International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 11, November 2018, pp. 1763–1771, Article ID: IJCIET_09_11_172 Available online at http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=11 ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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EXPERIMENTAL STUDY ON STRENGTH OF CONCRETE BY PARTIAL REPLACEMENT OF CEMENT BY NANO SILICA AND FLY ASH
Tipraj, E. Laxmi Prasanna, N. Prabhanjan, A. Shiva Krishna, M. Guru Prasad Assistant Professor, Civil Department, S R Engineering College, Ananthasagar Warangal, Waranagl, India
ABSTRACT Concrete is the most broadly utilized man made development material in the world & is second just to water as the used substance on the planet. It is obtained by mixing cementing materials, water & aggregate, & sometimes admixtures, in required proportion. The mixture when placed in forms & allowed to cure hardens into a rock- like mass known as concrete. Concrete is weak compared steel. It is also brittle. Yet it is most widely used building material. This is because of its versatility. It can be moulded into any shape & the surface can be textured & colored for aesthetic purpose. Most importantly it is produced with cost effective materials. Concrete possesses very good water-resistant properties & hence, can be used in intake towers for drawing water, dames & water tanks for storing, & canal lining for transporting water. Concrete is a strong & tough materials. Reinforced concrete resists cyclones, earthquakes, blasts & fires much better timber & steel if designed properly. When compared to wood & steel, concrete has an inherent fire resisting properly. It regains its properties on cooling when the temperature reached & the duration of the fire is not abnormally high. Key words: Concrete, Fly ash, Nano silica, Compression, C-S-H gel Cite this Article: Tipraj, E. Laxmi Prasanna, N. Prabhanjan, A. Shiva Krishna, M. Guru Prasad, Experimental Study on Strength of Concrete by Partial Replacement of Cement by Nano Silica and Fly Ash, International Journal of Civil Engineering and Technology (IJCIET) 9(11), 2018, pp. 1763–1771. http://iaeme.com/Home/issue/IJCIET?Volume=9&Issue=11
1. INTRODUCTION Cementtastatbindingtmaterialtmosttwidelytusedtintallttypestoftconstructiontactivity.Concrete is heterogeneous material composed of cement, sand, coarse aggregate & admixture. In construction, concrete is the only material which has qualities such as Strength, Durability, & Resistant to Absorption. The development & use of mineral admixtures for cement
http://iaeme.com/Home/journal/IJCIET 1763 [email protected] Tipraj, E. Laxmi Prasanna, N. Prabhanjan, A. Shiva Krishna, M. Guru Prasad replacement is developing in construction industries due to Cost effective, energy saving, ecofriendly & low usage of naturally available resource there by using the by-product that are present. Mineral admixture normally used are Fly ash, rice husk ash, silica fumes etc. most of these are carried out on replacement of cement in concrete by these mineral admixtures to develop the concrete with desired strength, durability & impermeability “Design & testing of Fly-ash based Geo Polymer Concrete” A.Siva Krishna [1]. About fly ash Fly ash is consists of the non-burnable mineral portion of coal. Fly ash is one of the end products originated in combustion, & consists of the fine particles that rise with the flue gases. Ash which does not rise is known as bottom ash. In an industrial context, fly ash normally means to ash obtained during burning of coal. “Structural properties of lightweight self-compacting Concrete made with Pumice stone and mineral admixtures” by V. Karthika1 [2]. Presently about 105 million tons fly ash is generated every year in India as a by-product of coal consumed in the thermal power plants. The thermal power plant is alone a source to manufactures sixty % of the entire electricity production in India. Several million tons of coal for manufacturing the electricity is being taken in India out of which forty % of coal is counted for production of fly ash as a bye product “Performance analysis of Black Cotton Soil treated with Granite dust and Lime” Shaik Khader Vali Bab [3]. Fly Ash particles are mostly small solid spheres & hollow ecospheres with a few particles not withstanding being plerospheres, which are circles containing smaller spheres. The Fly Ash is taken from the fumes gases by electrostatic precipitators or pack channels “Load studies on Granular Pile with and without Geogrid encasement in non-swelling Clay beds” Suravaram Siva Sai Pratap Reddy[4]. Fly ash is the fine end product produced from the burning of pulverized coal in electric & steam generating plants. In India, thermal power plants are the prime source for manufacturing electricity. Though attempts are being made to find solutions for cleaner manufacturing of electricity, but still there is a long way to go and we may depend on traditional coal combusting thermal power plants for quite some more time (50-100 years). “Experimental Investigation of Partial Replacement of Fly Ash in Concrete by Varying Naoh Concentration” by R. Prabakaran, [6].
2. CONCRETE: DEFINATION AND COMPOSITION Concrete is a composite material comprises of coarse granular material (the total or filler) implanted in a hard lattice (the bond or fastener) that fills the space between the total particles & tie them together. We can likewise consider concrete as a composite material that is comprised of basically of a coupling medium inside which are inserted particles or sections of totals. As indicated by the sort of bonder utilized, there are numerous assortments of cement. For instance, Portland The cement concrete, asphalt concrete, and epoxy concrete. In solid development, the Portland cement concrete is utilized the most. In this manner, in our course, the term concrete typically alludes to Portland The cement concrete. Here we require to show the admixtures are quite often utilized in present day development practice & therefore turn into an important part of modern concrete. Admixtures are characterized as materials other than total (fine or coarse), water, fiber and bond, which are blended into concrete batch unexpectedly previously or amid blending. The utilization of admixture is mostly because of the numerous advantages made conceivable by their application. For instance, compound affecting the rate of concrete hydration. Water- decreasing admixture can plasticize new solid blend by dying down surface strain of water;
http://iaeme.com/Home/journal/IJCIET 1764 [email protected] Experimental Study on Strength of Concrete by Partial Replacement of Cement by Nano Silica and Fly Ash air-entraining admixtures can enhance the durability of concrete. Furthermore, mineral admixtures, for example, pozzolona (materials containing responsive silica) can diminish thermal cracking.
3. INTRODUCTION OF NANO SILICA Advance cement made by the investigation of concrete at Nano scale have demonstrated Nano silica superior to anything silica utilized in traditional cement, however engineering investigations demonstrates that likewise with silicon powder, additionally bring two issues, from one perspective is the cohesiveness increment of cement to development cause certain issue .
Figure 1 Nano silica
4. WHY NANOTECHNOLOGY FOR CONCRETE • Development of high-performance cement & concrete materials as estimated by their mechanical & strength properties; • Development of sustainable concrete materials & structures through designing for various unfavorable situations, decreasing vitality utilization amid bond generation, & improving security • Development of intelligent concrete materials through the joining of nanotechnology-based self-detecting & self-fueled materials & digital foundation innovations • Development of novel concrete through nanotechnology-based creative handling of concrete & bond glue; & • Development of principal multi scale model(s) for cement through cutting edge portrayal & displaying of cement at the Nano-, miniaturized scale and large scale scales. • Improves the material's mass properties. • Ability to control or control materials at the atomic scale. • To get thinner final products & quicker setting time. • Cost adequacy. • Lowered levels of natural sullying.
5. BENEFITS OF NANO CONCRETE • Concrete is stronger, lighter & more sturdy. • Concrete with great workability. • Lower expense for each building site.
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• Cessation of tainting caused by miniaturized scale silica strong particles. • Concrete with high initial & final compressive & tensile strengths.
6. PROPERTIES OF NANO SILICA Physical Properties Nano silica particles are very small, with more than 95% of the particles finer than I micron. Its physical properties are given in below Nano silica color is white.
Table 1 Typical physical properties of Nano silica
property values
Specific gravity 2.2 – 2.4
Partial size 17 Nano
Ph value 3.7 – 4.5
Specific surface area 200 ± 20
Sieve residue ≤0.04
Chemical Properties of Nano Silica Nano silica is composed primarily of pure silica in non-crystalline form x –ratification analysis of different Nano silica reveals that materials is essential its typical physical properties are given below: • Amorphous • Silicon dioxide≥99.8 • Carbon content ≤0.15 • Chloride content≤0.0202
Mix Proportion Cement = 270kg/m3 Fly ash = 115 kg/m3 Fine aggregate = 817.64 kg/m3 Coarse aggregate = 1032.43kg/m3 Water = 156.54 kg/m3 Super plasticizer = 7.827 kg/m3 Mix ratio (M30) 1: 2.63: 2.08
7. COMPRESSIVE STRENGTH TEST In the present investigation the cubes were casted with fly ash & Nano silica replacing cement, & tested. The dimensions of the cube are 150X150X150 mm in accordance to IS 456- 2000. The casted cubes kept for curing & tested after 3days, 7days, & 28days & the capacity
http://iaeme.com/Home/journal/IJCIET 1766 [email protected] Experimental Study on Strength of Concrete by Partial Replacement of Cement by Nano Silica and Fly Ash of concrete cube noted in KN .i.e. Force (P) by placing on any one side of the cube. The cross sectional area (A) of cube is 22500mm2. Finally the division compressive force by cross sectional area of cube gives the compressive strength of that particular cube. This test is carried out for M30 grade after 3days, 7days & 28 days. The compressive strength is represented in N/mm2. The Mathematical representation of compressive strength, σc =P/A. N/mm2
Table 1 Compressive strength of conventional concrete Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 23.66 22500 10.31 2 7 Days 39.00 22500 17.01 3 28 Days 72.89 22500 38.68
Table 2 Compressive strength of concrete with 5% of Nano silica Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 39.33 22500 17.15 2 7 Days 65.66 22500 27.63 3 28 Days 84 22500 37.33
Table 3 Compressive strength of concrete with 10% of Nano silica Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 48 22500 20.94 2 7 Days 79.00 22500 34.44 3 28 Days 92.33 22500 41.04
Table 4 Compressive strength of concrete with 15% of Nano silica Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 30.5 22500 13.55 2 7 Days 42 22500 18.22 3 28 Days 68 22500 30.22
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Figure 2 Comparison between Conventional concrete with different Replacements 8. TESTS FOR SPLIT TENSILE STRENGTH At first, take the wet Cylinder from water after 7, 28 of curing or any coveted age at which Split tensile strength to be evaluated. At that point, wipe out water from the surface of Cylinder after that, draw polar lines on the two ends of the Cylinder to guarantee that they are on the same plane. Next, record the weight & measurement of the Cylinder. Set the pressure testing machine for the required range. Place pressed wood strip on the lower plate & place the Cylinder. Adjust the Cylinder with marked the lines set apart on the edges or ends are vertical & centered over the base plate. Place the other pressed wood strip over the Cylinder. Lower the upper plate with the so as to just contacts the compressed wood strip. Apply the weight persistently without abrupt load at a rate inside the range 0.7 to 1.4 MPa/min (1.2 to 2.4 MPa/min based on IS 5816 1999) finally, note down the breaking load (P).
Table 5 Split tensile strength of conventional concrete Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 7.50 17673.75 1.06 2 7 Days 10 17673.75 1.14 3 28 Days 18.5 17673.75 2.61
Table 6 Split tensile strength of concrete with 5% of Nano silica Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 11 17673.75 1.55 2 7 Days 19.5 17673.75 2.75 3 28 Days 22.5 17673.75 3.18
Table 7 Split tensile strength of concrete with 10% of Nano silica Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 24.5 17673.75 3.47 2 7 Days 26.5 17673.75 3.74 3 28 Days 29.5 17673.75 4.17
Table 8 Split tensile strength of concrete with 15% of Nano silica Sl no Days Load in Area in Strenth Kn mm2 N/mm2 1 3 Days 13 17673.75 1.83 2 7 Days 16 17673.75 2.26 3 28 Days 18 17673.75 2.54
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Figure 3 Comparison between Conventional concrete with different Replacements
9. RESULTS • From the above compression strength values, Fly Ash & Nano silica concrete at 10% replacement is 41.04 N/mm2 which is 6.10% higher than target mean strength of M30 design mix at 28 days. • The specimen strength for compression of fly ash & Nano silica concrete at 15% replacement after 28 days is 30.22 N/mm2 which is lesser than conventional concrete by 21.8%. • The optimum replacement for the Nano silica is of 10% replacement of dry weight of cement as increase in the Nano silica content beyond this value reduces the strength of concrete when compared to conventional concrete. • The tensile strength of fly ash & Nano silica blended concrete is more than conventional concrete at 10% being optimum replacement which is one & half times more than the strength of conventional concrete at 28 days. • The tensile strength of concrete beyond the 10% replacement has shown considerable reduction in strength which is in the range of 2.54% less when compared to conventional concrete. • From the overall experimental results we can conclude that, by fly ash & Nano silica in concrete gives good compressive & tensile upto 10% replacement after 28 days.
10. CONCLUSIONS • From the compressive strength results, it can be observed that increase in concrete strength is observed on addition of a certain minimum quantity of Nano SiO2. The increase in strength is maximum for NS (nano silica) 1% b.w.c & least for NS 0.3% b.w.c (by dry weight of concrete).
• Addition of Nano silica (SiO2) there is considerable increase in the early-age strength of concrete when compared to the later strength of the concrete i.e. after 28 days strength. • The strength of concrete for compression is increased because of the changes in microstructure of the concrete i.e. the filling of voids in the microstructure by the Nano SiO2 particles which avert the growth of Ca(OH)2 crystals. Apart from this the Nano silica readily under goes and reacts with calcium hydroxide crystals changing them into C-S-H gel. Decrease in the Ca(OH)2 content is the reason for increase in concrete compressive strength.
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• Ca(OH)2 crystals are present in the Transition Zone which lies in between the aggregates and the hardened cement paste. Nano SiO2 reacts with these crystals & reduces their concentration, hence, strengthen the Transition Zone. Due to lesser availability of Nano SiO2 are utilized in the reaction and hence the increase in strength is inhibited with time.
• The research of pertaining papers reveals that concrete mixed with Nano SiO2 sets abruptly when compared to normal concrete. Since, the mix design is done in the absence of supper- plasticizers, the mix losses its moisture fast which affected the compaction of the mix using mechanical vibration. Lumps of the mix could be seen during the mixing of concrete. With increase in percentage of Nano SiO2 the compaction becomes tougher & tougher. This is the reason for to get inferior quality of concrete. It is recommendable to use superplasticizers with Nano silica.
• The Nano SiO2 mixed with concrete it will close the cavity in between the C-S-H gel, hence, making the microstructure more dense & uniform. REFERENCES
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