Ijciet 08 02_017

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 8, Issue 2, February 2017, pp. 153–162 Article ID: IJCIET_08_02_017
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
COMPRESSIVE STRENGTH AND CARBONATION
OF SEA WATER CURED BLENDED CONCRETE
T. Jena
Research Scholar, Department of Civil Engineering,
SOA University, Bhubaneswar, Odisha, India
K. C. Panda
Associate Professor, Department of Civil Engineering,
SOA University, Bhubaneswar, Odisha, India
ABSTRACT
This paper investigates the influence of sea water on pre-cast concrete containing
industrial by-product materials such as fly ash (FA) and silpozz. The mix design is targeted for
M30 grade concrete. Ten concrete mixtures were designed to have the same degree of
workability with water to cementitious material ratio of 0.43. The studied parameters include
the compressive strength of normal water curing (NWC) and sea water curing (SWC) samples
after 28 days of NWC for 7, 28, 90, 180 and 365 days curing period. The carbonation depth of
concrete samples for 28, 90, 180 and 365 days SWC after 28 days of NWC was measured. It
was found that the higher the FA content the higher is the carbonation process occurred. The
percentage increase in compressive strength for blended cement concrete in NWC is better
than the samples in SWC after 28 days of NWC.
Key words: Pre-cast, Workability, Carbonation and Compressive strength.
Cite this Article: T. Jena and K. C. Panda, Compressive Strength and Carbonation of Sea
Water Cured Blended Concrete. International Journal of Civil Engineering and Technology,
8(2), 2017, pp. 153–162.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
1. INTRODUCTION
Deterioration of reinforced concrete structures in marine environments is generally associated with
external agents such as chlorides that penetrate into concrete and carbonation induced corrosion
causing damage. A number of factors affecting durability may be defined as the concrete type, cover
depth to reinforcement, site practice and severity of exposure. Durability of concrete may be enhanced
by utilizing waste by-products possessing hydraulic and pozzolanic properties such as fly ash and
silipozz. Some of the researchers have reported the utilization of supplementary cementitious materials
(SCM) to improve concrete properties in marine climate. Jena and Panda (2015) studied the
development of compressive strength in blended concrete made with silpozz which is used as a
substitute material of silica fume (SF) to improve the durability of marine structures. Anwar and

Compressive Strength and Carbonation of Sea Water Cured Blended Concrete
Roushdi (2014) showed the properties of concrete containing PC, FA and SF as blended cements for
improvements in concrete to resist environmental causes of deterioration. Anwar et al. (2013)
concluded that the combinations of 15 to 25% of FA with 5 to 10% SF show satisfactory performance
in both fresh and hardened concrete. The SF improves early age performance of concrete with FA
continuously refining the properties of hardened concrete as it matures and the replacement of 35% of
cement quantity with 25% FA and 10% SF increased the compressive strength by 20% at 180 days.
Wegian (2010) investigated on the effects of mixing and curing concrete with seawater on the
compressive, tensile, flexural and bond strengths of concrete and the reduction in strength increases
with an increase in exposure time, which may be due to salt crystallization formation affecting the
strength gain. Sunil (2009) investigated the effects of the quality of mixing water and initial curing on
plain and blended cement concrete made with FA were exposed to seawater attack for a period of 1
year and the performance of these concrete specimens were evaluated by reduction in compressive
strength. The results of this study showed that the use of pre casting in place of casting-in-situ
mitigates the effect of marine environments on concrete specimens considerably. Thomas et al. (1999)
reported that the combination of PC, SF and FA in a ternary cement system should result in a number of
obvious synergistic effects. Maltais and Marchand (1997) showed that carbonation could have both
positive and negative effect on concrete durability. Naik and Singh (1998) mentioned that the steel
passivation layer of oxide film may be destroyed due to carbonation and accelerating the start of
uniform corrosion. On the contrary, the carbonation process seems to densify the concrete surface
reducing surface porosity and reduce chloride ion permeability (Mehta, 1994). Ho and Lewis (1987)
conclude that due to replacement of cement with FA, the rate of carbonation increases significantly.
However, Papadakis (2003) reported that in the case FA is introduced as a fine aggregate replacement,
the carbonation rate is reduced. This paper focuses the compressive strength and carbonation of pre-
cast concrete with FA and silpozz in sea water for different curing periods and the utilization of waste
by-product such as FA and silpozz which creates environmental problems after disposal.
2. EXPERIMENTAL SETUP
The experimental study was carried out using ten different mixes of concrete mixed and cured in
normal water for 7, 28, 90, 180 and 365 days and subsequently cured in sea water after 28 days of
NWC. Among ten concrete mixes, one is control mix with 100% OPC and the rest nine mixes are
blended cement concretes. From nine blended concrete mixes, five are FA based ranging 10 – 50%
replacement with OPC and the rest four mixes are FA and silpozz based concrete with FA replacement
is 10% fixed and the replacement of silpozz is 10 - 40% with OPC. The fresh concrete properties such
as slump and compaction factor were studied for workability of concrete. The hardened concrete
property such as compressive strength was measured at 7, 28, 90, 180 and 365 days for NWC samples
and SWC precast samples. Carbonation depth was determined at 28, 90, 180 and 365 days for SWC
precast samples.
2.1. Materials used and Properties
The material used in the present study is OPC, FA, Silpozz, fine aggregate, coarse aggregate, normal
water and sea water. The physical properties of OPC obtained from experimentally and the value
specified by IS 8112:1989 are presented in Table 1. The properties of aggregates obtained
experimentally as per IS: 383-1970 is presented in Table 2. Sea water is collected from Puri Beach of
Bay of Bengal, Konark, Odisha. In this study, FA was supplied by NALCO, Angul, Odisha. Silpozz is
supplied by N. K. Enterprises, Singhania House, Jharsuguda, Odisha. The sample of FA and silpozz is
shown in Figure1. The physical and chemical compositions of FA and silpozz specified by the supplier
are presented in Tables 1

T. Jena and K. C. Panda
Figure 1 FA and Silpozz
Table 1 Physical and chemical properties of cementitius Materials
Oxides (%) Cement (OPC) Silpozz FA
SiO2 20.99 88.18 58.13
Al2O3 6.05 1.61 31.00
Fe2O3 6.01 0.56 4.10
Carbon - 2.67 -
CaO 62.74 1.59 0.60
MgO 1.33 1.63 0.10
K2O 0.40 1.67 0.90
Na2O 0.04 - 0.05
SO3 1.82 - 0.12
TiO2 .025 - 1.63
Others - 2.09 0.011
Moisture content (%) - 0.79 3.0
Loss on ignition (%) 1.14 0.04 0.29
Physical properties
Bulk Density (gm/cc) 1.43 0.23 1.2
Specific gravity 3.15 2.3 2.12
Particle size (Micron) 35 25 34
Specific surface, m2
/g 0.33 17 33
Color Gray Gray black Gray
Table 2 Properties of Aggregates
Specifications Value obtained experimentally as per IS : 383-
1970
Coarse aggregates Fine aggregates
Fineness modulus 7.0 3.03 (Zone-3)
Specific gravity 2.86 2.67
Water absorption (%) 0.2 0.4
Bulk density (kg/m3
) 1424 1568
Abrasion value (%) 34.78 -
Impact value (%) 24 -
Crushing value (%) 23.3 -

2.2. Mix Proportions and Identifications
Usually, in marine environments, relatively richer mixes with low water to cementitious material ratio
are used. This aspect was kept in mind in planning the experimental program. Therefore concrete
mixture of M30 is designed as per standard specification of IS 10262-2009 to achieve target mean
strength 39 MPa. The concrete mix proportion was (1: 1.44: 2.91), w/b 0.43. The controlled specimen
made 0% replacement of FA and silpozz with Ordinary Portland Cement (OPC). The blended concrete
samples made with 0% replacement of silpozz and 10%, 20%, 30%, 40% and 50% replacement of fly
ash with OPC. Another blended cement concrete samples made with 10% replacement of FA and
10%, 20%, 30%, and 40% replacement of silpozz with OPC. Two set of samples (cubes) have been
prepared. One set of sample, after 28 days of normal water curing (NWC) was being immersed in sea
water for 7, 28, 90, 180 and 365 days (Pre-cast samples) and the other set of samples have been cured
in normal water for 7, 28, 90, 180 and 365 days.The concrete mix proportion along with their mix
identification was designated according to their replacement ratio as given in Table 3.
Table 3 Mix Proportions and identity for plain and blended cement concrete.
Mix Identity Cement (%) FA (%) Silpozz (%)
MC100F0S0 100 0 0
MC90F10S0 90 10 0
MC80F20S0 80 20 0
MC70F30S0 70 30 0
MC60F40S0 60 40 0
MC50F50S0 50 50 0
MC80F10S10 80 10 10
MC70F10S20 70 10 20
MC60F10S30 60 10 30
MC50F10S40 50 10 40
2.3. Specimen Preparation and Curing Condition
Standard concrete cubes of size 150 × 150 × 150 mm3
were used for measuring the compressive
strength. Depending upon the ingredients used in mixing and curing conditions, the concrete samples
were divided into two groups. The first groups of samples (cubes) were cured in normal water for 7,
28, 90, 180 and 365 days for determination of compressive strength. The second groups of samples
were cured in sea water for 7, 28, 90, 180 and 365 days after 28 days of NWC and compressive
strength was tested. The carbonation profile was also determined on SWC samples after 28 days of
NWC for 28, 90 180 and 365 days. The cube samples are shown in Figure 2 and compressive strength
test set up is shown in Figure 3.
Figure 2 Casting of cubes Figure 3 Compressive test

3. RESULTS AND DISCUSSIONS
3.1. Properties of Fresh Concrete
Workability is defined as “that properties of freshly mixed concrete or mortar that determines the ease
with which it can be mixed, placed, consolidated and finished to a homogenous mass” (ACI
Committee 116). Sufficient workability is necessary so that concrete can be placed and compacted to
maximum density. The slump ranged from 32 to 40 mm. According to the results, most of the
concretes made had a moderate slump value and were workable. No wide variations in the slump
value for the mixes containing increased amounts of silpozz were observed. The compaction factor
ranges from 80 to 86.20% which shows good workable concrete at all levels. At the level of 20%
replacement of FA showed optimal workability and maximum slump value. The workability of
concrete increases as the FA percentage is higher. At the 50% replacement of FA, the workability of
concrete slightly decreases as compared to control specimen. The slump value ranged from 38 to 39
mm and compaction factor varied from 85.60 to 86% in the ternary system of concrete with 10% FA
and upto 20% silpozz. It is observed that the sump value and compaction factor slightly decreases as
the silpozz replacement ratio is high.
3.2. Properties of Hardened Concrete
Many properties of concretes can be estimated from the results of better controlled and standard tests
on the plain and blended concrete, such results still should be verified on concrete and more realistic
values should be established. With such a consideration, the hardened concrete properties such as
compressive strength was determined as per IS 516-1959. The compressive strength of NWC and
SWC after 28 days NWC samples was tested for 7, 28, 90, 180 and 365 days of curing.
3.2.1. Compressive Strength
Compressive strength test determines behavior of materials under compressive loads. The specimen is
compressed and the maximum peak load is recorded. In this study, the compressive strength test was
performed on 150 mm cube specimens at the age of 7, 28, 90,180 and 365 days for NWC and pre-cast
SWC samples. Three specimens were tested at each testing age and the average compressive strength
was reported. The specimens were tested for compressive strength using a 3000 KN capacity concrete
compression testing machine. The compressive strength verses age in days for NWC samples are
presented in Figure 4. It is observed from the Figure 4 that the concrete containing 10% FA and 20%
silpozz replacing with OPC contributes higher strength after 90 days to 365 days as compared to
control specimen. The compressive strength of mixes containing 10% FA fixed and silpozz varies
from 10 to 30% is higher than all other FA based concrete after 90 days to 365 days in NWC but the
sample containing 10% FA and 40% silpozz showed less result than the control specimen at all ages
after NWC. All the ternary systems compressive strength is lower than the control mix at 28 days of
curing in normal water. After 90 days age, the ternary system containing 10% FA and upto 20%
silpozz showed higher compressive strength as compared to control mix at 365 days of NWC. The mix
containing 10% FA and 30% silpozz performed better than the control mix after 180 days upto 365
days of NWC. The later age strength is more after 180 days to 365 days for FA based concrete
samples containing 30% FA as compared to control specimen.

Figure 4 Compressive strength verses age in days (NWC)
Figure 5 Compressive strength verses age in days (SWC)
It is also studied that the higher portions of silpozz in the presence of certain FA percentage
decreases the compressive strength gain of blended concrete at early ages, but does increase in gain of
compressive strength beyond the 28 days than that of control mix and is reported by Khalil and Anwar
(2015). The compressive strength verses age in days of SWC samples after 28 days of NWC is
presented in Figure 5. The compressive strength of concrete specimens in SWC is almost same upto
28 days and in later age the strength increases in all the specimens. The compressive strength of
specimen with 10% replacement of FA and upto 20% silpozz with cement gives higher value as
compared with control specimen in later age. The rate of increase in compressive strength for SWC
samples is relatively lower as compared to NWC samples. The rate of increment of compressive
strength is 4.56% and 4.65% at 180 and 365 days respectively for the samples of 10% FA and 30%
silpozz replacement with OPC as compared to control specimen. The percentage reduction in
compressive strength is increasing in age of concrete for SWC samples after 28 days of NWC which is
reported by Sunil (2000). The rate of deterioration of concrete in marine structures is dependent on its
total porosity of concrete decreases with time due to the process of cement hydration and carbonation.
The percentage decrease in compressive strength is varying from 5% - 7.54% at 90 days age and
5.3% – 9.7% at 180 days age for all specimens. At the age of 365 days the rate of decrease in
compressive strength is varying from 2.46% - 9.57%. It was found that the FA replacement upto 20% -
30% with OPC in binary system performed better in sea water and replacement of silpozz upto 20%
with OPC have improved its resistance against sea water at all the ages after 28 days. The compressive

strength of SWC samples after 28 days of NWC have a little more or equal to NWC samples but after
28 days the sea water has a negative effect on compressive strength by Wegian (2010).
4. DURABILITY PROPERTY
Durability of hydraulic-cement concrete is defined as its ability to resist weathering action, chemical
attack, abrasion, or any other process of deterioration. Durable concrete will retain its original form,
quality, and serviceability when exposed to its environment (ACI 201-2R). Deterioration of reinforced
concrete structures in marine environments is generally associated with external agents when carbon
dioxide intrusion takes place into concrete cover and reaches the reinforcement causing corrosion in
presence of moisture and oxygen. In this article the durability property in term of carbonation depth
measurement is presented for SWC precast concrete samples at 28, 90, 180 and 365 days.
4.1. Carbonation Effects
Carbonation is the process by which carbon dioxide (CO2) in the atmosphere reacts with water in
concrete pores to form carbonic acid. The acid reacts with alkaline in the pores, neutralizing them.
This reaction reduces the pH of concrete pore solution from 12.6 to less than 9. Naik and Singh (1998)
observed that the steel passive oxide film gets destroyed and reinforcement leads to corrosion. The
depth of carbonation is measured by spraying a phenolphthalein indicator on fresh concrete chiseled
and cleaned by wire brush. The phenolphthalein solution will remain clear where concrete is
carbonated and turn pink where concrete is still alkaline. For each sample, the average carbonation
depth of the four measurements is reported. The depth of carbonation is increased with time of
exposure at all ages. The depth of carbonation verses age in days is given in Figure 6. It found that as
the percentage of FA increases, the depth of carbonation increases. The carbonation coefficient is
calculated using the empirical relationship, X = K √T Where X is the depth of carbonation in mm, T is
the period of exposure in Years and K is the coefficient of carbonation. The coefficient of carbonation
verses concrete mix is shown in Figure 7. It is found that the carbonation coefficient increases along
with increase in FA content. When silpozz is replaced with OPC, the coefficient of carbonation is
decreasing.
Figure 6 Carbonation depth verses age in days

Figure 7 Carbonation coefficient verses concrete mix
5. CONCLUDING REMARKS
 Much attention must be given to the development of a new generation of cements incorporating
combination of by-product materials in binary and ternary systems. The test results show that ternary
blends of PC, silpozz, and FA offer significant advantages over binary blends and plain PC. Also, the
combination of silpozz and FA is complementary.
 The silpozz improves the early age performance of concrete with the FA continuously refining the
properties of the hardened concrete as it matures. Combinations of 10-20% silpozz with 10–30% FA
show satisfactory performance in both fresh and hardened concrete. Such combinations produce
concrete with generally good properties especially the resistance to carbonation.
 Silpozz is having most particles size of 25 microns and below, so that it fills the interstices in between
the cement in the aggregate as fine filler which gives better strength and resistance to chloride and
carbonation.
 It is expected that the sea water attack will be less in structures made of precast elements and the
hardened concrete will be subjected to seawater attack at mature state.
 It may be concluded that resistance against all possible forms of deterioration is distinctly improved by
using mineral admixtures like FA and silpozz up to certain percentage of cement.
 It is found from the experimental results that the use of precast concrete increases the resistance of
concrete against marine environments appreciably. Blending a suitable proportion of FA and silpozz
with PC can further reduce the effect of seawater on marine structures.
 The utilization of silpozz and FA solves the problem of its disposal thus keeping the environment free
from pollution. It may be recommended that while manufacturing of concrete, care should be taken to
produce impermeable and dense concrete in order to resist the sea water attack.
6. ACKNOWLEDGEMENTS
The author would like to thanks S ‘O’ A University for the support of conducting the experimental
work and also thankful to the N K Enterprises, Jharsuguda and Nalco, Angul for supplying of
materials.

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AUTHOR’S PROFILE
Trilochan Jena is a research scholar in department of civil engineering, SOA University,
Bhubaneswar, Odisha, India. He obtained his Master degree in Structural Engineering and Natural
Disaster Management from GITAM University in 2008. His research interest is mechanical and
durability properties of construction materials.
Dr. Kishor Chandra Panda is currently working as Associate Professor in the Department of Civil
Engineering, Institute of Technical Education and Research, Siksha ‘O’ Anusandhan University,
Bhubaneswar, Odisha, 751030, India. In 2010, he obtained Ph.D (Engg.) from Indian Institute of
Technology, Kharagpur, India. He received the degrees of B.E. (Civil) from Utkal University, IGIT,
Saranga, Talcher in 1990 and M.Sc. Engg. (Civil) with specialization in Structural Engineering in
1992, from Sambalpur University, REC, Rourkela, India (Presently NIT Rourkela). His research
interests are FRP-Concrete Composite Systems, Strengthening, Rehabilitation and Retrofitting of
structures, Durability of concrete structure in marine environment, Self Compacting Concrete using
different types of waste material, Sustainable material in construction field and bacterial concrete. He
has published more than 70 papers in journals and Conference proceedings and Book chapters. He has
guided 14 M Tech Students and 1 Ph. D student. He has member of some professional bodies like ICI,
ISTE and IET.

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