chemistry and performance of different lignosulfonates

8/11/2019 CHEMISTRY AND PERFORMANCE OF DIFFERENT LIGNOSULFONATES

1/13

CHEMISTRY AND PERFORMANCE OF DIFFERENT

LIGNOSULFONATES

K. Reknes*, Borregaard LignoTech R&D, Norway

28thConference on OUR WORLD IN CONCRETE & STRUCTURES: 28 - 29 August 2003,Singapore

Article Online Id: 100028049

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2/13

28

th

Conference on

OUR WORLD

IN CONCRETE STRUCTURES: 28 - 29 August 2003,

Singapore

CHEMISTRY AND PERFORMANCE OF DIFFERENT

L GNOSULFONATES

K. Reknes*, Borregaard LignoTech R D, Norway

Abstract

Lignosulphonate from different sources is being used in concrete admixture

formulations in Asia. The properties o the different lignosulphonate can vary, as the

lignosulphonate are different both

in

chemistry

and

in performance in the concrete.

Lignosulphonate produced in China, Norway

and

South Africa were compared in an

investigation including chemical analysis and concrete performance testing. The

purpose of

the

investigation was to correlate some of the differences in chemical

composition, with the concrete performance of the materials.

There are performance differences between the samples investigated. The molecular

weight is the highest for Borresperse CA and the lowest for the Chinese samples. All

the three Chinese samples have the same molecular weight distribution. The

Chinese samples are Mg lignosulphonate and the Borresperse samples are Ca

lignosulphonate. The Chinese I sample contain a high amount of insoluble. The air

entrainment is the lowest with Borresperse CA-SA and the highest with the Chinese

samples. The air entrainment affects the compressive strength. The compressive

strength is lower with the admixture samples entraining the most air than with the

admixture

samples entraining the least air. The Chinese samples contain chloride in

high concentration and are thus not suitable for formulation of concrete admixtures.

Keywords: lignosulphonate, concrete, water reducing admixture

Introduction

Lignosulfonate has been used in chemical admixture for concrete since the 1930-ties. The probably

most important single group of materials used

in

chemical admixture for concrete was

and

still is

lignosulfonate. The way lignosulfonate is being modified and altered has changed since the beginning

in the 1930-ties. During the

20

t

century, a wide range of new materials found their way into the

formulations of chemical admixture for concrete. The

use

of gluconate started

in

the 1940-ties. PNS

(naphthalene sulfonate) were developed

and

introduced in the early 1970-ties. Melamine sulfonate

(MS) were introduced around 1980, poly vinyl copolymers (VC) around 1990 and the poly carboxylic

copolymer PC) around 2000.

As

new materials have been added to the range o raw materials, new

formulations have been developed with combinations of these materials and lignosulfonate.

Lignosulphonate from different sources is being used in concrete admixture formulations in Asia.

The properties of the different lignosulphonate can vary, as the lignosulphonate are different both in

chemistry

and in

performance

in

the concrete. Difference

in

chemical composition can have big impact

on the performance o the lignosulfonate in concrete 11

2/.

These differences can be overcome by

different ways of modifying the lignosulfonate to results

in

the same performance in the concrete.

These differences do also have impact on the formulation of the concrete admixture. Lignosulphonate

439


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produced in China, Europe and South Africa were compared in an investigation including chemical

analysis and concrete performance testing. The purpose of the investigation was to correlate some of

the differences in chemical composition, with the concrete performance

of

the materials. The results of

the investigation are reported here.

2 Experimental

2 1 Samples

The samples used in the experimental work are described in Table 1. The three Chinese samples

were provided from Korea. The origin is not known to us. They are expected to be sodium

lignosulphonate. Borresperse CA-SA is a hardwood lignosulphonate. Borresperse CA is a softwood

lignosulphonate.

2.2 Concrete test ing

The samples were tested on performance in concrete. concrete mix proportion is

~ e s i g ~ e d

according to the European standard EN

480-1

and is shown

In

Table

2.

The aggregate particle size

distribution is composed according to the European standard EN 480-1.

8mm

8 11 mm

1116mm

Admixture

The following concrete properties were determined:

slump: initial and after

15

minutes and 30 minutes when possible,

air content and fresh density,

set time

by

measurement

of

the temperature increase in isolated box and

compressive strength and density after

24

h, 7 days and 28 days.

3 Results and discussion

The results of the chemical analysis conducted are shown in Table 3. The molecular weight of the

Chinese Iignosulphonate samples is low, and lower than that of Borresperse CA-SA. The molecular

weight distribution

of

the samples is shown in Figure

1

The weight average molecular weight (Mn) of

the Chinese and the Borresperse CA-SA is the same, but there is difference in the weight average

molecular weight (Mw). The molecular weight of Borresperse CA is much higher that that of the other

samples. This is valid for both Mn and Mw.

The amount of reducing sugar is slightly different in the samples. The Borresperse CA-SA

sample contains 2.0 reducing sugar, while the other samples contain 5-6 reducing sugar. The

total sugar content of the samples is low, as the term reducing sugar also includes other reducing

components than only sugar, i.e. reducing sugar

is

equal to reducing matter. The content of reducing

I sbwc = solids by weight of cement

44


4/13


5/13

Chinese sample I is 2-3 higher than that with the other samples,

in

spite of the 0.8 dosage of

defoaming agent.

The initial set time is the same for the samples of Borresperse CA, Borresperse CA-SA,

Chinese H and Chinese A up to the dosage of 0.40 sbwc. The initial set time with the Chinese I

sample

is

higher than with the other samples at the 0.40 sbwc dosage. All the Chinese samples

have approximately the same initial set time at the 0.60 sbwc dosage. The two Borresperse

samples have much longer set time than the Chinese samples at the 0.60 sbwc dosage. The

accuracy of the test method is approximately 0.5 hours.

A principle component analysis (PCA, mUltivariate data analysis) was conducted on the

concrete performance data from the data set with 0.8 TBP. The PC1 and PC2, that are explaining

91 PC1 64 and PC2 27 ) of the variation of the data, are shown

in

Figure 4. Slump (Slump_O)

and initial set time (Set) correlates with the dosage (DOS) of the admixture. This

is

as expected. The

air entrainment (Air) correlates with the admixture dosage

on

PC1, but

is

negatively correlated

on

PC2. This can be explained by the increase in air entrainment with increasing dosage (PC1). Increase

in

workability (slump) makes it easier for the entrained air to escape from the concrete. Increasing

workability

is

a result of increase

in

admixture dosage resulting in the negative correlation between air

entrainment and admixture dosage on PC2. The positive correlation between air content and slump

on PC1 implies that increased air entrainment also improves the workability of the concrete. Air

content

is

negatively correlated to the density of the fresh concrete (Dens-f) on both PC1 and PC2.

This

is

as expected: Increasing air content results

in

lower density. Density and compressive strength

are positively correlated on

PC1

both at 24 hours (C24,

024

and at 7 days (C7, 07). The 24 hour

compressive strength is negatively correlated to the density

on

PC2. The 24 hours compressive

strength

is

negatively correlated to set time on both PC1 and PC2. Increasing set time results

in

reduced 24 hours compressive strength, as expected.

-

::I

o

E

Chinese

t

hinese

Chinese

/ Borresperse CA

Borresperse CA-SA

Molecular weight

Figure 1 Molecular weight distribution for all samples used in the investigation

The normal probability plot

of

the air content

of

the fresh concrete

is

shown

in

Figure 5 and of

the initial set time in Figure 6. Some of the samples are not following the normal distribution fully. The

scores and correlation loadings from the PCA are shown in Figure 7. The scores plot show that the

Chinese I sample is grouping differently from the other samples. The other samples are grouping very

similar to each other indicating that they are not very different.

44


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Control

22 9 0 5 53 7

1,0

68 2

O,7

2426

11

2443 9 2440

5

The compressive strength development at the different dosages used

is

shown in Figure 8 and Figure

10. The main factors affecting the compressive strength are

s

follows:

initial set time affects the 24 hours compressive strength and

air content affects the 7 days and 28 days compressive strength.

The 24 hours compressive strength is reduced with increasing set time (Figure 9). The

compressive strength at 7 days is mainly affected by the air entrainment. Increasing air entrainment

reduces the compressive strength.

The concrete performance was also determined without addition o defoaming agent (TBP). The

data

o

this data set

is

shown

in

Figure 11. The air entrainment

o

the Chinese samples

is

higher than

that

o the Borresperse samples. Borresperse CA-SA has a much lower air entrainment than the other

samples. The need for defoaming agent needed to control the air entrainment is thus the lowest with

this material.

The difference between the set time with the different samples is

in the data set without defoaming

agent reduced relative to the data-set with 0.8 TBP, The initial slump is lower with the Chinese

samples than with the Borresperse samples.

444


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200r--------------------------------,

2 0 0 - - - - - - - - - - - - - - - - - - t , - - - ~ ~ ~ - - _ 1

E 5 0 - - - - - - - - - - - - - ~ - - ~ ~ ~ ~ ~ ~ - - ~

..

Q.

1 0 0 - - - - - - - - . ~ ~ ~ ~ - - - - - - - - - - - - - - _ 1

iii

0 0 ~ ~ ~ ~ ~ ~ - - - - - - - - - - - - - - - - - - - - _ 1

O - - - ~ - - ~ - - - - ~ - - ~ - - ~ - - ~ - - ~

0 00 0 10 0 20 0 30 0 40 0 50 0 60 0 70

Dosage rio sbwc)

30 0

-,----------------------------------,

25 0 --------------------------/------\

~ 20 0 t - - - - - - - - - - - - - : : : : t===----1

c.

i

15 0

+----------------; ;"-, .-: i is; ; , . . .-e ' - ' -----------\

I/) 10 0

+ - - - - - - - - - - : : l ~ ; : : i : ; ; : ; . . = = - - - - - - - - - - - - - - - - - - - \

5 0 . ,= - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -1

0 0

- - - ~ - - _ _ _ _ , - - - - _ , _ - - _ _

- - - .__- -_ ,_- - - -

5 0

4,5

4 0

~ 3 5

"0

~

3 0

... 2 5

c

8 2 0

C

1 5

1 0

0 5

0 0

0 00 0 10 0 20 0 30 0 40 0 00 0 60 0 70

Dosage rio sbwc)

T

r

../

J..

~ - - -

-l

-

F

: : :

-

--

-- . - , " " . ~

0 00 0 10

0,20

0 30

0 40

0 50 0 60

0 70

Dosage rio sbwc)

Borresperse CA

_ _ _ _ Borresperse CA-SA

- - t - - -

Chinese Sample I

--* --

Chinese Sample H

-

-lI(

-

Chinese Sample A

Borresperse CA


- - t - - -

Chinese Sample I

-. * . -

Chinese Sample H

- -lI( - Chinese Sample A

Borresperse CA

_ _ _ _

Borresperse CA-SA

- - t - - -

Chinese Sample I

. -* . -

Chinese Sample H

- -lI( - Chinese Sample A

Figure

2

he concrete performance as function o dosage for all samples with 0,8 defoaming agent

TBP).

he

slump is shown at the top. The set time is shown

in

the middle and the air content

o the

fresh concrete is shown at the bottom.

445


9/13


10/13

96.88

> : SA

90.63

84.38

78.13

71.88

65.63

59.38

53.13

46.88

40.63

34.38

28.13

-' .

21.88

..,.

,

15.63

9.38

3.13

-

5

10

15

20

25

30

Figure

6

Normal probability plot

of

set time

of

concrete with 0.8 defoaming agent (TBP).

PC

.

.

.

RESULT2.X.eJIi

64 1,,2PJ.

Scores

.

peA

1 2 ...

X-ex lained:

64

.

27

orrelation Loadin

1 0

PCZ

5

10

Fef

10

RESU.T2.

X-flJ;lt 64 1t..21 1.

0 5

Figure

7

Scores and loadings calculated for the concrete performance data

of

the concrete with 0.8

defoaming agent (TBP). Outliers are eliminated from the data set.

iii'

D-

i

c

e

i

ci

E

8

Figure

8

The compressive strength of the concrete with 0.8 defoaming agent (TBP).

447

P f

10


11/13

25,0 -.-----------------

20,0 - I - - - - - - I ~ - : : - - - - - - - - - - I

.

::

g 15,0 - I - - - - - - - - ~ ~ ~ - - - - - - - l

1:

"

10,0 - I - - - - - - ~ ~ i 1 i _ - - - - - - l

8

.c

5 0

+ - - - - - - - - - - ~ ~ ~ - - - - - 1

0,0

~ - . . . . , . . . . - _ _ _ . _ - - r _ _ - . . . . _ - _ _ , _ ~ H

0,0 5,0 10,0 15,0 20,0 25,0 30,0

Set time [h]

- + - - Borresperse CA

Borresperse CA-SA

Chinese Sample I

- - -x - -

Chinese Sample H

- * - Chinese Sample A

Figure 9

The

24 hours compressive strength as function o the set time for the concrete with 0.8

TBP

Conclusion

There are chemical differences and performance differences between the samples investigated,

The molecular weight

is

the highest for Borresperse CA and the lowest for the Chinese

samples. All the three Chinese samples have

the same

molecular weight distribution. The Chinese

samples are Mg lignosulphonate

and

the Borresperse samples are

Ca

lignosulphonate. The Chinese I

sample contain a high amount of insoluble.

The air entrainment is the lowest with Borresperse CA-SA and the highest with the Chinese

samples, The air entrainment affects the compressive strength. The compressive strength is lower

with

the

admixture samples entraining the most air than with

the

admixture samples entraining the

least air

The Chinese samples contain chloride

in

high concentration. Chloride can be harm full

in

reinforced concrete and these lignosulfonates are thus not suitable for formulation of concrete

admixtures.

5 Reference

Gustafsson,

J.

and Reknes,

K.

Adsorption

and

dispersing properties of lignosulfonate

in

model

suspensions and cement pastes, Proceedings of the Sixth CAN M ET/AC I International

Conference on Superplasticizers

and

Other Chemical Admixtures in Concrete, Nice, October,

2000

/2/ Reknes,

K.

and Gustafsson,

J.

Effect of modifications oflignosulfonate

on

adsorption

on

cement

and fresh concrete properties, Proceedings ofthe Sixth CANMET/ACI International Conference

on Superplasticizers and Other Chemical Admixtures in Concrete, Nice, October, 2000

448


12/13

0.20 sbwc

80,0

70,0

f

60,0

::5

50,0

tj,

~ ' ; ~

~ . - .

I

;

40,0

Q.

30,0

1

E

c 20,0

IJ

10,0

0,0

0

0.40 sbwc

90,0

80,0

ii

70,0

Q..

i

60,0

. :

i

50,0

1: 40,0

II

~ 30,0

c 20,0

10,0

0,0

0

0.60 sbwc

80,0

70,0

f

60,0

::5

50,0

tj,

; 40,0

7 14 21

28

Time [days]

7 14

21 28

Time [days]

=:;::t

~ - - -

.

:,.:.:..- -:..::-+

. : : . . ; -

~ :

/ /

II

.

30,0

20,0

10,0

0,0

.J

o

7

14 21 28

Time [days]

5

5

35

_ _ _ _ Borresperse CA

Borresperse CASA

-+ - -Ch inese

Sample I

..

*

..

Chinese Sample H

-

*

-

Chinese Sample A

----

Borresperse CA

Borresperse CA-5A

- --

Chinese Sample I

Chinese Sample H

-

*

-

Chinese Sample A

_ _ _ _

Borresperse CA

Borresperse CASA

- --

Chinese Sample I

..

* ..Chinese Sample H

-

*

- Chinese Sample A

Figure 10 The compressive strength as function of ime for the concrete with 0.8 defoaming agent

TBP).

449


13/13

250

200

E 150

.E.

co

E

100

iii

50

a

0 00

30 0

25 0

_ 20 0

=.

15 0

' ;

II

10 0

5 0

0 0

0 00

10 0

9 0

8 0

0

7 0

a

6 0

5 0

0

4 0

3 0

2 0

1 0

0 0

0 00

0 10

0 20

0 30

0 40 0 50 0 60

0 70

Dosage

r o

sbwc)

0 10 0 20 0 30 0 40 0 50

0 60 0 70

Dosage

[ sbwc

0 10 0 20 0 30 0 40 0 50 0 60 0 70

Dosage r o

sbwc)

- - + -

Borresperse CA


- --- Chinese Sample I

- - .)

chemistry and performance of different lignosulfonates

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