CSA cement ( CSA binder )
Introduction
General
characteristics
CSA Cement, also named
Calcium Sulpho Aluminate Cement with grade: 42.5, 52.5, 62.5, 72.5, 82.5, 92.5,
is a hydraulic binder based on calcium sulpho aluminate, rather than calcium
aluminates which are the basis of Calcium Aluminates Cement or calcium
silicates which are the basis of Portland Cement. It can be used on its own
(with a Lithium accelerator), or with an Anhydrite, Portland cement mix, Metakaolin
or a combination of all.
CSA Cement has the benefit
of being readily adaptable to suit many different applications where both rapid
set and / or high early strength gain are required. It yields controlled set,
enhanced early strengths, shrinkage compensation or expansion and sulphate
resistance. Uses include any cement-based product in need of these properties.
CSA Cement products exhibit a range of properties to suit a wide spectrum of
cement-based applications, like fast setting cements, self-leveling or self-smoothing
compounds, self compacting concrete,rapid hardening mortars, tile adhesives,
non-shrink grouts, water stopping mortars, repair mortars, high early strength
concrete, GRC, etc.
Within CSA (Calcium Sulpho
Aluminate) Cement Ettringite formation is typical. Ettringite is an expansive
crystalline substance formed when sulphate reacts with tri-calcium aluminate
(C3A) and calcium hydroxide (Ca(OH)2). It occupies twice the volume of the
original compounds so an expansion occurs. In the CSA Cement, 85% of ettringite
is developed at a very early stage in the process, before the aluminates and
silicates start to hydrate. The risk of late ettringite formation is very
limited and the ettringite which is formed is very stable over time. This is
the fundamental difference between CSA and CAC (Calcium Aluminate Cement)
Cement.
Be it a mortar or a
concrete, making a composite cement which exhibits rapid setting, high early
strength development, with little or no loss of late strength, no risk of
conversion or late formation of ettringite. Depending on the level of addition
of calcium sulphate, either shrinkage compensation or positive expansion can
also be controlled.
Potential advantages of the
CSA Cements are low CO2 emissions, improved sulphate resistance, low
permeability, enhance durability and a good workability at low temperatures.
CSA Cement is manufactured
under a strict quality assurance systems GB/T 19001-2000 (i.e. ISO9001:2000)
and GB/T 24001-1996 (i.e. ISO 14001:1996)) which accommodates the technical
requirements of building chemistry formulators.
Properties
Incorporation of Calcium
Sulpho Aluminated Cement into a variety of mix designs, CSA Cement products exhibit
a range of properties,like :
Rapid Set Adjustable Setting Time High Early Strength
Increased strength in time Minimal Shrinkage Shrinkage compensation
Expansion Sulphate Resistance Reduced Alkalinity
Low CO2Emissions Rheology Adapted to the Application, etc.
Chemical
Analysis
The chemical analysis of
CSA Cement has been determined according to the following:
GB/T 176-1996 Methods of
chemical analysis for cement.
Main
constituents (%)
Component
|
Type I
|
Type II
|
Type III
|
Type IV
|
Type V
|
SiO2
|
≤7.0
|
≤8.5
|
≤10.5
|
||
Al2O3
|
≥36
|
≥35
|
≥34
|
≥32
|
≥28
|
Fe2O3
|
1.5-2.5
|
1.5-3.5
|
1.5-3.5
|
||
CaO
|
40.0-41.5
|
40.5-42.5
|
41.5-43.5
|
||
MgO
|
≤ 3.5
|
≤ 3.5
|
≤ 3.5
|
||
SO3
|
8.5-11.0
|
8.0-10.5
|
7.5-9.5
|
||
TiO2
|
1.0-2.0
|
1.0-2.0
|
1.0-2.0
|
Fineness
Specific Surface Area:
according to standard GB/T 8074-2008:
Usual range: 400(+/-20)
m2/kg, Specification limit: >360 m2/kg;
Usual range: ≥ 480 m2/kg,
Specification limit: >450 m2/kg.
Mineral
composition
C=CaO, A=Al2O3, S=SiO2 ,
F=Fe2O3, S =SO3
−Principal mineral phase:
calcium sulphoaluminate C4A3S-
−Secondary phases: C2S,
C4AF
Notes: This information is
given for reference only.
Hydraulic
Properties
The characteristics of CSA
Cement have been tested in accordance with the Chinese standards: GB20472-2006.
Setting time determined at
20℃,
using Vicat needle according to GB/T 1346-2001.
Mechanical strength at 20℃, 95% relative humidity
according to GB20472-2006 .
Item
|
Type I
|
Type II
|
Type III
|
Type IV
|
Type V
|
|
Bending
Strength
(Mpa)
|
1d
|
≥8.0
|
≥7.0
|
≥6.0
|
||
3d
|
≥10.0
|
≥9.0
|
≥8.0
|
|||
7d
|
≥11.0
|
≥10.0
|
≥9.0
|
|||
Compressive
strength
(Mpa)
|
1d
|
≥60.0
|
≥50.0
|
≥50.0
|
||
3d
|
≥85.0
|
≥75.0
|
≥65.0
|
|||
7d
|
≥95.0
|
≥85.0
|
≥75.0
|
|||
Setting time
|
Initial
|
≥25min
|
≥25min
|
≥25min
|
||
Final
|
≤300min
|
≤300min
|
≤300min
|
|||
Applications
These properties are
applied to obtain a wide range of products:
-
Rapid repair mortars
- Fast
setting tile adhesives
- Fast
setting tile grouts
-
Shot-crete / Gun-nite
-
External renders
- Self
smoothing mortars
- Self
leveling mortars
-
Anchor bolt grouts
- Non
shrinking grouts
- etc.
Use
of Additives
CSA Cement may be used in
combination with chemical additives such as:
-
polymers, either in latex form or redispersible powder form
-
defoamers
-
retarders
-
accelerators
-
plasticizers/superplasticizers
-
rheology modifiers
- fibers
Reactivity
with Portland cement
CSA Cement may be used in
combination with other mineral products, for example Portland cement, calcium
sulphates and fillers, or with organics such as polymers in latex foam or in
redispersible foam.
Depending on the type of
mixes and technology employed, CSA Cement can be used to obtain and control
various properties.
The behavior of Portland
cement is very variable. In general, acceleration of set increases
progressively with the addition of HCSA Binder. The amount of HCSA Binder
needed to obtain a specific setting time varies considerably depending on the
origin of the Portland cement and performance can be modified with the use of
additives.
The strength development of
CSA Cement/Portland cement and/or Calcium Sulphates depends on the nature of
the Portland cement and/or Calcium Sulphates used. In general these mixes will
develop mechanical strength at a very early stage (several hours). With some
type of Portland cements and in formulated products containing additives which control
the setting and hydration, the long term properties is similar to those of the
original Portland cement, however it is necessary to check the behavior of each
Portland cement used.
The characteristics of
Portland cement to be considered are:
C3A content
Mineral admixture type and
content
Type of Calcium Sulphate
used
Additives will also
influence the properties of these mixes:
Setting time
Rheology
Mechanical performance
Storage
CSA Cement is normally
supplied in one-tonne bag which include a moister resistant barrier. However,
in common with all hydraulic binders HCSA BINDER must be kept from moisture,
and can retain its properties for up to six months when properly stored.
Note: Edit by Jack Young, as references
only. For more informations, please contact:
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