20320130406013 2-3

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)

IJCIET

ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 4, Issue 6, November – December, pp. 126-133
© IAEME: www.iaeme.com/ijciet.asp
Journal Impact Factor (2013): 5.3277 (Calculated by GISI)
www.jifactor.com

©IAEME

EFFECT OF RAPIDITE ON STRENGTH OF CONCRETE IN WARM
CLIMATES
Sameer ul Bashir1,
1

Younis Majid2,

Ubair Muzzaffer Rather3

B.Tech, NIT, Hazratbal, Srinagar
B.Tech, COET, BGSBU, Raouri

2, 3

ABSTRACT
The Present work is a part of series of experiments to study the influence of rapidite on
strength of concrete. Rapidite is an admixture, which is used in cold weather concreting especially in
Kashmir, as of its availability, low costs and non-existence of other alternatives which could nullify
the effects of low temperatures on strength of concrete. In Kashmir, the winter temperatures fall to
sub zero level and thus, rapidite is used as it has been a determined Accelerator and anti freeze agent.
The present work has, however, been carried out in warm climate, when temperature was around 20
degree Celsius, to check the influence and hence, its suitability regarding various properties of
concrete, particularly the strength of concrete.
A nominal mix of M20(1:1.5:3) was used. Various strength tests were carried out after 7 days
and 28 days of curing. 50% of specimen were tested at 7 days and remaining 50% at 28 days age.
Various tables and various Graphs were prepared to study the effect of Rapidite on various properties
of concrete which are discussed in the following sections of this paper.
Keywords: CONCRETE, RAPIDITE, 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.
126

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.
Considering the above criteria our work can definitely be not called as the cold weather
concreting as the temperature was around 20 degree Celsius.
•
•

ADMIXTURES
Definition
IS 9103 : 1999 defines admixture as “A material other than water, aggregates, and hydraulic cement
and additives like pozzolana or slag and fibre reinforcement used as an ingredient of concrete or
mortar and added to the batch immediately before or during its mixing to modify one or more of the
properties of concrete in the plastic or hardened state.”
Benefits of Admixtures
Admixtures confer several beneficial effects on concrete including reduction in water
requirements, increased workability, controlled setting, accelerated hardening, improved strength,
better durability, desired coloration and volume changes.
The major reasons for using admixtures are:
1. To achieve certain properties in concrete more effectively than by other means.
2. To maintain the quality of concrete during the stages of mixing, transporting, placing, and curing
in adverse weather conditions.
3. To overcome certain emergencies during concreting operations.
Despite these considerations, it should be borne in mind that no admixture of any type or
amount can be considered a substitute for good concreting practice.
127

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 antifreeze, depressing the freezing point of water and hence protecting the fresh
concrete.
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.
EXPERIMENTAL INVESTIGATION
Objective
The objective of this project was to study the effect of a commonly used admixture
RAPIDITE in Kashmir on the strength of concrete. Casting was done during March and April. The
Percentage of RAPIDITE was varied to find its effect on the strength. Two castings for every
percentage of rapidite, one plain and one with admixture, and relative change in various strengths of
concrete at various ages was found. Following tests were conducted on concrete to study the effects
of rapidite on concrete.
TESTS CONDUCTED ON FRESH CONCRETE
Slump Test for Workability
Only slump test was used to find the workability of fresh concrete in each casting separately
for PCC and Rapidite castings.
TESTS CONDUCTED ON HARDENED CONCRETE
COMPRESSION TEST: This test is conducted on cubes (150mm) which are loaded on their
opposite faces in a Compression Testing Machine (CTM).The load at which first crack appears is
considered as failure load and the compressive strength is calculated corresponding to this particular
value of load.
Compressive strength

= Load at failure /Cross sectional area

Where, cross-sectional area = (150×150) mm2
128

SPLIT TEST: The test is carried out by placing a cylindrical specimen, horizontally between the
loading surfaces of a Compression Testing Machine and the load is applied until failure of the
cylinder, along the vertical diameter. The loading condition produces a high compressive stress
below the two surfaces to which the load is applied. But the larger portion corresponding to depth is
subjected to a uniform tensile stress acting horizontally. It is estimated that the compressive stress is
acting for both (1/6) th depth and the remaining (5/6) th depth is subjected to tension. The horizontal
tensile stress is given by the following equation:
Horizontal tensile stress=2p/πDL
Where,

P = Load at failure
L = Length or height of cylinder (300mm)
D = Diameter of cylinder (150mm)

FLEXURAL TEST: Flexural strength test of concrete is performed on beams. The loading applied
on the beam is a two point loading in which loads are applied at (1/3) rd points of the beam. The
beam is placed in the testing machine in such a way that the load points are 16.6 cm apart from each
other as well as from each support. The load is increased until the specimen fails and this load is
noted as failure load. Flexural strength is then calculated from the following formula:
Flexural strength =2pl/bd2
Where,
P
l
b

= (Load at failure)/2
= Length of beam between supports (500mm)
= Breadth of beam (100mm)

TEST RESULTS
Rapidte percentage was changed as 0.8,1,1.2, 1.4 and 1.6 and mean temperature noted was 20
degree celcius.

Casting
Number

TABLE 1 SLUMP TEST RESULTS
Volume of
Slump for
Rapidite
water
PCC (cm)
Percentage

Slump for
concrete with
rapidite(cm)

1

0.4×15 kg=6 kg

15.5

0.8%

12.8

2

6 kg

14.5

1%

16

3

6 kg

13.5

1.2%

16.6

4

6 kg

16

1.4%

16.8

5

6 kg

15.3

1.6%

16.2

Note : w/c ratio used was =0.4

129


Casting
Number

Table 2: 7 and 28 day Average Strength test Results
Description
Compressive
Tensile
strength(cube) in
strength(cylinder) in
Mpa
Mpa

Flexural
strength(beam) in
Mpa

7 day

5

28 day

PCC

20.46

24.88

1.134

1.59

3.33

3.72

17.21

20.64

1.175

1.43

1.76

2.55

PCC

19.64

23.08

1.185

1.67

2.94

5.21

17.1

21

1.499

1.67

2.94

3.33

PCC

21.5

30.8

1.487

2.05

2.19

4.9

17.9

26.18

1.4

1.7

1.37

4.9

PCC

20.5

26.2

1.26

1.7

3.5

3.7

Concrete with
1.4% Rapidite

4

7 day

Concrete with
1.2% Rapidite

3

28 day

Concrete with
1% Rapidite

2

7 day

Concrete with
0.8% Rapidite

1

28 day

18.21

23

1.29

1.58

2.1

3.33

PCC

20.5

26.2

1.26

1.7

3.72

3.9

1.56

3.33

0.981

Concrete with
17.49
21.9
0.88
1.6% Rapidite
Note: Rapidite was taken as Percentage by weight of cement
PCC means plain cement concrete.

RESULTS AND DISCUSSIONS: In order to study the effects of using accelerating admixture
Rapidite at varied dosages (as shown in Table 5.3) onvarious strengths at 7 days and 28 days
respectively, a comparative study of the test results achieved at different Rapidite percentage is
performed.
Following Comparisons are studied by plotting the graphs:
•
•
•
•
•
•

Variation of 7 day compressive strength with Rapidite %
Variation of 28 day compressive strength with Rapidite %
Variation of 7 day tensile strength with Rapidite %
Variation of 28 day tensile strength with Rapidite %
Variation of 7 day flexural strength with Rapidite %
Variation of 28 day flexural strength with Rapidite %

130

The following graphs represent the comparative study:
25

1.6

PCC

1.4
20

Rapidi
te

Tensile Strength In Mpa

Compressive Strength in Mpa

1.2

15
PCC

10

Rapidite

1
0.8
0.6
0.4

5

0.2
0

0

0
0

0.5

1

1.5

0.5

1

1.5

2

2
Rapidite %

Rapidite %

G1: Variation of 7 day compressive strength
with Rapidite %

G2: Variation of 7 day tensile strength
with Rapidite %

35

3.5

30

Flexural Strength in Mpa

4

PCC
Rapi
dite

3
25
Strength (Mpa)

2.5

20

2

15

1.5
1

10

0.5
5
0
0
PC
C

0.5

1

1.5

0

2

0

Rapidite %

G3: Variation of 7 day flexural strength
with Rapidite %

0.5

1
1.5
Rapidite %age

2

G4: Variation of 28 day compressive strength
with Rapidite %

131


6
5

2

4
1.5
Flexural Strengt in Mpa

Tensile Strength in Mpa

2.5

1
PCC
0.5
Rapidite

3
2
PCC

1

Rapidite

0

0
0

0.5

1

1.5

2

0

0.5

1

1.5

2

Rapidite %

Rapidite %

G5: Variation of 28 day tensile strength
with Rapidite %

G6: Variation of 28 day flexural strength
with Rapidite %

INFERENCES
From the study of Graph G1 it is clear that by adding Rapidite the 7 day compressive strength
decreases when compared to the plain concrete casted at the same temperature. Peak values of
compressive strength of PCC and Rapidite castings are 20.5 and 18.21 respectively. So, the
percentage decrease in strength is about 11% at maximum values.
From Graph G2 it is clear that for 7 day tensile strength of cylinders Rapidite castings have
higher peak strength at about 1.2% rapidite dosage as compared to PCC castings. However, the
average strength decreases with dosage of rapidite.
From Graph G3 it is evident that the flexural strength in general decreases with usage of
Rapidite. However, the flexural strengths are almost equal at a rapidite dosage of 1%.
G4 shows general decrease in compressive strength. However, the decrease in peak 28 day
compressive strength for the concrete with Rapidite is about 15% which is greater than decrease in
peak compressive strength of 11% for 7 day compressive strength.
In G5, Tensile strength is decreased. However, at exactly 1% dosage of rapidite the Tensile
strengths are equal of the PCC and concrete with Rapidite. The 7 day tensile strength at 1% Rapidite
dosage was however, greater for Concrete with rapidite as that of PCC.
In G6, A very little decrease in 28 day Flexural strength occurs with usage of rapidite from
1.2% to 1.4% dosages of rapidite. From, exactly 1.2% to 1.4% dosages of rapidite the flexural
strengths of PCC and Rapidite castings is approximately same. However, the decrease in flexural
strength for rapidite casting is about 73% at the rapidite dosage of 1.6%, which is quiet high.

132

CONCLUSIONS
After comparing the various test results at 7 days and 28 days we can see that there are varied
responses of concrete added with accelerating admixture Rapidite. Following conclusions were
drawn:
• There is a general decrease in Compressive strength (7day as well as 28 day) with usage of
accelerating admixture rapidite as compared to PCC. The peak value of 7 day compressive
strength was obtained at 1.2% but was still less than the peak value of PCC by about 11%.
The peak value 28 day compressive strength was also obtained at 1.2% rapidite dosage but it
was lesser than that of PCC by about 15%. So, the decrease in compressive strength is
substantial.
• The comparison of tensile strengths of PCC and Rapidite castings shows varied results at
different rapidite dosages. The 7 day tensile strength of Rapidite casting is higher than that of
PCC from 0.8% to 1.2% rapidite dosage and then it is lesser than PCC from 1.2% to 1.6%
rapidite dosage. The maximum value of 7 day tensile strength is 0.8% higher than that of
PCC. The 28 day tensile strength is in general lesser for rapidite castings as compared to
PCC but are equal at 1% rapidite casting.
• Flexural strength of Rapidite casting is in general lesser than that of PCC castings at both 28
day and 7 day ages. However, the 28 day flexural strength is almost equal for concrete with
rapidite and PCC from rapidte dosages of 1% till 1.2%. Also, the peak values of 28 day
flexural strengths are equal of about 4.9 Mpa.
• Slump tests revealed that there is an increase in workability. Workabillity was increased with
usage of rapidite at every dosage other than at 0.8%. There is a decrease of workability 0.8%
rapidite dosage by 17.4%. At 1%, 1.2%, 1.4% and 1.6% rapidite dosages there is an increase
in workability by 9.3%, 18.6%, 4.76% and 5.55% respectively as compared to the
workability of PCC at same conditions.
RECOMMENDATIONS
After seeing the results of various tests it can be concluded that Usage of Rapidite has
Adverse effects on various strengths of concrete at higher temperatures of around 20 degree celcius.
Although, its usage shows increase in Workability but that increase in workability can be achieved
by adopting other means which will not decrease the strengths at the same time. Hence it is not
recommended to be used at higher temperatures of around 20 degree celcius.
REFERENCES
Books
1) A.M.Neville., Properties of Concrete., 4thEd.,Pearson Education., New York.
2) M.S. Shetty., Concrete Technology., 6thEd., S. Chand publishing., New Delhi.
I.S Codes
3) IS 9103: 1999, Concrete Admixtures, First revision, Bureau of Indian Standards.
4) IS 9013: 1978, Method of making, Curing and determining compressive strength of
accelerated-cured concrete test specimens, Bureau of Indian Standards.
Web Pages and On-line Material
5) <http://civilblog.org/2013/05/10/compressive-strength-test-of-concrete-is516-1959/>
6) <http://www.hatricproducts.com/?file=kop8.php>
133

20320130406013 2-3

Recommended

Recommended

More Related Content

What's hot

What's hot (19)

Viewers also liked

Viewers also liked (20)

Similar to 20320130406013 2-3

Similar to 20320130406013 2-3 (20)

More from IAEME Publication

More from IAEME Publication (20)

Recently uploaded

Recently uploaded (20)

20320130406013 2-3