Hydraulic binder made
with Calcium Sulpho
Aluminate clinker
user manual
Special Products
Buzzi Unicem Next
the line of binders made
with Calcium
Sulpho Aluminate
Calcium Sulpho Aluminate clinker is obtained by
burning Bauxite, Gypsum and Limestone in an industrial
rotating kiln at a temperature of approximately 1,300°C
and by subsequently grinding it.
Below is the composition of the raw materials:
Limestone ≈ 30 % – 40 % –>main source of CaO
Bauxite ≈ 35 % – 45 % –> main source of
Al2O3 , Fe2O3 and SiO2
Gypsum ≈ 20 % – 30 % –> main source of CaSO4
The main mineralogical phase obtained from the
burning process is Calcium Sulpho Aluminate:
4CaO + 3Al 2 O 3 + SO 3
–>
4CaO 3Al 2 O 3 SO 3
(Yeelimite)
Buzzi Unicem identifies with the name Next
a family of innovative binders made in Italy
capable of opening a new frontier in the field
of constructions and, specifically, of hydraulic
binders with high performances.
The hardening of each one of these binders
is mainly due to the hydration reaction of
the Calcium Sulpho Aluminate (CSA), unlike
Portland cements and aluminous cements for
which hardening takes place following the
hydration of Calcium Silicates and Calcium
Aluminates.
Next binders are recommended in the
pre-mix dry mortar and precast sectors,
which require quick setting, fast development
of strength, use at low temperatures, low
shrinkage and resistance to sulphate attacks.
Electron microscope scanning of one grain of Calcium
Sulpho Aluminate observed during the formation phase
at a temperature of approximately 150°C less than the
optimal firing temperature. Three areas can be clearly
observed: the dark internal area, rich in Aluminium
Oxide (Al2O3), the lighter external area rich in Calcium
Sulphate (CaSO4), and the intermediate one in which
the Calcium Sulpho Aluminate has already formed
(4CaO Al2O3 SO3).
Buzzi Unicem “Next” line of binders
The hydration reaction of the Calcium Sulpho
Aluminate leads to the quick formation of nonexpansive Ettringite, Hydrate Monocalcium Sulpho
Aluminate and, partially, amorphous Aluminium
Hydroxide. In order for this reaction to fully
develop, the presence of Calcium Sulphate is
necessary, as indicated in the following formula:
C4A3Ŝ + 2CŜ + 38H –> C6A Ŝ3H32 + 2AH3 (1)
Where:
Belite Dicalcium Silicate crystal (C2S) under electron
microscope scanning; Belite represents the mineralogical
phase which hydrates during long curing periods in CSA
cement.
CŜ Calcium Sulphate
C4A3Ŝ Calcium Sulpho Aluminate
C6A Ŝ3H32 Ettringite
AH3
Aluminium Hydroxide
H
water
Scanning carried out on Next base using an electron microscope 24 hours after the hydration: it can be clearly
observed that the crystals of non-expansive Ettringite with their typical prismatic shape whose reaction is described by
formula (1).
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At ordinary water/cement ratios (0.40 < w/c < 0.55),
mortar and concrete prepared with CSA clinker show
an extremely reduced capillarity together with a very
fast drying of the hardened paste, as a result of the
quick hydration reaction.
Moreover, it is interesting to note how the quick
formation of Ettringite prismatic crystals (which take
up approximately twice the space occupied by the
CSA molecule that generates it) is responsible for the
formation of a much less porous and more compact
structure in short curing periods compared to the
one produced by the Calcium Hydrate Silicate crystals
(C-S-H) in ordinary Portland cements. In the long
term, we can say that the microstructure of the two
systems looks very similar.
The sulfoaluminate clinker made by Buzzi Unicem has
the following average characteristics.
Environmental
sustainability
Binders made with Calcium Sulpho
Aluminate can be considered
eco-sustainable for the following reasons:
• The production cycle is characterized by
reduced CO2 emissions in the environment
for the low content of Calcium Carbonate
Physical characteristics
Characteristics Standard
Average values
density
2,800 kg/m3
spec. surface Blaine
UNI EN 196-6
4,800 cm2/g
colour light grey
C4A3Ŝ Calcium Silicate C2S Calcium Sulphate
CŜ
Calcium Aluminate
C3A Brownmillerite
C4AF free Lime
C
consumption during the firing phase.
• Compared to Portland cement, the energy
impact is lower, since the temperatures
reached in the kiln during meal firing
Mineralogical composition
Calcium Sulpho Aluminate
among raw materials and for the lower fuel
> 50%
25%
5%
5
3%
< 1%
are approximately 200°C less than the
temperatures used for the production of
regular Portland clinker.
• CSA clinker requires less grinding energy
compared to Portland clinker.
• The following table can be used to compare
CO2 emissions in terms of m tons of CO2
Chemical analysis
per m ton of binding product. The values
CaO
44.0%
Al2O3
26.5%
SiO2
9.5%
SO3
12.0%
F2O3
2.5%
MgO 1.3%
TiO2
1.3%
Na2O
0.6%
K2O
0.6%
are expressed as percentages with respect to
Portland cement.
CEM I 42.5 R Next base Next binder
Emissions for
calcination
100% 36%
56%
Total
emissions
100% 56%
65%
Next base
Next base
The characteristics
Mechanical performances
Buzzi Unicem indicates with the name of Next
base a binder consisting of a mix of CSA clinker
and Anhydrite at a ratio guaranteeing that all the
C4A3Ŝ content, if hydrated, turns into non-expansive
Ettringite.
Product performances are characterized by constant
quality over time, a result of the fact that Next base
is a product obtained through mixing. In fact, through
the measured dosing of specific mineral admixtures,
the natural variability of the raw material of which it
is made up can be compensated. The properties thus
obtained make it possible to use Next base both by
itself as a fast binder and in ternary systems in order
to obtain a high number of products characterized by
low shrinkage and fast development of mechanical
strength.
Graphs that show the average development of
strength of standard mortar prepared with Next base
are stated below.
Development of average compressive strength
Compressive strength [ MPa ]
during the first 24 h
50
40
30
20
10
0
0
4
8
12
16
20
24
Time [ h ]
The average values of the physical and chemical
characteristics of Next base are specified below.
Development of average compressive strength
Calcium Sulpho Aluminate
C4A3Ŝ > 40%
Calcium Silicate C2S 20%
Calcium Sulphate (Anhydrite)
CŜ
25%
Calcium Aluminate
C3A 5%
Brownmillerite
C4AF 3%
free Lime
C
< 1%
Compressive strength [ MPa ]
during the first 28 days
Mineralogical composition
70
60
50
40
30
0
7
14
21
28
Time [ days ]
Chemical analysis
43.0%
Development of average compressive strength
Al2O3
20.5%
during the first year
SiO2
7.0%
SO3
22.0%
F2O3
2.0%
MgO 1.0%
TiO2
1.0%
Na2O
0.5%
K2O
0.5%
Compressive strength [ MPa ]
CaO
90
80
70
60
50
40
0
Time [ days ]
90
180
270
360
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Intensity [ cps ]
The graphs show that the values of compressive
strength, calculated in standard mortar, reached after
just a few hours are values that traditional Portland
cement reaches after one week. Strength continues
to increase at a slower rate but gradually as time
goes by.
It is however possible to change the mortar
performaces by varying the water/binder ratio (using
water-reducing admixtures) or using accelerator
admixtures (Lithium Carbonate) and retarder
admixtures (Citric Acid and Tartaric Acid).
The performances offered by Next base stay
16000
constant over time, with no risk of loss of strength
in the long term or of dimensional changes caused
by delayed formation of Ettringite (expansions) or
shrinkages. The diffractograms below show the
results of the analysis carried out using an X-Ray
Diffractometer (XRD*) on a sample of non-hydrated
Next base and 3h, 16h and 1 year after the
hydration: it can be seen that 16 hours after the
mixing with water, the free Calcium Sulphate has
practically disappeared and that the diffractogram
obtained after only 16 hours (green) does not differ
much from the one obtained after about one year
(blue).
Ettringite
14000
C4A3Ŝ
CŜ
12000
10000
8000
6000
4000
2000
0
5
Angle [ 2 theta ]
10
15
20
25
30
35
40
Hydrated Next base, after 1 year
Hydrated Next base after 16h
Hydrated Next base after 3h
Anhydrous Next base
* XRD (X-Rays Powder Diffraction) is an instrumental technique used to determine the mineralogical composition of a
crystalline material: in the diffractograms shown above, the abscissa identifies the diffraction angle while the ordinate
refers to the diffraction intensity of a specific mineralogical phase.
45
Next base
Other performances
Next base is also synonymous of a durable material for the following reasons.
• Next base shows an increase in physical-mechanical
(binder content = 300 kg/m3 and w/b ratio = 0.6)
shows a weight reduction of less than 0.5%.
strength in the long term: the fast transformation
of Ettringite does not inhibit the development of
• The reduced formation of Calcium Hydroxide
medium and long-term strength due to hydration
during the hydration reaction makes the hardened
of the Dicalcium Silicate (C2S), similar to what
product extremely resistant to sulphate attacks, as
happens in Portland cements.
demonstrated by the diagrams provided here below.
The tests, carried out with the method of flat
• The dense crystalline structure, created during
the initial moments of hydration, reduces the
prism samples 10x40x160 mm in compliance with
capillary porosity of the hardened paste, making
standard SVA Flat Prism Method at 5° and at 20°C,
it poorly permeable to the inlet of water and of
show how the mortar samples prepared with
aggressive substances coming from the surrounding
Next base are more resistant to sulphate attacks
environment, which is a sign of excellent durability
even compared to those prepared with a sulphateresistant blast furnace cement (RS according
of the element poured with Next base. Low
to UNI EN 197-1:2011).
permeability to water makes the application using
CSA clinker resistant to attacks by aggressive
• Next base, just like all the other Next products, is
more resistant to aging (prolonged direct contact
The test conducted in compliance with standard
with the environment) compared to all binders
UNI CEN/TS 12390-9 shows that after 100 freezing
prepared with aluminous cements, which are more
and thawing cycles, the cubic sample of concrete
susceptible to water.
Sulphate-attack resistance accelerated test at 5°C
Sulphate-attack resistance accelerated test at 20°C
8
Expansion [ 10-3 ]
Expansion [ 10-3 ]
substances and to freezing and thawing cycles.
7
6
8
7
6
5
5
4
4
3
3
0
0
1
1
0
0
0
20
Time [ days ]
40
60
80
CEM I-HS
100
120
140
CEM III/B-HS
160
180
Next base
0
20
Time [ days ]
40
60
80
CEM I-HS
100
120
140
CEM III/B-HS
160
180
Next base
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Ternary binders prepared with Next base
Next base can be used as a component of mixes
with Portland cement in percentages that vary
from 40% to 60% of the total weight. In fact,
it is possible to obtain products characterized by
fast development of the mechanical strength and by
limited shrinkage without having to use the usual
expansive or Shrinkage Reducing admixture (SRA).
These binders, made by mixing Next base (binary
binder made of CSA clinker and Anhydrite) and
Portland cements are known as ternary binders
as they are made of Calcium Sulpho Aluminate
clinker, Anhydrite and Portland cement.
Portland cement mixed with Next base
significantly changes the hydration processes
of Calcium Sulpho Aluminate: the fast
transformation of Portlandite caused by the
hydration of the C3S contained in Portland
cement, activates the precipitation of expansive
Ettringite according to the hydration reaction
illustrated here below:
C4A3Ŝ + 6CH + 8CŜ + 90H –> 3C6A Ŝ3H32 (2)
Where:
C4A3Ŝ Calcium Sulpho Aluminate
CH
Portlandite - Calcium Hydroxide
CŜ Calcium Sulphate
C6A Ŝ3H32 Ettringite
Reaction (2) requires a greater quantity of water
and Calcium Sulphate compared to the one that
generates non-expansive Ettringite (reaction 1);
Moreover, each amount of Calcium Sulpho Aluminate
yields 3 amounts of Ettringite, unlike what happens
in the hydration reaction with no Portlandite (1).
Once the reaction ends, its products remain
dimensionally stable.
Electron microscope scanning of Next base in a mix with Portland cement 6 hours after hydration. The diffused
formation of small ettringite crystals capable of compensating for the shrinkage can be observed.
Next base
In this case too, the performances (setting time and
development of strength) can be modified by using
retarder and accelerator admixture, such as Citric
Acid, Tartaric Acid, Lithium Carbonate and Calcium
Oxide. The binder obtained with this method can
be used in combination with all materials and
admixtures commonly used in the construction
industry.
In addition to Next base, other ready-to-use
products made with Calcium Sulpho Aluminate for
special applications can be requested.
Next clinker:
finely ground clinker made with Calcium Sulpho
Aluminate suited for accelerating the setting time of
Portland cement used for the preparation of mortars,
hydraulic adhesives and other pre-mix dry products.
Next binder:
ready-to-use ternary binder for pre-mix dry mortar
and small prefabrication industry.
In order to make it easier to understand the
relationships that bind the different formulations,
please find below a scheme that shows how you can
go from one formulation to the other.
Production process diagram of Next formulations
BAUXITE
LIMESTONE
GYPSUM
KILN
NEXT CLINKER
NEXT CLINKER
SULPHO ALUMINATE
CLINKER
CEMENT SETTING
A C C E L E R AT O R
NEXT BASE
ANHYDRITE
CITRIC OR
TARTARIC ACID
NEXT CLINKER
LITHIUM
CARBONATE
MILL
MIXER
NEXT BINDER
PORTLAND
CEMENT
ANHYDRITE
CITRIC OR
TARTARIC ACID
LITHIUM
CARBONATE
H I G H P E R F O R M A N C E M O RTA R
T E R N A RY P R O D U C T S
MIXER
P R E - M I X D RY P R O D U C T S
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Ternary diagrams
The ternary diagrams illustrated below describe in graph form the possible binder formulations that can be
obtained by the mixing of CSA clinker, Calcium Sulphate and Portland cements. It is possible to pinpoint three
areas that identify three different levels of performances that can be achieved by using the family of Next binders.
Area that corresponds to formulations of binders
consisting of Portland cements with accelerated
setting in proportion to the content of Next clinker.
times; they also represent the ideal starting
products for the design of ternary binders.
Area that corresponds to ternary systems, which
allow, in products to which they are added,
optimized balance between quick setting times,
fast development of strength, quick drying and
dimensional stability (such as Next binder).
Area that corresponds to binary systems made
with Next clinker and Calcium Sulphate, to
which Next base belongs, characterized by high
mechanical performances and shorter setting
100
Su
um
lci
20
30
60
40
50
50
40
nt
Ca
70
10
me
100
80
Ce
lph
ate
90
60
30
70
20
80
10
10
80
100
Next clinker
20
70
30
ium
40
50
50
40
t
Ca
lc
Next clinker
Proper diagram reading
method
n
me
60
Composition with
fast development of
strength
60
30
70
20
Compositions with
low shrinkage and
fast development
of strength
80
10
90
100
100
90
80
70
60
50
90
100 90 80 70 60 50 40 30 20 10
Ce
Su
lph
ate
90
40
Next clinker
30
20
10
Accelerator for
Portland cement
Next base
Fields of application of Next base
Next base is the ideal product for a large number of applications in the prefabrication and pre-mix dry
mortars industry.
1. High strength mortars and Hydraulic adhesives.
7. Latest-generation self-levelling screeds.
2. Quick-hardening pre-mix dry mortar and concrete.
8. Quick-drying self-levelling screeds.
3. Pre-mix dry mortar and concrete for applications
at low temperatures.
9. Self-levelling screeds with low risk Alkali-Silica
Reaction (ASR).
4. Pre-mix dry mortar and concrete with low
permeability and high resistance to sulphates.
5. Pre-mixed mortar and concrete packaged in bags
that retain their performances after the package
has been opened for a longer time compared
to the same products made with aluminous
cements.
6. Injection and shotcrete products.
10. Self-levelling screeds subject to sulphate attack or
to freezing and thawing cycles.
11. Small precast elements that must be quickly
removed from the formworks.
12. Small precast elements of any colour.
13. Small precast elements with high resistance to
sulphates and to freezing and thawing cycles.
Conclusions
Next base is the ideal binder for a large number of
applications in the precast and pre-mix dry products
industry because, when mixed with Portland
cements in percentages that may vary from 40%
to 60%, it allows the formulation of products
characterized by fast development of the strengths
and low shrinkage.
The performances of ternary mixes made with
CSA clinker, such as, for example, setting times
and workability, consistency, drying speed, and so
on, can be optimized by using traditional chemical
admixtures: setting regulators (Lithium Carbonate
and Citric Acid being the most recommended
ones), plasticizers (Naphthalene Sulphonates and
Polycarboxylate Ethers), accelerators, retarders,
aerating, etc.
Of course, as for traditional cement, the addition of
each element requires a suitable experimentation
phase in order to verify the expected performances,
especially in view of the large number of cements
and admixtures available today on the market.
In this phase, Buzzi Unicem is available to assist its
customers in the design of ternary systems through
its technical assistance service.
Next | user manual
Other Next formulations
In addition to the Next base binder, other ready-to-use formulations made with Calcium Sulpho Aluminate
are available for special applications: Next clinker and Next binder.
Next clinker
Next clinker identifies the finely ground CSA
clinker. When used in mixes with Portland cement in
percentages included between 6% and 10% it speeds
up setting and initial hardening time. By increasing
the dosing up to a maximum of 30%, mixed with
cements CEM I 52,5 R, it allows the formulation
of binders for quick-setting mortars. The diagrams
provided here below describe the effects obtained
following the addition of Next clinker to a cement
CEM II/A-LL 42,5 R.
Time of workability at 20°C [ min ]
Workability Portland - Next clinker
160
140
120
100
Both binders use as raw materials Bauxite which,
following industrial burning, originates compounds
made with Calcium Aluminates (especially CA and
C12A7) in aluminous cement and Calcium Sulpho
Aluminate in Next clinker. In presence of water and
Calcium Sulphate, they both react quickly to form
Ettringite. Both binders can be used to accelerate
Portland cements or to prepare quick-setting
products or ternary products with low shrinkage
mixed with Portland cement and Anhydrite. Since
the hydration reaction of these products produces a
smaller quantity of Portlandite compared to ordinary
Portland cements, the both offer excellent resistance
to sulphate attacks and to washing out.
80
60
Below is a list of the main characteristic of the
two binders, many of which are transferred to the
formulations in which they are used.
40
20
0
0
5
10
15
20
25
30
Next clinker [ % ]
Mixes CEM II/A-LL 42,5 R and Next clinker
Compressive strength at 20°C [ MPa ]
Differences between binders made with
aluminous cement and Next clinker
20
1. Next clinker lasts longer than aluminous
cements, both in its original packaging and when
added to products, with no significant loss of its
performance characteristics.
2. Next clinker, due to its reduced iron content
compared to aluminous cements, shows a grey
colour that is lighter and more constant in time.
16
12
3. Next clinker is fired at a lower temperature
compared to aluminous cement, thus reducing
the impact on the environment.
8
4
0
0
Time [ h ]
4
8
12
16
30%
20
7%
24
0%
4. It is worthy to point out, however, that
Next clinker cannot be used as binder for
applications as refractory material, as can be done
with certain categories of aluminous cements.
Other Next formulations
Next binder
Next binder is a ready-to-use hydraulic binder
in which the percentages of CSA clinker, Calcium
Sulphate, Portland cement and setting-regulator
admixtures have been optimized in order to
guarantee performances suited for the preparation of
self-levelling screed or of fast precast.
In fact, Next binder can be used as ordinary
cement to prepare mixes with low shrinkage, fast
development of mechanical strength and
quick drying.
Next binder can also be obtained by mixing Portland
cement with the formulation Next SN05. This
solution reduces transportation costs and allows
the final user to choose type, class and colour of
the Portland cement to be used. Naturally, the
binder thus obtained requires a careful preliminary
verification of the performances.
Latest-generation self-levelling
screeds
The trend on the screed market is undoubtedly
pointing in the direction of self-levelling screeds made
with cement. Next binder can be used to prepare
self-levelling screeds with significant dimensional
stability, low shrinkage, quick drying and excellent
strength in short curing (operational in short time).
These properties are obtained thanks to a special
formulation that takes advantage of innovative
hydration reactions which are not the result of the
use of expansive or SRA admixtures.
The table on the right shows the mix, for 1 m3 of
self-levelling screed prepared with Next binder,
with the relevant characteristic performances. By
varying the content of binders in the mix and dosing
the admixtures as desired, you can obtain a wide
range of self-levelling screeds with different costs
and performances.
Next binder (SL06) is recommended for all producers
and placing operators of pre-mix dry mortar for
self-levelling cementitious screeds, due to the
constant performances and the possibility to manage
only one binder in their formulations.
Example of mix design for self-levelling screed.
Raw material
u.o.m. Quantity
Next binder
Kg/m3
350
Citric Acid
kg/m3
1.5
Limestone filler
Kg/m3
250
Kg/m3
1,400
l/m3
260
acrylic plasticizer powder admixture
sand 0-4
water
Performance
Test Avg.
method
u.o.m. values
workability at 20°C
Internal method* minutes
60
setting start time
Internal method* minutes
75
setting end time
Internal method* minutes
85
flow
Internal method**
mm
230
µm/m
250
hydr. shrinkage (l0 at 2h) UNI 6687-73
* tests carried out with penetrometer
** test carried out with truncated-conical ring conforming to
standard UNI 7044 (average of diameters)
Curing
Average compressive
strength [MPa]
5h
5.0
24h
14.0
7 days
27.0
28 days
35.0
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Quick precast
In order to quickly meet the needs of its customers
in terms of reducing storage and curing costs, and
to shorten the time-to-market, the precast industry
can benefit from the use of an innovative product
such as Next binder.
This phenomenon is particularly felt in the field of
small precast, such as tiles, self-locking concrete
blocks, panels, etc, where the number of pieces
made with a single mould is higher. In fact, with
Next binder curing time deriving from the use
of Portland cement can be reduced and removal
of the formwork can be speed up. Moreover, the
quick development of mechanical strength offered
by these binders in no way reduces the strength to
medium and long curing time.
Next binder can be used in any type of mix
from humid to fluid consistency, up to the
self-compacting one.
The table on the right shows the mix for 1 m3
of concrete prepared with Next Binder for the
construction of prefabricated elements in fluid
consistency, with the relevant characteristic
performances measured at 20°C.
Example of mix design for quick-setting concrete with
fluid consistency for precast use.
The table on the right shows the mix for 1 m3
of a mortar prepared with Next binder for the
construction of precast elements in humid consistency,
with the relevant characteristic performances
measured at 20°C, comparing it with a similar mix
prepared with 350 kg of cement CEM II/A-LL 42,5 R.
Example of mix design for quick mortar in humid
consistency for precast. In the page at the side, the
comparison with a similar mortar prepared using 350 kg
of cement CEM II/A-LL 42.5 R is shown.
Raw material
u.o.m
Quantity
Next binder (SL06)
Kg/m3
330
sand
kg/m3
1,064
gravel 4-20
Kg/m3
764
l/m3 170
mm
160
water
super plasticizer admixture
slump
water/binder ratio
Curing
0.51
Average compressive
strength [MPa]
5h
15
24h
20
28 days
40
Raw material
u.o.m
Quantity
Next binder (SL06)
Kg/m3
290
sand
kg/m3
1,760
gravel 5-8
Kg/m3
320
l/m3 110
water
plasticising admixture
Other Next formulations
Kerbs made using Next binder (SL06)
Comparison of strength in the first 24h
Indirect Tensile Strength [ MPa ]
Indirect tensile strength tests were carried out in
compliance with standard UNI EN 12390-6 and on
cylindrical samples (diameter = height = 100 mm)
prepared with compactor according to standard
NT Build 427 (NORDTEST Scandinavian method),
which guarantees good repeatability in laboratory.
The results obtained from the comparative analyses
of mixes prepared with Portland cement and with
Next binder (SL06) are shown in the graph at
the side. It is possible to observe how the use
of Next binder significantly affects strength in
extremely short curing periods. In 28 days, the two
formulations offered the same strength.
2,0
1,5
1,0
0,5
0
0
Time [ h ]
6
12
CEM II/A-LL 42,5 R
18
24
Next binder (SL06)
CA.05 13.500
Note: The instructions provided above are the result of our best experience and are merely indicative. No responsibility is taken for
defects or damages caused by misuse of the product or when the conditions of its use differ from our instructions. The Technical Assistance
Department is always available for any advice and suggestions concerning proper use of the product and for the performance of technical tests.
Buzzi Unicem S.p.A
via Luigi Buzzi, 6
15033 Casale Monferrato [AL]
Italia
tel +39 0142 416219
fax +39 0142 416320
[email protected]
www.buzziunicem.it