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    Influence of Nanocomposites on Reinforced Concrete
    Influence of Nanocomposites on Reinforced Concrete
    Influence of Nanocomposites on Reinforced Concrete
    Ebook245 pages1 hour

    Influence of Nanocomposites on Reinforced Concrete

    By Zachary Virginia

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    About this ebook

    The use of nanocomposites in reinforced concrete has emerged as a promising approach to enhance the mechanical properties and durability of conventional concrete. This experimental investigation by G. Cibilakshmi focuses on the influence of nanocomposites on the performance of reinforced concrete incorporating PVA fibers.

    Nanocomposites are materials composed of a polymer matrix reinforced with nanoparticles or nanofillers. These materials have gained significant attention in recent years due to their unique mechanical, thermal, and chemical properties. In the context of concrete, nanocomposites can improve the strength, toughness, and durability of the material by enhancing the interfacial bonding between the matrix and reinforcement and reducing the porosity of the cementitious matrix.

    The experimental investigation carried out by Cibilakshmi involves the synthesis and dispersion of various nanoparticles including carbon nanotubes, graphene, silica, titanium dioxide, zirconia, and alumina in the polymer matrix. The nanocomposite was then incorporated into the concrete mix along with PVA fibers. The resulting reinforced concrete specimens were tested for mechanical properties such as compressive strength, tensile strength, flexural strength, and hardness, as well as for durability properties such as corrosion resistance, chemical resistance, and thermal conductivity.

    The results of this investigation showed significant improvements in the mechanical and durability properties of the reinforced concrete specimens with the addition of nanocomposites. The interfacial bonding between the matrix and reinforcement was enhanced, resulting in an increase in compressive, tensile, and flexural strength. The addition of nanocomposites also improved the durability of the concrete, with increased resistance to corrosion and chemical attack. The study concludes that the use of nanocomposites in reinforced concrete has the potential to significantly enhance the performance of the material, contributing to the development of sustainable and green building materials with reduced carbon footprints and improved energy efficiency.

    LanguageEnglish
    PublisherZachary Virginia
    Release dateMay 31, 2024
    ISBN9798227850058
    Influence of Nanocomposites on Reinforced Concrete

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      Influence of Nanocomposites on Reinforced Concrete - Zachary Virginia

      ABSTRACT

      In the modern construction industry, the increased utilization of concrete leads to an increase in CO2 emission, which highly contributes to global warming and pollution health risks. The replacement or substitution of cement by supplementary cementitious materials in concrete considerably enhances the engineering properties of concrete. In recent  years,  the utilization of nanoparticles in cement composites has received specific attention from researchers. The integration of nanoparticles with conventional concrete materials improves the bulk properties of concrete by transforming molecular structures and allows the cement-based materials become high-strength and durable products. Though, the concrete is the widely used construction material, due to its high durability to cost ratio, the  reduced tensile properties of the concrete confines its applications where the flexural and tensile properties of the concrete are predominant. It has been well documented that the inclusion of different types of fibres (steel and synthetic fibres) significantly enhanced the tensile, toughness, impact resistance and energy absorption capacity of the concrete. Even though the inclusion of fibre improved the tensile strength capacity of the concrete, it hasn’t improved the compressive strength capacity of concrete significantly. Therefore, it is very imperative to increase the compressive strength of the concrete where the compressive tensile properties of the concrete are predominant for its application.

      In order to fulfill the above research gaps, firstly (Phase I) an investigation was carried to study the influence of nano-Al2O3, nano-Fe2O3, and their hybrid combinations on the setting time, microstructure, fresh, and strength properties of conventional cement concrete. The binding material of

      concrete mixtures was replaced by different nanoparticles, namely nano-Fe2O3 and nano-Al2O3, with four replacement rates (up to 3%). The quantity of the binding material and the water–binder ratio of all mixtures were kept constant. A Vicat apparatus was used to measure the initial and final setting time of the binding material, and the slump cone test was performed to assess the workability of concrete mixtures. Strength characteristics were evaluated, including the compressive, split tensile, and flexural strengths, for mixtures hardened after 7, 28, and 90 days. To investigate the filling ability of nanoparticles, mortar portions present in concrete (28-day hardening) were extracted, and their microstructure was analyzed using Scanning Electron Microscopy (SEM). The surface energy exerted by nanoparticles accelerated hydration and reduced the initial and final setting time of binding materials. Moreover, the slump value of the mixture was decreased with an increase in the replacement rate of nanoparticles. However, slump values were within the acceptable workability and did not affect concrete compaction. The  test  results revealed that nanoparticles can enhance the strength  and  microstructure properties of concrete. However, the strength enhancement of the hybrid nano  mixtures was relatively equal to that of the mixtures with  only nano-Fe2O3 or nano-Al2O3. Because highly reactive nano-Fe2O3 and nano-Al2O3 present in the mixture reacted distinctly and no reaction occurred between nano-Fe2O3 and nano-Al2O3, the strength values of the mixtures with only nano-Fe2O3 or nano-Al2O3 were nearly equal to those  of  the mixtures with a hybrid combination of nano-Fe2O3 and nano-Al2O3. The SEM results revealed that the pore sizes of the mixture with nanoparticles were considerably small, and the high free energy of nanoparticles reduced the Ca(OH)2 crystal size and content.

      Another part (Phase II) of investigation was focused to improve the strength properties of PVA Fiber Reinforced Concrete (PFRC) by incorporating nano-Fe2O3. The fibres were added in to the concrete in volume

      fraction and the fraction was 0.2%, 0.4%, 0.6%, and 0.8%. The cement content of the concrete replaced by nanoparticles with the replacement rate of 0.75%, 1.50%, 2.25% and 3.00%. Slump test was performed to determine the workability of the fresh concrete. Compressive strength test and flexural tensile test was performed to evaluate the strength properties.

      Since the fibre and nano-Fe2O3 was too expensive, it is very imperative to design a favorable and optimistic proportion of PVA and nano-Fe2O3 in concrete production. The present study also focused to determine the influence of PVA fibre and nano-Fe2O3 combination on the  fresh and strength properties of concrete. Central Composite Design of RSM was used to acquire the optimal composition of process variables and the influence of process variable on the fresh and strength properties of concrete was also verified. A total of five responses (YSlump, fck,7, fck,28, ft,7 and ft,28) were considered in this study, the factors and the level of each response was 2 and  3, respectively. Regression model for YSlump, fck,7, fck,28, ft,7 and ft,28 were tested, statistical significance of each process variable assessed through analysis of variance (ANOVA) and Pareto chart and the obtained models were expressed in the form of second-order polynomial equation. The test results  revealed  that incorporation of PVA and high reactive nano–Fe2O3 improved the  strength of the concrete, however, the higher level incorporation exhibited unpronounced effect on the strength enhancement. The incorporation of nano-Fe2O3 enhanced the compressive strength to the maximum of 7.44%.  The high reactive nano–Fe2O3, accelerated the hydration process of concrete and enhanced the particle packing density of the concrete through filling the micro pores. However, the higher incorporation of nano-Fe2O3, leached out  the surplus silica from the concrete and reduced the strength enhancement of the cement composite matrix. The regression analysis results revealed that the most significant and contribution factor for fck,7 and fck,28 is the linear term nano-Fe2O3 (X2) (99.81% contribution) and the linear term of PVA (X1) is the

      most significant and contribution factor (75.75% contribution) for ft,7 and ft,28. Pareto chart and surface plot analysis also revealed the same above. The optimal proportion of design variables against fck,7, fck,28, ft,7 and ft,28 were obtained and the percentage of error of the confirmation tests of YSlump, fck,7, fck,28, ft,7 and ft,28 were less than 3%.

      LIST OF FIGURES

      ––––––––

      FIGURE NO. TITLE PAGE NO.

      ––––––––

      Progress of cement production and CO2

      emission in worldwide 1

      Steel fibres and synthetic fibres 3

      Nanoparticles in spherical form and in tubular

      form 4

      Two factor model 10

      SEM micrograph of cement paste (a) without Al2O3 nanoparticles and (b) with Al2O3

      nanoparticles cured in saturated limewater 15

      Failure mechanism and the effect of fibers 24

      NanoComposite Materials (Al:Fe2O3) 41

      Nano Fel2O3: a) XRD analysis results, b) SEM

      analysis results 42

      Nano-Al2O3: a) XRD analysis results, b) SEM

      analysis results 43

      PVA fibre 44

      Mixing of concrete 46

      Slump cone test to verify the workability 47

      Compaction of cubes 48

      Fabrication of cubes 48

      Fabrication of cylinders 49

      Fabrication of beams 49

      Water immersed curing for 28 days 50

      Testing of cube specimens 51

      Initial setting time of mixtures with

      nanoparticles – Comparison 57

      Final setting time of mixtures with

      nanoparticles – Comparison 57

      SEM images of nano-Fe2O3 58

      SEM images of nano-Fe2O3  and nano-Al2O3 58

      Slump value of mixtures with nanoparticles –

      Comparison 61

      Relation between slump value and density at

      the age of 7, 28 and 90 days 62

      Compressive strength of mixtures with

      nanoparticles – Comparison 63

      Relation between compressive strength and

      density at the age of 7, 28 and 90 days 65

      Relation between measured and computed compressive strength of

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