This paper aims to investigate the effect of use of Rapidite in cold weather concreting. In order to illustrate such effect, a series of laboratory tests were conducted. Workability tests, compressive strength tests, flexural tests and split tensile strength tests were carried out on concrete specimens having different percentage of Rapidite and the results thus obtained were compared with those of normal concrete. The results indicated that all the three strength parameters viz, compressive strength, split tensile strength and flexural tensile strength of concrete increase when compared with plain one. The increase in strength reaches the maximum value at the Rapidite percentage of 1.5%, beyond which it starts decreasing. The increase in 7 day strength is much higher than increase in 28 day strength. Further adding Rapidte has shown increase in the workability of mix with respect to the plain mix.

1. http://www.iaeme.com/IJCIET/index.asp 58 editor@iaeme.com
International Journal of Civil Engineering and Technology (IJCIET)
Volume 6, Issue 12, Dec 2015, pp. 58-65, Article ID: IJCIET_06_12_006
Available online at
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=12
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
ACCELERATING ADMIXTURE
“RAPIDITE”-ITS EFFECT ON PROPERTIES
OF CONCRETE
Dr. Javed Ahmed Naqash
Associate Professor, National Institute of Technology Srinagar, J&K, India
Ifrah Habib Lone, Amir Majid, Bisma Gayas, Itret Hussaini, Mubashir Hassan
Department of Civil Engineering, University of Kashmir, J&K India
ABSTRACT
This paper aims to investigate the effect of use of Rapidite in cold weather
concreting. In order to illustrate such effect, a series of laboratory tests were
conducted. Workability tests, compressive strength tests, flexural tests and
split tensile strength tests were carried out on concrete specimens having
different percentage of Rapidite and the results thus obtained were compared
with those of normal concrete. The results indicated that all the three strength
parameters viz, compressive strength, split tensile strength and flexural tensile
strength of concrete increase when compared with plain one. The increase in
strength reaches the maximum value at the Rapidite percentage of 1.5%,
beyond which it starts decreasing. The increase in 7 day strength is much
higher than increase in 28 day strength. Further adding Rapidte has shown
increase in the workability of mix with respect to the plain mix.
Key words: Rapidite, Workability, Compressive Strength, Flexural Strength
and Split Tensile Strength.
Cite this Article: Dr. Javed Ahmed Naqash, Ifrah Habib Lone, Amir Majid,
Bisma Gayas, Itret Hussaini and Mubashir Hassan, Accelerating Admixture
“Rapidite”-Its Effect on Properties of Concrete. International Journal of Civil
Engineering and Technology, 6(12), 2015, pp. 58-65.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=12
1. INTRODUCTION
Rapidite is a specially developed Concrete Set Accelerator, a ready-to-use, liquid
admixture. It accelerates initial setting time (cement-water chemical reaction
HYDRATION) of normal mortar and concrete and acts as anti-freeze within cement
concrete. It improves workability and strength while fastening the hydration of
cement. It makes the mix easier to place and speeds construction by shortening the
initial set and curing time. Time and labor are saved, because forms and other
protection can be removed earlier and finishing can be started. Rapidite is

2. Accelerating Admixture “Rapidite”-Its Effect on Properties of Concrete
http://www.iaeme.com/IJCIET/index.asp 59 editor@iaeme.com
recommended for use during cool and cold weather to accelerate the set time and
reduce the risk of frozen mortar and concrete mixes.
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 India
certain regions experience sub-zero temperatures in winter. Concrete structures in
such regions undergo cycles of freezing and thawing and their durability is affected
due to frost action. Fresh concrete contains considerable quantity of fresh water which
gets converted into ice lenses at freezing temperature. The ice formation in fresh
concrete results in about 9% rise in volume and causes permanent damage to concrete
and structural integrity cannot be recovered even if the concrete is made to harden
later at high temperature. Thus, in winters, especially in Kashmir where the
temperatures are below zero degree in winters some admixtures need to be added to
nullify the effects of cold temperature on the strength of concrete. Rapidte is a
commonly used admixture in Kashmir during winter to accelerate the strength gain of
concrete.
2. MATERIALS USED
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;
Aggregates:
Fine aggregates used throughout the work comprised of clean river sand with
maximum size of 4.75mm conforming to zone III as per IS:383-1970 [5] 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 .
Rapidite
Properties
Color- Lemon-Orange
Appearance-Clear bright Liquid
Relative Density (g/ml)-1g/ml
3. EXPERIMENTAL PROGRAM
Mix Used: Nominal mix M20 (1:1.5: 3) with water to cement ratio of 0.5.
In total five castings were done at the Rapidite percentage of 0.75, 1.25, 1.5, 1.75
and 2
Fineness
%
Standard
Consistency
(%)
Initial
Setting
Time
Final Setting
Time
Soundness
(mm)
Compressive
strength(N/mm2)
2.3 28 1 hr. 22 min 6 hrs.10 min 2 38

3. Dr. Javed Ahmed Naqash, Ifrah Habib Lone, Amir Majid, Bisma Gayas, Itret
Hussaini and Mubashir Hassan
http://www.iaeme.com/IJCIET/index.asp 60 editor@iaeme.com
First Casting Average Temp: 1.30
C
Percentage of Rapidite by weight of cement = .75%
Compressive Strength (σc)
Cube
size(mm)
7 Days Strength 28 Days Strength
Strength (N/mm2
)
Average Strength
(N/mm2
)
Strength (N/mm2
)
Average Strength
(N/mm2
)
P.C.C
C.C with
Rapidite
P.C.C
C.C with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C with
Rapidite
150 15.8 16.8
15.9 16.8
20.4 21.3
20.85 21.85150 16 16.8 21.3 22.4
100 12.5 13.7
13.3 14.75
21.2 23.5
21.9 23.5100 14.2 15.8 22.6 23.5
Split Tensile Strength (σt) and Flexural Strength (σb)
Type of concrete
(σt)
(N/mm2
)
(σb)
(N/mm2
)
Slump
Compaction
factor
PCC 2.49 3.12 10mm .72
CC with Rapidite 2.57 3.35 20mm .77
Second Casting Average Temp: 20
C
Percentage of Rapidite by weight of cement = 1.25%
Compressive Strength (σc)
Cube
size(mm)
7 Days Strength 28 Days Strength
Strength (N/mm2
)
Average Strength
(N/mm2
)
Strength (N/mm2
)
Average Strength
(N/mm2
)
P.C.C
C.C with
Rapidite
P.C.C
C.C with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C with
Rapidite
150 14 15
13.3 15
22.4 24
21.8 23.2150 12.6 15 21.3 22.4
100 13 18
13.4 16.15
22.2 24.5
22.8 25.7100 13.7 14.3 23.3 26.9
Split Tensile Strength (σt) and Flexural Strength (σb)
Type of concrete
Split tensile
strength (N/mm2
)
Flexural strength
(N/mm2
)
Slump
Compaction
factor
PCC 2.43 3.31 15mm .74
CC with Rapidite 2.67 3.67 26mm .81
Third Casting Average Temp: 1.50
C
Percentage of Rapidite by weight of cement = 1.5%

4. Accelerating Admixture “Rapidite”-Its Effect on Properties of Concrete
http://www.iaeme.com/IJCIET/index.asp 61 editor@iaeme.com
Compressive Strength (σc)
Cube
size(mm)
7 Days Strength 28 Days Strength
Strength (N/mm2
)
Average Strength
(N/mm2
)
Strength (N/mm2
)
Average Strength
(N/mm2
)
P.C.C
C.C with
Rapidite
P.C.C
C.C with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C with
Rapidite
150 10.3 16.2
10.5 16
20.7 28.69
21.1 29.2150 10.8 15.8 21.6 29.7
100 11.3 17
11.3 16.7
21.8 26.78
21.15 28.23100 11.3 16.4 21.2 29.68
Split Tensile Strength (σt) and Flexural Strength (σb)
Type of concrete
σt
(N/mm2
)
σb
(N/mm2
)
Slump
Compaction
factor
PCC 2.24 3.02 10mm .77
CC with Rapidite 2.92 3.65 50mm .86
Fourth Casting Average Temp:-10
C
Percentage of Rapidite by weight of cement = 1.75 %
Compressive Strength (σc)
Cube
size(mm)
7 Days Strength 28 Days Strength
Strength
(N/mm2
)
Average
Strength
(N/mm2
)
Strength
(N/mm2
)
Average
Strength
(N/mm2
)
P.C.C
C.C
with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C
with
Rapidite
150 14.4 11.29
14.6 11.6
26 21.2
26.4 20.72150 14.8 11.9 26.7 20.24
100 14.2 13.3
14.5 12.65
28 22.8
26.5 22.95100 14.9 12 25 23.1
Split Tensile Strength (σt) and Flexural Strength (σb)
Type of concrete
σt
(N/mm2
)
σb
(N/mm2
)
Slump Compaction factor
PCC 1.91 4.08 20mm .75
CC with Rapidite 1.75 3.84 50mm .88
Fifth Casting Average Temp:-1.20
C
Percentage of Rapidite by weight of cement = 2 %

5. Dr. Javed Ahmed Naqash, Ifrah Habib Lone, Amir Majid, Bisma Gayas, Itret
Hussaini and Mubashir Hassan
http://www.iaeme.com/IJCIET/index.asp 62 editor@iaeme.com
Compressive Strength (σc)
Cube
size(mm)
7 Days Strength 28 Days Strength
Strength
(N/mm2
)
Average
Strength
(N/mm2
)
Strength
(N/mm2
)
Average
Strength
(N/mm2
)
P.C.C
C.C
with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C
with
Rapidite
P.C.C
C.C
with
Rapidite
150 12.73 11.35
13.13 11.31
23.5 20.4
23.95 20.05150 13.53 11.26 24.4 19.7
100 12.3 10.7
12.3 10.85
20.4 22
23.7 21100 12.3 11 27 20
Split Tensile Strength (σt) and Flexural Strength (σb)
Type of concrete
σt
(N/mm2
)
σb
(N/mm2
)
Slump
Compaction
factor
PCC 1.86 4.42 12mm .73
CC with Rapidite 1.68 4.02 55mm .88
4. DISCUSSION
In order to study the rate of variation of strength with respect to the Rapidite
percentage, a comparative study of the test results achieved at different Rapidite
percentage is performed.
Following Variations are studied
 Variation of increase in 7 day strength with Rapidite %
 Variation of Increase in 28 day strength with Rapidite %
 Variation of split and flexural tensile strength with Rapidite %
 Comparison of Avg. Increase in 7 and 28 day strength for 150mm cube
 Comparison of Avg. Increase in 7 and 28 day strength for 100mm cube
 Variation of compaction factor on adding Rapidite.
Average increase in 7 days and 28days strength (%age)
Percentage of Rapidite
Average % increase 7 days
strength
Average % increase in 28
days strength
150mm cube
100mm
cube
150mm cube
100mm
cube
0.75 5.66 10.40 5 7.3
1.25 12.78 21 6.17 13
1.5 51.94 47.78 38.26 31
1.75 -20.27 -13.1 -21.46 -13.4
2 -13.86 -11.78 -16.28 -11.4

6. Accelerating Admixture “Rapidite”-Its Effect on Properties of Concrete
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G1: Variation of 7 day strength with Rapidite %
G2: Variation of 28 day strength with Rapidite %
The increase in 7 day strength is much higher than increase in 28 day strength, in case
of 150mm cubes former is 180% more increase and in case of 100mm cubes former
shows 214% more increase. Thus increase in early strength is more significant than
increase in lateral strength
Average increase in Split tensile strength (σt) and Flexural strength (σb)
Percentage of
Rapidite
Average percentage
increase in Split tensile
strength
Average percentage increase in
Flexural strength
0.75 3.2 7.37
1.25 9.8 10.87
1.5 30.35 20.86
1.75 -8.3 -5.88
2 -9.69 -9
0
5
10
15
20
0.75 1.25 1.5 1.75 2
CompressiveStrength
%age of Rapidite
Avg 7 day strength of
P.C.C OF 100mm cube
Avg 7 day strength of
C.C with rapidite OF
100mm cube
Avg 7 day strength of
P.C.C OF 150mm
cube
0
10
20
30
40
0.75 1.25 1.5 1.75 2
CompressiveStrength
%age of Rapidite
Avg 28 day strength
of P.C.C OF 100mm
cube
Avg 28 day strength
of C.C with rapidite
OF 100mm cube
Avg 28 day strength
of P.C.C OF 150mm
cube
Avg 28 day strength
of C.C with rapidite
OF 150mm cube
G2:Variation of 28 day strength with Rapidite %

7. Dr. Javed Ahmed Naqash, Ifrah Habib Lone, Amir Majid, Bisma Gayas, Itret
Hussaini and Mubashir Hassan
http://www.iaeme.com/IJCIET/index.asp 64 editor@iaeme.com
G3: Variation of split tensile strength with Rapidite %
G4: Variation of Flexural strength with Rapidite %
There is an increase in both split and flexural tensile strengths up to the 1.5% of
rapidite, beyond this value the strength decreases in both the cases.
G5: Variation of Compaction factor with Rapidite %
The compaction factor always increases when compared with the plain concrete, thus
workability increases by the addition of rapidite.
-15
-10
-5
0
5
10
15
20
25
0 0.5 1 1.5 2 2.5
Avg %age increase in
flexural strength
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.75 1.25 1.5 1.75 2
P.C.C.
-20
-10
0
10
20
30
40
0 0.5 1 1.5 2 2.5
Avg %age increase in
split tensile strength

8. Accelerating Admixture “Rapidite”-Its Effect on Properties of Concrete
http://www.iaeme.com/IJCIET/index.asp 65 editor@iaeme.com
5. CONCLUSION
 The use of admixture Rapidite increases the compressive, flexural and split tensile
strength of concrete compared to plain concrete. The increase in strength reaches the
maximum value at the Rapidite percentage of 1.5%, beyond which it starts
decreasing.
 The increase in 7 day strength is much higher than increase in 28 day strength, in case
of 150mm cubes former is 180% more increase and in case of 100mm cubes former
shows 214% more increase. Thus increase in early strength is more significant than
increase in lateral strength
 There was no freezing of water as there is increase in early strength of concrete so
whole water was available for complete hydration of cement. The admixture used is
an anti freezing agent which depressed the freezing point of water mixed and
protected the concrete from freezing in early age.
 The compaction factor always increases when compared with the plain concrete, thus
workability increases by the addition of Rapidite.
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Chairman, p. 306 R-1.
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[3] Concrete Technology, A. M. Neville and J. J. Brooks.
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[5] Specification for Coarse and Fine Aggregates from Natural Sources for Concrete.
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[6] Recommended Guidelines for Concrete Mix Design. IS: 10262-1982, Bureau of
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[8] Concrete Technology, A. M. Neville and J. J. Brooks.
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