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  1. 1. Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print), ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME 40 AN EXPERIMENTAL RESEARCH ON ENHANCING THE STRENGTH AND ITS RESISTING PROPERTY OF NANO SILICA FLY ASH CONCRETE Yuvaraj Shanmuga Sundaram1, , Dr. Sujimohankumar2 1Research Scholar, Karpagam University, Coimbatore 2Dean/Civil Engineering RVS Faculty of Engineering, Coimbatore, India ABSTRACT This paper deals with the study of Nanotechnology experimentation in Civil Engineering which includes the development, advantages and limitations of Nano concreting technologies. For reducing carbon emission during cement manufacturing fly ash is used as a replacement in ordinary Portland cement which is termed as Portland pozzolana cement(PPC), this inclusion relatively increases the workability and the corrosion resisting capacity in concrete, but this replacement of fly ash in the ordinary Portland cement deviates the concrete strength consequently. Therefore, here we added Nano silica as an additive to fill up the deviation, and it is possible because the silica (S) in the sand reacts with calcium hydrate (CH) in the cement at Nano scale to form C-S-H bond as it improves the strengthening factor of concrete, which are in turn helpful in achieving high compressive strength even in early days. This process proved that the increase in strength may have a possibility of turning the concrete less alkaline because as the concentration of CH crystals is reduced the alkalinity of concrete will be reduced which can cause corrosion in reinforcement bars, Hence by the addition of Nanosilica, a significantly improved corrosion resistant property was identified in our experimental research. Also, the performance of reinforced Nano concrete and the fly ash added RC Beam Column joints were casted and their flexure strength results were compared with one another and their test results are presented in this paper 1. INTRODUCTION Concrete is at something of a crossroads: there are many prospects and some risks involved in it. Regarding the opportunities concrete comes into a practice in the implementation by various researches, areas to innovate for engineers, use of different material which ensures the manufacturers to learn and to produce the concepts of new JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY (JCIET) ISSN 2347 –4203 (Print) ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), pp. 40-45 © IAEME: JCIET © IAEME
  2. 2. Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print), ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME 41 ingredients to be use which focus on the changes that are required to champion concrete and maintain its dominance within the global construction industry. Many researches has shown that a state-of-the-art process for high-performance cement adds a new changes to ‘modern’ cement technology, similarly it’s the time to understand about what is “NANO TECHNOLOGY” and their development and use in construction industry as many innovations in concrete techniques are adopted. As concrete is most usable material in construction industry it’s been requiring to improve its quality. The main aim of this research is to outline promising research areas in the field of Nano technologies in the Construction world. 1.1 WHAT IS NANO TECHNOLOGY? Nanotechnology is defined as fabrication of devices or materials with atomic or molecular scale precision” Nanotechnology is usually associated with study of materials of micro size i.e. one billionth of a meter (a Nanometer) or 10-9 m. 1.2 DEFINITION OF NANO-CONCRETE For discussions presented in this research, Nano-concrete is projected as concrete made with Portland cement particles that are less than 500 Nano-meters as the cementing agent. Normally, cement particle sizes ranges from a few Nano-meters to a maximum of about100 micro meters, at this point the average particle size of micro cement is reduced to 5 micro meters as an order of magnitude reduction is needed to produce Nano-cement. The SEM image of the Nano silica we had taken for our investigation is shown in Fig.1 Fig 1: The SEM image of Nano silica 1.3 NANOSCALE CONCRETE A. Cement Reactivity at Nano Scale We need to better know how to control the setting time of concrete. The evolution of the hydrogen profile shows the timing of the surface layer's breakdown. This information can be used to study the concrete setting process as a function of time, cement chemistry and temperature. For example, researchers used NRRA (Nuclear Resonance Reaction Analysis) to determine that in cement hydrating at 30°C, the breakdown occurs for about 1.5 hours. The surface disintegration then releases accumulated silicate into the surrounding solution, as it reacts with calcium ions to form a calcium-silicate hydrate gel, which acts as a binding agent with cement grains together and sets the concrete.
  3. 3. Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print), ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME 42 2. OBJECTIVES OF THIS INVESTIGATION To determine the improvement of Corrosion resistance and concrete Strength by using Nano silica in concrete: A. The objective of this investigation is 1. Studies on the Corrosion resisting property and Flexural strength of concrete were made separately by partially replacing of cement with fly ash and find out the optimum replacement percentage of fly ash to the weight of cement. 2. Different proportions of replacing of fly ash with cement for studies are 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70% and 80%. 3. Same proportions of replacing of cement with fly ash with addition of Nano silica at a rate 2.5% to the weight of cement are done and their results are studied. 4. A comparative analysis of Corrosion resistance of partially replaced fly ash (10%, 20%, 30%, 40%, 50%, 60%, 70% and 80%) Concrete with the Nano concrete were carried out. 5. A comparative analysis of Flexural strength of partially replaced fly ash (20%, 40% and 60%) Concrete with the Nano concrete were carried out. 6. Then a comparative analysis Fly ash concrete and Nano Silica Fly ash concrete were listed out. 3. MATERIALS AND METHODS. 3.1 An investigation of Nano silica in cement hydration process With the introduction of nano technology, materials have been urbanized that can be applied to high performance concrete design mix. Nano silica get reacts with calcium hydroxide (CH) to increase the strength carrying structure of cement: calcium silica hydrate (CSH). In this paper, interaction has been developed to distinguish the benefits when using unusual sizes of nano silica in cement. An experimental analysis was carried out to determine the performance of Nano silica. From these experiments the heat of hydration of several cement design mix was calculated. Finally, the compressive strength was determined for each cement paste. During these experiments it was found that as the silica particles decreased in size and their size distribution broadened, the CSHs became more inflexible; this increased the compressive strength. 3.2 Specimen casting and curing • Initially cement, fly ash and Nano silica are taken and mixed for one minute and after that the fine aggregate was also included and mixed and coarse aggregate was mixed thoroughly in dry state and cement were mixed for one minute. • Mixing with Super plasticizer is done with water as its being added within two minutes and the concrete was allowed to mix for three minutes overall. • Compaction process is done by using table vibrator and the specimens are cured for 7, 14 and 28 days respectively.
  4. 4. Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print), ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME 43 4. CORROSION TEST SETUP The test was carried out on 150 x 300 mm size concrete cylinders with a rod of height 450 mm in the center throughout the specimen. The test specimens are marked and removed from the moulds after 24-48 hours from casting depending upon the percentage of fly ash and submerged in clean fresh water for curing. The impressed current technique, which is commonly used for accelerating reinforcement corrosion in concrete specimen, was used for testing. The specimen was placed in water bath containing calculated quantity of dissolved sodium chloride (table salt) to act as electrolyte. Calculated voltage of current was passed through the concrete specimen till the concrete cracks. The percentage weight loss in rebars and the width of cracks in concrete were studied. Fig 2: Impressed current test setup 4.1 Results attained for corrosion test: The testing was carried out using the Test Set Up and the graphs for the comparison of Mass of Actual Rust, Degree of Induced Corrosion and Crack Width between the Fly Ash added concrete and nS + Fly ash added concrete are plotted. Graph 1: Degree of induced corrosion comparison result for (M40) 28 day Graph 2: Crack width comparison result for (M40) 28 days 0 0.05 0.1 0.15 0.2 0.25 0.3 0 10 20 30 40 50 60 70 80 ACTUALMASSOFRUST(INmm) PERCENTAGE REPLACEMENTOF CEMENT( IN mm ) nS+FA FA 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0 10 20 30 40 50 60 70 80 CRACKWIDTH(INmm) PERCENTAGE REPLACEMENT OF CEMENT ( IN % ) nS+FA FA
  5. 5. Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print), ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME 44 5. FLEXURE TEST The beam specimen casted for determining the flexure strength of concrete is 15cm x 15cm x 75cm. The bed of machine should be provided with two steel rollers of 38mm diameter on which the specimen is supported. Rollers are placed at centre to centre distance of 60cm. The test specimen is casted and cured for 28 days and tested for maximum load. The Flexural strength or Modulus of rupture (fb) is calculated using the formula, fb= 3Pa/bd2 Where, P - maximum load, a - distance of loading from support, b - Breadth of specimen, d - Depth of specimen. 5.1 RESULTS AND DISCUSSIONS For the sample under three-point bending setup the following results are made: At the outside of the bend (convex face) the stress will be at its maximum tensile value. These inner and outer edges of the beam or rod are known as the 'extreme fibers'. Table 1: Flexural Strength Attained Specime n Average load in (kN) Flexural Strength σ=3FL/2BD2 (kN/m2) CS 17.74 3.94 F20 18.09 4.02 F40 15.48 3.44 F60 11.48 2.55 NC 33.81 7.5 FN20 22.14 5.76 FN40 20.68 4.92 FN60 17.82 3.96 Graph.3 Flexural Strength Chart 0% 20% 40% 60% Control Specimen 3.94 3.94 3.94 3.94 Flyash-Concrete 3.94 4.02 3.44 2.55 Nano Concrete 7.5 5.76 4.92 3.96 0 2 4 6 8 FleturalStrength(kN/m2) Flextural Strength Chart
  6. 6. Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print), ISSN 2347 –4211 (Online) Volume 1, Issue 1, July-December (2013), © IAEME 45 6. CONCLUSIONS From the above experiments and results we safely conclude the points as follow. A. Nano concrete could control the carbon dioxide emission from the earth which is shown by using fly ash concrete products instead of cement concrete. B. Thus the Nano particles which is in the form of silica can easily react with cement particles which are normally in Nano scale initiate the CSH reaction and hence its tend to accelerate the flexural strength of concrete. C. It is found that the corrosion resisting property of the nS added concrete is comparatively higher than ordinary fly ash concrete. D. The corrosion resistance of optimum percentage replacement of fly ash is higher in nano concrete than the ordinary fly ash concrete. E. From the flexure graph, it is obvious that within FN20 and FN40, the efficiency of concrete is maximum. F. For concrete structures construction for petrol tanks, bunkers and silos, oil well, this type of special concrete can be preferred to influence more strength and performance. REFERENCES 1. Balaguru, P. N. (2005), “Nanotechnology and Concrete: Background, Opportunities and Challenges.” Proceedings of the International Conference – Application of Technology in Concrete Design. 2. Boresi, Arthur P.; Chong, Ken P.; Saigal, Sunil. “Approximate Solution Methods in Engineering Mechanics”, John Wiley, New York, 2002, 280 pp. 3. Balaguru, P.; and Shah, S.P. “Fiber Reinforced Cement Composites”, McGraw- Hill, New York, 1992, 530 pp. 4. Srivastava, D.; Wei, C.; and Cho, K. “Nanomechanics of carbon Nanotubes and composites.” Applied Mechanics, Review, 56, 2003, 215-230. 5. LI, G. “Properties of high-volume fly ash concrete incorporating Nano-SiO2”. Cement and Concrete, Research. 34. 2004. P. 1043 – 1049. 6. Abdelsamie Elmenshawi and Tom Brown “Hysteretic energy and damping capacity of flexural elements constructed with different concrete strengths” Engineering Structures 32 (2010) 297_305 from the journal Elsevier. 7. Abhijit Mukherjee and Mangesh Joshi “FRPC reinforced concrete beam-column joints under cyclic excitation”, Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai. 8. Bjornstrom J, Martinelli A, Matic A, Borjesson L, and Panas I, “Accelerating effects of colloidal nano-silica for beneficial calcium–silicate–hydrate formation in cement”,Chemical Physics Letters 392 (2004), pp 242–248.