Development of eco friendly concrete produced with Rice

Advances in Concrete Construction, Vol. 9, No. 2 (2020) 139-147

DOI: https://doi.org/10.12989/acc.2020.9.2.139 139

Copyright © 2020 Techno-Press, Ltd. http://www.techno-press.org/?journal=acc&subpage=7 ISSN: 2287-5301 (Print), 2287-531X (Online)

1. Introduction

Development in civil engineering has enabled

urbanization and overall lifestyle enhancement. Production

of Ordinary Portland Cement (OPC) consumes massive

energy and raw materials while emitting a huge amount of

CO2 into the atmosphere (Ganesan et al. 2013).

Geopolymer technology was identified as an alternative to

OPC due to the consumption of lesser energy during

production and reduced CO2 emission compared to OPC

(Geraldo et al. 2017, Borges et al. 2014). Recently, the

inclusion of minerals to concrete becomes essential due to

the sustainability and environmental implications (Zerbino

et al. 2012). It would be much useful for the society if waste

materials like fly ash and rice husk ash are utilized as

pozzolanic substances in the preparation of eco-friendly

geopolymer concrete (Yang et al. 2016). Pozzolanic

materials like fly ash (Nath et al. 2015, Ganesan et al.

2014a, b), blast furnace slag, bottom ash (Matthes et al.

2018a, b). and other materials are also used in concrete

production. Rice Husk Ash (RHA) an agricultural deposit

generated during rice milling seems the correct option for

cementitious materials. Annual paddy production estimates

for 2010 was 678 million tons (MT), which produced

149.16 million tons (MT) of rice husk. Nearly 37 million

tons of RHA can be obtained from this (Rice Market 2009).

Corresponding author, Assistant Professor

E-mail: [email protected]

During milling, nearly 22% of the weight is received as

husk (Khan et al. 2012a, b).

Ungrained RHA produced is of poor quality and

contains residual carbon (which requires more water)

containing crystalline silica. The quality of residual RHA

can be enhanced by grinding it to the desired particle size at

a high cost. (Rodriguez et al. 2006a, b, Cordeiro et al.

2009a, b). During the burning of the husk, about twenty-

five percentage of the weight is transformed to ash,

notorious as Rice Husk Ash and the remaining 75%

contains organic volatile matter. It is well known that by

burning Rice Husk Ash in controlled conditions, non-

crystalline silica and highly reactive pozzolan are obtained

(Mehta 1977, Mehta 1994, RILEM committee 1988). Burnt

RHA contains approximately 85-90% silica, in an

amorphous state based on burning time and temperature.

The chemical composition of RHA differs from sample to

sample due to husk type and burning temperature. RHA,

when not used properly, turns into waste becoming a

massive threat to the environment and damaging the

surroundings when it is dumped. Use of RHA in concrete

reduces its impact during dumping and reduces CO2

emission to the atmosphere due to reduced cement

production (Nazari et al. 2011a, b, Ramasamy et al. 2012).

Geopolymer concrete is a polymer developed by

incorporating silica and alumina rich pozzalonic materials

(like RHA, Fly ash) with alkaline solutions (Combination of

potassium or sodium silicate and potassium/sodium

hydroxide) (Prabu et al. 2017a, b, Ganesan et al. 2015a, b).

Development of geopolymer concrete using RHA with FA

and GGBS is novel and has not been investigated in

Development of eco-friendly concrete produced with Rice Husk Ash (RHA) based geopolymer

Shalini Annadurai1, Kumutha Rathinam2 and Vijai Kanagarajan3

1Department of Civil Engineering, Sona College of Technology, Salem-636005, Tamil Nadu, India 2Department of Civil Engineering, Sri Venkateswara College of Engineering, Sriperumbudur-602117, Tamil Nadu, India

3Department of Civil Engineering, St. Joseph’s College of Engineering, OMR, Chennai-600119, Tamil Nadu, India

(Received August 11, 2019, Revised November 21, 2019, Accepted November 27, 2019)

Abstract. This paper reports the effect of Rice Husk Ash (RHA) in geopolymer concrete on strength, durability and

microstructural properties under ambient curing at a room temperature of 25°C and 65±5% relative humidity. Rice husk was

incinerated at 800°C in a hot air oven. and ground in a ball mill to achieve the required fineness. RHA was partially added in 10,

15, 20, 25, 30 and 35 percentages to fly ash with 10% of GGBS to produce geopolymer concrete. Test results exhibit that the

substitution of RHA in geopolymer concrete resulted in reduced strength properties during initial curing. In the initial stage,

workability of GPC mixes was affected by RHA particles due to the presence of dormant particles in it. It is evident from the

microstructural study that the presence of RHA particles densifies the matrix reducing porosity in concrete. This is due to the

presence of RHA in geopolymer concrete, which affects the ratio of silica and alumina, resulting in polycondensation reactions

products. This study suggests that incorporation of rice husk ash in geopolymer concrete is the solution for effective utilization

of waste materials and prevention of environmental pollution due to the dumping of industrial waste and to produce eco-friendly

concrete.

Keywords: rice husk ash; microstructure; bond strength; strength; curing; carbonation

Shalini Annadurai, Kumutha Rathinam and Vijai Kanagarajan

(a) (b)

(c)

Fig. 1 SEM images (a) RHA, (b) Fly ash and (c) GGBS

ambient curing conditions. The strength and microstructure

of RHA, Fly ash and GGBS based geopolymer concrete

have not been discussed widely and hence it is the focus of

this investigation. This paper presents the strength and

micro structural characterization of RHA and Fly ash with

GGBS geopolymers to make a green geopolymer binder.

This study aims to formulate a new concrete mixture using

industrial waste products-fly ash, GGBS and RHA. These

materials are used as binder to produce geopolymer

concrete in this research. GGBS content was kept constant

while RHA and Fly ash were replaced at different

percentages to study its effect on mechanical properties like

tensile strength, modulus of rupture, compressive strength.

and bond strength, microstructural characterization by SEM

and EDX and properties like pH and carbonation.

2. Experimental investigation

2.1 Materials used

For this research Rice Husk was obtained from a Rice

mill and incinerated at 800oC in a microwave incinerator to

obtain Rice Husk Ash (RHA). To attain the required

fineness, RHA was ground in ball mill for 1000 cycles.

RHA’s physical properties and Oxide composition are

shown in Table 1 and 1(a). An SEM image of RHA is

presented in Fig. 1(a) and those of RHA are irregular in

shape with cellular porous surface. Fly ash (FA) was

obtained from the Mettur Thermal power station and

categorized as Class F Fly ash [ASTM 2006, IS 3812].

Physical and oxide compositions of FA are described in

Table 1 and 1(a). Fig. 1(b) shows the SEM image of FA and

the particles are in spherical shape. In this research, Ground

Granulated Blast furnace Slag (GGBS) [IS 12089] was

purchased from M/s. Quality Polytech, Mangalore.

The physical properties and Oxide composition of

GGBS are presented in Tables 1 and 1(a). Fig. 1(c) shows

the SEM image of GGBS which are in flakes shape and in

Table 1 Physical properties of fly ash, GGBS and rice husk

ash

Property Fly Ash GGBS Rice Husk Ash

Specific gravity 2.46 3.11 2.13

Blain Fineness 2351cm2/g 4580 cm2/g 5675cm2/g

Table 1 (a) Oxide composition of fly ash, GGBS and rice

husk ash

Oxides

Fly Ash GGBS Rice

Husk

Ash %

Requirement as

per IS 3812-

2003

%

Requirement

as per IS

12089-1987

SiO2 55.90 SiO2>35% 41.24 88.64

Al2O3 15.23 Total-70% 20.64 1.23

Fe2O3 21.78 - 7.28 1.19

CaO 0.17 - 25.45 1.09

MgO 2.45 < 5% 2.93 <17% 1.76

LOI 0.60 < 12% Nil - <6%

Table 2 Physical properties of fine and coarse aggregates

Property FA CA

Specific gravity 2.6 2.91

Bulk density 1675 kg/m3 1520 kg/m3

Fineness modulus 2.65 (Zone II) 5.4

aggloramation.

Naturally, available river sand was used as Fine

aggregate (FA) in this research. and its properties were

tested in accordance with IS: 2386 (Part-I)-1963. Fine

aggregate was dried in a hot air oven, to remove moisture.

Coarse aggregate (CA) of 12 mm was used in all mixes and

tested following IS 2386 (Part -I)-1963.

The physical properties of FA and CA are presented in

Table 2. Sodium hydroxide (NaOH) and Sodium Silicate

(Na2Sio3) solution were used as the alkaline solution part of

the mixture. 10M of Sodium hydroxide was kept as constant

for all mix preparations. The alkaline solutions were

prepared 24h before mixing to avoid excess heat in NaOH

solution during mixing.

2.2 Mix proportioning and curing

There is no standard code provision for mix design of

geopolymer concrete. The calculations of mix proportions

were arrived based on the report submitted by Wallah and

Rangan (2006). The density of geopolymer concrete was

assumed as 2400 kg/m3. In this study, seven mixtures, one

control mix with 90% of fly ash and 10% of GGBS and six

other mixtures with different proportions of RHA with

control mix were prepared. The content of GGBS was kept

as 10% constant for all mixtures. Percentage of fly ash and

RHA were varied by mass. The ratio of binder to the

alkaline solution was 0.4. The ratio of Na2Sio3 to NaOH

was kept as 2.5.

Additional water and superplasticizer (SP) were added

by 15% and 3% respectively, to the cementitious material to

140


Fig. 2 Test setup of accelerated carbonation chamber

enhance its workability properties. Total cementitious

material content was fixed at 394 kg/m3. The mixture code

and proportion of various materials for each designated

mixture are presented in Table 3. All specimens were cured

at room temperature till the testing period.

2.3 Test program

Workability of GPC and RHA based mixtures were

evaluated using the slump test. The slump of fresh concrete

was measured as per IS: 1199-1959. Cubes of 100 mm×100

mm×100 mm size were used for the compressive strength

test. The specimens were tested at 7, 28. and 56 days as per

IS 516:1959. The specimen samples were tested in a 2000

kN Compression testing machine. and the load was applied

up to failure. Three samples were used for each test. For the

evaluation of tensile strength of concrete, a cylindrical

specimen of 150 mm diameter and 300 mm height were cast and tested in a compression testing machine as per

IS: 5816- 1999. The plain beam specimen of size 100 mm× 100 mm× 500 mm was tested as per IS

516:1959 by Universal testing machine to obtain modulus

of rupture of geopolymer concrete. Similar to the

compressive strength, modulus of rupture and tensile

strength were evaluated at 7, 28. and 56 days.

The specimens bond strength was assessed by a pull-out

test as per IS: 2770 (Part-I)-1967. A cylindrical specimen

of 150 mm diameter and 300 mm height with a TMT bar of

12 mm diameter and 450 mm length were used to evaluate

the bond strength of geopolymer concrete. The specimens

were tested after 28 days in a Universal testing machine.

Bond strength was computed from the load at which the slip

was 0.25 mm. Tests were performed in triplicate specimens.

and average bond strength calculated.

It is well known that progress of carbonation in concrete

is a long-time reaction. However, for testing the carbonate

concrete samples a short-term accelerated carbonation

testing system was used. The test set up of carbonation

chamber is shown in Fig. 2 performed accelerated

carbonation tests for 56 days to calculate pH value with a

5% concentration of CO2, the relative humidity of 70±1%

and temperature of 20+1°C (Law et al. 2014a, b).

A sophisticated electronic apparatus was attached to the

chamber to calculate the temperature and relative humidity

in the system. A timer was used to control the system. The

timer switches on and switches of the system for 15 minutes

continuously. It ensures constant relative humidity in the

chamber. The Carbon di-oxide concentration was associated

comparative to the concentration of O2 in the chamber. Pore

water from concrete samples was got through a constructed

pore press. The pH value of each sample was measured

electronically using a water analyzer 371, with a sample

amount of 0.5 mg in 50 ml or 1000 ppm.

3. Results and discussions

Table 3 Details of mixture proportions

Mix

Code

RHA

content (%)

Proportion in kg/m3

Fly Ash GGBS RHA FA CA NaoH Mol/L Na2SiO3 Water SP

GPC 0 354.6 39.4 0 554.4 1294 45.1 10 112.6 59.14 11.83

R10 10 315.2 39.4 39.4 554.4 1294 45.1 10 112.6 59.14 11.83

R15 15 295.5 39.4 59.1 554.4 1294 45.1 10 112.6 59.14 11.83

R20 20 275.8 39.4 78.8 554.4 1294 45.1 10 112.6 59.14 11.83

R25 25 256.1 39.4 98.5 554.4 1294 45.1 10 112.6 59.14 11.83

R30 30 236.4 39.4 118.2 554.4 1294 45.1 10 112.6 59.14 11.83

R35 35 216.7 39.4 137.9 554.4 1294 45.1 10 112.6 59.14 11.83

Table 4 Strength development of RHA concrete

Mix Compressive strength (MPa) Tensile strength (MPa) Modulus of rupture (MPa) Bond strength

(MPa)

Slump

(mm) 7 d 28 d 56 d 7 d 28 d 56 d 7 d 28 d 56 d

GPC 21.20 31.30 32.32 1.62 2.25 2.64 2.12 3.26 3.42 5.32 40

R10 20.19 29.96 30.65 1.53 1.94 2.21 2.28 3.50 3.67 5.29 60

R15 19.33 25.80 27.12 2.21 2.51 2.69 2.11 3.25 3.48 5.99 50

R20 17.33 24.46 25.95 2.08 2.39 2.54 2.06 3.17 3.39 5.27 40

R25 18.23 27.80 29.17 1.94 2.19 2.38 2.19 3.37 3.57 5.01 15

R30 18.43 28.06 30.33 2.06 2.32 2.49 2.20 3.39 3.62 5.44 10

R35 18.10 24.26 26.93 1.51 2.06 2.19 2.05 3.15 3.32 4.63 5

141


Fig. 3 Compressive strength results of RHA geopolymer

specimens

3.1 Workability of geopolymer concrete mix

Table 4 presents the slump values for the mixes. The

results of the slump test revealed that the increase in the

RHA in GPC mixes percentage revealed reduced

workability due to higher viscous and stiffness. Slump

values ranged from medium to very low. Reduction in

slump value is due to high water absorption capacity of

RHA resulting in increase in surface area and decrease the

water availability for the ingredients in the mix to flow.

3.2 Hardened properties

Earlier research revealed that GPC specimen’s hardened

properties were lesser in ambient temperature compared to

specimens exposed to heat curing. Reduction in strength

properties was due to the slower dissolution of Al and Si

monomers. In this research, 10% of GGBS was added to all

mixes. The final setting properties of all the mixes at 28

days of curing in room temperature are similar to the

conventional concrete. Alkaline activators (OH-) in

geopolymer concrete enhanced reactivity in GGBS,

promoting bond breaking in the structure and forming

dissolved species. It also generated the C-S-H matrix and C-

A-S-H, leading to denser microstructure (Patet and Shah

2014). Addition of RHA changed reaction process, physical

properties. and the matrix of geopolymer concrete. RHA,

which contains higher SiO2, can be used to fix the

Sio2/Al2O3 ratio in the source material. Fine-grained RHA

particles enhanced reactivity resulting in superior

geopolymerization. Table 4 gives the compressive strength

of GPC and RHA geopolymer concrete at different ages.

Higher RHA amount resulted in reduced strength due to

slow geopolymerization at ambient curing caused by porous

and loose microstructure.

On the other hand, there was a slight increase in the

compressive strength of GPC with 30% of RHA due to an

enhanced quantity of reactive silica in RHA which leads to

superior density in the Si-O-Si bonds in the geopolymer

matrix (Zabihi et al. 2018a, b, Fan 2015). Another reason is

that a higher amount of RHA has higher surface area

compared to cement making stronger products by refining

the pores. Compared to Si-O-Al and Al-O-Al bonds, Si-O-

Si bonds are stronger. According to Fig. 3, replacement with

35% RHA based geopolymer concrete reduced compressive

Fig. 4 Tensile strength results of RHA geopolymer

specimens

strength caused by obstruction of Al and Si reorganization

due to an increased amount of soluble Si reducing the

skeletal density of geopolymer binder (Duxson et al. 2005a,

b), leading to a weaker geopolymer. Increased unreacted

RHA in the final product results in a less ductile and weaker

geopolymer causing it to suffer from lower strength.

Increase in RHA geopolymer concrete’s compressive after

28 days of curing reveals that as time increases, dissolution

of reactive aluminosilicate species and their

polycondensation strengthen the geopolymer gel matrix. To

wrap up, RHA geopolymer concrete’s compressive strength

at 28 days and 56 days varied from 28.06 MPa to 30.33

MPa, which is near the strength of M30 grade concrete.

The results provide an opportunity to use this type of

concrete in structural applications. RHA based geopolymer

concrete can be used as cementitious materials in civil

engineering constructions for building and roadways. Also,

geopolymeric binders immobilize radioactive waste and

toxic chemicals within the structures (Van Jaarsveld et al.

1997a, b, Hart et al. 2006a, b). Hence, the use of waste

containment and capsulation are the reasons for producing

RHA as a binder in geopolymer concrete. By utilizing the

RHA in geopolymer concrete, both economic and

environmental issues are resolved. The production of RHA

based geopolymer concrete, not only reduces problems in

waste disposal but it also reduces the production cost of

OPC. It also saves energy in cement manufacture and

diminishes CO2 emission into the atmosphere by firing

carbonates (Davidovit 1991). Utilization of rice husk ash in

geopolymer concrete mix is a good strategy to reduce its

harmful potential to affect human health and the

environment.

Tensile strength is an essential mechanical property used

in the different design guidelines for structures like

anchorage and shear reinforcement steel. The tensile

strength of different GPC mixes with RHA is presented in

Table 4. The test was carried out at 7, 28. and 56 days. The

GPC mix with 35% RHA exhibits lesser tensile strength

value at all curing periods. Tensile strength of 30% RHA

had 2.32 MPa at 28 days, which was higher compared to the

GPC mix. Test results disclosed that during ambient curing,

the rate of increase of tensile strength in increased amounts

of fly ash mix was slow as it was hard to break the Al and

Si monomers bond from fly ash particles to start the

reaction. There is a reduction in tensile strength with the

0

5

10

15

20

25

30

35

GPC R10 R15 R20 R25 R30 R35

Co

mp

ress

ive

stre

ngth

(MP

a)

Mix ID

7 days 28 days 56 days

0

1

2

3

GPC R10 R15 R20 R25 R30 R35

Ten

sile

str

ength

(M

Pa)

Mix ID


142


Fig. 5 Modulus of rupture results of RHA geopolymer

specimens

addition of RHA in geopolymer concrete.

As seen in Fig.4, the tensile strength of GPC mix with

RHA ranges from 1.62 MPa to 2.21 MPa at 7 days, 2.25

MPa to 2.51 MPa at 28 days and 2.64 MPa to 2.69 MPa at

56 days. Increase in RHA percentage in GPC mix decreases

tensile strength. A similar statement was reported by

(Venkatesan and Pazhani 2016, Liu et al. 2014 a, b) in

geopolymer concrete made with palm oil fuel ash as a

binder. RHA particles acquire various structures. and when

the ratio between SiO2 to Al2O3 is high, the kinetics of

polymerization is slowed due to differences in the solubility

of Fly ash, GGBS. and RHA. Therefore the production rate

of geopolymer gel is reduced as reported by (Kusbiantoro et

al. 2012a, b) Appreciable tensile strength in a lower

percentage of fly ash and RHA based GPC was achieved in

7 days due to the premature precipitation of C-S-H and

geopolymeric gel.

The test results of modulus of rupture of GPC mixes

with different proportions of RHA are presented in Table 4

and Fig. 5. Comparable to compressive strength, the

addition of RHA in the GPC mix resulted in increased

modulus of rupture of RHA based geopolymer concrete.

Enhancement in the strength of RHA concrete is due to the

excellent interfacial bond between the aggregate and paste.

It increased by 30% RHA, but beyond it, strength was

reduced. However, modulus of rupture with 30% of RHA

geopolymer concrete was higher than that of GPC mix

without RHA. Fig. 4 shows that the modulus of rupture

increases with an increase in the age of concrete. The

highest modulus of rupture of 3.50 MPa was obtained for

the mix R10 at 28 days. and the lowest modulus of rupture

was observed for the R35 mix. Modulus of rupture of mix

R35 was 3.15 MPa at 28 days.

Higher mechanical properties were achieved using a

higher ratio of silica to alumina in the geopolymer mix with

higher elasticity. The temperature in ambient curing is

insufficient to dilute the particles of binders of SiO2 in the

alkaline solution resulting in superior unreacted particles

which obstruct geopolymerization and weaken the density

of the geopolymer matrix. When applying the load, such

weaker geopolymer concrete specimens cannot transfer the

load which induces cracks and reduces its strength. It was

pragmatic that percentage increase in strength decreased as

RHA content increased from 10% to 35% in the mixes

irrespective of age. This is due to the enhanced ratio of

Fig. 6 Bond strength results of RHA geopolymer specimens

Table 5 pH of RHA geopolymer concrete specimens after

Carbonation

Mix pH

0 d 3 d 7 d 28 d 56 d

GPC 11.43 11.20 11.17 11.10 11.04

R10 11.20 10.91 10.86 10.75 10.72

R15 10.58 10.23 10.17 10.12 10.08

R20 11.08 10.82 10.76 10.69 10.61

R25 11.18 10.88 10.83 10.79 10.71

R30 11.03 10.77 10.69 10.61 10.58

R35 10.98 10.64 10.61 10.58 10.54

silica to alumina and the difference in the solubility of fly

ash, GGBS. and RHA which produce a weaker geopolymer

matrix; the reason is the same as mentioned in the

compressive strength discussion.

Past research reports on Geopolymer concrete state that

it acts as an excellent corrosive environment for steel

reinforcement in concrete. This research revealed that the

pH of Geopolymer concrete ranged from 10.58-11.43, but it

varied slightly for OPC concrete where pH value ranges

from 12 to 13. Hence this research aims to confirm the null

contribution of Geopolymer concrete with rich husk ash for

corrosion of reinforcement steel due to the substituted

cementitious materials. Corrosion of steel reinforcement

mainly affects the bonding capacity of reinforced steel with

concrete. Load transformation inside the concrete will be

affected. and reinforced steel might slip out due to

inadequate friction between the reinforced steel and

geopolymer concrete. Bond strength of Geopolymer

concrete with different percentages of rice husk ash was

found out by pull out test.

Fig. 6 depicts the bond strength of Geopolymer concrete

specimens. Test results of bond strength revealed that

addition of RHA does not enhance strength in the pull-out

test. Other factors influencing bond strength are reactivity

of source material used, curing temperature. and the

alkaline activator solution used. Due to the quick

dissolution of Si-O bond from rice husk ash contributes to

polycondensation of Geopolymer gel and enhances the

bond capacity of Geopolymer concrete with reinforced

steel.

The pH concentration of blended, fresh. and Ordinary

Portland Cement concrete was more than 13. The

carbonated concrete had a pH value of less than 9, due to

0

1

2

3

4

GPC R10 R15 R20 R25 R30 R35

Mo

du

lus

of

Ru

ptu

re (

MP

a)

Mix ID


0

1

2

3

4

5

6

7

GPC R10 R15 R20 R25 R30 R35

Bo

nd

str

ength

(M

Pa)

Mix ID

143


Fig. 7 EDX profiles of RHA geopolymer specimens; (a)

10% of RHA, (b) 15% of RHA, (c) 20% of RHA, (d) 25%

of RHA, (e) 30% of RHA and (f) 35% of RHA

calcium carbonate formation. C-S-H and Ca(OH)2 gel

supports buffering to preserve pH value more than 13 in

Ordinary Portland cement concrete. However, in

geopolymer concrete, such buffering is not supported by the

(Mz(AlO2)x(SiO2)y.nMOH.mH2O) gel. Carbonation in

geopolymer concrete is hypothesized as the chemical

process of NaOH with carbon-di-oxide making sodium

carbonate hydrates. The output of this is a lesser

minimization of pH value, which ranges from 10.58. The

obtained results compared to earlier reports for alkali-

activated slag concretes reported no harmful effects due to

carbonation (Deja 2002, Shi et al. 2006a, b). The pH value

proves that it can provide safety to steel reinforcement after

carbonation.

3.3 Microstructural properties

Fig. 7 presents the energy dispersive X-ray spectrometry

(EDX) profile of RHA based geopolymer concrete.

Different percentages of RHA added concrete were selected

after 28 days of curing for the EDX analysis. Table 6

presents the test results of EDX analysis under ambient

curing conditions. They reveal that elements like O, Al, Si,

Na and Ca are common elements in the RHA based

geopolymer framework. At 28 days of curing, the ratio of

silica to alumina detected is 1.96 for fly ash and the GGBS

based specimen. and the ratio varied from 3.08 to 4.46 for

rice husk ash-based geopolymer concrete specimens. The

variation was due to the presence of unreactive silica

particles and dissolution of silica particles on RHA

surfaces. Observations from earlier literature on RHA based

geopolymer concrete with fly ash reveals that increase in

(a) (b)

(c) (d)

(e) (f)

Fig. 8 Morphological changes of RHA geopolymer

specimens; (a) 10% of RHA, (b) 15% of RHA, (c) 20% of

RHA, (d) 25% of RHA, (e) 30% of RHA and (f) 35% of

RHA

Table 6 EDX element weight percentage analysis of

ambient cured specimens

Element Mix

GPC R10 R15 R20 R25 R30 R35

O 46.03 55.75 53.24 55.22 56.58 54.47 54.82

Na 6.70 5.73 5.69 4.23 5.22 4.21 5.45

Al 10.34 8.26 6.98 7.57 6.35 6.99 6.62

Si 27.42 25.45 28.25 28.06 27.02 31.22 28.90

K 1.54 0.52 0.47 0.93 3.47 0.43 0.49

Ca 6.00 3.14 4.12 2.80 0 2.68 2.61

Fe 1.96 1.15 1.24 1.19 1.36 0 1.11

Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00

age reduces reactive silica particles in the specimen due to

the instantaneous reaction of silica and alumina precursor’s

dissolution- polycondensation progression of the framework

in the geopolymer and the steady low down rate diffusion of

residual ions in fly ash particles to attain equilibrium.

Addition of GGBS with fly ash and RHA accelerated

polycondensation and dissolution of aluminosilicate gel in

the geopolymer.

The absorption of H+ (hydrogen ion) by the Al-Si-rich

layers results in the further dissolution of silica particles

from RHA surfaces due to an increase in the pH in solution.

The RHA and fly ash based specimen face dissolution of

144


silica particles from RHA particles continuously to increase

the ratio of Si and Al development. Configuration of the Si-

O based geopolymer networks results in denser geopolymer

paste, with good bonding at interfacial transition zones and

the nanopores structure of the geopolymer matrix.

The absorption of H+ (hydrogen ion) by the Al-Si-rich

layers results in the further dissolution of silica particles

from RHA surfaces due to an increase in the pH in solution.

The RHA and fly ash based specimen face dissolution of

silica particles from RHA particles continuously to increase

the ratio of Si and Al development. Configuration of the Si-

O based geopolymer networks results in denser geopolymer

paste, with good bonding at interfacial transition zones and

the nanopores structure of the geopolymer matrix.

Progression of morphological changes in geopolymer

concrete with additions of 10%, 15%, 20%, 25%, 30% and

35% RHA at 28 days is seen in Fig. 8. Investigation of

SEM analyses images revealed that RHA particles added to

geopolymer concrete had a dense and compact matrix with

a high geopolymerization, whose dominant elements were

Si, Al. and Na. It was seen from SEM images that fly ash

particles were not recognized denoting that chemical fusion

in the dissolution of the alkaline environment was

proficient, particularly in RHA geopolymer concrete from

28 days.

Fig. 7 shows that RHA based geopolymer concrete

samples contained micro voids with a non-homogeneous

and porous microstructure on the surface. These cracks are

due to the following two reasons: (1) shrinkage cracks

developing due to water evaporation during curing of

geopolymer specimens; (2) Load based cracks during

compression testing. Voids may also be due to two

inferences: (i) due to residual air bubbles created in the

geopolymer precursor during the first stage of mixing; (ii)

initially the gap engaged by water and then remained as

void later on it evaporated. Earlier studies state that in early

ages, the geopolymer matrix contains insolubilized

particles. RHA contains unreactive particles and impurities

and influences geopolymerization (Duxson et al. 2007a, b,

De Vargas et al. 2011a, b). It is a significant factor that

influences the strength properties of RHA geopolymer

concrete, making them inconsistent and complicated. It is seen from Fig 8(e), at 28 days, the matrix’s

morphology is denser without particles of the geopolymer matrix. Morphology change implies that polymerization of the geopolymer matrix is reliable at 28 days and supports a strength increase in geopolymer concrete samples. This is due to the involvement of organic molecules present in rice

husk ash which eliminates the steric hindrance between the reacting species and assists development of the sialate-siloxo link which enhances its nature of amorphous and densifies the bonding of the matrix to be flexible, strong and homogeneous with better properties.

4. Conclusions

The study focuses on the influence of Rice Husk Ash

(RHA) in addition to GGBS and Fly ash in geopolymer

concrete on the strength properties. Test results exhibit that

the substitution of 30% of RHA in the geopolymer mix

shows better mechanical, durability. and microstructural

properties. RHA geopolymer concrete’s bond strength was

higher compared to other mixes due to good friction caused

by RHA’s higher fineness. Test results of microstructural

study revealed that, the presence of RHA in the geopolymer

mix densifies the concrete and makes it as homogeneous

and enhances its strength properties. Carbonation results

revealed that the pH value of RHA geopolymer concrete

was similar to that of conventional concrete. This research

suggests that RHA can be used to prepare eco-friendly

geopolymer concrete. It also reduces environmental

pollution caused by dumping of industrial by-products as

wastes in landfills.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest

with respect to the research, authorship. and/or publication

of this article.

Funding

The author(s) received no financial support for the

research, authorship. and/or publication of this article.

References ASTM D3682-01(2006), Standard Test Method for Major and

Minor Elements in Combustion Residues from Coal Utilization

Processes, American Society for Testing and Materials. USA.

Bakharev, T., Sanjayan, J.G. and Cheng, Y.B. (1999), “Alkali

activation of Australian slag cements”, Cement Concrete Res.,

29(1), 113-120. https://doi.org/10.1016/S0008-8846(98)00170-7.

Borges, P.H.R., Lourenço, T.M. de F., Foureaux, A.F.S. and

Pacheco, L.S. (2014), “Estudo comparative da análise de ciclo

de vida de concretos geopoliméricos e de concretos à base de

cimento Portland composto (CP II)”, Ambient. Construído,

14(2), 153-168. https://doi.org/10.1590/s1678- 86212014000200011.

Cordeiro, G.C., Toledo Filho, R.D. and De Moraes Rego

Fairbairn, E. (2009), “Use of ultrafine rice husk ash with high-

carbon content as pozzolan in high performance concrete”,

Mater. Struct. Constr., 42(7), 983-992.

https://doi.org/10.1617/s11527-008-9437-z.

Davidovits, J. (1991), “Geopolymer-Inorganic polymeric new

materials”. J. Therm. Anal., 37(8), 1633-1656.

https://doi.org/10.1007/BF01912193.

Davidovits, J. (2005), “Geopolymer chemistry and sustainable

development. The poly(sialate) trminology: a very useful and

simple model for the promotion and understanding of green-

chemistry”, Proceedings of Geopolymer, Green Chemistry and

Sustainable Development Solutions, Institut Ge opolyme`re,

Saint-Quentin, 9-15.

de Sensale, G.R. (2006), “Strength development of concrete with

rice-husk ash”, Cement Concrete Compos., 28(2), 158-160.

https://doi.org/10.1016/j.cemconcomp.2005.09.005.

De Vargas, A.S., Dal Molin, D.C.C., Vilela, A.C.F., Silva, F.J. Da,

Pavão, B. and Veit, H. (2011), “The effects of Na2O/SiO2 molar

ratio, curing temperature and age on compressive strength,

morphology and microstructure of alkali-activated fly ash-

based geopolymers”. Cement Concrete Compos., 33(6), 653-

660. https://doi.org/10.1016/j.cemconcomp.2011.03.006.

145

https://doi.org/10.1016/S0008-

https://doi.org/10.1590/s1678-


Deja, J. (2002), “Carbonation aspects of alkali activated slag

mortars and concretes”, Silicates Industriels, 67(1), 37-42.

Duxson, P., Fernández-Jiménez, A., Provis, J.L., Lukey, G.C.,

Palomo, A. and Van Deventer, J.S.J. (2007), “Geopolymer

technology: The current state of the art”, J. Mater. Sci., 42(9),

2917-2933. https://doi.org/10.1007/s10853-006-0637-z.

Duxson, P., Provis, J.L., Lukey, G.C., Mallicoat, S.W., Kriven,

W.M. and Van Deventer, J.S.J. (2005), “Understanding the

relationship between geopolymer composition, microstructure

and mechanical properties”, Coll. Surf. A Physicochem. Eng.

Asp., 269(1-3), 47-58. https://doi.org/10.1016/j.colsurfa.2005.06.060.

Fan, F. (2015), “Mechanical and thermal properties of fly ash-

based geopolymer cement”. M.Sc. Thesis, Agricultural and

Mechanical College, Louisiana State Univetsity.

Ganesan, N., Abraham, R. and Deepa Raj, S. (2015), “Durability

characteristics of steel fibre reinforced geopolymer concrete”,

Constr. Build. Mater., 93, 471-476.

https://doi.org/10.1016/j.conbuildmat.2015.06.014.

Ganesan, N., Abraham, R., Deepa Raj, S. and Sasi, D. (2014),

“Stress-strain behaviour of confined Geopolymer concrete”,

Constr. Build. Mater., 73, 326-331.


Ganesan, N., Indira, P.V. and Santhakumar, A. (2013),

“Engineering properties of steel fibre reinforced geopolymer

concrete”. Adv Concete Constr., 1(4), 305-318.

https://doi.org/10.12989/acc2013.1.4.305.

Geraldo, R.H., Fernandes, L.F.R. and Camarini, G. (2017), “Water

treatment sludge and rice husk ash to sustainable geopolymer

production”, J. Clean. Prod., 149, 146-155.

https://doi.org/10.1016/j.jclepro.2017.02.076.

Hart, R., Lowe, J., Southam, D., Perera, D. and Wal, P. (2006),

“Aluminosilicate inorganic polymers from waste material, In

Green Processing 2006”, 3rd Int. Conf. on the Sustainable

Processing of Minerals, Carlton, VIC, Australia.

IS 1199:1959, Methods of Sampling and Analysis of Concrete,

Bureau of Indian standards, New Delhi, India.

IS 12089:19887, Specification for Granulated Slag for the

Manufacture of Portland Slag Cement, Bureau of Indian

standards, New Delhi, India.

IS 2386: 1963 (Part-I), Methods of Test for Aggregates for

Concrete, Bureau of Indian standards, New Delhi, India.

IS 2770:1967 (Part I), Methods of Testing Bond in Reinforced

Concrete, Bureau of Indian standards, New Delhi, India.

IS 3812:2003, Specification for Fly Ash for Use as Pozzolana and

Admixture, Bureau of Indian Standards, New Delhi, India.

IS 516: 1959, Method of Test for Strength of Concrete,

Reaffirmed 2004, Bureau of Indian standards, New Delhi, India.

IS 5816:1999, Indian Standard Method of Test for Splitting

Tensile Strength of Concrete, New Delhi, India.

Khan, R., Jabbar, A., Ahmad, I., Khan, W., Khan, A.N. and Mirza,

J. (2012), “Reduction in environmental problems using rice-

husk ash in concrete”, Constr. Build. Mater., 30, 360-365.


Kusbiantoro, A., Nuruddin, M.F., Shafiq, N. and Qazi, S.A.

(2012), “The effect of microwave incinerated rice husk ash on

the compressive and bond strength of fly ash based geopolymer

concrete”, Constr. Build. Mater., 36, 695-703.


Law, D.W., Adam, A.A., Molyneaux, T.K., Patnaikuni, I. and

Wardhono, A. (2014), “Long term durability properties of class

F fly ash geopolymer concrete”, Mater. Struct. Constr., 48(3),

721-731. https://doi.org/10.1617/s11527-014-0268-9.

Liu, M.Y.J., Chua, C.P., Alengaram, U.J. and Jumaat, M.Z.

(2014), “Utilization of palm oil fuel ash as binder in lightweight

oil palm shell geopolymer concrete”, Adv. Mater. Sci. Eng.,

2014, Article ID 610274, 6.

https://doi.org/10.1155/2014/610274.

Lloyd, R.R., Provis, J.L. and Van Deventer, J.S.J. (2010), “Pore

solution composition and alkali diffusion in inorganic polymer

cement”, Cement Concrete Res., 40(9), 1386-1392.

https://doi.org/10.1016/j.cemconres.2010.04.008.

Matthes, W., Vollpracht, A., Villagrán, Y., Kamali-Bernard, S.,

Hooton, D., Gruyaert, E. and De Belie, N. (2018), “Ground

granulated blast-furnace slag”, RILEM State-of-the-Art

Reports, 25, 1-53. https://doi.org/10.1007/978-3-319-70606-1_1.

Mehta, P.K. (1977), “Properties of blended cements made from

rice husk ash”, J. Am. Concrete Inst., 74(9), 440-452.

https://doi.org/10.14359/11022.

Mehta, P.K. (1994), “Highly durable cement products containing

siliceous ashes”, United States Patent Number 5, 346, 548.

USA, 15.

Nath, P., Sarker, P.K. and Rangan, V.B. (2015), “Early age

properties of low-calcium fly ash geopolymer concrete suitable

for ambient curing”, Procedia Eng., 125, 601-607.

https://doi.org/10.1016/j.proeng.2015.11.077.

Nazari, A., Bagheri, A. and Riahi, S. (2011), “Properties of

geopolymer with seeded fly ash and rice husk bark ash”, Mater.

Sci. Eng. A, 528(24), 7395-7401.

https://doi.org/10.1016/j.msea.2011.06.027.

Patel, Y.J. and Shah, N. (2018), “Development of self-compacting

geopolymer concrete as a sustainable construction material”,

Sustain. Envir. Res., 28(6), 412-421.

https://doi.org/10.1016/j.serj.2018.08.004.

Prabu, B., Kumutha, R. and Vijai, K. (2017), “Effect of fibers on

the mechanical properties of fly ash and GGBS based

geopolymer concrete under different curing conditions”, Ind. J.

Eng. Mater. S., 24(1), 5-12.

Puertas, F., Fernández-Jiménez, A. and Blanco-Varela, M.T.

(2004), “Pore solution in alkali-activated slag cement pastes.

Relation to the composition and structure of calcium

silicatehydrate”, Cement Concrete Res., 34(1), 139-148.

https://doi.org/10.1016/S0008-8846(03)00254-0.

Ramasamy, V. (2012), “Compressive strength and durability

properties of Rice Husk Ash concrete”, KSCE J. Civil Eng.,

16(1), 93-102. https://doi.org/10.1007/s12205-012-0779-2.

Rice Market Monitor, Vol. XII-Issue No. 4; December 2009.

RILEM committee 73-SBC (1988), “Final report: siliceous by-

products for use in concrete”. Mater. Struct. Constr., 21(121),

69-80. https://doi.org/10.1007/BF02472530.

Shi, C., Krivenko, P.V. and Roy, D.M. (2006), Alkali Activated

Cement Concretes, Taylor and Francis, Abingdon.

Song, S. and Jennings, H.M. (1999), “Pore solution chemistry of

alkali-activated ground”, Cement Concrete Res., 29, 159-170.

Van Jaarsveld, J.G.S., Van Deventer, J.S.J. and Lorenzen, L.

(1997), “The potential use of geopolymeric materials to

immobilise toxic metals: Part I. Theory and applications”, Mine.

Eng., 10(7), 659-669. https://doi.org/10.1016/S0892-

6875(97)00046-0.

Venkatesan, R.P. and Pazhani, K.C. (2016), “Strength and

durability properties of geopolymer concrete made with Ground

Granulated Blast Furnace Slag and Black Rice Husk Ash”,

KSCE J. Civil Eng., 20(6), 2384-2391.

https://doi.org/10.1007/s12205-015-0564-0.

Wallah, S.E. and Rangan, B.V. (2006), “Low-calcium fly ash-

based geopolymer concrete: Long-term properties”, Research

Report GC 2, Faculty of Engineering, Curtin University of

Technology, Western Australia.

Yang, K.H., Jung, Y.B., Cho, M.S. and Tae, S.H. (2016), “Effect

of supplementary cementitious materials on reduction of CO2

emissions from concrete”, Handbook of Low Carbon Concrete,

2, 89-110. https://doi.org/10.1016/B978-0-12-804524-4.00005-1.

Zabihi, S.M., Tavakoli, H. and Mohseni, E. (2018), “Engineering

and microstructural properties of fiber-reinforced rice Husk-Ash

based geopolymer concrete”, J. Mater. Civil Eng., 30(8),

146

https://doi.org/10.1016/j.conbuildmat.2014.09.092

https://doi.org/10.12989/acc2013.1.4.305

https://doi.org/10.14359/11022




04018183. https://doi.org/10.1061/(asce)mt.1943-

5533.0002379.

Zerbino, R., Giaccio, G., Batic, O.R. and Isaia, G.C. (2012),

“Alkali-silica reaction in mortars and concretes incorporating

natural rice husk ash”, Constr. Build. Mater., 36, 796-806.


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Development of eco friendly concrete produced with Rice