FLEXURAL BEHAVIOUR OF REINFORCED GEOPOLYMER CONCRETE BEAMS PARTIALLY REPLACED WITH RECYCLED COARSE AGGREGATES

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 6, Issue 7, Jul 2015, pp. 13-23, Article ID: IJCIET_06_07_003
Available online at
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=7
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
___________________________________________________________________________
FLEXURAL BEHAVIOUR OF REINFORCED
GEOPOLYMER CONCRETE BEAMS
PARTIALLY REPLACED WITH RECYCLED
COARSE AGGREGATES
M. K. Thangamanibindhu and Dr. D. S. Ramachandra Murthy
St. Peter’s University, Chennai
ABSTRACT
Concrete is the most widely used construction material which required
large quantities of Portland cement. The production of Ordinary Portland
cement causes pollution to the environment, due to the emission of CO2 and
also large amount of natural resources is consumed for the cement
production. The large global production of flyash and rapid advances in
geopolymer technology leads to the alternate material for OPC that is
Geopolymer concrete (GPC). Geopolymers are showing great potential and
several researchers have critically examined the various aspects of their
viability as binder material. In this paper, results of the studies carried out on
the behaviour of ambient cured Reinforced GPC (RGPC) flexural member
have been presented..A total of 9 beams were tested in flexure, out of which
three were conventional concrete mixes and six GPCmixes having varying
combinations of flyash, GGBS and recycled coarse aggregates. The
reinforcement was designed considering a balanced section and all the
specimens were tested under two point loading The studies showed that the
load carrying capacity of the RGPC beams was more than that of the
corresponding conventional RCC beam and the load carrying capacity of the
beams were decreased when replaced with recycled aggregates. The
deflection, cracking load, ultimate load and crack width were recorded.
Key words: Geopolymerconcrete (GPC), Flyash, GGBS, Recycled Coarse
Aggregates and Beams
Cite this Article: Thangamanibindhu, M. K. and Dr. Ramachandra Murthy,
D. S. Flexural Behaviour of Reinforced Geopolymer Concrete Beams Partially
Replaced with Recycled Coarse Aggregates. International Journal of Civil
Engineering and Technology, 6(7), 2015, pp 13-23.
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=7
_____________________________________________________________________

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1. INTRODUCTION
Utilization of the industrial by-products and recycled coarse aggregates in the
construction industry could become a safe disposal of the industrial wastes, and
reduction of construction cost. In 1978, Joseph Davidovits developed inorganic
polymeric materials and coined the term geopolymer. Geopolymer concrete is
concrete which does not utilize any Portland cement in its production; the binder of
GPC is produced by the reaction of an alkaline liquid with a source material that is
rich in silica and alumina. The research in this area has gained some momentum to
extend the range of application. As in conventional reinforced concrete, the GPC also
needs to be reinforced with steel bars for its large scale utility in civil engineering
structural applications. Hence, the investigations on behaviour of RGPC incorporated
with recycled coarse aggregates were undertaken. Different mixes with partial
replacement of recycled coarse aggregates in GPC and OPC were designed as per IS
code, prepared and tested for comparison of performance. A total of 9 beams
consisting of 6 GPC mixes and 3 OPCC mixes were tested. Performances such as load
carrying capacity, moments and deflection at different stages were studied. Crack
widths for all the specimens were measured. This paper compares the performance of
reinforced geopolymer concrete beams with reinforced cement concrete beams when
replaced with recycled coarse aggregates.
2. MATERIALS
2.1. Cement
Cement Ordinary Portland cement 53 grade conforming to Indian Standard is used in
the present investigation of specific gravity 3.12.
2.2. Fly ash
Flyash used in this study was obtained from National Thermal Power Corporation,
Ennore and the specific gravity of flyash is 2.14 [1, 7, 14]
2.3. Ground granulated blast furnace slag
Ground granulated blast furnace slag (GGBS) is a by-product from the blast-furnaces
used to make iron. GGBS is a glassy, granular, non-metallic material consisting
essentially of silicates and aluminates of calcium and other bases. The specific gravity
of GGBS is 2.9 [8, 12, 13].
2.4. Fine Aggregates
The locally available river sand of zone III was used as fine aggregate in the present
investigation. The properties of the aggregates and sieve analysis results are given in
Table 1 and 2.
Table 1 Material properties of fine aggregates
Name of test Test Results
Specific gravity 2.6
Water Absorption (%) 1.15
Bulk Density (kg/m3) 1678

Flexural Behaviour of Reinforced Geopolymer Concrete Beams Partially Replaced with
Recycled Coarse Aggregates
Table 2 Sieve Analysis of fine aggregates
IS Sieve Size
Weight
retained(gms)
Percentage
retained
Cumulative
percentage
retained
Cumulative
percentage
passing
4.75 mm 15 1.5 1.5 98.5
2.36 mm 45 4.5 6.0 94,0
1.18 mm 195 19.5 25.5 74.5
600 micron 195 19.5 45.0 55.0
300 micron 385 38.5 83.5 16.5
150 micron 135 13.5 97.0 3.0
Lower than 150
micron
30 3.0 3.0 0
2.5. Coarse Aggregates
Natural and recycled aggregates were used as the coarse aggregates in the concrete
mixtures. Locally available crushed granite of medium size 20 mm and 12.5 mm was
used as the natural coarse aggregate. Recycled aggregates obtained from demolished
building of having age 8 years were used [14]. Various properties of coarse
aggregates are given in Table 3. The results of sieve analysis are given in Table 4 and
5.
Table 3 Material properties of coarse aggregates
Name of test
Test Results
Natural aggregates Recycled
Aggregates20 mm 12.5 mm
Specific gravity 2.79 2.71 2.75
Water Absorption (%) 0.5 0.67 1.5
Bulk Density (kg/m3
) 1636 1561 1548.6
Percentage Voids (%) 0.41 0.44 0.43
Crushing value (%) ---- 22.6 ----
Impact value (%) 28.7 20.82 30.5
Table 4 Sieve Analysis of Coarse aggregates of size 20 mm
IS Sieve Size
Weight
retained
(gms)
Percentage
retained
Cumulative
percentage
retained
Cumulative
percentage
passing
40 mm 0 0 0 100
20 mm 90 3.0 3.0 97
10 mm 2885 96.16 99.16 0.84
4.75 mm 25 0.833 99.993 0.007
pan 0 0 100 0

Table 5 Sieve Analysis of Coarse aggregates of size 12.5 mm
IS Sieve Size
Weight
retained
(gms)
Percentage
retained
Cumulative
percentage
retained
Cumulative
percentage
passing
16 mm 0 0 0 100
12.50 mm 70.0 2.33 2.33 97.67
10.00 mm 1705.1 56.83 59.16 40.84
4.75 mm 1223.5 40.78 99.94 0.06
2.30 mm 1.4 0.046 99.986 0.014
pan 0
2.6. Alkaline activator
The alkaline activator liquid used was a combination of sodium silicate solution and
sodium hydroxide. An analytical grade sodium hydroxide in Flakes form (NaOH with
98% purity) was used. To avoid effects of unknown contaminants in laboratory tap
water, distilled water was used for preparing activating solutions.. The activator
solution was prepared at least one day prior to its use in specimen casting.
2.7. Water
Distilled Water for GPC and Potable water for normal concrete which are free from
chemicals and organic materials was used for the study.
2.8. Super plasticizer−−−−MasterGlenium SKY 8233
PERFORMANCE TEST DATA: Aspect Light brown liquid ,Relative Density 1.08
±0.01 at 25 °C , pH >6 ,Chloride ion content < 0.2% .DOSAGE: Optimum dosage of
MasterGlenium SKY 8233 should be determined with trial mixes. As a guide, a
dosage range of 500 ml to 1500 ml per 100 kg of cementitious material is normally
recommended by manufacturer. The hyperplasticiser shall be MasterGlenium SKY
8233, high range water reducing, Superplasticiser based on polycarboxylic ether
formulation. Specific gravity of 1.08 and solid contents not less than 30% by weight.
The product complies with ASTM C494 Type F and free of lignosulphonates,
naphthalene salts and melamine formaldehyde.
3. DETAILS OF EXPERIMENTS
3.1. Mix design of Geopolymer concrete
In the design of geopolymer concrete mix, total aggregate (fine and coarse) is taken as
77% of entire concrete mix by mass. This value is similar to that used in OPC
concrete in which it will be in the range of 75 to 80% of the entire concrete mix by
mass. Fine aggregate was taken as 30% of the total aggregates. From the available
literature, it is observed that the average density of flyash-based geopolymer concrete
is similar to that of OPC concrete (2400 kg/m3
). Knowing the density of concrete, the
combined mass of alkaline liquid and flyash can be arrived at. By assuming the ratios
of alkaline liquid to flyash as 0.35, mass of flyash and mass of alkaline liquid were
obtained. The addition of sodium silicate is to enhance the process of
geopolymerisation [9]. For the present study, concentration of sodium hydroxide was
taken as 10 M and alkaline solution ratio as 2.5. The various mix proportions are
given in Tables 6 and 7 for GPC and normal concrete [2, 10].

3.2. Mix design of Cement concrete
The mix design was done as per IS: 10262 (2009). The grade of concrete adopted for
this study is M20. Maximum size of aggregate taken is 20 mm. The water−cement
ratio adopted for concrete mix was 0.45 [3, 4, 5, 6, 7, 11].
Table 6 Mix Proportions of Geopolymer concrete
Material Mix-1 Mix-2 Mix-3 Mix-4 Mix-5 Mix-6
Coarse
aggregates
Kg/m3
20 mm 388.2 258.8 ----- 388.2 258.8 -----
12.5 mm 905.8 905.8 905.8 905.8 905.8 905.8
RCA (20 mm) ---- 129.4 388.2 ---- 129.4 388.2
Fine aggregates, Kg/m3
554 554 554 554 554 554
Flyash, Kg/m3
306 306 306 204 204 204
GGBS,Kg/m3
102 102 102 204 204 204
SodiumHydroxide, Kg/m3
41 41 41 41 41 41
SodiumSilicate Kg/m3
solution
103 103 103 103 103 103
Superplasticizer, lit/m3
4.89 4.89 4.89 4.89 4.89 4.89
ExtraWater, lit/m3
22.5 30.5 44.5 22.5 30.5 44.5
Alkaline solution / Flyash
(ratio)
0.35 0.35 0.35 0.35 0.35 0.35
Table 7 Mix proportions of Cement concrete
Material Mix-7 Mix-8 Mix-9
Coarse aggregates
Kg/m3
20 mm 379.76 253.18. ------
12.5 mm 859.23 859.23 859.23
RCA (20
mm)
------- 123.52 370.55
Fine aggregatesKg/m3
781.31 781.31 781.31
Cement Kg/m3
320.00 320.00 320.00
Water/Cement ratio 0.45 0.45 0.45
Figure 1 Concrete ingredients in the pan mix

Figure 2 Super plasticizer
3.3. Specimen details
Nine numbers of reinforced concrete beams with and without GGBS were cast and
tested. The span of the beam was 1200 mm and of size 100 mm x 200 mm. Beams
were simply supported over an effective span of 1000 mm. Out of the 9 specimens
tested, Mixes-7, 8 and 9 and cast with cement and 0%, 10% and 30% partial
replacement of recycled coarse aggregates. and mixes-1, 2 and 3 were cast with
GGBS as 25% and replacement for flyash and 0%,10% and 30% partial replacement
of recycled coarse aggregates..and mixes 4, 5 and 6 were cast with GGBS as 50%
and replacement for flyash and 0%,10% and 30% partial replacement of recycled
coarse aggregates, specimens were tested at the age of 28th day from the date of
casting. The clear cover of the beam was 25 mm and reinforcement details of the
specimens tested are given in Figure.
Figure 3 Beam specimens reinforcement details
3.4. Preparation of Specimens
Prior to casting, the inner walls of moulds were coated with lubricating oil to prevent
adhesion with the hardening concrete. Both OPCC and GPC were mixed in a tilting
drum mixer machine for about 6−8 minutes. The steel bars as per the design is placed
over the 25 mm cover block .the Concrete was placed in the mould in three layers of
equal thickness and each layer was vibrated until the concrete was thoroughly
compacted. Specimens were demoulded after 24hrs. The RCC beams were water
cured for a period of 28 days while the RGPC beams were cured in ambient
temperature, in the laboratory for a period upto 28 days after casting, After the curing
period the specimens were tested.
1200mm
#2-10mmdia.
200mm
Two legged -#6mm dia. stirrups @ 100mm c/c
100

Figure 4 Demoulding of a beam
3.5. Test Procedure
The test setup is shown in Figure 5. The testing was carried out in a UTM of 1000 KN
capacity. The beam was simply supported over a span of 1000 mm. The load was applied
on two points each 333.33 mm away from the supports. One dial gauges was used at mid
span for measuring deflections. All the specimens were white washed in order to facilitate
marking of cracks . The beams were subjected to two-point loads under load control
mode. The load was applied in increments of 5 KN. The deflections at mid span was
measured using dial guage. The behaviour of the beam was observed carefully. The
development of cracks was observed and the crack widths were measured using a hand-
held microscope with an optical magnification of X50 and a sensitivity of 0.02 mm.
Figure 5 Test setup
Figure 6 UTM

Figure 7 Beam under loading condition
4. RESULTS AND DISCUSSION
4.1. General observations
The beam specimens were tested under two point loading until failure. As the load
increased, beam started to deflect and flexural cracks developed along the span of the
beams. All the beam specimens failed in the same manner due to yielding of the
tensile steel. Crack formations were marked on the beam at every load interval. The
first crack appeared close to the mid span of the beam. As the load increased existing
cracks propagated and new cracks developed along the span. The spacing of cracks
varied along the span. The total number of the flexural cracks developed for 30%
replacement of RCA in concrete was more than the 0% Replacement of RCA in
concrete The crack widths of concrete beams for various Geopolymer concrete
mixtures ranged between 0.06 mm to 1 mm.
4.2. Load-deflection characteristics
The experimental load-deflection curves of the RC beams with 0%, 10% and 30%
RCA and partial replacement of GGBS when tested at 28th day for all mixes are
shown in Figure 9. The average ultimate loads for beams of various mixes were
ranging from 38 kN to 103.55 kN respectively. The Deflection of concrete beams for
geopolymer concrete ranged between 5.28 mm to 7.04 mm. and for Cement concrete
ranged between 3.35 mm to 4.54 mm.
Table 8 Summary of beam test results
Mix
Beam
ID
Crack
Load
(KN)
Theoretical
Ultimate
Load WT
(KN)
Experimental
Ultimate
Load WE
(KN)
Theoretical
Ultimate
Moment MT
(KNm)
Experimental
Ultimate
Moment ME
(KNm)
Deflection
(mm)
Mix-1 Beam-1 23 80.52 84.15 13.42 14.025 5.28
Mix-2 Beam-2 22 72.16 77.35 12.028 12.892 5.43
Mix-3 Beam-3 20 62.39 65.50 10.40 10.917 6.65
Mix-4 Beam-4 29 101.21 103.55 16.87 17.259 5.79
Mix-5 Beam-5 27 89.13 92.75 14.856 15.459 6.17
Mix-6 Beam-6 24 76.66 83.85 12.778 13.975 8.34
Mix-7 Beam-7 17 53.83 55.6 8.973 9.267 3.85
Mix-8 Beam-8 16 45.22 50.35 7.537 8.392 4.43
Mix-9 Beam-9 13 31.70 38.10 5.284 6.350 5.50

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Fig
Figure 9 Load versus Mid Span Deflection of various mixes
4.3. Failure mode and crack pattern
The cracks at the mid-span opened widely thereafter with the yielding of steel when
the beams reached above the ultimate load. The failure pattern of the beam sp
was found to be similar for both RCC and RGPC beams.
5. CONCLUSIONS
1. Conventional methods of mixing, compaction, moulding and demoulding can be
adopted for GPC’S,.
0 0.2
Mix-1
Mix-2
Mix-3
Mix-4
Mix-5
Mix-6
Mix-7
Mix-8
Mix-9
MIXID
0
20
40
60
80
100
120
0 2
LOADinKN
Figure 8 Crack Width versus various mixes
Load versus Mid Span Deflection of various mixes
Failure mode and crack pattern
span opened widely thereafter with the yielding of steel when
the beams reached above the ultimate load. The failure pattern of the beam sp
was found to be similar for both RCC and RGPC beams.
Conventional methods of mixing, compaction, moulding and demoulding can be
adopted for GPC’S,. As the GPCs do not have any Portland cement, they can be
0.2 0.4 0.6 0.8
Crack width in mm
4 6 8
DEFLECTION in mm
editor@iaeme.com
Load versus Mid Span Deflection of various mixes
span opened widely thereafter with the yielding of steel when
the beams reached above the ultimate load. The failure pattern of the beam specimens
Conventional methods of mixing, compaction, moulding and demoulding can be
As the GPCs do not have any Portland cement, they can be
0.8 1
10
Mix-1
Mix-2
Mix-3
Mix-4
Mix-5
Mix-6
Mix-7
Mix-8
Mix-9

considered as less energy intensive and GPC utilizes the industrial wastes such as fly
ash and GGBs for producing the binding system in concrete. Therefore these
concretes can be considered as eco-friendly materials.
2. The cracking load of reinforced geopolymer concrete beams is higher when compared
to reinforced cement concrete beams.
3. The ultimate load carrying capacity of reinforced geopolymer concrete beams is
slightly higher when compared to reinforced cement concrete beams.
4. The crack width under load is within the permissible limit for the reinforced
geopolymer concrete beams and reinforced cement concrete beams for 0%
replacement of recycled coarse aggregate and the crack width for 30% replacement of
RCA in normal concrete and GPC was above than the permissible limit.
5. The experimental Values are higher when compared with theoretical values for all the
beams.
6. The load deflection characteristics obtained for the reinforced cement concrete beams
and reinforced geopolymer concrete beams are almost similar for 0% and 10%
replacement of RCA.
7. The crack patterns and failure modes observed for geopolymer concrete beams are
found to be similar to the cement concrete beams. The beams failed initially by
yielding of the tensile steel followed by the crushing of concrete in the compression
face.
REFERENCES
[1] Hardjito D. and Rangan B. V. Development and properties of low calcium fly ash
based geopolymer concrete, Perth, Australia: Curtin University of Technology,
2005.
[2] Madheswaran, C. K., Ambily, P. S. and Rajamane, N. P. Arun G. Studies on
flexural behaviour of reinforced geopolymer concrete beams with light weight
aggregates. Tamilnadu College of Engineering, Coimbatore, 2014.
[3] IS 456: 2000, Indian Standard Code for Plain and reinforced Concrete-Code of
practice, BIS, New Delhi.
[4] IS 2386: Part-I Methods of tests for aggregates for concrete
[5] Dattatreya, J. K., Ambily, P. S., Madheswaran, C. K., Sabitha, D. and
Neelamegam M. Experimental Studies on Shear Behaviour of Reinforced
Geopolymer Concrete Beams, SERC Research Report No. RR-2, June 2010.
[6] Dattatreya, J. K., Rajamane N. P. and Ambily, P.S. Structural Behaviour of
Reinforced Geopolymer Concrete Beams and Columns. SERC Research Report,
2009.
[7] Kumaravel, S. and Thirugnanasambandam, S. Flexural behaviour of low calcium
fly ash based Geopolymer Concrete Beams. Annamalai University,
Annamalainagar, 2013.
[8] Dr. Muthupriya, P. An Experimental Investigation on Effect of GGBS and Glass
Fibre In High Perfomance Concrete. International Journal of Civil Engineering
& Technology (IJCIET), 4(4), 2013, pp. 29−35.
[9] Lianyang, Z. Complete Recycling and Utilization of Recycling of Waste through
Geopolymerisation, 2009.
[10] Anaur, K. A., Ridzuan A. R. M. and Ismail, S. Strength Characteristics Of
Geopolymer Concrete Containing Recycled Coarse Agrregates, IIESM.
[11] Johny, B. Prof. George, M. V. Dr. John, E. Study of Properties of Sustainable
Concrete using Slag and Recycled Concrete Aggregate, India

[12] Sangeetha, S. P. and Joanna, P. S. Flexural Behaviour of Reinforced Concrete
Beams with Partial Replacement of GGBS, Hindustan University, Chennai, 2014.
[13] IS 12089: 1987, Specification for granulated slag for the manufacture of Poland
slag cement.
[14] Prof. Vyas, C. M. and Prof. Pitroda, J. Fly Ash and Recycled Coarse Aggregate
in Concrete: New Era for Construction Industries − A Literature Review 2013.

FLEXURAL BEHAVIOUR OF REINFORCED GEOPOLYMER CONCRETE BEAMS PARTIALLY REPLACED WITH RECYCLED COARSE AGGREGATES

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