Experimental study of effects of potassium carbonate on strength parameters of concrete

Experimental Study of Effects of Potassium Carbonate on Strength Parameters of Concrete,
Dr. Javed Ahmed Naqash, Saiqa Nabi, Mehvish, Tehseena Ali, Mahapara Firdous, Insha
Bashir, Journal Impact Factor (2015): 9.1215 (Calculated by GISI) www.jifactor.com
www.iaeme.com/ijciet.asp 204 editor@iaeme.com
1
Associate Professor National Institute of Technology Srinagar, J&K, India
2,3,4,5,6
UG Students, Department of Civil Engineering, S S M College of Engineering & Technology,
J&K, India
ABSTRACT
This study presents the effects of Potassium Carbonate (K2CO3) on plain concrete. Potassium
carbonate as depressant admixture was added in different percentages by weight of cement. The
concrete specimens were tested for compressive, flexural and split tensile strengths and the results
obtained were compared with those of normal concrete. The optimum percentage of admixture that
could be used without harming the properties of concrete was also assessed. The results concluded
permissibility of using admixture (K2CO3) up to 2.6% by weight of cement.
Key words: Potassium Carbonate, Workability, Compressive Strength, Flexural Strength, Split
Tensile Strength.
I. INTRODUCTION
Winter has some peculiarities that affect construction in general and concreting in particular.
Its duration is different in different parts of globe, but cold weather with white frosts may also
happen in spring and autumn- not just in winter only. In central part of Russia, the cold period
including winter early spring and late autumn may be as long as five to six months reaching eight to
ten months in north. The situation is same in Canada, Alaska, Northern China, Finland, Sweden and
Norway. Kashmir is also a cold region and cold weather conditions prevail over a period of about
four months.
The cold weather conditions warrant special precautions to be taken while placing, finishing
and curing of concrete, so as to protect concrete against the effects of cold weather. Concrete has to
be protected from freezing until it reaches a minimum strength of 3.5 Mpa. If concrete freezes while
it is still fresh or before it has developed sufficient strength to resist the expansive forces associated
with the freezing water, ice formation results in the disruption of the cement paste matrix causing an
irreparable loss in strength. Once the concrete has attained a compressive strength of around 3.5
MPa, it is generally considered to have sufficient strength to resist significant expansion and damage
if frozen [2].
Concreting in winter conditions is quite difficult. It is possible to create favourable conditions
for concrete to harden when the ambient air temperature is below 00
C but that requires additional
EXPERIMENTAL STUDY OF EFFECTS OF POTASSIUM CARBONATE
ON STRENGTH PARAMETERS OF CONCRETE
1
Dr. Javed Ahmed Naqash, 2
Saiqa Nabi, 3
Mehvish, 4
Tehseena Ali, 5
Mahapara Firdous,
6
Insha Bashir
Volume 6, Issue 6, June (2015), pp. 204-212
Article Id: 20320150606021
International Journal of Civil Engineering and Technology (IJCIET)
© IAEME: www.iaeme.com/Ijciet.asp
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
IJCIET
© I A E M E

energy, material and labour. The energy cost for thermal protection is estimated to be 800 million
dollar in US alone. So, it is not only a technical problem but a problem of cost effectiveness.
Stopping the process of concreting in winter is uneconomical due to long downtimes of
equipment and workers. It is better to bear additional costs and trying to minimize them as much as
possible. In some cases when construction schedule is very tight and project is to be completed in
winter, the additional costs are inevitable. The simplest and the least expensive way is to use a
chemical depressant like potassium carbonate.
In order to study the effects of K2CO3 on properties of concrete, to get the optimum
percentage of the chemical and to compare the various properties of concrete; a number of castings
were done with varying percentages i.e., 2%, 2.2%, 2.4%, 2.6% and 3% by weight of cement. Also
cost analysis reveals that cold weather concreting using chemical depressants is cost effective and
economical than any other conventional methods.
II. MATERIALS USED
2.1) Cement: Ordinary Portland Cement (OPC) 43 Grade (Khyber cement) confining to IS: 4031[4]
has been used for this Work. The properties of the used cement are shown in Table 1.
2.2) Aggregates: Fine aggregates used throughout the work comprised of clean river sand with
maximum size of 4.75mm conforming to zone II as per IS:383-1970 [5] with specific gravity of 2.6
and Fineness Modulus of 2.6. Coarse aggregates used consisted of machine crushed stone angular in
shape passing through 20mm I S sieve and retained on 4.75mm I S sieve with specific gravity of 2.7
and Fineness Modulus of 6.18.
2.3) Potassium Carbonate: K2CO3 was used as depressant admixture and was obtained from local
market. Potassium Carbonate was in white fine powder form so it was easy to add it in mix. Fig. 1
shows Potassium carbonate.
Function of Potassium Carbonate as Admixture: When K2CO3 is added as admixture, it depresses
the freezing point of water by increasing the ions in the water. Also it accelerates the initial setting of
concrete. It allows concrete to gain early strength at sub-freezing temperature.
III. EXPERIMENTAL INVESTIGATION
3.1) Mix Proportion: The concrete mix design was proposed by using IS 10262 [6]. The grade of
concrete used was M20 with water to cement ratio of 0.45.The ratio obtained from mix design was
1:1.6:3.2.
3.2) Tests on Fresh Concrete: The workability of all concrete mixtures was determined through
Slump test and Compaction factor test. The slump tests were performed according to IS: 1199-
1959[9]. Compaction factor test works on the principle of determining the degree of compaction
achieved by a standard amount of work done by allowing the concrete to fall from a standard height.
The degree of compaction, called the Compaction Factor is measured by the density ratio i.e., the
ratio of the density actually achieved in the test to density of same concrete fully compacted.
3.3) Tests on hardened concrete: From each concrete mixture, cubes of size 150mm x 150mm x
150mm, 150mm dia. 300mm cylinders and 500mm x 100mm x 100mm beams were cast for the
determination of compressive strength, split tensile strength and flexural strength respectively. The
concrete specimens were cured under normal conditions as per IS:516-1959 [10] and were tested at 3
days, 7 days and 28days for determining compressive strength as per IS:516-1959 [11], split tensile
strength as per IS:5816-1999 [12] and flexural strength as per IS:516-1959 [13].

IV. RESULTS AND DISCUSSION
4.1) Fresh concrete: The values of slump and compaction factor (C.F) of all the mixtures are
presented in Tables 3-15. No considerable change in slump and C.F values was observed in fresh
concrete samples containing potassium carbonate as admixture as compared to those of normal
concrete.
4.2) Hardened concrete
4.2.1. Compressive strength: The compressive strength test results are presented in Table 2.
Compressive strength tests, split tensile strength tests and flexural strength tests were carried out at 3,
7 and 28 days. An increase in compressive strength was observed up to 2.6% addition of potassium
carbonate as admixture and thereafter a decrease in strength properties was observed.
4.2.2. Split tensile strength: The split tensile strength tests are presented in Table 3. Split tensile
strength witnessed an increase of 33%, 14% and 10% at 3, 7 and 28 days of age respectively,
corresponding to concrete mix containing 2.6% of potassium carbonate by weight of cement.
4.2.3. Flexural strength: The flexural strength tests are presented in Table 4. Flexural strength
witnessed an increase of 21%, 25% and 25% at 3,7 and 28 days of age respectively, corresponding to
concrete mix containing 2.6% potassium carbonate by weight of cement. Both split tensile strength
and flexural strength for concrete mix with 3% potassium carbonate by weight of cement was found
to be less than that of reference mix. Fig. 4, 5 and 6 present compressive strength of all mixtures at 3,
7 and 28 days respectively. Fig. 7, 8 and 9 present flexural strength of all mixtures at 3, 7 and 28
days respectively. Fig. 10, 11 and 12 present split tensile strength of all mixtures at 3, 7 and 28 days
respectively.
Fig. 1 K2CO3 Fig. 2 Test Samples Fig. 3 Curing Tank
TABLE 1: Properties of cement
Fineness
%
Standard
Consistency (%)
Initial Setting
Time
Final Setting
Time
Soundness
(mm)
Compressive
strength(N/mm2
)
2.3 28 1 hr 10 min 5 hrs 15 min 2 32.28

A) Compressive Strength Test Results.
TABLE 6.1: Compressive Strength using 2% K2CO3 (Casting Month Nov.)
S. No. 1 2 3
Slump (mm) 26
Compaction Factor 0.86
Day of Testing 3rd 7th 28th
Average Strength (Plain) N/mm2
14.03 17.09 21.28
Slump (mm) 25.5
Average Strength (Admixtured) N/mm2
16.91 18.47 22.83
TABLE 6.2: Compressive Strength using 2.2% K2CO3 (Casting Month Nov-Dec)
S. No. 1 2 3
Slump (mm) 27.5
15.15 17.73 22.03
Slump (mm) 26.9
17.51 19.31 23.75
TABLE 6.3: Compressive Strength using 2.4% K2CO3 (Casting Month Dec)
S. No. 1 2 3
Slump (mm) 25
16.05 17.23 22.29
Slump (mm) 24.5
18.65 19.98 24.11
TABLE 6.4: Compressive Strength using 2.6% K2CO3 (Casting Month Jan)
S. No. 1 2 3
Slump (mm) 25.1
17.90 18.88 22.34
Slump (mm) 24.7
19.82 21.67 24.67

TABLE 6.5: Compressive Strength using 3% K2CO3 (Casting Month Jan-Feb)
S. No. 1 2 3
Slump (mm) 25
17.98 18.35 24.49
Slump (mm) 23.00
17.57 18.26 23.89
B) Flexural Strength Test Results.
TABLE 6.6: Flexural Strength using 2% K2CO3 (Casting Month Nov.)
S. No. 1 2 3
Slump (mm) 26
Compaction factor 0.86
1.16 1.57 2.34
Slump (mm) 25.5
1.23 1.98 2.41
TABLE 6.7: Flexural Strength using 2.2% K2CO3 (Casting Month Nov-Dec)
S. No. 1 2 3
Slump (mm) 27.5
1.02 1.4 2.20
Slump (mm) 26.90
1.53 2.01 2.68
TABLE 6.8: Flexural Strength using 2.4% K2CO3 (Casting Month Dec)
S. No. 1 2 3
Slump (mm) 25
1.18 1.65 2.35
Slump (mm) 24.50
1.73 2.29 2.86

TABLE 6.9: Flexural Strength using 2.6% K2CO3 (Casting Month Jan)
S. No. 1 2 3
Slump (mm) 25.1
1.20 1.73 2.40
Slump (mm) 24.70
2.01 2.51 2.97
TABLE 6.10: Flexural Strength using 3% K2CO3 (Casting Month Jan-Feb)
S. No. 1 2 3
Slump (mm) 25.00
1.10 1.70 2.37
Slump (mm) 23.00
1.02 1.56 2.28
C) Split Tensile Strength Test Results.
TABLE 6.11: Split Tensile Strength using 2% K2CO3 (Casting Month Nov.)
S. No. 1 2 3
Slump (mm) 26
Strength of Cylinder 1 (Plain) N/mm2
1.07 1.31 1.65
Slump (mm) 25.5
Split tensile strength (Admixtured) N/mm2
1.21 1.36 1.70
TABLE 6.12: Split Tensile Strength using 2.2% K2CO3 (Casting Month Nov-Dec)
S. No. 1 2 3
Slump (mm) 27.5
1.11 1.43 1.72
Slump (mm) 26.9
1.28 1.54 2.2

TABLE 6.13: Split Tensile Strength using 2.4% K2CO3 (Casting Month Dec)
S. No. 1 2 3
Slump (mm) 25
1.12 1.42 1.67
Slump (mm) 24.50
1.31 1.53 2.3
TABLE 6.14: Split Tensile Strength using 2.6% K2CO3 (Casting Month Dec-Jan)
S. No. 1 2 3
Slump (mm) 25.1
1.21 1.52 1.98
Slump (mm) 24.70
1.42 1.82 2.5
TABLE 6.15: Split Tensile Strength using 3% K2CO3 (Casting Month Jan-Feb)
S. No. 1 2 3
Slump (mm) 25.00
1.12 1.67 2.38
Slump (mm) 23.00
1.10 1.71 2.25
Variation of Compressive, Flexural & Split Tensile Strengths with different %ages of
Admixtures.
0
5
10
15
20
25
30
Compressivestrength
%age of Admixture
3rd day 7th day 28th day
0
0.5
1
1.5
2
2.5
3
3.5
FlexuralStrength
%age of Admixture

V. CONCLUSIONS
On the basis of results obtained, following conclusions can be drawn:
1. The use of admixture K2CO3 in cold weather increases the compressive, flexural and split
tensile strength of concrete compared to plain concrete. The percentage of potassium carbonate
which gives maximum strength is 2.6% beyond which the strength decreases. Beyond this
dosage of K2CO3 a decrease in strength parameters was observed.
2. 2.6% Potassium carbonate addition as accelerating admixture showed optimum increase in
compressive strength, flexural strength and split tensile strength of concrete with respect to
reference mix at 3, 7 and 28 days.
3. From the study of the characteristics of K2CO3 it can be concluded that it does not corrode the
reinforcement provided in the RCC sections.
4. For M20 mix having w/c as 0.45, 2.6% K2CO3 by weight of cement is recommended as
optimum dosage in cold weather.
0
0.5
1
1.5
2
2.5
3
SplitTensileStrength
%age of Admixture
0
5
10
15
20
25
30
CompressiveStrength
%age of Admixture
0
0.5
1
1.5
2
2.5
3
3.5
0% 2% 2.20% 2.40% 2.60% 3%
FlexuralStrength
%age of Admixture
0
0.5
1
1.5
2
2.5
3
SplitTensileStrength
%age of Admixture

REFERENCE
1. Cold weather concreting, reported by ACI committee 306, Nicholas J. Carino, Chairman, p.
306 R-1.
2. Annual book of ASTM Standards (1979), part 13, ASTM C 191 – 77: Standard test method for
time of setting of hydraulic cement. ASTM Race St. Philadelphia, pa. 19103.
3. Concrete Technology, A. M. Neville and J. J. Brooks.
4. 43 Grade Ordinary Portland Cement – Specification. IS 8112:1989, Bureau of Indian
Standards, New Delhi.
5. Specification for Coarse and Fine Aggregates from Natural Sources for Concrete. IS: 383-
1970, Bureau of Indian Standards, New Delhi.
6. Recommended Guidelines for Concrete Mix Design. IS: 10262-1982, Bureau of Indian
Standards, New Delhi.
7. Concrete Technology, A. M. Neville and J. J. Brooks.
8. Concrete Technology, A. M. Neville and J. J. Brooks, p. 166
9. Methods of Sampling and Analysis of Concrete. IS: 1199-1959, Bureau of Indian Standards,
New Delhi.
10. Methods of Tests for Strength of Concrete. IS: 516-1959, Bureau of Indian Standards, New
Delhi.
Delhi.
12. Split Tensile Strength of concrete – Methods of test. IS: 5816:1999.
Delhi.
14. Khaza Mohiddin Shaik and Prof. Vasugi K, “Partial Replacement of Wood Ash and Quarry
Dust with Cement and Sand To Study The Strength Parameters of Concrete” International
Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 8, 2014, pp. 32 - 43,
ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
15. Ananthayya M.B. and Prema Kumar W. P., “Influence of Steel Fibers and Partial Replacement
of Sand by Iron Ore Tailings on The Compressive and Splitting Tensile Strength of Concrete”
International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 3, 2014,
pp. 117 - 123, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
16. Harish.L., “The Permeability and Indirect Tensile Strength Characteristics of Porous Asphalt
Mixes” International Journal of Civil Engineering & Technology (IJCIET), Volume 5, Issue 8,
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