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Experimental Study Of Compressive Strength
And Micro Structural Analysis Of Reactive
Powder Concrete With Different Dosages Of
Nano-Silica
I. vamsi krishna, V.K Visweswara Rao
Abstract: Reactive powder concrete is a composite material used for strong and Durable structures. In this experimental study compressi ve strength of RPC with different dosages of nano-silica replacement is studied with combination of Quartz and Barite fine aggregates. compressive strength is carried out at the age of 28 days, the micro structural analysis SEM,EDS,FTIR shows formation of hydrated products like portlandite, Tobermorite, xonotlite and C-S-H gel.
Index Terms: Nano-silica, Silica Fume, Quartz sand, Barite, Quartz powder, Super Plasticizer, Reactive powder concrete, Interfacial Transition Zone(ITZ), Agglomeration, Thermal curing, Portlandite, Tobermorite, Xonotlite Reactive powder concrete (RPC).
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1
INTRODUCTION
Every year 10 to12 billion tone of concrete used in the world. Concrete is the one of the most extensively used engineering material composed of cement, aggregates, water and admixture. To increase its strength, durability many investigations are going to be conducted. In the construction sector the development of building materials improved a lot in mechanical, durability, excellent toughness for infrastructure. Now the investigation are going on a microscopic scale leads to development of ultra high performance concrete (UHPC) which constitute of only fine materials. More recently the use of RPC applications has expanded due to its high strength narrow profiles, such as bridge spans and building facades in which materials strength, wear resistance, chlorides and chemical attack. Pierre Richard and marcel cheyrezy[1] developed the first UHPC in the 19000,s at Bouygues laboratory in France. The first UHPC structure was sherbrooke bridge constructed in Canada. When compared with traditional concrete RPC consumes more portlandite. The secondary hydration is promoted by thermal curing between the mineral admixtures and Ca(OH)2 in concrete.(Dehui wang, caijun shi et al)[2]. M.K. Marloiya et al [3] Good bond strength is present at the interfacial zone of RPC between hydrated cement matrix and steel fiber .Now a day’s Nano-technology plays a key role in rpc, nano-silica, nanoclays, calcium carbonate, nano particles, increases in mechanical properties of cementitious materials. In this test results it conformed that nano-silica can improve the micro micro structural analysis with improving mechanical properties. A large amount of Ca(OH)2 crystals produced i.e portlandite formed due to
hydration reaction between water and cement.
It has high galatic specific surface area, it can react with Ca(OH)2 crystal quickly and the product of this reaction C-S-H
gel. The stability and integrated of the hydration products of the structure are improved as nano-silica particle act as nuclei in the C-S-H gel which improves mechanical and durability properties of concrete are expected to increased[4]. The main reference of this experiment is taken from [5] which explained the experiment investigation on RPC with Quartz and baryte aggregates with 0%, 2%, 5% of nano-silica by explaining the formation of Ca(OH)2 crystals reduced with addition of
silica which analyzed through the TG curves, But due to nano-silica interfacial transition zone between aggregates and binding paste matrix. The thermal curing for 48hours from 3 day of casting at initial stages is done due to good influence of hydration conditions and 1day specimen cubes kept in water before thermal curing, and kept in water till age of 28 days [6].Nano material effects comprise inter particle void filling, acceleration of cement hydration, formation of additional C-S-H gel by pozzolanic reaction, higher compressive strength, improved frost resistance, lower permeability. Nano silica do not only fill in the voids left by the larger size particles, but by being highly reactive they react with calcium hydroxide and additionally act as nucleation sites for the production of very fine C-S-H phase [7]. In the present investigation 53 grade ordinary Portland cement of brand BirlaA1 [7] and silica fume [8].Barite influenced on the internal structure of the element.Beside the Tobermorite, xonotlite, and CSH phase a high strength has been created, CSH phase is clearly amorphous. BaSO4 which is present in the product in the form
of flakes( unreacted barium). In research it has shown that barium sulphate does not fill the all the voids because of some phases present in product microstructure.In addition of BaSO4
only certain points connect to the phases, but after saturation it is only a filler of silicate mass. A high strength phase equated with Tobermorite, xonotlite, occurs in product with various frequency which are cristalline structures resembling to C-S-H gel are formed under thermal curing of 200oc[9].
2 OBJECTIVE OF THE STUDY
The preliminary objective of the study is comparing
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• I. Vamsi krishna, Department of civil engineering, G. Pulla Reddy Engineering College, Kurnool, Andhra Pradesh, INDIA Email: [email protected]
compressive strength of reactive powder concrete for 28 days by replacing (0-4%) of nano-silica in cement and micro structural analysis for high strength concrete sample is analyzed among all samples.
3 MATERIAL PROPERTIES
3.1 CEMENT
In the present investigation IS12269-2013 used for 53 grade cement of Birla A1 brand.
3.2 SILICA FUME
Silica fume is amorphous polymorph of sio2 which was brought
from the Astra chemicals Ltd Chennai confirmed to ASTM 1240 and IS 15388:2003. Packing density is done with silica fume by filling the voids between large particles of cement and filler grains as it is pozzalonic material which enhances mechanical properties to concrete.
fig.1 silica fume
Table- I: PROPERTIES OF SILICA FUME
S.NO PROPERTIES
1.
Form Ultrafine amorphous powder
2. Colour White
3. Specific gravity 2.63
4. Packing density 0.76 gm/cc
5. Specific surface 20m2 /g
6. Particle size 15µm
7. SIO2 98.9%
3.3 NANO-SILICA
Nano-silica is very fine amorphous polymorph of sio2 which
was brought from the Astra chemicals Ltd Chennai confirmed to ASTM 1240 and IS 15388:2003.
fig.2 nano-silica
Table- II: PROPERTIES OF NANO-SILICA
SNO. PROPERTIES
1. Form Ultra fine amorphous
powder
2. Colour White
3. Specific gravity 1.03
4. Density 2.2-2.6 g/ml
5. Specific
surface 200m
2
/g
6. Particle size 15µm
7. Sio2 99.89%
3.4 QUARTZ POWDER
The quartz powder is brought from astra chemicals Ltd, Chennai with the size of less than 150µm which has specific gravity of 2.6 Quartz powder increases packing density of mix by consuming portlandite through pozzalonic activity.
fig.3 Quartz powder
3.5 BARYTE
The baryte sand is brought from Gudumba thanda near kaluva bugga in Kurnool District. It is white in colour with specific gravity of 4.5 which particle size ranges from 600µm-150µm.
fig.4 Baryte sand
3.6 QUARTZ SAND
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fig.5 Quartz sand
3.7 MICRO STEEL FIBER
Brass coated steel fiber is brought from Fiber Zone, Ahmadabad, India with aspect ratio of 38 having length of 13mm, diameter of 0.35mm with Tensile strength of 2000Mpa.
fig.6 Micro steel fiber
3.8 SUPER PLASTICIZER
Master Glenium sky 8233 Super plasticizer is brought from ready mix concrete plant Nellore
Table- III: PROPERTIES OF SUPER PLASTICIZER
S.NO PROPERTIES MASTER GLENIUM SKY 8233
1. Type of sp Polycarboxylic ether
2. Appearance Ligth brown
3. PH value > 6
4. Specific gravity 1.08
5. Solid content Less than 30% by weight
6. Chloride content <0.2%
4 EXPERIMENTAL PROGRAMME
4.1 Mixing Procedure
1. A pan mixer machine of 40kg is used to mix RPC.
2. Dry ingredients like cement, quartz powder, silica fume are placed in the mixer and mixed for about 3 minutes.
3. Required percentage of Nano-silica 30% of water at high speed 120 rpm for 1minute let it mix.
4. Then quartz sand & Barite added to the mix depend on type of mix then 70% of water along half of sp is added and mixed for 2 minutes.
5. Then add steel fiber slowly then mixing continued for 2 minutes.
4.2 CURING PROCESS
1. After 24 hours of casting specimen cubes are de-moulded and allow for water curing for 24 hours and removed from water allow the cube to dry at room temperature.
2. Then allow the specimen cubes for thermal curing at temperature of 200oc through oven.
3. After 48 hours completion sample was taken outside enable to cool till thermal equilibrium was attained with atmospheric temperature and they were kept in the water till age of 28days.
Table- IV: mix proportions
4.3 MIX proportions
The following details explained about designation of mix used in the table-IV
QB0-quartz and barite aggregates with 0% nano-silica QB1-quartz and barite aggregates with 1% nano-silica QB2- quartz and barite aggregates with 2% nano-silica QB3- quartz and barite aggregates with 3% nano-silica
QB4- quartz and barite aggregates with 4% nano-silica
5 RESULTS AND DISCUSSION
5.1 Compressive strength
The high compressive strength is obtained for optimum of 3% of nano-silica with 182mpa. Due to well packing taken place
Kg/m3 QB0 QB1 QB2 QB3 QB4
CEMENT 1000 990 980 970 960
NANO-SILICA 0 10 20 30 40
SILICA FUME 250 250 250 250 250
QUARTZ POWDER 390 390 390 390 390
QUARTZ SAND 500 500 500 500 500
BARYTE 849 849 849 849 849
MICRO STEEL FIBER 198 198 198 198 198
SUPER PLASTICIZER 19 19 19 19 19
WATER 295 295 295 295 295
with nano-particles and reason behind to decrease strength agglomeration of particles.
fig.7 compressive strength
5.2 MICRO STRUCTURAL ANALYSIS
5.2.1 Scanning Electron Microscope (SEM)
SEM provides detailed high resolution images of sample by rastring a focussed electron beam across the surface detecting secondary or backscattered electron signal. Through SEM examination of the RPC not only quartz the baryte influenced on the internal structure of the element.
fig.8 formation of xonotlite in 3% of nano-silica
fig.9 formation of Xonotlite in 3% of ns
Beside the Tobermorite, xonotlite, and CSH phase a little
strength has been created BaSO4 which is present in the
product in the form of flakes( unreacted barium). In research it has shown that barium sulphate does not fill the all the voids because of some phases present in microstructure product.In addition of BaSO4 only certain points connect to the phases,
but after saturation it is only a filler of silicate mass. A high strength phase equated with Tobermorite, xonotlite, occurs in product with various frequency which are cristalline structures resembling to C-S-H gel are formed under thermal curing of 200oc. Tobermorite(Ca5Si6O16(OH)24H2O) has been reported
as predominent phase at temperature in the range of 1200 c-1800c.Xonotlite (Ca6Si6O17(OH)2) forms at a temperature
above 1500c and has a neddle like habit.
5.3 Energy Dispersive X-ray Spectroscopy
fig.10 formation of peaks in 3% of ns mixIn this present investigation the EDX analysis of RPC with combination of Quartz and Baryte with 3% Nano-Silica is studied. It is an analytical technique used for chemical characterization of sample. The above figure shows the main chemical compositions are formed like C, O, Na, Al, Si, Mo, Ca, Ba, Fe, in traces amount where in RPC are shown.
Table- V: percentages of materials in 3% of ns mix
Element Weight% Atomic% Net Int.
C K 4.64 8.84 4.59
O K 40.25 57.55 87.10
Na K 1.00 0.99 2.45
Al K 1.59 1.35 7.12
Si K 24.09 19.62 121.04
Mo L 2.33 0.55 4.32
Ca K 13.04 7.44 30.66
Ba L 6.96 1.16 4.51
Fe K 6.10 2.50 5.90
fig.10 chemical composition of RPC with 3% nano-silica
5.4 Fourier Transformation Infrared Spectroscopy:
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fig.11 ftir for 3% nano-silica
The wave number is represented in X-axis, Percentage of Transmitance in Y-axis, the formation of hydrated products like Portlandite, C-S-H gel, Tobermorite, Xonotlite ploted as shown in fig11C-S-H: It has rich structure and contain peaks for si-o stretching, si-o-si bending,internal eformation of si-o tetra hedra and ca-o poly hedra characteristic peaks at frequiences in between 940 cm-1 to 980-1 which denoted as 1 in graph. Tobermorite: The bands of Tobermorite formed in the reigon between 800 cm-1 to 860 cm-1 which is denoted with 2 in the above fig11. Xonotlite: The bands of xonotlite formed in the reigon between 590 cm-1 to 670 cm-1 which is represented as 3.. It contains the peaks releated to the vibrations of sio4, tetra
hedra o-si-o bending which is mineral layered structure. Portlandite: The bands of portlandite is formed in the region 3600 cm-1 which is denoted with 4 in graph.
6. CONCLUSIONS
1. The Highest compressive strength obtained is 182 mpa at 3% of Nano-silica Replacement.
2. The compressive strength increases by 10.9% with respect to mix with 0% Nano-silica replacement. 3. The decrease of compressive strength for 4% is due
to formation agglomeration due to over dosage of nano-silica percentage.
4. High silica contain is one of the factor to increase strength with formation of Interfacial transformation zone between fine aggregates and paste.
5. The formation C-S-H gel, Tobermorite, Xonotlite crystal is conformed through SEM images, FTIR , EDS graphs.
6. Thermal curing process played a major role in this investigation after 1 day of water curing and 2 days of thermal curing at inital stages hydrated products like C-S-H gel, Tobermorite, Xonotlite crystal formation taken place at particular temperature upto 2000c.
7.
REFERENCES
[1] Pierre Richard, Marcel Cheyrezy, “composition of the Reactive Powder concrete”, cement and concrete Research journal, pp 1501-1511.1995. [2] Dehui Wang, caijun shi, “A review on ultra high
performance concrete: part II. Hydration,
microstructure and properties”, Construction and building material 96(2015) 368-377.
[3] M.K Maroliya, “Micro structure analysis of Reactive powder concrete”, Interantional Journal of Engineering research and Development volume 4, issue 2 (October 2012), pp. 68-77.
[4] T. JI, preliminary study on the water permeability and microstructure of concrete incorporating nano-sio3. Cem. Concr. Res. 35(2005) 1943-1947. [5] Influence of nano-silica and baryte aggregate on
properties of ultra high performance concrete. [6] T. Chandra Sekhara Reddy “Study of the effect of
quartz powder on compressive strength in ultra high performance of concrete”. IJTIMES ISSN: 2455-2585, IF:5,22(SJIF-2017)
[7] V.K Visweswara Rao “A study on the mechanical properties of reactive powder concrete using granite powder and nano-silica” ISSN: 2319-8753. [8] IS 12269-1987 Specification for 53 Gade ordinary
Portland cement
[9] ASTM 1240 and IS15388:2003 specification for silica fum
