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514 | P a g e
EXPERIMENTAL INVESTIGATIONS ON THE
EFFECT OF INCORPORATING GEOSYNTHETICS
FIBRES IN GEOPOLYMER CONCRETE (GPCC)
Prof. Ashok W.Yerekar1, Dr. Rajabhau S. Londhe
2, Vikram Khajekar
3
1Assistant Professor and Research Scholar, Department of Civil Engineering, P.E.S. College of
Engineering, Aurangabad; affiliated to Dr. B.A.M.U., Aurangabad; Maharashtra - 431005,(India.)
2Associate Professor, Applied Mechanics Department, Govt. College of Engineering, Aurangabad;
affiliated to Dr. B.A.M.U., Aurangabad; Maharashtra - 431005, (India.)
3P.G.Student, Department of Civil Engineering, P.E.S. College of Engineering, Aurangabad;
affiliated to Dr. B.A.M.U., Aurangabad; Maharashtra - 431005, (India),
ABSTRACT
This paper describes the impact of incorporation of single type Geosynthetic fibres like GGR (Tensar SS40-
Biaxial);having aspect ratio >50 with volume fractions(Vf ) ranging from 0% to 0.8% at an interval of 0.1% by
mass of normal GPC used ; with low calcium fly ash- based GPCC / GPC, samples are cured at constant
temperature of 900C in an Oven & tested for its Compressive( σcu ),Flexural( σcr ),Split tensile( σcys )and Bond
strengths( σbd ) for various mix strengths, which are identified by performing rigorous trials-and-errors during
experimental investigations. These experimental tests were carried out according to test procedures in the
relevant Indian Standards given for OPC wherever applicable and explains the manufacturing and design
methodology by using various ingredients like AAS with 13 Molar NaOH , 2.5 mass ratio with dosage of
Sikament 610 ut.250 Kg (Naphthalene based) as Super-Plasticizer. It has been experimentally revealed that the
inclusion of GGR fibres in to GPC enhances the Mechanical and Elastic properties of GPCC and they are also
compared and verified by various analytical formulae available in the literature. Thus the test results so
obtained may proved that the GPCC is a viable and promising composite construction material for the future
having good performance characteristics and eco-friendly behaviour as well compared to conventional
concretes.
Keywords : Geosynth etically reinforced Geopolymer Concrete (GSRGPC/GPCC), low calcium
Class F Fly Ash , Alkaline Activated Solution, Super- Plasticizer, Molarity, Aspect ratio ,GGR
fibres, volume fractions(Vf ).
I. INTRODUCTION
Today’s world is a concrete world for global construction industries. While in manufacturing process of cement,
the Global cement industries contributes more than @ 1.35 billion tones of Green House Gas (GHG) emissions
annually & approx. 7% of total man made GHG emissions into the earth atmosphere [1-2].Also during the
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manufacturing of cement, a very large amount of CO2 is emitted into the atmosphere. This CO2 emission
increases the temperature and resulted in an increase in the overall Global Warming. Therefore in very near
future, there will be an adverse impact on both cement productions and construction industries. Although the use
of Portland cement is still unavoidable, many efforts are being made in order to reduce the use of OPC in
conventional concretes. J. Davidov its [3] has invented a new technology with its chemistry and terminology
called ―Geopoly mer‖, in which cement is totally replaced by fly ash and activated by alkaline solution.
Geopoly mers thus forms the Three-dimensional disordered frameworks of the tecto- aluminosilicate types with
the general empirical formula as…
M n [- (SiO2) Z -AlO2] n.wH2O……………. (1)
where n is the degree of polycondensation, M is predominantly a monovalent cations [ like K+, Na] though Ca2+
may replace two monovalent cations in the structures[4]. The present experimental investigations are carried out
by the new method of design to produce GPCC matrixes analogous to the OPCC and similar to IS: 10262-2009
as basic method [5].
II. LITERATURE SURVEY
McCaffrey R. [2] suggested three alternatives to reduce the amount of CO2 from Cement Industries...they are (1)
To decrease the amount of calcinide material in the cement, (2) to decrease the amount of cement from the
concrete and (3) to reduce the number of buildings i.e. construction industries those using cement. Mehta, P.K.
[6] also proposed two stages in the production of environmental friendly concrete…(1) A ―short term effort
―also known as an industrial ecology , is an attempt to use fewer natural resources, and to utilize the least energy
and minimizing CO2 emissions and (2) the ―long term view‖ is to reduce the impact of unwanted industrial by-
products by lowering down the rate of natural material consumptions. Thus development of GPC is an
indispensible step towards the production of eco-friendly concrete. GPC is an inorganic compound made up
from alumino- silicates [7] in an amorphous form. GPC technology not only substantially reduces CO2 emission
from cement industries, but also utilizes the waste materials or industrial by-products like fly ash(FA), silica
fume(SF), GGBS etc. The fly ash is one of the reliable basic source material for making GPC, which is
abundantly available worldwide and its usage is very limited [1-5, 8].With silicon (Si) and aluminium (Al) as its
main constituents, the fly ash has found to have great potential as a cement replacing material in concrete & the
concrete made with such an industrial wastes is also eco-friendly. As GPC is the new concrete in global
perspective, the properties of fresh and hardened GPC are yet to be studied systematically. It is observed that the
fresh GPC has stiff consistency and high viscosity [9–11].It is also found that geo-polymerization can make
profitable contributions towards recycling and utilization of waste materials. This technology is, however, still
fairly unknown and predictably viewed with skepticism by most workers in the field of traditional waste
processing techniques [12–14]. Joseph Davidovits, the founder of GPC [9-10] claims that the Egyptian
Pyramids were built by casting GPC on site and reported that this concrete has an excellent mechanical
properties, it neither dissolved in an acidic solutions nor generates any deleterious Alkali-Aggregate-Reaction,
even in the presence of high alkalinity ambiences [7].
Chinda prasirt et al. [15] studied the workability and strength of coarse high calcium fly ash based geopolymer
concrete. Prof B.V. Rangan [16] has proposed the Mix Design procedure for production of fly ash based
516 | P a g e
Geopolymer Concrete, where as Anuradha et al. [17] have presented Modified Guidelines for Mix Design of
GPC using IS: 10262-2009. Patankar et al. [18] studied the effect of sodium hydroxide on flow and strength of
fly ash based geopolymer mortar. Theory and applications about the potential use of geopolymeric materials to
immobilize toxic metals have been presented by Van Jaarsveld et al. [19]. The effect of recycled concrete
aggregate on various strengths of geopolymer concrete has been studied by Anuar et al. [20]. Alonso and
Palomo [21] have used metakaolin as a substitute for the fly ash to study the effect of temperature and activator
concentration on geopolymer concrete. Sumajouw et al. [22] have carried out a study on slender reinforced
columns using fly ash-based geopolymer concrete. Bakharev ,T., [23] studied the resistance of geopolymer
material to acid attack, whereas Pernica et al. [24] studied the effect of test condition on the bending strength of
a geopolymer reinforced composite. Vijai et al. [25–27] has studied effect of glass fibres and steel fibres on
various strengths of geopolymer concrete. Sathish Kumar et al. [28] also studied the properties of glass fibre
reinforced geopolymer concrete. Bhowmick and Ghosh [29] studied the effect of synthesizing parameters on
workability and compressive strength of fly ash based geopolymer mortar. Y.M.Ghugal and Bhalchandra [30]
studied the effect of steel fibres on mechanical and elastic properties of high strength silica fume concrete.
Earlier work by D. Hardjito et.al. [31-32] reported that the manufacturing process and effects of various
parameters such as elevated curing temperatures, curing time, ratios of (Sodium silicate/sodium hydroxide), and
admixture dosages are reported on compressive strength of GPC.
III. EXPERIMENTAL PROGRAMME
3.1 Materials
Fly ash-(as cementitious/source material) ASTM low calcium - type F- Fly ash is the residue from the
combustion of pulverized coal collected by mechanical or electrostatic separators from the flue gases of thermal
power plants. The important characteristics of fly ash are its particles are in spherical form, which improves the
flowability and reduces the water demand. The fly ash used in this experimentation is obtained from the silos of
Thermal Power Station situated at Parali -Vaijanath, Dist. Beed, Maharashtra State, India; which is of low
calcium, Class F type. The chemical composition of fly ash is shown in table I, with its specific gravity 2.3,
obtained from test reports of CSRL–STRUCTWEL LAB. Pune PVT. ltd., Maharashtra, India.
Table 1: Chemical Composition of Fly Ash
Sr.No.
Chemical constituents
in % or Type of Test
Percentages
As per Test
Result%
Requirement as per IS:3812-2003 [33]
Part-I Part-II
Siliceous fly
ash
Calcareous
fly ash
Siliceous
fly ash
Calcareous
fly ash
1 Silica content SiO2 61.49 35.0 min. 25.0min. 35.0 min. 25.0min.
2
Alumina content(Al2O3)
Ferric Oxide(Fe2O3) 31.34
---- ---- ---- ----
---- ---- ---- ----
3 Silica+ Alumina +Ferric
Oxide 92.83 70 min. 50min. 70min. 50min.
4 Calcium Oxide(CaO) 1.92 ---- ---- ---- ----
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5 Magnesium
Oxide(MgO) 0.56 5 max. 5max. 5max. 5max.
6 Sulphur Tri –Oxide(SO3) 0.51 3max. 3max. 5max. 5max.
7 Loss on Ignition(LOI) 0.49 5max. 5max. 7max. 7max.
8 Chloride ---- 0.05 max. 0.05 max. 0.05max. 0.05max.
F.A. and C.A:- Locally available Godavari (Paithan) river sand as fine Aggregates and Crushed Basaltic stones
(from stone crushers near outskirts of Aurangabad city of Waluj premises) were used as fine Aggregates and
Coarse Aggregates respectively with C.A. of NMS as 20 mm and 12.5 mm having their physical properties as
shown in Table 2 and their gradings are shown in Table 3 and Table 4 respectively.
Table 2: Physical Properties of Aggregates (FA &CA) [34]
Physical Properties Coarse Aggregates(CA) Fine Aggregates(FA)
CA-I CA-II FA (Sand)
Type crushed Crushed Godavari sand
Maximum size 20mm 12.5mm 4.75mm
Specific Gravity 2.641 2.639 2.563
Water Absorption 0.58% 0.84% 1.58%
Moisture content Nil Nil Nil
Table 3: Gradings of CA {In Saturated Surface Dry- Conditions}
Sr.No.
IS Sieve
sizes in
mm
Cumulative percentage Passing for
CA-I
20mm
CA-II
12.5mm
Combined Aggregates
CA-I :CA-II 65:35
Required grading as
per BIS 383:1970 34]
1 40 100 100 100 100
2 25 100 100 100 ---
3 20 87.50 100 89.90 90-100
4 16 6.80 100 39.42 --
5 12.5 0.40 96.5 35.04 --
6 10 0.00 76.40 27.75 25-35
7 4.75 0.00 0.96 0.35 0-10
8 2.36 0.00 0.00 0.00 ---
Table 4: Grading of FA {Saturated Surface Dry- conditions}[34]
Sr.No. IS Sieve size
designation mm
Cumulative percentage Passing
for Godavari river sand Remarks
1 10 100
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2 4.75 92 FM = 3.74
Confirming to Zone II,
As per IS 383-1970
[34]
Specific Gravity-2.61
3 2.36 84.80
4 1.18 59.90
5 600µ 35.30
6 300µ 10.60
7 150µ 0.62
8 75µ 0.10
Total 374.32
3.2 Alkaline Activated Solution (Aas)
Sodium Hydroxide (NaOH) - (Laboratory Grade):- in flake or pellets/solid form and its cost is mainly varied
according to its purity and its main function is to activate the Sodium Silicate solution hence it is better to use
it within economical purity i.e. up to the purity range from 94% to 96%.The concentrations of NaOH used was
13 Molarity as per previous research[5].
Sodium Silicate (Na2SiO3) Solution - In Gel form (known as Water Glass) with a ratio of oxides between (SiO2
to Na2O ) = 2 was used ;which were silicates which are supplied to the detergent company and textile industries
as bonding agent; same type of silicates were used for this investigation for making Geopolymer concrete. The
Chemical Compositions of both NaOH and Na2SiO3 are presented in Table 5.
Table 5: Chemical Compositions of NaOH and Na2SiO3
Chemical Compositions of
NaOH
(Min. Assay)
Percentages
97%
Chemical compositions
of Sodium Silicate (Na2SiO3)
Solution
Colour-light yellow liquid
Percentages
Carbonate(Na2O3) 2 Na2 O (%) 16.37%
Chloride(Cl) 0.01 Si O2 (%) 34.31
Sulphate(SO2) 0.05 Ratio of Na2O: SiO2 1:2.09
Potassium(K) 0.1 Total Solids (%) 50.68
Silicate(Si2 O3) 0.05 Water content H2 O(%) 49.32
Lead(Pb) 0.ooi Appearance Liquid(Gel)
Zink(Zn) 0.02 Boiling point 102
0c for 40%
aq.soln
Specific gravity 1.16 Specific gravity 1.57
Colour Colourless Molecular Weight 184.04
Preparation of Sodium Hydroxide Solution: -Sample case explained as per [18]
1 Mole of Sodium Hydroxide Solution = [40 gm Flakes of NaOH + Distilled Water] {Since Molecular Weight
of NaOH is 40 = 1 Litre Solution of NaOH} temp.rises to 700 to 80
0C.
519 | P a g e
Hence, it is suggested to prepare NaOH Solution 3 days prior to the casting of concrete cubes etc to avoid any
contaminations during the mixing of ingredients of GPC. For e.g. for the preparation of 13M NaOH Solution =
{520gms flakes of NaOH+750 ml water} steered solution and after cooling; add remaining quantity of water to
make one litre complete solution. Always avoid direct contact with skin and eyes to avoid severe burns.
Water:-Potable water which is available in laboratory was used for mixing purposes.
Geosynthetics Fibres (Tensar SS40-Biaxial)-Since Geopolymer cement concrete is more brittle than
conventional concrete, in these investigations Geosynthetics fibres (GGR Types only) are used to convert GPCC
into more ductile or elastic one. Geogrids fibres with aspect ratio (𝐿𝑓/ h𝑓= 35.54/1.27 =28) 28 to 50 is used with
modulus of elasticity (E) in the range of 12000 -18000 MPa {MN/m2} say 15000 MPa, Specific Gravity ranging
from 1.22-1.38, melting point @ 2600C., unit mass or weight/unit area-345-930 g/m
2, thickness ranges from 10-
300 mils or generally 20 mils i.e.0.025 mmx20 = 0.5mm (since 1 mil=0.025mm).
Super-plasticizers: -Sikament 610 ut.250 Kg (Naphthalene based) was used as super plasticizer/ an admixture,
its Quality Assurance Certificate shown in Table 6.
Table 6: Quality Assurance Certificate
Property
Specifications
Actual
Results Test Results
Min Max
Aspect Dark Brown Lump Free
Liquid OK PASS
pH Value 7.00 9.00 8.80 PASS
Specific Gravity 1.15 1.19 1.18 PASS
Solid content (%
by wt.) 30.88 34.13 32.42 PASS
Chloride content,%
by wt. 0.00 0.20 0.00 PASS
AAS Preparations:-For preparing 13 Molarity NaOH solutions: - {500gm water + 520 gm pallets} are used.
For making Alkaline Activator Solution …NaOH is mixed with Na2SiO3 at room temperature, in the ratio of
{Na 2SiO3 to NaOH =2.5} were kept constant [14]. When both the solutions mixed together then both the
solutions start to react .i.e. polymerization takes place: during these, it liberates large amount of heat, so it is
recommended to leave it for 24 hours prior to its use and if it exceeds 36 hours then it terminates to semi-solid
liquid state, so the presently prepared solution should be used within this time; therefore Alkaline Activator
Solution is to be prepared one day before casting both GPCC or GPC sample’s.
Mix Proportion of Geopolymer Concrete. Fly ash, CA, FA are initially mixed together in dry state and then the
liquid component of the mixture i.e. AAS is added to prepare wet mix until it gives homogeneous mix with or
without super plasticizer as per workability requirements. Mix proportions and fibre quantity of geopolymer
concrete per cubic meter are given in Tables 7 and 8 respectively.
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Table 7: Mix Proportion of Geopolymer Concrete per Cubic Meter
Fly
ash
NaOH
(13M) Na2SiO3 FA CA
Extra
water
Total Quantity of Ingredients
(kg)
310 54.25 54.25 744 1387.90 62.00
2612.401
1part 0.175
part
0.175
part
2.40
part
4.4771
part
0.20 part
Proportions [AAS/FA]=105/300
= 0.35
Table 8: Quantity of fibres for Various Mixes
Geosynthetics
(Geo-grids
only) fibre
(%)
0.0 0.1 0.2 0.3 0.4 0.5
0.6 0.7 0.8
Fibre
quantity
(kg/m3)
0.0 2.6
13
5.2
2
7.84 10.45
2
13.06
5
15.67
8
18.286 20.899
Super
plasticizer[as
per actual]
(kg/m3)
0.0 0.1
0
0.2
00
0.22
5
0.370 0.500 0.723 0.981 1.052
3.3 Specimen Preparations and Test Results
For testing the GPC/GPCC , Specimens are casted as per IS Codal requirements like (1) cubes for Compression
tests: size (150x150 x150) mm; (2) Cylinders 150 mm diameter x 300 mm height for Split Tensile tests, (3)
Beams of sizes (100 × 100) mm c/s and 500mm length with two-point loads applied at the middle third of the
span for Flexural strength tests and (4) For Bond Strength samples as per IS:2770-1997; out of which three
specimens each were used to determine the corresponding Compressive Strength ,Split Tensile Strength,
Flexural strength and Bond strength each at 7 days for different grades of GPC/GPCC and the reported
strengths are shown in Table 9. A total of (3x9x4=) 108 and more specimens were tested in this experimental
investigations so as to arrived at the Optimized Grades of GPCC both with and without incorporating
Geosynthetics Fibres- in the form of rectangular pieces of the cube sizes within the cubes /or in the form of
circular discs of cylindrical sizes at proper spacing and strips having beam c/s into the beams of beam length
etc.. {Only Geo-gride type’s fibres were used} and the results are shown in Table 9.
521 | P a g e
Table 9: Comparison of compressive strengths (σcu), flexural strengths (σcr ), split-tensile
strengths
(σ cys), and bond strengths (σ bd) for various percentages of Geosynthetics fibres (𝑉𝑓).
Strengths (MPa) Percentage increase in strength
𝑉𝑓 σcu σcr σ cys σ bd σcu σcr σ cys σ bd
0.0 28.90 3.20 3.41 12.10 0.00 0.00 0.00 0.00
0.1 31.50 3.63 3.71 12.40 8.99 13.55 8.80 2.84
0.2 33.60 4.16 4.41 12.80 16.26 30.00 29.32 5.78
0.3 34.50 4.20 4.51 13.40 19.38 31.25 32.26 10.74
0.4 34.68 4.26 4.62 14.10 20.00 33.12 35.48 16.53
0.5 34.72 3.86 4.41 13.60 20.14 20.63 29.33 12.40
0.6 31.50 3.50 3.93 13.30 8.99 9.53 15.25 9.91
0.7 31.40 3.33 3.81 13.01 8.65 3.33 11.73 7.52
0.8 29.35 3.32 3.63 12.96 1.56 3.32 6.45 7.10
All in aggregates were prepared by bringing them in Saturated Surface Dry (SSD) conditions. All the GPCC and
GPC samples were made with mix design procedures as follows and mentioned in [35] all respects as far as
possible.
1. All ingredients of GPCC/ GPC are collected separately and mixed in the Pan Mixture for @ 5 minutes.
2. The Alkaline Activated solution/liquid was then added to dry mixture with actual quantity of super
plasticizers, as necessary for workability and then mixing was done for another 5 minutes so as to obtain a
homogeneous matrix.
3. After this mixing, the flow values /slump values of fresh GPCC/GPC was determined as per slump tests
confirming to the IS: 516-1959[36] same as for OPCC in Concrete Technology.
4. After flow test, the fresh GSRGPC/GPC were placed in corresponding moulds as described in the IS: 516-
1959[36] and compacted by usual methods that are used in OPCC and the test results are shown in Table
no10.
Table 10: Workability, Wet Density, and Dry Density of GPCC Mixes.
𝑉𝑓 (%) Flow
(mm)
Decrease in
flow (%)
Degree of
workability
Density (kg/m3) Increase in Density (%)
Wet Dry Wet Dry
0.0 63.23 0.00 High 2586 2465 0.00 0.00
0.1 59.20 6.37 High 2594 2469 0.31 0.163
0.2 56.43 10.75 High 2620 2478 1.32 0.53
0.3 53.56 15.29 High 2638 2499 2.01 1.38
0.4 50.75 19.73 High 2649 2510 2.44 1.83
0.5 48.10 23.93 Medium 2670 2520 3.25 2.07
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0.6 46.10 27.09 Medium 2674 2530 3.40 2.47
0.7 45.10 28.67 Low 2678 2533 3.56 2.60
0.8 44.80 29.15 Low 2680 2536 3.64 2.88
5 The specimens both GPCC and GPC were left standing for at least 1 hour and then cured at 900C in the
thermostatically controlled oven for 7days.
6 Demoulding was then done after 7 days curing age and then all the specimens were left at room
temperature for @ an hour for cooling and then the specimens were ready for testings.
7 Then, the various types of strength tests were performed as per IS Codal provisions for both GPCC & GPC.
3.4 Analysis of Test Results
The workability of fresh geopolymer concrete is measured by flow table apparatus as per IS: 1199–
1959[37].After making the homogeneous mix, concrete was placed in two layers; each layer should be
compacted 20 times with the tamping rod and then level the top surface. Lift the mould away from the concrete
one minute after completing the mixing operation. Then apply fifteen jolting and measure the average diameter
of subside concrete at minimum six equal intervals expressed as a percentage of the original base diameter.
Examination of Table 10 indicates that the workability of geopolymer concrete including Geosynthetics fibre
reduces with increase in fibre contents. It might be due to viscous nature of geopolymer concrete and uneven
distribution of matrix in the fibres incorporated into it.The maximum decrease in flow is 29.15% at 0.8% of
fibre content. Both the wet and dry densities were recorded throughout the experimental program and the
average values for densities are listed for various volume fractions of fibres. Table 10 shows that the inclusion
of fibres increases the density of concrete due to good particle packing and reduction in air content. The
maximum increase in wet density is recorded to be 3.64 %, whereas it is 2.88% in case of dry density.
Discussion on Mechanical Properties:- The tests on hardened GPCC are carried out according to the relevant
BIS standards wherever applicable. New formulae based on law of mixtures for mechanical properties of GPCC
are proposed in this investigation. The various strengths were calculated and they are compared with the
strengths obtained by using experimental work is presented in Table 9.
Compressive strength is determined by carrying out compressive strength test on cubes of sizes (150 ×
150×150) mm and the same is calculated by
σcu= (P/A)…………………………(2)
From the table 9, it is clearly seen that the compressive strength of concrete increases w.r.t. fibre content up to
0.5% and then it decreases, because higher percentage of fibre content reduces the workability of GPCC. The
maximum increase in compressive strength of GPCC is 20.14% over that of normal GPC. The new expression
for compressive strength in the third degree polynomial in terms of �f is proposed and it is obtained by plotting
the curve, as shown in Graph-1between percentage V f v/s σcu given by the following equation:-
σcu = 27.20 Vf3 -67.26 Vf
2 + 37.12Vf + 28.71……………. (3)
Flexural test is carried out on beams of size (100×100) mm c/s and 500mm length with two-point loads applied
at the middle third of the span. The flexural strength is obtained by using the analysis of law of mixtures
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Graph No.1: Showing Relationship Between Percentage �� % Of Fibres V/S Σcu
Σcr = (PL /B D2) …………..(4)
Table 11: Optimum fibres and Maximum Percentage Increase in Various Strengths
Strengths Vf % Maximum strength
(MPa)
Percentage increase in
Strength (%)
σcu 0.5 34.72 20.14
σcr 0.4 4.26 33.12
σ cys 0.4 4.62 35.48
σ bd 0.4 14.10 16.53
From Table 11, it is observed that the maximum increase in flexural strength is 33.12 % with 0.4% of fibre
contents over that of GPC. The proposed new expression for flexural strength in the third degree polynomial in
terms of �� can be obtained from the Graph 2, given by the following equation:
σcr = 12.98 �f3 – 21.22��
2 + 8.873�� + 3.110……. (5)
Graph No. 2: Showing Relationship between Σcr V/S Vf % Of Fibres
y = 27.20x3 - 67.26x2 + 37.12x + 28.71R² = 0.942
0
5
10
15
20
25
30
35
40
0 0.2 0.4 0.6 0.8 1Cu Poly. (Cu)
y = 12.98x3 - 21.22x2 + 8.873x + 3.110R² = 0.943
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 0.2 0.4 0.6 0.8 1
Poly. (6cr)
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Cylinders of size 100 mm diameters and 300mm lengths are used to obtain Split-Tensile Strength. The Split-
tensile strength is obtained by using,
σ cys = 𝟐𝐏
𝛑𝐝𝐋…………….. (6)
The maximum increase in split-tensile strength is 35.48% with 0.4 % of fibre content over that of normal GPC.
The proposed new expression for split-tensile strength in the third degree polynomial in terms of �� is obtained
from the relationship between �� % v/s Split Tensile Strength (6Cys) as shown in Graph no.3 by the following
equation
Graph No.3: Showing Variation of Split Tensile Strength (Σ Cys) W.R.T. �� % Of Geo-Synthetic
Fibers
Σ Cys = 8.013��3 −16.21�� 2 +
8.202�� + 3.290…. (7)
The bond strength test was carried out according to IS: 2770 [47].In this test a 16mm dia. deformed steel
reinforcing bar was embedded into the Geopolymer concrete cube mixed with fibres, at centre up to depth of
150 mm. The total length of bar is 600 mm. All specimens are tested up to failure of bar matrix interfacial bond.
The peak load at failure of bond and maximum slip is observed. All specimens failed with vertical crack along
the embedded length of bar with cracking sound. The maximum increase in strengths is 16.53% with 0.4% of
fibre content over that of normal GPC. The bond strength has been computed from the following expression:-
σ bd =𝐏
𝛑𝐃𝐋 ...................................... (8)
The proposed new expression for bond strength in the third degree polynomial in terms of �� is given by the
following equation:-
y = 8.013x3 - 16.21x2 + 8.202x + 3.290R² = 0.913
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
0 0.2 0.4 0.6 0.8 1
Cys Poly. (Cys)
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Graph No.4: Showing Relationship Between Σ Bd V/S %
Σ Bd = 18.82��3
– 37.73��2 + 21.00�� + 10.38…. (9)
Optimum fibre content for various strengths of GPCC are presented in Table 11. The comparison of various
strengths of Geopolymer Concrete Composites obtained by using proposed empirical formulae are presented in
Table 12.
Table 12: - Determinations of Compressive strength (𝟔 cu), flexural strength (𝟔 cr), split-tensile
strength (𝟔 cys), and bond strength (𝟔 bd) for various percentages of Geosynthetics fibres (��)
obtained by applications of proposed equations….
Strengths Percentage increase in strength
by proposed equations
��
%
σ cu
by
Eqn.2
σ cu by
Eqn.3
σ cr
by
Eqn .4
σ cr by
Eqn.5
σ cys
by
Eqn. 6
σ cys
by
Eqn.7
σ bd by
Eqn.8
σ bd by
Eqn.9 σ cu σ cr σ cys σ bd
0.00 28.90 28.710 3.20 3.110 3.41 3.290 12.10 10.38 0.00 0.00 0.00 0.00
0.1 31.50 28.750 3.63 3.118 3.71 3.298 12.40 10.401 0.139 0.257 0.243 0.202
0.2 33.60 28.784 4.16 3.127 4.41 3.306 12.80 10.422 0.257 0.547 0.243 0.405
0.3 34.50 28.820 4.20 3.136 4.51 3.314 13.40 10.443 0.383 0.836 0.729 0.606
0.4 34.68 28.860 4.26 3.145 4.62 3.3225 14.10 10.464 0.522 1.124 0.987 0.810
0.5 34.72 28.900 3.86 3.154 4.41 3.330 13.60 10.484 0.661 1.415 1.215 1.002
0.6 31.50 28.930 3.50 3.163 3.93 3.338 13.30 10.504 0.766 1.704 1.459 1.195
0.7 31.40 28.970 3.33 3.180 3.81 3.346 13.01 10.525 0.906 2.250 1.702 1.396
y = 18.82x3 - 37.73x2 + 21.00x + 10.38R² = 0.935
11.5
12
12.5
13
13.5
14
14.5
0 0.2 0.4 0.6 0.8 1 1.2
6bd Poly. (6bd)
526 | P a g e
Elastic Properties: Elastic properties such as modulus of elasticity, modulus of rigidity, and Poisson’s ratio
are the important parameters in the analysis of structures. These properties are obtained by various methods
available in the literature. As per IS: 456[41], the Modulus of Elasticity is obtained by the formula
Efc =5000√Fcu……………………...(10)
Modulus of Elasticity: The modulus of elasticity is obtained by various methods available in the literature as
given below. Modulus of elasticity of fibre reinforced composites (FRC) can be calculated by using law of
mixtures as suggested by Hannant [38] and Tan et al. [39] as follows:
�fc = (1 − �1�2��) Em + �1 �2 �f Ef… (11)
Where �1=fibre orientation factor (1 for aligned fibres), �2 = efficiency factors (0.98 for all practical purposes),
�f = fibre content (%), Em = modulus of elasticity of matrix (GPa) = 5√σ cu, and modulus of elasticity of fibre
(GPa) = (12 to 18 GPa = 15 GPa). The equation of modulus of elasticity in terms of compressive strength (σ cu)
and specific gravity (�) is also given by Kakizaki et al. [40] as …
�fc = 0.8 × 105(� /2.3)
1.5 x √ (σ cu / 350)…… (12)
Where � = specific gravity of concrete (dry density of composite/1000). As per IS: 456 [41], the modulus of
elasticity is calculated by the formula as �fc = 5√ σ cu, Hence for average value of specific gravity, Eqn.(11)
leads to the following form :
�fc = 4846√ σ cu …….. (13)
The modulus of elasticity obtained by using equations (10) through (13) is shown in Table 13. Help in Tsai
equations [41] based on Micro-Mechanics Analysis can also be used to predict the elastic constants of fibre
composites. The longitudinal (��) and transverse moduli (��) can be evaluated by using following equations:
�� = ��. {1+ (2�����) / (1–����)}……(14)
ET = {1 + (2����) / (1 – ����)………….(15)
Where �� = (�� / ��) – 1 / (��/��) + 2 � …. ….. (16)
�T = (��/��) – 1 / (��/��) +�…………..(17)
where � is the aspect ratio of fibre = (��/h�) & where �� = length of fibre , h� = thickness of fibre.
Table13: Elastic Properties of GPCC.
�� %
Modulus of elasticity (�fc)
Poisson’s ratio
(�)
Equation
(10)
Efc = 5√ σ cu
GPa
Equation (11)
�fc = (1 − �1�2��)
E�
+ �1 �2 �f ��
GPa
Equation (12)
�fc = 0.8 × 105x
(� /2.3)1.5
√ (σ cu
/350) GPa
Equation (13)
�fc = 4846 √ σ
cu GPa
Equation (21)
� =( σ cr / σ cu )
0.0 26.879 28.062 25.505 26.051 0.1107
0.1 28.062 28.053 26.690 27.198 0.1153
0.2 28.980 28.962 27.720 28.090 0.1238
527 | P a g e
0.3 29.368 29.34 28.450 28.463 0.1217
0.4 29.440 29.40 28.708 28.540 0.1228
0.5 29.460 29.407 28.897 27.293 0.1111
0.6 28.062 28.030 27.688 27.209 0.1112
0.7 28.018 27.95 27.694 27.166 0.1060
0.8 27.083 27.010 26.822 26.260 0.1131
Table 14: Modulus of Elasticity and Shear Modulus Using halpin Tsai Equations [41]
��
%
Equation
(16)
�� = (�� /
��)– 1 /
(��/��) + 2
�
Equation
(17)
� T
=(��/��)-1
/(��/��) + �
Equation (14)
��=��.{1+(2�
����) / (1–
����)}
GPa
Equation
(15) �T={1 +
(2����) / (1
– ����)
GPa
Equation
(18)
�� = [1/8
(3��+ 5��)
(GPa)
Equation
(19)
��=1/8(
��+2�T)
(GPa)
Equation
(20)
�fc =(1
−��) ��
(GPa)
0.0 0.0773 0.141 26.879 26.879 26.879 10.079 26.879
0.1 0.0816 0.1493 28.030 28.030 28.030 10.511 28.00197
0.2 0.0848 0.1556 28.948 28.954 28.951 10.855 28.893
0.3 0.0862 0.1582 29.319 29.075 29.166 10.933 29.078
0.4 0.0865 0.1330 29.380 29.396 29.390 11.0215 29.272
0.5 0.0866 0.1580 29.380 29.390 29.386 11.020 29.239
0.6 0.08165 0.1493 27.975 27.986 27.981 10.493 27.813
0.7 0.0816 0.1492 27.918 27.929 27.924 10.472 27.728
0.8 0.0780 0.1423 26.981 26.993 26.989 10.1211 26.773
Modulus of elasticity and shear modulus of randomly oriented fibre reinforced concrete can be predicted using
the following relations:
�� = [1/8 (3��+ 5��) … (18)
GR = 1/8 (��+ 2�T)……, (19)
Where �� and �� respectively are the longitudinal and transverse moduli of fibre composite having the same
fibre aspect ratio and fibre volume fraction . The results obtained by using (12) are modified according to (13) to
have the similar trends with the other results and all they are presented in Table 14; similarly the results obtained
by using equation(18) and(19) are modified by equation(20) as follows:
�fc = (1 −��) ��…………... (20)
The behavior of geopolymer concrete is very complex. So, the modulus of elasticity calculated by various
methods does not match with each other. But it is observed that the modulus of elasticity increases with
incorporation of Geosynthetics fibres up to 0.5% by volume and then decreases with increase in fibre contents
but higher than plain geopolymer concrete. This means that the fibre improves the elastic behavior of
Geopolymer Concrete Composites which is more brittle than GPC.
528 | P a g e
Poisson’s Ratio (�):-The Poisson’s ratio (�) is determined according to Ghugal [43] using strength of material
theory based on flexural strength and compressive strength and is given by the following relation:
� = [σ cr /σ cu ] …………………….. (21)
Table 13: Last Column, Shows the Effect of Geosyn thetics Fibers on Poisson’s Ratio.
V. CONCLUSIONS
1 Geopolymer concrete is a modern invention in the world of concrete wherein the portland cement is 100%
replaced by an industrial waste materials which contributes towards the global warming by eliminating or
decreasing the use of cement and thereby utilization of by-products like fly ash. Geosynthetic fibres are
incorporated so as to increase the ductility of GPC to make it more elastic since GPC is more brittle than CC’s.
From the literature survey on geopolymers, by adopting the currently used concrete technology to manufacture
OPCC, a rigorous trial-error method was adopted to develop a process of manufacturing fly ash-based
geopolymer concrete. The trial-and-error method thus yielded successful results for the manufacture of low-
calcium ASTM Class F Fly Ash based Geopolymer concrete. Thus GPCC is an excellent alternative solution to
the CO2 producing conventional concretes like OPCC.
2 Low-Calcium fly ash-based GPCC has excellent compressive strength and it is suitable for structural
applications [10].
3 It is also observed that Compressive Strength results obtained for GPCC are more than that of GPC similarly
tensile strength of the GPCC are also higher w.r.t the GPC.
4 It is also concluded that the wet and dry densities of GPCC increases continuously with increase in fibre
contents, whereas the workability of GPCC reduced with increase in fibre content. Optimum Geosynthetics
fibre contents for the maximum values of various strengths of GPCC are 0.4%. The maximum percentage
increase in compressive strength, flexural strength, split tensile strength, and bond strength is 20.14%, 33.12%,
35.48% and 16.53% respectively.
5 The proposed analytical equations for modulus of elasticity yielded good result and Poisson’s Ratio also varies
within the limiting specified values.
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