A lignosulphonate superplasticizer for concrete
dr. Kåre Reknes1), Prashant Jha2), Surendra Sharma2), Philip Chuah3)
1) Borregaard Ind. Ltd., LignoTech, Sarpsborg, Norway
2) Elkem Borregaard India, Mumbai, India
3) Borregaard South East Asia, Singapore
Abstract: Lignosulphonate have been used as plasticizer for concrete for decades. It has a well documented and proven
performance. The cost/performance ratio of lignosulphonate is very good. A novel lignosulphonate superplasticizer has been
developed. The performance is achieved by modification of the lignosulphonate. The workability retention with the
lignosulphonate superplasticizer is extremely good. The water reduction and the workability retention are improving with
increasing temperature whilst the same performance of NSF is being reduced by the same temperature change. This is a unique
property of the lignosulphonate superplasticizer. Field tests with the novel lignosulphonate superplasticizer were conducted in
different regions. The teste were carried out in concrete containing, OPC, PPC and combination of OPC and GGBS.
Key words: lignosulphonate, superplasticizer,
1 INTRODUCTION
Lignosulphonate have been used as plasticizer for concrete
for decades. It has a well documented and proven
performance. The cost/performance ratio of
lignosulphonate is in general very good. The water
reduction of lignosulphonate plasticizing admixtures is in
the range of 8-12 %. This is depending on the type and
quality of the lignosulphonate. The main limiting factor for
the use of lignosulphonate is in many cases the set
retardation caused by increased dosage.
A novel lignosulphonate superplasticizer has been
developed. The performance is achieved by modification of
the lignosulphonate and not through making a formulation.
The water reduction is in the range of 20-30 % with set
retardation in the order of that achieved with NSF-based
superplasticizing admixtures. The workability retention
with the lignosulphonate superplasticizer is extremely good
(Banfill 2007). The water reduction and the workability
retention are improving with increasing temperature whilst
the same performance of NSF is being reduced by the same
temperature change (Wallevik 2003). This is a unique
property of the lignosulphonate superplasticizer.
Development versions of the new lignosulphonate
superplasticizer have been used in designing selfcompacting
concrete (Reknes, 2003) (Petersen 2003)
(Reknes 2001).
This article discusses test results obtained in field tests with
the novel lignosulphonate superplasticizer in different
regions. The tests were conducted at ready mixed concrete
plants to verify the performance of the new lignosulphonate
superplasticizer under real field conditions.
2 EXPERIMENTAL
2.1 General
A series of tests with the new lignosulphonate
superplasticizer (LSS) were conducted at different ready
mixed concrete plants. The LSS was tested against
superplasticizers in use at the different ready mixed
concrete plants using a concrete mix proportion run daily at
the plant: medium to high strength and low w/c. The
concrete mix proportion selected for the testing represented
a substantial volume of concrete produced at that plant.
2.2 Laboratory testing
The admixture dosage and mix proportion parameters were
adjusted and optimised in a series of laboratory trials at the
actual concrete plant before going into full scale testing.
The plasticizer and superplasticizer combination used at the
plant was substituted by LSS and the dosage of LSS was
adjusted to produce concrete with the same performance as
the original concrete.
2.3 Field testing
After having conducted the laboratory optimisation of LSS
dosage a series of tests were run at the ready mixed
concrete plant. The first concrete to be batched in the series
was the control concrete containing the plasticizer and
superplasticizer combination being used in the plant. The
admixtures were then substituted by LSS at the dosage
identified during the laboratory program. The LSS dosage
had in all cases to be adjusted (reduced) as it was more
effective in the plant than in the laboratory. The following
concrete parameters were determined:
⇒ Workability and workability retention
⇒ Air content and fresh density
⇒ Compressive strength at 1-3 days, 7 days and 28
days.
The main performance parameter was the workability at 60
minutes in all the tests. This was the main criteria as
workability retention was typically required for 60 minutes.
A target slump after 60 minutes was defined as “required
delivered slump on the construction site after 60 minutes”.
3 RESULTS AND DISCUSSION
3.1 Singapore
A concrete mix proportion containing 380 kg of OPC was
selected for the testing. The w/c ratio was 0.437. The
admixture combination used in the concrete was a
plasticizer and superplasticizer at the ratio 1.00:1.06
plasticizer to superplasticizer. The superplasticizer was
added to the concrete through the dosing equipment at the
ready mixed concrete plant whilst the LSS was added
manually directly into the concrete pan mixer.
The batch size at the laboratory was 60 litre of concrete
batched in a 100 litre capacity mixer. The batch size in the
ready mixed concrete plant was 2 m3. The concrete was
stored in a concrete truck mixer during the testing period.
The concrete truck was parked in the sunlight to simulate
typical Singapore driving conditions. All concrete samples
were taken from the back of the truck. The concrete was
remixed at maximum drum speed for approximately 2
minutes prior to each sampling. The concrete temperature
was approximately 27 oC.
The new lignosulphonate superplasticizer was much more
dosage effective than the admixture combination used. The
same workability and workability retention was produced
with the LSS as with the plasticizer and superplasticizer
combination used. This is shown in Figure 1. The dosage of
LSS needed to do this was much lower than the admixture
dosage used in the concrete. The relationship between the
admixture dosage and dosage of LSS to produce the same
initial slump, the same slump after 60 minutes and the same
slump after 60 minutes with 30 kg less cement in the
concrete is shown in Figure 2.
The dosage of LSS needed to produce the same slump as
the admixture after 60 minutes was approximately 60 % of
the total admixture dosage, calculated as polymer (solids)
dosage.
The compressive strength was lower with LSS than with
the admixtures (Figure 4). A minor adjustment of the w/cratio
is expected to have corrected this.
0
25
50
75
100
125
150
175
0 30 60 90 120
Time [min]
Slump [mm]
Superplasticizer
LSS + less cement: 30 kg
LSS
Figure 1 The concrete workability as function of time for
the superplasticizer concrete, the LSS concrete and
the LSS concrete with 30 kg less cement per m3 of
concrete.
Figure 2 The dosage of LSS (yellow) vs dosage of
superplasticizer (grey) needed to produced the
required workability. The dosage is calculated on
amount of polymer (DM = dry matter).
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0 7 14 21 28 35
Time [days]
Compressive strength [MPa]
Superplasticizer
LSS + less cement: 30 kg
LSS
Figure 3 The compressive strength as function of time.
3.2 Dubai
The concrete mix proportions selected for the testing was a
60 MPa concrete with high durability. The w/c ratio was
0.33. The concrete contained 210 kg of OPC, 210 kg of
slag (GGBS) and 15 kg of micro silica per m3 of concrete.
There was also a substantial amount of dune sand in the
mix. The concrete produced was cohesive. The admixture
used was a NFS based superplasticizer. The
superplasticizer was added to the concrete through the
dosing equipment at the ready mixed concrete plant. The
LSS container was also connected to the admixture
dispenser system in the plant and LSS was added through
the computerised dosing system.
The batch size in the concrete laboratory was 35 litre. 3 m3
of concrete was batched during the testing in the ready
mixed concrete plant. The truck size was 9 m3. The
concrete was stored in a concrete truck, parked in the
sunlight to simulate Dubai driving conditions. The air
temperature was “cold” during the testing period: only 24
oC.
The LSS produced concrete with very good workability
retention. The workability after 60 minutes was much
higher with LSS than with the NFS based superplasticizer,
starting at the same initial workability. This is shown in
Figure 4. The dosage of LSS was adjusted to produce the
same workability after 60 minutes as the NFS-based
superplasticizer did. Then the concrete mix proportions
were adjusted and the cement content was reduced by 10 kg
per m3 of concrete. The workability with LSS was much
better than with the NFS-based superplasticizer also after
the cement reduction of 10 kg per m3 of concrete.
The relationship between dosage of LSS and the NFS based
superplasticizer to produce the same initial slump, the same
slump after 60 minutes and the same slump after 60
minutes with 10 kg less cement is show in Figure 5. The
dosage of LSS needed is 60-80 % of that of the NFS based
superplasticizer.
The compressive strength and strength development was
the same for all the three concrete mixes.
0
50
100
150
200
250
0 15 30 45 60 75 90 105
Time [min]
Slump [mm]
LSS
LSS + less cement: 10 kg
Superplasticizer
Figure 4 The concrete workability as function of time for
the superplasticizer concrete, the LSS concrete and
the LSS concrete with 10 kg less cement per m3 of
concrete.
Figure 5 The dosage of LSS (yellow) vs dosage of
superplasticizer needed to produced the reuired
workability.
3.3 Mumbai
A concrete mix proportion containing 380 kg of a PPC per
m3 was selected for the testing. The superplasticizer used in
that concrete was a pure NFS. W/c was 0.587 in all the
concrete mixes. The superplasticizer was added to the
concrete through the dosing equipment at the ready mixed
concrete plant whilst the LSS was added manually directly
into the concrete pan mixer.
The batch size in the laboratory was 30 litres. 1 m3 was
batched at the ready mixed concrete plant. Totally 2 m3 of
concrete was made for each admixture and dosage
combination, i.e. for each test. The 2 m3 of concrete was
stored in a concrete truck mixer on slow agitation during
the testing period. The concrete was re-mixed before
sample was taken from the truck. The concrete truck was
parked in the sunlight during the testing period to simulate
the conditions of driving through Mumbai and the heat of
the sun on the concrete. The concrete temperature was
approximately 30 oC.
The effect of admixture dosage on initial workability and
workability retention is shown in Figure 6 and Figure 7.
0
25
50
75
100
125
150
175
200
225
250
0 30 60 90 120
Time [min]
Slump [mm]
Supperplasticizer (0.40 % sbwc)
Superplasticizer (0.48 % sbwc)
LSS (0.60 %)
Figure 6 The concrete workability as function of time and
admixture dosage (% solids by weight of cement).
0
25
50
75
100
125
150
175
200
225
250
0.00 % 0.20 % 0.40 % 0.60 % 0.80 % 1.00 %
Dosage [% sbwc]
Initial slump [mm]
Superplasticizer LSS
Figure 7 The concrete workability as function of admixture
dosage (% solids by weight of cement).
The NFS based superplasticizer produced a slightly higher
initial slump than LSS did with the same dosage (% solids
by weight of cement). The slump retention starting from the
same initial slump was better with LSS than with NFS as
shown in Figure 6. This allowed a reduction in the LSS
dosage to produce the same slump after 60 minutes as with
NFS.
4 CONCLUSIONS
The new modified lignosulphonate superplasticizer (LSS)
produced concrete with higher initial slump and higher
slump after 60 minutes than the alternative superplasticizer
did. The dosage of LSS could be reduced further to copy
the performance of the alternative superplasticizer.
LSS performed very well in the field testing and produced
good workable concrete.
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