kitapta verilmiştir. Necat CİLASON 1989.

- by Necat Cilason
- •
- Recycling, Durability of Concrete, Cement, Istanbul