Influence of Type of Superpalsticizers On

International Journal of Advanced Engineering Technology E-ISSN 0976-3945

IJAET/Vol.I/ Issue II/July-Sept.,2010/123-130

Research Article

INFLUENCE OF TYPE OF SUPERPALSTICIZERS ON

WORKABILITY AND COMPRESSIVE STRENGTH

OF REACTIVE POWDER CONCRETE

1M K Maroliya* ,

2C D Modhera

Address for Correspondence

*1Research Scholar, Department Of Applied Mechanics, S.V. National Institute Of

Technology, Surat-395007, Gujarat, India

E-mail: [email protected] 2Professor, Department Of Applied Mechanics, S.V. National Institute Of Technology,

Surat-395007, Gujarat, India

ABSTRACT

Reactive powder concrete is a special concrete having ultra high strength and ductility. It is an engineered cementitious composite where the microstructure is optimized by precise gradation of all particles in the mix to yield the maximum density. It uses extensively the pozzolanic properties of highly reactive silica fume and optimization of Portland cement to produce the highest strength hydrates. Potential application of reactive powder concrete (RPC) include, prestress structures without passive reinforcement, pressure precast pipe, impermeable container for hazardous fluids of nuclear waste. RPC is a cold cast cementitious material, in which the mechanical properties of the composite matrix are improved by,

• Suppression of the weak interfacial transition Zone normally developed around the aggregates through improved particle packing and,

• Refinement of the hydrated paste microstructure by extensive use of pozzolanic silica and elevated temperature curing.

RPC is unique in attempting to optimize the entire grain size distribution of the composite matrix in particular; there are five central design tenets for RPC

• Enhancement of homogeneity by the elimination of coarse aggregate

• Enhancement of the compacted density by optimizing the granular mixture and optionally applying pressure before and during setting.

• Enhancement of the microstructure by heat treatment after hardening

• Improved ductility through the incorporation of steel fibers.

• Maintaining mixing and casting procedure as close as to existing concrete industries practice.

This paper reports the influence of the type of superplasticizers (SNF, SMF, Polycarboxylic ether) on strength and workability of reactive powder concrete.

KEYWORDS: Reactive Powder Concrete, workability, super plasticizer, Curing Condition.

INTRODUCTION

Over the year, concrete has become

considerably more complex than the

original crushed stone plus sand, lime and

water used by the Romans. The use of

supplementary cementations materials

and additives designed to enhance the

properties of concrete has grown

significantly. The primary focus of this

development has been on the

achievement of greater compressive

strength and it is now no longer possible

to refer all concrete as merely concrete.



Reactive Powder Concrete (RPC) is ultra

high strength cementitious material

composed of very fine powder with a

maximum particle size of approximately

800 and containing very high silica fume

and very low water cement ratio.

The silica fume by itself, do not

contribute to the strength dramatically,

although it does contribute to the strength

property by being very fine pozzolanic

material and also creating dense packing

and acting as pore filler of cement paste.

Silica fume is much more reactive than

fly ash or any other natural pozzolana.

The reactivity of pozzolana can be

quantified by measuring the amount of

Ca(OH)2 in the cement paste at different

times. Pozzolanic silica is added in the

stoichiometric quantity necessary to react

with all the calcium hydroxide that would

be produced assuming complete cement

hydration. The Hydration reaction is as

follows;

2C3S + 6H C3S2H3 + 3CH

2C2S + 4H C3S2H3 + CH

[Where C = CaO; S = SiO2; H = H2O]

The C3S2H3 is referred to as C-S-H or

calcium silicate hydrate. The calcium

hydroxide (CH) produced by hydration

occupies 20 – 25% of the cement paste by

volume and makes no contribution to

strength and durability. Addition to

amorphous silica forms further desirable

C-S-H at the expense of calcium

hydroxide.

CH + S + H C-S-H

However, metakaolin is easily available

in India and High reactive metakaolin

shows high pozzolanic reactivity and

reduction in Ca(OH)2 even as early as one

day. It is also observed that the cement

paste undergoes distinct densification.

The improvement offered by this

densification includes an increase in

strength and decrease in permeability.

MATERIAL SELECTION

Silica Pozzolan

a. A highly reactive silica pozzolan is

an essential component of reactive

powder concrete, performing three

vital roles for which it needs the

following properties:

b. It must be sufficiently fine to pack

closely around the cement grains,

improving the density of the

composite matrix and minimizing the

potential for voids between the

particles.

c. It should possess considerable

pozzolanic activity, such that the non-

cementing portlandite crystals

[Ca(OH)2] generated by hydration of

the cement react with the silica to form

additional C-S-H gel, reinforcing the

binding of the composite.

d. The particles should have a basically

spherical shape to act as a lubricant

within the fresh mix, improving its

ability to flow and be cast into

moulds.



Cement

Due to the very high cement factor, the

choice of cement can be an important

factor in the performance of RPC. Based on

published practice, the ideal cement has a

high C3S and C2S (di-& tri-calcium

silicate) content and very little C3A (tri-

calcium aluminates). This is

understandable because C3A has little

intrinsic value as a binding agent and is

primarily included in cement due to its

role as a flux during the calcinations

process. Ordinary Portland cement

commercially available is used in the

investigation.

Quartz Sand

For RPC mixes designed to be cured at

temperatures exceeding 90°C, including

autoclaving at elevated pressures,

additional silica is necessary to modify

the CaO/SiO2 ratio of the binder. In

these cases powdered quartz flour with

a mean particle size of 10 - 15 µm was

employed.

Fine Aggregates

The maximum size of the ingredients in

RPC is 600µm, and that is of fine

aggregates. The fine aggregate used is

the normal sand with size of particles

between 150 to600µm. As the coarse

aggregates are totally removed so these

fine aggregates give strength.

Super Plasticizer

The very low w/b (cement + silica fume)

ratios used in RPC are only possible

because of the fluidizing power of high-

quality third generation super-

politicizing agents. So SMF, SNF and

Polycarboxylic ether is used which is

designed specifically for ultra-high

water reduction applications.

Three different types of super

plasticizers have been used to check the

effects on the workability and

compressive strength of RPC.

Super plasticizer used are as below

followed by their technical data

• Supercon – 100 (Sulfonated

melamine-formaldehyde), Procured

from Krishna Conchem Products

Pvt. Ltd. (Table 1)

• Fosroc (Sulfonated naphthalene-

formaldehyde) Procured from

Fosroc Chemicals Ltd. (Table 2)

• Glenium-51 (Polycarboxylic ether)

Procured from BASF Chemicals

(India) Pvt. Ltd. (Table 3)

The specifications of all the materials

used for RPC is shown in Table 4.

Table 1: Supercon – 100(Sulfonated melamine-formaldehyde)



Sr.

No.

Properties Units Specification Limit

1. Specific Gravity -- 1.10 to 8.5

2. Appearance -- Slightly bazy

3. pH -- 7.8 to 8.5

4. Water Reduction % 13 to 20

Table 2: Fosroc (Sulfonated naphthalene-formaldehyde)

Sr.

No.


1. Specific Gravity -- 1.10 to 8.5

2. Appearance -- Slightly bazy

3. pH -- 7.8 to 8.5

4. Water Reduction % 13 to 20

Table 3: Glenium-51 (Polycarboxylic ether)

Sr.

No.


1. Specific Gravity -- 1.095

2. Chloride % ≤ 0.10

3. pH -- 7.2

4. Alkali % ≤ 4

Table 4: Specification of The Materials Used For RPC.

Sample Specific Gravity Particle Size Range

Cement

(IS 12269: 1987) 3.15 31 µm – 7.5 µm

Silica fume

(ASTM C1240-97B) 2.2 5.3 µm – 1.8 µm

Quartz sand 2.7 5.3 µm – 1.3 µm

River sand

(IS 383: 1970) 2.61 2.36 mm – 0.15 mm

EXPERIMENTAL PROGRAM

RPC Mixture Design

Optimization of the granular mixture is

achieved by trial and error mixes in the

experimental method is adopted. Table 2

presents various mixture proportions for

RPC obtained from the available

literature



.Table 5: Proportion of RPC Mixtures Tested For Workability and Compressive

Strength for various W/C ratios

(Without Steel Fibers)

Super-Plasticizer SMF SNF PCE SMF SNF PCE

Cement 1 1 1 1 1 1

Silica Fume 0.27 0.27 0.27 0.27 0.27 0.27

Quartz Sand 0.35 0.35 0.35 0.35 0.35 0.35

Sand 150 – 600µm. 1.55 1.55 1.55 1.55 1.55 1.55

Super Plasticizer 0.03 0.03 0.03 0.03 0.035 0.03

Water/Cement 0.25 0.25 0.22 0.27 0.27 0.25

Flow Table (mm) NW NW 128 NW NW 165

Compressive Strength

7 - Days --- --- 107 --- --- 101


28 - Days --- --- 124 --- --- 116

SMF: Sulfonated melamine-formaldehyde PCE: Polycarboxylic Ether, SNF:

Sulfonated naphthalene-formaldehyde NW: Not Workable

Table 6: RPC mixture design from literature

(Parts by mass)

Materials P. Richard,

M. Cheyrezy

S. A.

Bouygues

A. S. Dili,

M. Santhanam

Fibered

(12mm)

Fibred

(25mm)

Without

Fiber

Fibered

(25mm)

Cement 1 1 1 1

Sand 1.1 1.423 1.6 1.6

Silica fume 0.23 0.324 0.25 0.25

Powdered 0.39 0.296 0.31 0.31

Steel fibres 0.175 0.268 - 0.20

Water 0.19 0.282 0.25 0.25

Super-

plasticizer

0.019 0.027 0.03 0.03



Table 7: Proportion of RPC Mixtures Tested for Workability and Compressive

Strength for various W/C ratios (Without Steel Fibers)

The major parameter that decides the

quality of the mixture is its water demand

(quantity of water for minimum flow of

concrete). In fact, the voids index of the

mixture is related to the sum of water

demand and entrapped air. After selecting

a mixture design according to minimum

water demand, cubes were caste and

compressive strength is measured at 7

days and 28 days.

Sample Production

The RPC mixes were produced in batches

using an Epicyclic mixer compliant with

the requirements of ASTM C 305.

The mixing protocol adopted is shown in

Table 8.

Table 8: Procedure for Production of RPC mixes

Mixing protocol Elapsed time

(Minutes)

Lightly grind cement and silica fume to break-up agglomerates -

Add all dry powders and aggregate 0

Start mixing ½

Add 75% of water required 3

Add steel micro-fibres (if used) 5

Add remainder of water and super-plasticizer 8

Stop mixing and cast test specimens 30

Super-Plasticizer SMF SNF PCE SMF SNF PCE

Cement 1 1 1 1 1 1

Silica Fume 0.27 0.27 0.27 0.27 0.27 0.30

Quartz Sand 0.35 0.35 0.35 0.35 0.35 0.35

Sand 150 – 600 µm. 1.55 1.55 1.55 1.55 1.55 1.55

Super Plasticizer 0.035 0.035 0.028 0.03 0.03 0.03

Water/Cement 0.30 0.30 0.27 0.3 0.3 0.22

Flow Table (mm) NW NW 185 108 110 112


7 - Days --- --- 93.5 70 71 108


28 - Days --- --- 107 81 82.5 125



The extended mixing time is necessary

both to fully disperse the silica fume,

breaking up any agglomerated particles,

and to allow the super-politicizing agent to

develop its full potential.

At the conclusion of the mixing period,

the workability of the mix was assessed

according to the ASTM C 1437 'flow

table' test From the fresh RPC, 50 mm cube

specimens for determination of

compressive strength compacted into

moulds by first hand tamping in two layers

and then vibrating on the vibrator. The

specimens were allowed to harden in their

moulds for 24 hours at normal temp. &

Humidity, before being stripped and

subjected to curing at 90 °C for next 48

hours and then subjected to normal curing.

RESULTS AND DISCUSSION

Twelve number of unique composition of

RPC were produced to evaluate the

effect of different types of super

plasticizer at different water/cement ratio

on the workability and the compressive

strength of RPC. The results of the flow

test for workability of RPC and

compressive strength are summarized in

the Table 5 and Table 6 SMF and SNF

will not be helpful in producing workable

RPC. It requires compulsory polyacrylate

based or polycarboxylic based super

plasticizers.

0 0 0

108

0 0 0

110

128

165

185

215

0

50

100

150

200

250

0.22 0.25 0.27 0.3

W/C Ratio

Flow in mm.

SMF SNF PCE

Figure 1: Flow measurement for workability of RPC



50

60

70

80

90

100

110

120

130

140

150

0.2 0.22 0.24 0.26 0.28 0.3

W/C Ratio

Compressive Strength in N/mm2

7 days comprssive strength 28 days compressive strength

Figure 2: Variation of Compressive Strength of RPC with W/C ratio

CONCLUSION

1. The effect of different Super

plasticizer i.e. Sulfonated

melamine-formaldehyde and

sulfonated naphthalene-

formaldehyde has been checked in

the RPC. This shows that the

suitable workability in reactive

powder concrete is not possible

without new generation plasticizer

like polyacrylate (PA) based or

carboxylated acrylic ester (CAE)

super plasticizers as shown in

figure 1 and figure 2.

2. The studies on new generation

super plasticizer have shown that

the fluidity is due to the higher

polymer adsorption and steric

hindrance effect.

3. Because of the very low W/C

ratio and higher percentage of

plasticizers setting of RPC is

increased. But it is more sensitive

to water, so its flow will be

reduced with the time (like a

slump loss in ordinary concrete).

REFERENCES

1. A. S. Dili and Manu Santhanam.

“Investigation on reactive

powder concrete: a developing

ultra high-strength technology”.

April 2004, the Indian concrete

journal

2. Marcel Cheyrezy*, Vincent

Maret, And Laurent Frouin.

“Micro structural analysis of

RPC (Reactive powder

concrete)”. Cement and Concrete

Research, Vol. 25, No. 7. pp.

1491-1500.1995.

3. Pierre Richard, Marcel Cheyrezy,

“Composition of reactive powder

concretes”. Cement and Concrete

Research, Vol. 25. No. 7, pp.

1501-1511.1995.

4. Silvia Collepardi, Luigi Coppola,

Roberto Troli,Pasquale

Zaffaroni.“Influence of the

super plasticizers type on the

compressive strength of

reactive powder concrete for

precast structures”.

Documents

Influence of Type of Superpalsticizers On