Performance and Improvement Measures of Concrete with Internal
Addition of Water-based Organic Silicon
Kaili Yang
1,2
, Zhihong Fan
1,2
, Zhijie Zhang
3
, Wenjie Cen
1,2
, Mingfeng Zhong
3
and Chao Luo
1,2
1
.CCCC Fourth Harbor Engineering Institute Co.Ltd ,Guangzhou 510230 , China
2.
Key Laboratory of Harbor and Marine Structure Durability Technology, Ministry of Communications, PRC, Guangzhou 5
10230, China
3.
College of Materials Science and Engineering, South China University of Technology,Guangzhou 510230 , China
Keywords: Water-based organic silicon, modified meta kaolin, water absorption, compressive strength, chloride
diffusion coefficient.
Abstract: In this paper, the change laws of compressive strength, water absorption and chloride diffusion coefficient
of concrete mixed with different dosages of water-based organic silicon was studied. Meanwhile, the
influence of modified meta kaolin on concrete mixed with water-based organic silicon was studied. The
results show that the water-based organic silicon can significantly reduce water absorption of concrete,
nevertheless, it will reduce the compressive strength of concrete. The higher the dosage, the greater decrease
in strength. The mixing of meta kaolin can effectively improve the mechanical properties of the concrete
mixed with water-based organic silicon and its waterproof performance and chloride resistance.
1 INTRODUCTION
Concrete durability has become a hot spot in the
field of international concrete research, especially
the concrete structure in the marine environment and
chemical corrosion environment. It is noteworthy
that, in the pass century, a large number of
constructions had collapsed or demolished because
of poor durability performance[1-4]. Undesirable
ions penetrate into the concrete structure with water,
causing physically and chemically damage of it. In
order to improve the durability of the concrete
structure and ensure the structure meets the design
life requirements, when adopting the corrosion-
resistant high-performance concrete, the necessary
additional anti-corrosion technology measures
should also be taken in view of the corrosive
environment characteristics of different structure.
For the additional anti-corrosion technology, pieces
of research have been carried out in these years. At
present, it mainly includes two kinds of technical
method: external coating and internal addition.
External coating materials are easily affected by the
surface layer concrete properties and the anti-aging
properties of the materials. Once the surface
concrete occurs cracking, abrasion, or the anti-
corrosion materials are aging because exposed to the
outdoor environment for a long time, the protective
effect will be greatly reduced [5]. By mixing anti-
corrosion material in fresh concrete to produce
concrete with integral waterproof properties, the
above drawbacks of traditional surface anti-
corrosion materials can be effectively improved.
However, mixing the anti-corrosion materials by
internal addition generally has the problem of
reducing the compressive strength of the
concrete[6,7].
Metakaolin sakind of mineral admixture with
superpozzolanactivity, when modified by acid，the
thermal and mechanical activation, Activities of
SiO2and Al2O3 will be stimulated and give full play
to itspozzolanic effect and filling effect, and also
significantly improve strength and resistance
permeability of concrete[8-11]. In order to reduce
the side effect to the strength of concrete and greatly
improve the resistance permeability of concrete,
based on the study of the influence of the water-
based organic silicon on concrete, the modified
metakaolin and water-based organic silicon will be
mixed to explore the influence of the modified
metakaolin on water-based organic silicon concrete.

2RAW MATERIALS AND TEST
METHODS
2.1 Cement
The cement uses Yuexiu PII 42.5R portl and cement.
The main chemical composition of cement is shown
in Table 2.1, and the physical properties are shown
in Table 2.2.
Table2.1:Cement Chemical Composition(%).
composition SiO
2
Al
2
O
3
CaO SO
3
MgO Fe
2
O
3
LOI
cement 19.76 4.52 62.42 4.26 1.13 4.42 3.49
Table 2.2 :Cement Physical Properties.
Specificsurf
ace area（
m
2
/kg）
Standard
consistency
water demand P
（%）
Setting time（min
）
Flexural
strength（MPa）
Compressive
strength（MPa）
360 25.5
Initial
time
Final
time
3d 28d 3d 28d
121 197 6.82 8.86 32.43 52.09
2.2 Aggregate
Granite gravel (5~20mm) produced by Zhuhai
Jianbang Stone Field, apparent density is 2.70 g/cm
3, close bulk density is 1.63 g/cm 3, needle content
is 2.3%,crush value is 3.0%; fine aggregate with
Guangdong Xijiang sand, apparent density is
2.64g/cm 3, fineness modulus is 2.7, mud content is
0.4%, mud mass content is 0.2%.
2.3 Water-based Organic Silicon
The alkyl siloxane water-based organic silicon with
a long-chain molecular structure was used, and the
active ingredient was 40%.
The metakaolin made by calcining kaolin from
Guangdong Maoming was used. The main chemical
composition and specific surface area of metakaolin
are shown in Table 2.3. The metakaolin becomes
modified metakaolin when activated by acid,
thermal and mechanical activation methods.
2.4 Modified Metakaolin
Table 2.3:Metakaolin chemical composition (%) and specific surface area(m
2
/kg).
SiO
2
Al
2
O
3
CaO SO
3
MgO Fe
2
O
3
LOI Specific surface
metakaolin 53.00 42.67 0.04 0.14 0.08 0.73 1.35 15238
2.5 Concrete Mix Proportion
The mix proportion of the concrete specimens is
shown in Table 2.4. The 2%, 4% and 6% dosage of
water-based organic silicon was used to instead of
the total amount of cementitious materials, and the
same amount of mixing water was replaced at the
same time. Modified metakaolin replaces the total
amount of cementitious material with a 6% doping
amount.

Table 2.4: Mix proportion(kg/m
3
).
Mumber Cement
Modifiemeta
kaolin
Water
Water-
based
organic
silicon
Sand Gravel Superplasticizer
OPC 420 — 147 — 771.6 1065.6 2.58
SL2 420 — 142 8.4 771.6 1065.6 2.70
SL4 420 — 136.9 16.8 771.6 1065.6 2.66
SL6 420 — 121.8 25.2 771.6 1065.6 2.67
MK 394.8 25.2 147 — 771.6 1065.6 2.98
MKSL2 394.8 25.2 142 8.4 771.6 1065.6 3.07
2.6 Test Methods
2.6.1 Water Absorption Test
The water absorption test was conducted according
to the method in “Mortar, Concrete Waterproof
Agent”(JC474-2008).
2.6.2 Compressive Strength Test
According to the method in “Standard Test Method
for Mechanical Performance of Ordinary
Concrete”(GB/T50081-2002), the compressive
strengths on 3d, 7d and 28d ages of the concrete
were measured.
2.6.3 Rapid Chloride Migration Factor
Test(RCM Method)
Referring to “Standard Test Method for Long-
term Properties and Durability of Normal
Concrete”(GB/T50082-2009) to test the chloride
diffusion coefficient of concrete on 28d.
3. RESULTS AND DISCUSSION
3.1 Compressive Strength
Figure 1 shows the effect of different dosage water-
based organic silicon on concrete for 3d, 7d and 28d.
It can be seen from the figure that the compressive
Fig 1: Effect of water-based organic silicon on
compressive strength of concrete.
strength of concrete at the three ages are reduced
because of add with water-based organic silicon, the
greater the dosage is, the more the compressive
strength decreases. Compared with the OPC which
without water-based organic silicon, the
compressive strength of SL2, SL4 and SL6 on 28d
were reduced by 2.9%, 8.1% and 12.5% respectively.
When the Water-based organic silicon mixed in
concrete, it will adsorb on the surface of the cement
particles. The greater the content of the water-based
organic silicon, the greater the surface area of the
adsorbed cement particles, the smaller effective
contact area between the cement particles and water,
the slower hydration rate and lower hydration degree
of the concrete, and finally lead to a lower
compressive strength of concrete.
0123456
40
45
50
55
60
65
Compressive strength (MPa)
Waterproof admixture (%)
3d
7d
28d

Fig2: Effect of modified metakaolin on compressive
strength of concrete with water-based organic silicon.
Figure 2 shows the effect of modified
metakaolinon compressive strength of concrete with
water-based organic silicon. The addition of
modified metakaolin can effectively improve the
compressive strength of concrete with water-based
organic silicon.
Comparing with the OPC, the compressive
strength of MK increased by 7.3%, 13.7% and
18.3% respectively on 3d, 7d and 28d. Compared
with the SL2, the compressive strength of MKSL
increased by 8.1%, 11.5% and 9% respectively on
3d, 7d and 28d, and 28d compressive strength
increased 5.9% compared to OPC. After the acid
treatment to metakaolin ，thermal and mechanical
activation can effectively stimulate the activity of
SiO2 、 Al2O3 and other active substances, and
significantly improve the strength of concrete[11].
When mixing the modified metakaolin with the
water-based organic silicon, the strength promotion
effect of modified metakaolin effectively
compensates for the side effect of reducing the
strength of the concrete with water-based organic
silicon.
3.2 Water Absorption
Figure 3 shows the effect of different dosage water-
based organic silicon on water absorption of
concrete and the water-based organic silicon can
significantly reduce the water absorption of
concrete. Compared with the OPC , the water
absorption of SL2, SL4 and SL6 on 28d were
decreased by 64.4%, 69.9% and 65.8% respectively.
With the increase of the amount of water-based
organic silicon, there is little difference in reducing
water absorption of concrete. When the content of
water-based organic silicon increase to 6%, the
water absorption of concrete will also increase,
meaning the decrease of the waterproof ability. This
is because the water-based organic silicon has a low
surface tension and the surface energy promote a
fine hydrophobic performance, which can react with
cement in concrete and forms the interwoven
hydrophobic layer, preventing water molecules from
penetrating into the concrete, as well as reducing the
water absorption of concrete [6]. However, as the
content of water-based organic silicon increases, the
more cement particles adsorbed by water-based
organic silicon, the greater the influence on the
hydration of cement in concrete, which will reduce
its waterproof ability to a certain extent.
Fig 3:Effect of water-based organic silicon On water
absorption of concrete.
Fig4: Effect of modified metakaolin on water
absorption of concrete with water-based organic
silicon.
Figure 4 shows the effect of modified metakaolin
on water absorption of concrete with water-based
organic silicon ,the modified metakaolin and water-
OPC SL2 MK MKSL2
0
10
20
30
40
50
60
70
80
Compressive strength (M Pa)
3d
7d
28d
0246
2
3
4
5
6
7
8
Water absorption (%)
Waterproof admixture (%)
28d
OPC SL2 MK MKSL2
0
1
2
3
4
5
6
7
8
Water absorption(%)

based organic silicon both can significantly reduce
the water absorption of concrete. Compared with the
OPC , the water absorption of MK and MKSL were
decreased by 47.9% and 60.3% respectively.
However, when comparing with the SL2,the water
absorption of MK and MKSL was increased
by49.2% and 19.2%. With the increasing content of
SiO
2
and Al
2
O
3
modified within the metakaolin,
their secondary react with the cement hydration
product—Ca(OH)
2
will be generated and padding
the concrete pore, resulting in the increasing
compactness of the concrete structure and the
reducing of the water absorption performance of
concrete[12].
3.3 Resistance of Chloride Ion
Penetration
Corrosion of steel reinforcement in concrete is
considered to be one of the most significant reasons
for durability damage of marine concrete structures.
Cl- transmission from the concrete surface to the
internal surface of steel, when its accumulated to a
certain value of the concentration of the rebar
depassivation and rust occurs, the expansive
corrosion product make the concrete cover falls off,
and lead to the failure of the structure eventually.
Therefore, it is an important means to evaluate the
durability of concrete to test the Cl- permeability of
concrete. In addition, the transmission performance
of concrete reflected by the resistance to chloride
permeability of concrete is a fundamental problem
directly influencing the durability of concrete.
Figure 5 shows the chloride diffusion coefficient
of concrete with different dosage water-based
organic silicon by RCM method and the chloride
diffusion coefficient observably reduced with the
water-based organic silicon. Compared with the
OPC , the chloride diffusion coefficient of SL2, SL4
and SL6 on 28d were decreased by 23.6%, 30.6%
and 32.3% respectively. The effect of water-based
organic silicon on the diffusion coefficient of
chloride ions in concrete is similar to that of water
absorption, meaning that with the increase of water-
based organic silicon, the diffusion coefficient of
chloride ion is slightly changed. Water-based
organic silicon hydrophobicity changed the surface
tension of concrete and its internal pore, resulting in
a hydrophobic surface and scatter within the
concrete to block the connectivity of capillary pore
at the same time, which can effectively reduce the
chloride ion diffusion coefficient of concrete.
Fig 5:Effect of water-based organic silicon on chloride
diffusion coefficient of concrete.
Fig6: Effect of modified metakaolin on chloride
diffusion coefficient of concrete with water-based
organic silicon.
Figure 6 shows the chloride diffusion coefficient
of water-based organic silicon concrete with
modified metakaolin. Compared with the OPC , the
chloride diffusion coefficient of MK was decreased
by 43.8% and compared with the SL2, the chloride
diffusion coefficient of MK and MKSL were
decreased by 43.8% and 7%, the results show that
the effect modified metakaolin on the chloride
diffusion coefficient on concrete is much more
serious than that of water-based organic silicon. The
modified metakaolin can improve the compactness
of the pore structure, reducing the content of
capillary pore in concrete, improving the gel content,
and promoting the formation of F salt in the concrete
under the chloride environment. It can not only
reduce the transmission channel of Cl- in concrete
but also improve the curing capacity of Cl-.In this
way, the resistance of chloride permeation of
0246
5
6
7
8
9
10
Chloride ion diffusion coefficient(10
-12
m
2
/s)
Waterproof admixture(%)
28d
OPC SL2 MK MKSL2
0
1
2
3
4
5
6
7
8
9
10
11
12
Chloride ion diffusion coefficient(10
-12
mm
2
/s)

concrete with water-based silicone concrete is
improved[10].
4. CONCLUSIONS
1.Water absorption of concrete can be significantly
reduced by adding with water-based organic silicon
in concrete, when the dosage of water-based organic
silicon between 2%-6% , the water absorption of
concrete can be reduced by over 65%.
2.Adding water-based organic silicon in concrete
will reduce the compressive strength of concrete,
and it will be more distinct with the increase of the
concentration. Considering the water absorption and
compressive strength of concrete, the optimum
dosage of water-based organic silicon can be refined
as2%.
3.Mixing with modified metakaolin and water-
based organic silicon is able to improve the
compressive strength and waterproof ability at the
same time. Compared with OPC, the compressive
strength on 28d of MKSL was increased by 5.9%,
and the water absorption and the chloride diffusion
coefficient were decreased by 60.3% and
28.9%respectively.
ACKNOWLEDGEMENT
Thanks for support from Guangzhou science and
technology project-the key technology research and
industrialization of waterproofing strengthening
agent for concrete (201604016042)
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