فهرست مطالب

Journal of Civil Engineering and Materials Application
Volume:3 Issue: 4, Autumn 2019

  • تاریخ انتشار: 1398/09/10
  • تعداد عناوین: 5
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  • Alireza Behnamnia *, Maryam Barati Pages 183-192

    Lightweight concrete has been used in the construction industry for many years and by the introduction of modern technologies in the construction industry, this type of concrete has been accounted as one of the powerful and reliable materials in the construction industry. The density of lightweight concrete is about 0.56 that of the ordinary concrete. This type of concrete is commonly used as a flooring material in buildings. Thus there is possibility of its corrosion   in different climatic conditions. In the present research, we would investigate the compressive strength and durability of the lightweight concrete in the acid environment, so that by specifying the corrosion rate, one could have a better understanding of the behavior of these concretes. For making the lightweight concrete in the present research use has been made of pumice aggregate in the mix design, and the acid used is 1M sulfuric acid. Also, the effect of adding two types of Nanomaterials i.e., Nano silica and Nano clay on the concrete behavior is assessed. The results have shown that in case of keeping the specimens of lightweight concrete in the acid environment for 90 days, their weight reaches 0.56 that of the ordinary specimens. The results of the current research have shown that the use of Nano silica and Nano lime per 10 wt% of cement could result in the increased compressive strength of the lightweight concrete. So that the concrete compressive strength per 10 wt% of Nano lime increases by 1.43%. On the other hand, the concrete durability in the acid solutions reaches the maximum value per addition of 5% Nano silica and 5% Nano lime, and has lost a lower percentage of its weight.

    Keywords: Composite Column, thickness of steel layer, cyclic lateral loading
  • Amir Bahador Moradikhou, Alireza Esparham, Mohammad Jamshidi Avanaki * Pages 193-201
    In recent years, geopolymers, as a new class of green cement binders, have gained significant attention as an environmental-friendly alternative to Ordinary Portland Cement (OPC) which can potentially reduce negative environmental impacts of OPC. Fiber Reinforced Geopolymer Concrete (FRGPC) is known as a new type of concrete with enhanced ductility characteristics over conventional concrete. In this experimental study, hybrid fibers of 12mm modified polypropylene and 55mm polyolefin were used to manufacture FRGPC specimens based on Granulated Ground Blast Furnace Slag (GGBFS). In this regard, FRGPC and non-fiber specimens were produced. The specimens were subjected to compressive, indirect tensile and 3-point flexural tests, as well as water absorption capacity and specific density studies. The obtained results showed that using hybrid fibers decreased the specific density and water absorption, a slight increase in compressive strength and a significant improvement in tensile and flexural strengths of FRGPC specimens compared to non-fiber specimens.
    Keywords: Fiber Reinforced Geopolymer Concrete, Hybrid fibers, Compressive strength, tensile strength, Flexural Strength
  • Seyed Ali Mousavi Davoudi *, Morteza Naghipour Pages 203-213
    One of the most sensitive decisions a structural designer should consider is choosing the type of consumables in the structure. This decision is in many cases dependent on the type of structure, financial issues also the experience and skill of the designer. The main aim pursued in the design is to obtain highly secure, economical structures. Concrete and steel are materials that are widely used in construction. The benefits of both materials are well known today. The clever combination of these two materials, an effective explosion-proof system, will have the effect of exploding explosions in the Plasco building in Tehran compared to using any of the materials. Lack of efficient performance factors, lack of clear and valid guidelines for the seismic design of such columns, how to model their geometry and material can still be obstacles to using such systems. In this research, according to the objectives of the problem, different parameters should be evaluated, this parameter is the type of column cross-section geometry. The aim is to determine the effect of defined parameters, especially column geometry, on the behavior and seismic capacity of composite columns) CFST(, achieving high resistivity, especially for columns that, incidentally, increase their loading exponentially with increasing classes. It is found that circular sections of composite columns )CFST( show better behavior and performance than columns with square geometry and further show that composite columns) CFST( can be used as a basic solution. Use it to solve challenges between designers and architects.
    Keywords: CFST Column, Seismic Load, Nonlinear Analysis (NSP), finite element analysis
  • Neda Mohammadi, Davood Ghaedian Ronizi * Pages 215-223
    In today's advanced world and due to advances in various scientific fields of the concrete, industry has also evolved, and light concrete production is a result of these advances. It has had its advantages, many efforts have been made in the past to improve the quality and efficiency of concrete, and today the use of additives helps us to achieve this goal. The additive in this study is lubricant based on polycarboxylate brand SP200 and Powdered silica. The use of silica is also widely used in advanced countries due to its pozzolanic properties. In this study of 20 mixing designs, 2 of which were used as control sample and 18 with SP200 super-lubricant and micro silica powder, the results show that in the first mixing design with 0.49 water/cement ratio the highest compressive strength of The 7 and 28 days is related to M / 35/5 sample which has 0.35% super-lubricant and 5% micro silica powder And in the second mixing scheme with water/cement ratio of 0.55, the highest compressive strength is related to the sample of  M /35/10 It contains 0.35% super-lubricant and 10% Powdered silica.  The use of silica and super-lubricant in the manufacture of lightweight concrete has increased the compressive strength of lightweight concrete in some of the samples.
    Keywords: Structural lightweight concrete, Leca Industrial shell, Powdered silica, Super lubricant
  • Moslem Yousefvand *, Yaser Sharifi, Saeed Yousefvand Pages 225-233
    Structural engineers are generally aware of the intrinsic safety properties of concrete exposed to fire (non-flammability at high temperatures). However, the tendency of concrete for spalling at high temperatures is a significant defect, and recently many researchers have conducted studies on this issue. One of the primary objectives of this study is to assess the shear strength and modulus of rupture of concrete reinforced with different percentages of modified polyolefin synthetic fibers at different temperatures and to compare the results with the preliminary design. The other objective of the present study is to compare the behaviors of synthetic fiber concrete under the effect of the furnace temperature and direct fire. After adding fibers (1.5 volumetric percentage), a 29% increase in the tensile strength and a 56% increase in the modulus of rupture (the stress corresponding to the development of the first crack) were observed. Considering the fiber concrete results in the experimental temperature condition, it can put on an acceptable strength performance. However, at temperatures equal to or greater than 400 , the fibers lose their role in compensating the low tensile strength of concrete due to oxidation, causing porosity in the concrete and reducing its strength.
    Keywords: fiber-reinforced concrete, tensile strength, rupture modulus, high temperature