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DENKA POWER CSA Low Dosage Expansive Additives
History
When cracking occurs in concrete structures, water ingress into the concrete interior through the
cracks occurs and causes corrosion damage to the rebar. The durability of concrete is compromised,
and its appearance is affected. Recently, there is a shift from standard design specifications to
newer design specifications which consider quantitative analysis of the effect of cracking on
concrete durability and performance. As such, Denka’s “Power CSA” has come into the spotlight for
its effect on crack reduction and flexural strength improvements.
Denka, as experts on expansive additives,
has been developing and selling its
expansive additive “Denka CSA” since 1964.
Having established a firm understanding of
ettringite technology, we were able to
leverage that knowledge to control free lime
reactions and develop a revolutionary low
dosage expansive additive DENKA POWER
CSA (ettringite lime composite) in 2001.
Achieving the same effect even at lowered
dosage, cost is reduced and DENKA
POWER CSA becomes more affordable for
everyone.
Description / Outline
DENKA POWER CSA is a shrinkage-reducing, high-performance expansive additive used in
concrete and mortar.
POWER CSA cement
water
cement hydrate
cement water
POWER CSA
POWER CSA hydration products (ettringite, calcium hydroxide)
POWER CSA hydrate “ettringite” SEM image. Ettringite and calcium hydroxide formation leads to expansion in the concrete, compensating for shrinkage.
POWER CSA
Conventional expansive additive
Solid line : Expansion strain (left axis) Dashed line: Compressive strength (right axis)
Shrinkage- compensating concrete expansive
strain range
Expa
nsio
n s
train
(×
10
-6)
at D
ay 7
Com
pre
ssiv
e s
tren
gth
(N
/mm
2)
at D
ay 2
8
Expansive additive (kg/m3)
Composition (Arbitrary Values)
The composition of POWER CSA (arbitrary measured values) is as below.
SiO2 Fe2O3 Al2O3 CaO SO3 Total f-CaO
DENKA POWER CSA 1.0% 0.8% 7.2% 70.6% 18.5% 98.1% 49.8%
*Arbitrary values
Product Grades
POWER CSA is generally used to mitigate cracking in concrete structures. Depending on the
specific requirements, choose from 3 available grades of POWER CSA.
1) POWER CSA Type-S
a) Standard dosage
20kg/m3 (replace 20kg of cement by 20kg of Power CSA)
b) Purpose
Reduction of cracking caused by volume changes in general concrete infrastructure
Drying shrinkage mitigation
Autogeneous shrinkage mitigation
c) Applications
Ground slabs, composite slabs, deck slabs, walls, columns, floor
slabs, railings, bridge piers, bridge abutments, underground box
culverts, concrete for pavements, sewerages, underground pits,
earthquake-resistance enhancement, high flow concrete,
self-compacting concrete, high strength concrete
d) Packaging
20kg paper bags, 1MT jumbo bag
2) POWER CSA Type-R
a) Standard dosage
20kg/m3 (replace 20kg of cement by 20kg of Power CSA)
b) Purpose
Reduction of cracking caused by volume changes in general concrete infrastructure
Thermal cracking mitigation
Drying shrinkage mitigation
Autogeneous shrinkage mitigation
c) Applications
Large scale sewerage systems, underground pits, machinery
foundations, bridge abutments, box culverts, high flow concrete,
high strength concrete, massive concrete (all types)
d) Packaging
20kg paper bags, 1MT jumbo bag
3) POWER CSA Type-T
a) Standard dosage
20kg/m3 (replace 20kg of fine aggregates by 20kg of Power CSA)
b) Purpose
Reduction of cracking caused by volume changes in tunnel linings
Thermal cracking mitigation
Drying shrinkage mitigation
c) Applications
Tunnel lining concrete
d) Packaging
20kg paper bags, 1MT jumbo bag
Example
Example
Example
Power CSA Physical Properties (Hardened State)
Length change (in accordance to JIS A 6202: 1997 Appendix 2, Method B)
By using Power CSA, concrete shrinkage can be compensated for; and cracking can be mitigated.
The shrinkage compensation capabilities do not vary between the different varieties of Power CSA.
Compressive strength (in accordance to JIS A 1108:2006)
In general, Power CSA has no effect on the overall compressive strength. However, strength gain is
lower as compared to standard concrete for Type-T (1d strength) and Type-R (3d strength) due to
the addition of hydration retarders. However, this has no effect on long term strength.
Tensile strength
(in accordance to JIS A 1113:2006)
Water-tightness (output method)
Power CSA has no effect on the overall
flexural strength.
Power CSA improves water-tightness.
Standard Power CSA Type-S Power CSA Type-R Power CSA Type-T
[Arbitrary results]
Le
ng
th c
ha
ng
e(×
10
-6)
Shrinkage
Expansion
Water
curing
Compensate for concrete shrinkage by
using Denka Power CSA.
JSCE allowable range of expansive strain (150~250×10
-6)
AIJ allowable range of expansive strain
(≥150×10-6
)
time
0d 7d 1m 2m 3m 6m 1y
Restrained expansion shrinkage test
Standard Power CSA Type-S Power CSA Type-R Power CSA Type-T
Arbitrary results
Arbitrary results
d d d d
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
Age Age
d h d d d
Power CSA Type-S
Power CSA Type-R
Power CSA Type-T
0-3d strength details
Standard
Standard POWER CSA
Arbitrary results
The water ingress count of Power-CSA mixed concrete of W/C=65% is similar to that of standard concrete of W/C=50%; reflecting the increased water-tightness.
Compressive strength (N/mm2) Concrete W/C ratio (%)
Wa
ter
pe
rme
ab
ility
cou
nt
(×1
0-3
cm
/se
c)
Standard
Power CSA Type-S
Arbitrary results
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
Adiabatic temperature increase Thermal stress
There is no change to the final adiabatic
temperature increase when using Power
CSA.
With the addition of Power CSA, greater
compressive strength (as compared to standard
concrete) is introduced during early hydration
stages. Furthermore, for Type-R and Type-S,
compressive strain is effectively introduced during
temperature decrease; alleviating tensile stress.
Power CSA Physical Properties (Fresh State)
Slump (in accordance with JIS A1101:2005) Entrained air volume (in accordance with JIS A1128:2005)
There is no effect on slump with Power CSA
usage.
There is no effect on entrained air volume with
Power CSA usage.
Setting (in accordance with JIS A1147:2007)
When using Power CSA Type-R or Type-T,
final setting time tends to be slower
compared to standard concrete when
concrete mixing temperature exceeds 20°C.
Ad
iab
atic t
em
pera
ture
in
cre
ase
(°C
)
Str
ess (
N/m
m2)
Standard
Power CSA Type-S
Power CSA Type-R
Power CSA Type-T
Standard Power CSA Type-S
Power CSA Type-R
Power CSA Type-T
Standard
Power CSA Type-S
Power CSA Type-R
Power CSA Type-T
Elapsed time Elapsed time
Arbitrary results Arbitrary results Tensile
Compressive
d d d d d d d d d d d d
Standard (20°C)
Standard (30°C)
Arbitrary results Arbitrary results
Standard
Power CSA (20°C)
Power CSA (30°C)
Power CSA
Slu
mp
(cm
)
Air
vo
lum
e (
%)
min min min min min min min min
Expansive concrete pouring Power CSA has virtually no effect on the fresh state, so the concrete pour can be done as per standard concrete.
Power CSA Type-S Standard
Power CSA Type-T
Power CSA Type-R
Fin
al se
ttin
g (
ho
urs
)
Power CSA Usage in Conjunction with Other Admixtures
Shrinkage-reducing admixture DENKA SK GUARD combination usage
When Power CSA is used in conjunction with
shrinkage-reducing admixture Denka SK
Guard-containing concrete, there is virtually no
effect on slump or entrained air volume etc. in the
fresh state; nor does it affect the shrinkage
compensation performance of Power CSA or
compressive strength in the hardened state.
However, when Denka SK Guard is mixed with
standard concrete, the slump/air-entrainment
volume may be affected. Also, the compressive
strength has the tendency to be slightly lower, so
be sure to perform mixing trials beforehand to
confirm the concrete performance.
Length change (in accordance with JIS A6202:1997 Method B) Compressive strength (in accordance with JIS A1108:2006)
Structure waterproofing admixture DENKA SHAGUARD combination usage
When Power CSA is used in conjunction with
structure waterproofing admixture Denka
Shaguard-containing concrete, there is virtually
no effect on slump or entrained air volume etc.
in the fresh state; nor does it affect the
shrinkage compensation performance of
Power CSA or compressive strength in the
hardened state. Furthermore, the
waterproofing performance of Denka Shaguard
is not affected.
Water stop performance measurements
Length change (in accordance with JIS A6202:1997 Method B) Compressive strength (in accordance with JIS A1108:2006)
Example
Le
ng
th c
ha
ng
e (
×1
0-6
)
Arbitrary results Arbitrary results
SK Guard + Power CSA Standard
SK Guard s
SK Guard + Power CSA
Standard
SK Guard s
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
d m m m m Age
Compressive strength at 28d
Le
ng
th c
ha
ng
e (
×1
0-6
)
d m m m m Compressive strength at 28d
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
Age
Arbitrary results
Arbitrary results
Standard
Shaguard s
Shaguard + Power CSA
Standard Shaguard Shaguard + Power CSA
Arbitrary results
d m m m m
Wa
ter
lea
kin
g (
%)
age
Standard Shaguard Shaguard + Power CSA
Expansion
Shrinkage
Expansion
Shrinkage
Shaguard + Power CSA
Shaguard s
Standard
High performance AE water reducer combination usage
When Power CSA is used in conjunction with
high performance AE water reducer-containing
concrete, there is virtually no effect on slump or
entrained air volume etc. in the fresh state; nor
does it affect the shrinkage compensation
performance of Power CSA or compressive
strength in the hardened state. Length
change % and compressive strength arbitrary
measurements are recorded as below.
Length change (in accordance with JIS A6202:1997 Method B) Compressive strength (in accordance with JIS A1108:2006)
High performance AE water reducer combination usage
When Power CSA is used in conjunction with
high performance AE water reducer-containing
concrete, there is almost no effect on the
fluidity. Furthermore, there is virtually no effect
on the entrained air volume or slump etc. in the
fresh state; nor does it affect the shrinkage
compensation performance of Power CSA or
compressive strength in the hardened state.
Length change % and compressive strength
arbitrary measurements are recorded as
below.
Slump (in accordance with JIS A1101:2005)
Length change (in accordance with JIS A6202:1997 Method B) Compressive strength (in accordance with JIS A1108:2006)
Combination usage with other materials
There is no effect on the concrete characteristics when Power CSA is used in conjunction with
various kinds of fibres (steel, vinylon, PP).
Example
Expansion
Shrinkage
Le
ng
th c
ha
ng
e (
×1
0-6
)
Arbitrary results Arbitrary results
Power CSA
Standard
Standard Power CSA
d m m m m
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
age
Compressive strength at 28d
Slu
mp
(cm
)
Base After fluidization
(0min)
min min min
Arbitrary results
Power CSA
Standard
Power CSA
Standard
Arbitrary results Arbitrary results Expansion
Shrinkage
Le
ng
th c
ha
ng
e (
×1
0-6
)
Com
pre
ssiv
e s
tre
ng
th (
N/m
m2)
Standard Power CSA
d m m m m Compressive strength at 28d
Age
Job References (Drying Shrinkage Cracking Countermeasures)
Outline
DENKA POWER CSA TYPE-S was used in the concrete slab of a logistics warehouse as cracking
countermeasures. To assess its performance, a portion of the composite slab of its 2nd storey was
constructed with ordinary concrete for comparison. Assessment was done by embedding a strain
gauge to measure actual strain as well as visual inspection of cracking. To ensure the accuracy of
the comparison, concrete casting was carried out using 2 trucks on the same day; and the concrete
pour was completed at the same time.
Concrete Mix Proportion
The concrete used was termed “24-15-20N”, and the mix proportions are as follows.
Unit quantity (kg/m
3)
Admixture (kg/m
3)
Water Cement Expansive
additive Fine
aggregate Coarse
aggregate
Ordinary Concrete
174 300 0 855 978 3.000
Expansive concrete
174 280 20 855 978 3.000
Concrete Curing
Curing time : 5 days
Curing method : Water sprinkling + plastic sheet covering
Measurement results from the embedded strain gauges
The measurements taken from each embedded strain gauge
is as below. Based on the obtained results, it was shown that
while drying shrinkage occurred in ordinary concrete
immediately after curing, due to the expansive effect of
DENKA POWER CSA TYPE-S in the expansive concrete,
the strain first shifts to the expansive side. After which,
shrinkage occurs as per ordinary concrete. However, the
expansion introduced during the initial stage properly
remains. In this case study, the effect of DENKA POWER
CSA TYPE-S was measured to be 130 ×10-6 (0.13mm/m).
During curing
Expansion
Shrinkage
Actu
al str
ain
(×
10
-6)
Expansive concrete (left axis)
Ordinary concrete (left axis)
Power CSA Type S effect (left axis)
Temperature (right axis)
Te
mp
era
ture
(°C
)
d d d d d d d d d
Age
Cracking analysis by visual inspection of concrete after 4 months
Measurement cables
Embedded strain gauges
Embedded strain gauges Measurement cables Expansive concrete
Expansive concrete
Boundary
Ordinary concrete
Crack (≥0.30mm width)
Crack (0.20~0.30mm width)
Crack (0.10~0.20mm width)
Slab cross-section
Short side: D10@200 Long side: D10@200
Cracking results by visual inspection Ordinary Concrete
Number of cracks of width ≥0.30mm → 5
Number of cracks of width 0.20mm~0.30mm → 3
Number of cracks of width 0.10mm~0.20mm → 2
Expansive Concrete
No cracks were observed.
By the above results, the performance of DENKA POWER CSA TYPE-S in mitigating cracking due to drying shrinkage was confirmed.
Job References (Thermal Cracking Countermeasures)
Outline
As a countermeasure to thermal cracking in the concrete walls of water treatment plants, DENKA
POWER CSA TYPE-R was used. To assess its performance, ordinary concrete was cast under the
same conditions as reference. Assessment was done by embedding a strain gauge to measure
actual strain as well as visual inspection of cracking.
Concrete Mix Proportion
The concrete used was termed “24-8-20BB”, and the mix proportions are as follows.
Unit quantity (kg/m
3)
Admixture (kg/m
3)
Water Cement Expansive
additive Fine
aggregate Coarse
aggregate
Ordinary Concrete
163 292 0 888 1004 2.920
Expansive concrete
163 272 20 888 1004 2.920
Concrete Curing
Curing time: 3 days (left-in-formwork period) Curing method: Composite board formwork
Measurement results from the embedded strain gauges
The measurement results from each embedded strain gauge are as below.
In ordinary concrete, a temperature decrease is accompanied by a sudden shrinkage. However, in
expansive concrete using DENKA POWER CSA TYPE-R, the introduction of expansive strain
mitigates the shrinkage that occurs during temperature decrease. Also, the shrinkage strain in the
middle portion at 24 days, as well as the upper portion at 25 days is released in ordinary concrete
due to cracking.
Cracking analysis by visual inspection of concrete after 28 days
Expansion
Shrinkage
Actu
al str
ain
(×
10
-6)
Expansion
Shrinkage
Actu
al str
ain
(×
10
-6)
Middle portion Top portion
Expansive concrete Expansive concrete
Crack occurrence Crack occurrence
Ordinary concrete Ordinary concrete
d d d d d d d d d d age age
Ordinary concrete
Expansive concrete No cracking
Unit: mm
By the above results, the performance of DENKA POWER CSA TYPE-R in mitigating thermal cracking was confirmed.
Handling Precautions
Mix proportions calculations and mixing
Even though this material is not actually cement, treat it as per standard cement when deciding
concrete/mortar mix proportions.
With regards to the material dosage amount, please take into consideration the “Design and Construction
Guidelines” set by the Architectural Institute of Japan.
Take note that if the material dosage exceeds the stipulated amount for that specific purpose, excessive
expansion will occur; and may cause the strength to be lowered.
With regards to concrete mixing, take note to charge DENKA POWER CSA into the mixer at the same time
as cement. Ensure that the charging timing is not delayed, and carry out mixing for ≥10s longer for a
twin shaft cement mixer; or ≥30s longer for a vertical-axis cement mixer. Also, avoid mixing by hand.
If mixing is not done evenly, localized expansion may occur. Furthermore, make sure to equip PPE
(protective goggles, mask, gloves etc.) while handling the product.
When DENKA POWER CSA TYPE R is used, concrete setting may be delayed. This delay is especially
obvious during high ambient temperatures of 30°C. As such, take special care during trowel finishing etc.
The use of low-heat Portland cement in conjunction with expansive materials is extremely effective.
However, with regard to the test specimen used in daily management (test specimen made in accordance
to JIS A 1132, cured in accordance to JIS A 1108), carry out measures such as lengthening the duration in
which the test specimen is kept in the formwork. If the specimen is kept in the formwork for too short a time,
the strength may be lowered. For more details, refer to the technical information.
When using expansive additives at a W/C ratio of ≤30%, be sure to discuss beforehand.
Curing
Under rapidly drying environmental conditions, DENKA POWER CSA reactions are not fully complete due
to water shortage; and as such its expansive performance will be affected. Therefore, after the concrete is
cast, ensure that the surface does not dry out by carrying out curing (sprinkle water or use a curing mat
over the slab or ground; for walls, use a formwork to aid curing) for 5 days. Otherwise, use curing agents.
As for the formwork type, decorative or metal formworks are recommended. If other types of formworks
are used, the finish after formwork removal may be affected.
Compatibility with different admixtures, additives
The use of DENKA POWER CSA TYPE R and DENKA POWER CSA TYPE T in conjunction with
water-reducing retarders (AE water-reducing retarders, high performance water-reducing retarders)
should be avoided. If these are to be used together, please be sure to conduct trial mixes beforehand to
check the performance.
If calcium chloride is used as an accelerator, the expansion effect is reduced. As such, avoid simultaneous
usage.
While DENKA POWER CSA can be used with most admixtures, as there are numerous varieties of
admixtures, there may be some that proper tests have not been conducted on yet. If unsure, please
contact your local sales agent for more advice.
While the bonding between concrete and DENKA POWER CSA mortar is very strong, in drainage,
waterproof coating or asphalt construction, the bonding performance of DENKA POWER CSA mortar is
lost if it is applied to the top of those constructions. Also, detachment may occur due to expansion. Avoid
such construction methods.
Storage method
While DENKA POWER CSA is packaged in moisture-proof paper bags, as its hygroscopicity is the similar
to that of cement, store in a dry place.
Once opened, the product should be used up completely.
In the event that lumps are found within the bag, do not use that bag.
Shelf life: 12 months from production date. Determine the production date by reference to the lot
number. A lot number of “1AXXX” corresponds to production in Jan 2001; “2BXXX” to Feb 2002
and so on.
Limitation of Liability
The information contained in this brochure provides general advice for potential customers of DENKA about the basic properties and
characteristics of various DENKA products (hereafter referred to as “the Product Information”). DENKA makes no warranty or
representation as to the entire accuracy or completeness of the Product Information in this brochure. Nothing in this brochure will be
deemed to create any express or implied warranty or obligation of DENKA with respect to the Product Information or its use, including,
but not limited to, any warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property rights. Each
user of the Product Information and DENKA products assumes their own responsibility to properly determine the manner and suitability of
use of the Product Information and DENKA products in its own operations. The user should exercise proper care in considering the
Material Safety Data Sheet, Product Information and any other technical information provided by DENKA, including descriptions of the
conditions of use, warnings, and other cautionary instructions. DENKA reserves the right to change the Product Information from time to
time at its discretion and without notice.
Denka Co. Ltd. Special Cement Additives Department
TEL: +81-3-3507-5465 FAX: +81-3-3507-5085
-China-
DENKA INFRASTRUCTURE
TECHNOLOGIES SHANGHAI
ROOM 2807, NEW HONGQIAO
CENTER BLDG
NO.83 LOUSHANGUAN RD,
CHANG NING AREA, SHANGHAI CHINA
TEL: +86-21-6236-5510
FAX: +86-21-6236-5505
-Asia-
DENKA INFRASTRUCTURE
TECHNOLOGIES PTE LTD
4 SHENTON WAY #29-02 SGX
CENTRE 2 SINGAPORE 068807
TEL:+65-6216-0580
FAX:+65-6224-3840
-Europe-
DENKA CHEMICALS GMBH
WEHRHAHN-CENTER, CANTADOR STR.3,
DUSSELDORF, GERMANY
TEL: +49-211-130990
FAX: +49-211-329942
5J01JP
