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International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND
(Print), ISSN 0976 – 6316(Online) Volume 4, Issue 6, November – December (2013), © IAEME

TECHNOLOGY (IJCIET)

ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 6, November – December, pp. 116-125
© IAEME: www.iaeme.com/ijciet.asp
Journal Impact Factor (2013): 5.3277 (Calculated by GISI)
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IJCIET
©IAEME

HARMFUL EFFECTS OF RAPIDITE ON STRENGTH OF CONCRETE
Sameer ul bashir,

Shabbir Ahmad Parray,

Syed Rizwan Shah

B.Tech, NIT Hazratbal, Srinagar

ABSTRACT
This present paper presents the progress on research of use of rapidite in cold weather
concreting. The project aims at making and studying various properties of cold weather concrete
using admixture called rapidite which is locally available in oils and chemical industries of Kashmir.
The actual compressive strength of concrete depends on the percentage of Rapidite used in the
concrete. In recent years, concrete usage around the world is second only to water .Ordinary Portland
cement is conventionally used as a primary binder to produce concrete. But, the progress of strength
of concrete is a function of temperature. At relatively low temperatures, it gives low strength because
of the freezing action. 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. Considering the availability and cost of the admixture, Rapidite is mostly used
admixture in Kashmir in winters. This project aims at finding the optimum amount of percentage of
Rapidite at which the strength of concrete comes to be maximum.
Keywords: Cold Weather, Concreting Rapidite, Compressive Strength.
CONCRETE
Concrete is a composite construction material, composed of cement (commonly Portland
cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a
coarse aggregate made of gravel or crushed rocks such as limestone, or granite, plus a fine aggregate
such as sand), water and chemical admixtures.
Concrete is used to make pavements, pipe, architectural structures, foundations,
motorways/roads, bridges/overpasses, parking structures, brick/block walls and footings for gates,
fences and poles. Concrete is used more than any other man-made material in the world. As of 2006,
about 7.5 cubic kilometers of concrete are made each year—more than one cubic meter for every
person on Earth.
116

Reinforced concrete, prestressed concrete and precast concrete are the most widely used
types of concrete functional extensions in modern days.
Concrete solidifies and hardens after mixing with water and placement due to a chemical
process known as hydration. The water reacts with the cement, which bonds the other components
together, eventually creating a robust stone-like material.
PORTLAND CEMENT + H2O + ROCK = HARDENED CONCRETE + ENERGY (HEAT)
COLD WEATHER CONCRETING
In India certain regions experience sub-zero temperatures in winter. Concrete structures in
such regions undergo cycles of freezing and thawing and there 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. Even during hardening the concrete should be
protected from extremely low temperature hence while concreting in cold weather ensure that the
temperature of fresh concrete is maintained above 0 °C and temperature during first six hrs of casting
should not be less than 5 °C.
IS 7861 part II defines Cold Weather Concreting as Any operation of concreting done at
about 5°C atmospheric temperature or below.
ACI 306 “Cold Weather Concreting” defines cold weather concreting as a period when for more than
three (3) consecutive days, the following conditions exist:
• The average daily air temperature is less than 5°C (40°F) and,
• The air temperature is not greater than 10°C (50°F) for more than one-half of any 24 hour
period.
What Happens When Concrete Freezes?
• Pore water in concrete starts to freeze around -1°C (30°F)
• As some water freezes the ion concentration in the unfrozen water goes up, further depressing
the freezing point.
• At around -3 to -4°C (25 to 27°F), enough of the pore water will freeze so that hydration will
completely stop, and depending on the extent of hydration, and thus the strength of the
concrete, the forces generated by the expansion of ice (ice occupies ~9% more volume than
water) may be detrimental to the long term integrity of the concrete.
Objectives of Cold Weather Concreting
The objectives of cold weather concreting are to:
• Prevent damage to concrete due to freezing at early ages
• Assure that concrete develops the required strength for the safe removal of forms
• Maintain curing conditions that foster normal strength development without using excessive
heat
• Limit rapid temperature changes in the concrete to prevent thermal cracking
For every 10°C (18°F) reduction in concrete temperature, the times of setting of the concrete
double, thus increasing the amount of time that the concrete is vulnerable to damage due to freezing

117

Deleterious Effects
Following deleterious effect may occur due to cold weather concreting
• Hydration will be hampered
• Setting time will be prolong
• Disruption of freshly placed concrete because of freezing
• Low workability
• Freezing and thawing effect
• Improper curing
• Workmanship is affected
• Deicing effect
Recommended Practices and Basic Principles
Curing and Protection: Where a specified concrete strength must be attained in a few days or weeks,
protection at temperatures above 10°C (50°F) is required.
Temperature Records: Temperature of the concrete determines the effectiveness of protection,
regardless of air temperature. Maintaining temperature records of concrete in place is essential.
Heated Enclosures: Must be strong enough to be windproof and weatherproof. Combustion heaters
must be vented to the outside to prevent carbonation.
Exposure to Freezing and Thawing: Concrete should be properly air entrained if it will be saturated
and exposed to freezing and thawing cycles during construction.
Slump: All else being equal, lower slump and/or lower water/cement ratio mixes are particularly
desirable in cold weather for flatwork. This reduces bleeding and decreases setting time.
Truck Travel Time: The distance from the plant to the point of placement can have a severe effect on
the temperature of concrete.
Hot Water: While hot water improves setting time of cold weather concrete, after the first few
batches of concrete hot water heaters may not be able to maintain hot water temperature. Later in the
pour, concrete may be cooler than at the beginning of the pour.
Admixtures : Some admixtures, which act as accelerators ,can be used in cold weather concreting so
to increase the rate of hydration and thus decreasing the effect of cold weather on concreting.
RAPIDITE

Rapidte is a commonly used admixture in Kashmir during winter to accelerate the strength
gain of concrete. It falls under Type C on the basis of ASTM classification i.e., it acts as accelerator.
It also acts as anti freeze, depressing the freezing point of water and hence protecting the fresh
concrete.
118

Description
RAPIDITE 2 IN 1 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.
Uses
RAPIDITE 2 in 1 is recommended for use during cool and cold weather to accelerate the set
time and reduce the risk of frozen mortar and concrete mixes.
Features/Benefits
• Accelerates initial set time.
• Increases compressive strength.
• Provides Anti –freeze properties.
• Speeds up hydration of cement.
• Increases workability of concrete or mortar mix in colder temperatures.
Properties
Color : Lemon-Orange
Appearance : Clear bright Liquid
Relative Density (g/ml) :1gm/ml
EXPERIMENTAL PROGRAM
In total five castings were done at the Rapidte percentage of 0.5, 1, 1.25, 1.4 and 1.5% by
percentage of cement and the minimum and maximum temperature during the first 24 Hrs after
casting was observed.
The Temperature during first 24 Hrs after casting along with the results of various tests are
shown in tables below:
Variation of Increase in 7 day strength and Compaction Factor with Rapidite %
Temperature during 1st 24Hrs of
Average increase in 7
Compaction factor
casting (°C)
day strength %
Rapidite
%
150mm
100mm
Min
Max
Avg.
plain
Admixture
cube
cube
-1

7

3

0.50

3.6

8

0.77

0.88

-1

6

2.5

1.00

8.3

16.8

0.74

0.81

-2

6

2

1.25

106.3

96.2

0.68

0.77

-4

7

1.5

1.4

-30.2

-26.6

-2.5

6.5

2

1.50

-22

-20

0.74

0.88

119

Variation of Increase in 28 day strength and compaction factorwith Rapidite %
Temperature during
1st 24Hrs of casting
(°C)

Average Increase in 28 day strength %
Rapidite
%

Compaction factor

150mm
cube

100mm
cube

↑ in
Split
tensile
strength

↑ in
Flexural
tensile
strength

plain

Admixture

Min

Max

Avg.

-1

7

3

0.50

2.6

5.3

2.9

3.2

0.77

0.88

-1

6

2.5

1.00

5.2

10.4

6.4

6.7

0.74

0.81

-2

6

2

1.25

38

30.6

53.5

53.1

0.72

0.77

-4

7

1.5

1.4

-42.6

-26

-12

-21.1

0.73

0.8

-2.5

6.5

2

1.50

-18

-23

-17.4

-17.5

0.73

0.88

Variation of Compaction Factor for plain concrete and concret with admixture for different % of
rapidite
S. No

Rapidte %

Plain

Admixture

1

0.50

0.77

0.88

2

1.00

0.74

0.81

3

1.25

0.72

0.77

4

1.4

0.73

0.8

5

1.50

0.73

0.88

DISCUSSIONS
In order to study the variation in the rate of gain of strength with respect to the Rapidite
percentage, a comparative study of the test results achieved at different Rapidite percentage is
performed.
Following Variations were 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.

120

The results graphs and tables represent the comparative study:

G1-Variation of 7 day strength with
Rapidite %
Percent increase in strength

120
100
80
60
40

150mm

20

100mm

0
-20 0

0.5

1

1.5

2

-40
-60

Rapidite %

From the study of G1 it is clear that the by adding Rapidite the 7 day strength increases when
compared to the plain concrete casted at the same temperature. Also it can be seen that the at the
1.25% there is maximum increase in strength, beyond this value there is a decrease in the strength of
concrete with admixture ,when compared with plain one. Also the 100mm cube shows more increase
in strength when compared with 150mm cube, except at the optimum amount, the increase in
strength of 150mm cube is more than 100mm cube.
G2-Variation of 28 day strength with Rapidite
%

percent increase in strength

50
40
30
20
10
0
-10 0
-20
-30
-40
-50

0.5

1

1.5

2
150mm
100mm

Rapidite %

121

The G2 also shows same trend i.e, the 28 day strength also goes on increasing upto the
percentage of 1.25, beyond which it decreases.Also the 100mm cube shows more increase as
compared to 150mm cube except at the optimum amount.

percent increase in split and flexural strengths

G3-Variation of split and flexural tensile strength
with rapidite %
60
50
40
30
Split tensile
strength

20
10

Flexural tensile
strength

0
-10 0

0.5

1

1.5

2

-20
-30

Rapidte %

G3 shows that there is an increase in both split and flexural tensile strengths up to the 1.25%
of rapidite, beyond this value the strength decreases in both the cases. Also the two graphs almost
coincide showing that both strengths increase by equal amounts, flexural strength increasing slightly
more than split strength.
G4-Comparison of Avg. increase in 7 and
28 day strength for 150mm cube
120
100

Syrength MPa

80
60

Avg.↑ in 7 day
strength %

40
20
0
-20 0

1

2

-40
-60

Rapidite %

122

Avg. Average ↑
in 28 day
strength %

G4 shows that although both 7 and 28 day strength for 150mm cube increases and reaches
there maximum at the Rapidite percentage of 1.25% , the increase in 7day strength is 180% more
than increase in 28 day strength.

G5-Comparison of Avg. increase in 7 and 28
day strength for 100mm cube
120
100
80
60

Avg. ↑ in 7 day
strength %

%↑

40
20

Avg. Average ↑
in 28 day
strength %

0
-20 0

1

2

-40
-60

Rapidite %

G4 shows the same trend, that although both 7 and 28 day strength for 100mm cube
increases and reach there maximum at the rapidite percentage of 1.25% ,the increase in 7day strength
is 214% more than increase in 28 day strength.which is higher than in case of 150mm cube.

G6-Variation of C.F for plain concrete and concret
with admixture for different % of rapidite
Plain
0.88

0.81

0.77

0.74

1

2

Admixture

0.72 0.77

3

0.73

4

0.8

0.88
0.73

5

G6 shows that the compaction factor always increases when compared with the plain
concrete,thus workability increases by the addition of rapidite.

123

CONCLUSION
After analyzing the test results following important conclusions are drawn:
•

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 1.25%, beyond which it starts
decreasing. It must be noted that the avg temperature during the 1st 24 hrs after casting is
almost constant.

•

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.

•

The increase in early strength shows that the freezing of fresh concrete was not there, as such
the admixture also acts as a antifreeze, depressing the freezing point of water and protecting
the concrete from the affects of freezing in early age.

•

Adding Rapidte has shown increase in the workability of mix with respect to the plain mix.

Recommendations
•

The quantity of Rapidite to be added needs to be carefully controlled as there is a decrease in
the strength of concrete if the value passes 1.25% by weight of cement. The manual which
comes with the Rapidite recommends the percentage of Rapidite to be used in the range of 26%, which in excess of the optimum value of 1.25%. Thus the amount of the Rapidite should
be limited to the 1.25%.

•

When concreting is to be done in the period from November to February, Rapidte should be
used to accelerate the early gain of strength and protecting the fresh concrete from the effects
of freezing, as Rapidite acts as Antifreeze cum accelerator.

•

When there is intention of using Rapidite during warm weather for the purpose of early
removal of formwork, proper performance tests testing should be done to check the behaviour
of rapidite at the high temperature, as the behavior of a admixture depends on the
temperature.

•

Further proper testing should be done to check the compatibility of the Rapidite with the type
of cement to be used in actual construction.

•

Admixture should be uniformly distributed throughout the mix, and this best achieved by
dissolving the admixture in mixing water.

•

Trial tests should be carried out using the actual constituents of the mix to be used. Also,
adequate supervision should be provided at the batching stage so as to ensure correct levels of
dosage of the admixture.

124

REFERENCES
1)
2)
3)
4)

5)

6)

7)

8)

9)

M.S.Shetty, Concrete Technology, Chapters 1- 8,page nos. 1 – 330,
IS 9103 : 1999, Admixtures : definition, Page nos (23,24).
IS 456 : 2000, strength of concrete : tests, compressive strength .pages (2-7)
Abbas S. Al-Ameeri, K.A.Al- Hussain and M.S Essa, “Constructing a Mathematical Models
to Predict Compressive Strength of Concrete from Non-Destructive Testing”, International
Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 4, 2013, pp. 1 - 20,
ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
Alaa Abdul Kareem Ahmad, “The Effect of Gypsum Compensative on Mortar Compressive
Strength”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4,
Issue 3, 2013, pp. 168 - 175, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
P.J.Patel, Mukesh A. Patel and Dr. H.S. Patel, “Effect of Coarse Aggregate Characteristics on
Strength Properties of High Performance Concrete using Mineral and Chemical Admixtures”,
International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 2, 2013,
pp. 89 - 95, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.
Dr. Shanthappa B. C, Dr. Prahallada. M. C. and Dr. Prakash. K. B., “Effect of Addition of
Combination of Admixtures on the Properties of Self Compacting Concrete Subjected to
Alternate Wetting and Drying”, International Journal of Civil Engineering & Technology
(IJCIET), Volume 2, Issue 1, 2011, pp. 17 - 24, ISSN Print: 0976 – 6308, ISSN Online:
0976 – 6316.
M.Vijaya Sekhar Reddy, Dr.I.V. Ramana Reddy and N.Krishna Murthy, “Experimental
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Vinod P, Lalumangal and Jeenu G, “Durability Studies on High Strength High Performance
Concrete”, International Journal of Civil Engineering & Technology (IJCIET), Volume 4,
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