a. a. ramezanianpour
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Self-compacting concrete has been considered as a step towards progress in concrete technology in recent years. Self-compacting concrete mixtures can be used in different structures with heavy reinforcement such as bridges, walls and foundations, without bleeding and segregation. The utilization of new materials such as natural and by-product materials that could probably decrease the CO2 emission of cement factories, is the main goal of this study. In this study in order evaluate the results of fresh and hardened properties of self-compacting concrete, Portland cement was replaced by (5%, 10% and 15%) natural zeolite and (20%, 30% and 40%) slag in the binary mixtures. The mixtures
incorporating ternary cementitious blends (ZS20, ZS30 and ZS40) were made with 10% zeolite and (20%, 30% and 40%) slag. These materials are acting both as the cementitious admixtures as well as the fine filler in self-compacting concrete. Properties such as slump flow, J-ring, V-funnel and T50 were investigated for evaluating the fresh properties of self-compacting concrete mixtures. Also mechanical test such as compressive strength of hardened concretes was carried out. Replacement of supplementary cementitious materials improved the compressive strength of mixtures especially at later ages. At 180 days, the highest compressive strength of mixtures containing zeolite, slag and ternary mixtures belonged to Z10, S30 and ZS30 with 58.5, 58 and 58.7 MPa respectively.Keywords: Self-Consolidating Concrete, Slag, Zeolite, Fresh Properties, Compressive Strength -
Chromium (VI) is a highly toxic heavy metal which may be present in cementitious materials (CM) within its constituting elements or external sources and could alter the structure of CM and reduce its compressive strength. Therefore penetration of chromium is an important consideration in environmental engineering concrete structures. For estimating diffusivity of chromium (chromate ion) in cementitious materials, this paper presents an accelerated migration test method for determining the non-steady-state migration coefficient following the simplified Nernst-Planck equation. Likewise, the influence of water-to-cement ratio (w/c), the applied voltage the chromium binding capacity of cement mortar specimen (CMS) and the realistic concentration profile was investigated. For calculation of migration coefficient, the color reagent diphenylamine sulfonate was identified to determine the penetration depth of chromium into the CMS visually. The concentration of chromium was estimated to be about 0.025 percent (wt of CMS) at the discolored border region, and a drop of potential about 3.4 volts was derived. The changes in the microstructure of the CMS due to chromium migration testing were studied. The migration coefficient of CMS obtained between 1.06×10-12 m2/s to 3.25×10-12 m2/s. The w/c of about 0.50 has the highest migration coefficient. The realistic chromium concentration profile in the migration test has a gradual front, and a quadratic curve obeys.
Keywords: Chromate Ion, Cementitious Materials, Migration Coefficient, Profile -
These days, in the structural designing, the durability properties of materials should be considered as significant as the other specifications. Deterioration of concretes in corrosive environments leads to considerable costs in order to maintain the reinforced concrete structures. Usage of industrial pozzolans can improve quality and serviceability of concrete structures in such environments. Nowadays, one of the most common pozzolans in structural concretes is the rice husk ash (RHA) which enhances the mechanical and durability properties of concretes. In this paper, effects of nano RHA on chloride permeability, compressive strength, electrical resistivity and capillary absorption of mortars have been investigated. The results showed that the incorporation of RHA nanoparticles gradually increased the compressive strength. It was found that a partial replacement of cement by nano RHA would enhance the durability properties of mortars in the long-term.
Keywords: Rice Husk Ash, Nano, Durability, Mortar, Mechanical Properties -
Chloride and sulfate ions damage the reinforced concrete in marine environment due tothe corrosion and formation of expansive products, respectively. Interaction of chloride-sulfate ions onconcrete deterioration is very complicated. Little research has been conducted in this respect.In this study, the effect of chloride ions on sulfate attack and effect of sulfate ions on chloride attack werereviewed. According to the results, contradictory reports were observed in studies. However, most of theresearchers believed that chloride ions mitigate the sulfate attack in combined chloride- sulfate solutions.On the other hand, regarding the influence of sulfate ions on chloride attack, some of the researchersreported the mitigating effect, but others referred to the accelerating effect. Tricalcium aluminate (C3A)content, water to cement ratio (w/c), duration of submerging, corrosive ions concentrations, cation type,type of pozzolan and its replacement are important parameters that could affect the concrete performanceagainst combined chloride-sulfate solution.
Keywords: Review, Combined Effect, Sulfate, Chloride, Concrete Durability -
Applications of concrete are expanding rapidly all over the world, in a way that approximately7% of the entire CO2 emit into the atmosphere by human pertains to the interventions made to nature in orderto produce concrete. Hence, the need for producing types of concrete that are more compatible with sustainabledevelopment is felt more than ever. Finding novel methods for making cement-based materials to reducecement consumption and the resulting pollution are of great importance among researchers. Improving theproperties of these materials using microbial calcite sediments is an environment-friendly technique with anacceptable performance. To improve the compressive strength of cement mortar, microbial calcite sedimentsproduced by Bacillus Subtilis and Sporosarcina Ureae bacteria types were used in this study. Recent studieswere also investigated in this paper. To examine the effect of the culture environment, two general designs(with and without extra urea) with different concentrations of zero to 106 cells per milliliter were developed.Moreover, to study the effect of the curing method, two processing curing schemes (in distilled water and ina mineral-containing nutrient environment) were considered. The results show the proper effectiveness of thismethod, in a way that up to 35% increase in the samples’ compressive strength may be observed depending onbacterium type and curing method.
Keywords: Cement Mortar, Bacteria, Microbial Precipitation, Sporosarcina Ureae, Bacillus Subtilis -
از آنجا که شرایط محیطی برای بررسی یک ماده ی جدید حائز اهمیت است.
مطالعه ی اثر پوزولان زئولیت در شرایط مختلف عمل آوری برای آشنایی با خواص ناشناخته یی که ممکن است در یک سیستم عمل آوری خاص نمود پیدا کند، در این پژوهش مورد توجه قرار گرفته است. در این نوشتار، اثر دو نوع سیستم عمل آوری شامل: 1. دائما اشباع در آب، 2. هفت روز نخست در آب و سپس در محیط آزمایشگاه با رطوبت و دمای متوسط در 12 طرح اختلاط با 4 نسبت آب به سیمان و 3٪ جایگزینی زئولیت مورد بررسی قرار گرفته است. اگرچه نتایج مورد انتظار آزمایش های بتن با کاهش نسبت آب به سیمان و یا افزایش سن در دو سیستم عمل آوری به طور محسوسی با یکدیگر متفاوت است، لیکن افزودن زئولیت روند مشابهی در هر دو سیستم عمل آوری به دنبال داشته است.کلید واژگان: دوام بتن، پوزولان طبیعی، زئولیت، خواص مکانیکی، عمل آوریConcrete is the most widely used construction material in the world today. However, the cement industry is intensively energy consuming, and the emission of CO2 during cement production has created enormous environmental concerns. Therefore, using pozzolanic materials as a partial replacement of cement could be a useful remedy. Usual pozzolans, such as fly ash, silica fume, high-reactivity metakaolin and slag, are rarely available and are relatively expensive in Iran, whereas natural zeolite is abundantly deposited and can easily be quarried and processed. Because of these advantages, it seems that zeolite can be a suitable alternative as a high performance and accessible pozzolan for use in the construction industry in Iran. On the other hand, when most people think of curing, they think only of maintaining moisture on the surface of the concrete. But, curing is more than that. It is giving the concrete what it needs to gain strength properly. Concrete strength depends on the growth of crystals within the matrix of the concrete. These crystals grow from a reaction between Portland cement and water, a reaction known as hydration. If there is not enough water, the crystals cannot grow and the concrete does not develop the strength it should. In this article, the effect of two curing systems was investigated: 1) saturated in water all the time, and 2) 7 days in water and after in the lab. So, concrete containing natural zeolite was built. The percentage of zeolite that replaced Portland cement in this research was 0%, 10%, and 15% by mass and the water/binder ratios were 0.35, 0.4, 0.45 and 0.5. Various experiments were carried out to determine the properties of concrete incorporating zeolite at these curing systems. Experimental tests included compressive strength, water absorption, and chloride diffusion at different ages. Generally, results showed that zeolite improved the mechanical and durability properties of concrete, especially in the second system of curing.
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به نحوی که در بسیاری از پل های کشور شاهد هستیم، به علت عدم اعمال سیستم مدیریت نگهداری پل ها، دامنه نارسایی ها به تدریج گسترش یافته و منجر به زوال مقاومت و افزایش آسیب پذیری پل ها شده است. به علت شرایط آب و هوایی گرم و مرطوب و وجود املاح در منطقه خلیج فارس در بسیاری از دال های بتنی سازه ها و پل های منطقه، علایمی از خرابی شامل ترک های متعدد و خرابیهای موضعی دیده می شود. لذا ارزیابی وضعیت دال های بتنی سبب می شود تا از پیشرفت خرابی، از سرویس خارج شدن و تعمیر سازه جلوگیری شود. در این مقاله سیستم خبره Bridge Slab-Expert ، برای ارزیابی خرابی دال های بتنی ارایه شده است. سیستم خبره، برنامه کامپیوتری هوشمندی است که دانش و روش های استنباط و استنتاج را به کار می گیرد، تا مسایلی را حل کند. این سیستم شامل مفسر، روش استنباط دانش محور و پایگاه داده می باشد. خرابی های عرشه پل به علت شرایط محیطی و سازه ای به صورت ترک خوردگی در بتن، نارسایی های سطحی و نارسایی های سازه ای مورد ارزیابی قرار گرفته است. چندین مطالعه موردی و مقایسه بین نتیجه های بازرسی فنی و سیستم خبره، جهت کسب قابلیت اطمینان و درستی نتیجه های سیستم انجام شده است. نتیجه های سیستم شامل شناسنامه دال پل بتنی، استنتاج سیستم خبره بهمراه نارسایی ها و علل آنها، شاخص وضعیت، توصیف وضعیت، راهکار پیشنهادی جهت تعمیر و نمودار عمر مفید دال بتنی است.
کلید واژگان: دال بتنی، ارزیابی خرابی، تشخیص خرابی، سیستم مدیریت پل، عمر خدمت دهی، سیستم خبرهAs we can see in many bridges in the country, due to the lack of implementation of the bridge maintenance management system, the range of failures is gradually It has expanded and led to declining resistance and increasing the vulnerability of bridges. Due to the hot and humid weather conditions and the presence of salts in it The Persian Gulf region has seen signs of failure, including numerous cracks and local damage, in many of the concrete slabs in the area's structures and bridges. It is possible. Therefore, the assessment of the condition of concrete slabs prevents the progress of failure, removal from service and repair of structures.In this paper, the Expert-Slab Bridge expert system is presented to assess the failure of concrete slabs. Expert system, computer program It is intelligence that uses the knowledge and methods of inference and inference to solve problems. This system includes an interpreter, an inference method Knowledge-based and database. Bridge deck failures due to environmental conditions and cracked concrete structures, failures Surface and instrumental failures have been evaluatedSeveral case studies and comparisons between technical inspection results and the expert system In order to gain reliability and accuracy, the results of the system have been done. System outcomes include a concrete bridge slab identification, inference Expert system with failures and their causes, status index, status description, suggested solution for repair and diagram of useful life of concrete slab Is .
Keywords: : Concrete slab, failure assessment, fault diagnosis, Bridge management system, Service life, expert system -
ساییدگی کف بتن های صنعتی یک مشکل اساسی است که باعث پایین آمدن عمر آنها می شود. تلاش شده است تا مقاومت در برابر سایش بتن با مقاومت فشاری آن مرتبط شود. با این وجود عوامل دیگری نیز وجود دارد که در مقاومت در برابر سایش بتن موثر است. در این مطالعه ، چندین مخلوط بتونی حاوی انواع مختلف سیمان ، سنگدانه ، مواد افزودنی و مواد افزودنی مانند دود سیلیس و استایرن لاستیک بوتادین (S.B.R) پلیمر برای ارزیابی مقاومت در برابر سایش آنها ساخته شد. تمام نمونه های بتنی مطابق با روش های استاندارد استاندارد ASTM و EN برای عمل سایش مورد آزمایش قرار گرفتند. بر اساس داده های به دست آمده از آزمایشات ، یک مدل تجربی برای ارزیابی مقاومت در برابر سایش بتن های مختلف ارایه شده است. نتایج این تحقیق نشان می دهد که ترکیب ذرات سیلیس ، پلیمر S.B.R و مصالح گرانیتی در بتن باعث بهبود مقاومت در برابر سایش می شود. مدل ریاضی پیشنهادی قادر به پیش بینی مقاومت در برابر سایش بتن است و راهنمایی برای انتخاب مواد جهت تولید بتن با دوام بیشتر در هنگام قرار گرفتن در معرض سایش فراهم می کند.
کلید واژگان: مقاومت در برابر سایش، بتن، دوام، کف صنعتی، مدل ریاضی، دود سیلیس، لاستیک استایرن بوتادین (S.B.R) پلیمرAbrasion of industrial concrete floors is a major problem resulting in their lower service lives. Attempt has been made to relate the abrasion resistance of concrete to its compressive strength. However there are other factors which influence the abrasion resistance of concrete. In this study, several concrete mixtures containing different types of cements, aggregates, admixtures and additives such as silica fume and styrene butadiene rubber (S.B.R) polymer were made to assess their abrasion resistances. All concrete specimens were tested for wear action in accordance with ASTM and EN standard test methods. Based on data obtained from the tests, an empirical model was proposed to evaluate the abrasion resistance of different concretes. Results of this investigation show that the incorporation of silica fume, S.B.R polymer and granite aggregates in concrete improve its abrasion resistance. The proposed mathematical model is capable to predict the abrasion resistance of concrete and provide a guide for selection of materials to produce more durable concrete when subjected to wear action.
Keywords: Abrasion resistance, Concrete, Durability, industrial floors, Mathematical Model, Silica fume, styrene butadiene rubber (S.B.R) polymer -
هدف از این تحقیق بررسی تاثیر رفتار باندینگ بستر بتونی و مواد ترمیم شده است. سه ماده تعمیر سیمانی متفاوت یا اصلاح شده با سیمان و سه زبری سطح مورد بررسی قرار گرفت. مواد ترمیمی ملات معمولی ، ملات سیمانی اصلاح شده توسط دود سیلیس و ملات سیمانی اصلاح شده توسط لاتکس لاستیکی بوتادین استایرن بودند. سطح آماده سازی سطح صاف ، سطح خشن و چسب رزین اپوکسی به عنوان ماده اتصال دهنده بود. روش مورد استفاده برای ارزیابی استحکام باند ، آزمون کشش بود. تاثیر هدایت الکتریکی مواد ترمیم کننده با استفاده از تست نفوذپذیری سریع کلرید انجام شد. سرانجام ، عملکرد چسب ها با توجه به مقاومت باند و هدایت الکتریکی مورد بررسی قرار گرفت.نتایج به دست آمده از این آزمایشات نشان داد که زبری سطح بستر تاثیر اصلی در عملکرد پیوند بین چسب و بتن دارد. در استحکام باندینگ بین مواد مختلف تعمیر کننده تفاوت زیادی وجود ندارد ، اما با توجه به هدایت الکتریکی ، ملات های اصلاح شده سیمانی مواد بهتری برای استفاده در محیط های خورنده برای افزایش طول عمر سازه های تعمیر شده هستند.
کلید واژگان: مقاومت اتصالی، مواد ترمیم کننده، زبری، آزمون بیرون کشیدگی، نفوذپذیری کلورید، بتنThe purpose of this investigation was to study the effect of bonding behavior of concrete substrate and repair materials. Three different cementitious or modified-cementitious repair materials and three surface roughnesses were studied. Repair materials were ordinary mortar, modified cementitious mortar by silica fume and modified cementitious mortar by styrene butadiene rubber latex. Surface preparations were smooth surface, rough surface and epoxy resin adhesive as a bonding agent. The method used for evaluation of bond strength was pull-off test. the influence of the electrical conductivity of repairing materials was analyzed by rapid chloride permeability test. Finally, the performance of the adhesives was evaluated considering both the bond strength and electrical conductivity. Results obtained from these tests indicated that the roughness of substrate surface has a main effect on the performance of bond between adhesives and concrete. There are not great differences in bonding strength between various repairing materials but considering electrical conductivity, modified cementitious mortars are better materials for using in corrosive environments to increase service life of repaired structures.
Keywords: Bond strength, Repair material, Roughness, Pull-off test, Chloride permeability, Concrete
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