Polyurea Great Wall Beijing-Shanghai High Speed Railway Polyurea Protection Project

Huang Weibo * Liu Xudong Lu Ping Ma Xueqiang

Research Institute of Functional Materials, Qingdao Technological University, Qingdao, CHINA

*Corresponding author: POB No.111, 11 Fushun Road, Qingdao, CHINA

E-mail: spua@163.com liu.xu.dong-123@163.com

ABSTRACT This paper presented the polyurea protective project of Beijing-Shanghai High

Speed Railway. It also reviewed the polyurea history in China, introuduced research and development of polyurea in Qingdao Technological University. The analysis and discussion on the application problems exposed in the Beijing-Shanghai High Speed Railway project were performed in this paper. It proposed a polyurethane based all weather surface preparation system for Beijing-Shanghai High Speed Railway polyurea project and settled the long term problem confusing Chinese polyurea industry. The comprehensive perfermance of surface preparation systems for Beijing-Shanghai High Speed Railway polyurea project in jobsite was also investigated. The pull-off test, tack free time and visual inspection were employed to determine the adhesion and coverage effect of the bughole on shot blasted concrete surface. The results indicate that: polyurethane based system porformed an excellent comprehensive performance better than epoxy based system both in adhesion and in elimination of pinhole for up coming polyurea application. This polyurea project goes forward well even in both cold and dry season in the north, and hot and moist season in the south attributed to this novel polyurethane based system.

Keywords: Beijing-Shanghai High Speed Railway, polyurea, Polyurethane based surface preparation system, technical support

1 Introduction Concrete structures have been widely fabricated in the construction of civil

infrastructure facilities, such as high-speed railway, stadium, tunnels, and over sea bridges. All of the concrete structures are subjected to environment-induced deterioration and the concrete is degrading rapidly [1~2]. The new kind of coating protection technique was considered as the most effective method for improving the durability of the concrete. The preparation of new protective coating materials and the investigation of high performance coating techniques are significant since coating protection become the primarily and available method for the protection of concrete [3]. Polyurea is a class of excellent performance protective coating. Aromatic and normal aliphatic polyureas are there into generally applied in the preparation of the high weathering durability and anti-corrosion protective coatings [4~10]. The Beijing-Shanghai High-Speed Railway, concrete sub grade polyurea protective project,

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as well as a world famous giant polyurea project also wildly known as “Polyurea Great Wall” is unquestioned to be one of the most magnificent feats in polyurea history.

2 Review Polyurea in China 2.1 Application

The “Polyurea Great Wall” project is the largest one to use polyurea with 12,000,000 square meters in 2mm in the world since the first commercial application of the polyurea elastomeric coating/lining technology was used in 1991.With the successful research of this advanced technology in China, it has attracted much attention from both academic and industrial fields. This newest technology has been more than ten years and half of its experimental research and engineering practice is in China, from early small scale trial of Qingdao Dolphin Aquarium and Dalian Polar Zoo Stand to the giant project of Olympic stadium stands, Beijing-Tianjin inter-city railway, Taiwan High Speed Railway and Beijing-Shanghai High Speed Railway. In the past 15 years, polyurea traversed an extraordinary glorious experience and scored tremendous achievements in application. The polyurea achievement was shown in Table 1.

Table.1 Polyurea Achievement in China

Time Polyurea Project Name Areas, m2 1999-04-04 Qingdao Dolphin Aquarium 100 2000-07-25 Basketball Field of MCRI 560 2001-10-27 Dalian Polar Zoo Stand 4500 2003-08-16 Tennis Court of Qtech 450 2004-12-12 Taiwan High Speed Railway 50000 2006-07-01 Qingdao Polar Zoo Stand 5500 2006-09-10 Beijing Fengtai Stadium Stand 12000 2007-05-15 Beijing National Theatre Pool 60000 2007-11-20 Beijing-Tianjin Intercity Railway 1000000 2008-04-24 Stadiums of the 29th Olympic Games 300000 2009-05-04 Stadiums of the 11th City Games 150000 2010-08-28 Beijing-Shanghai High Speed Railway 12000000

2.2 Research and Development

The polyurea elastomer coating technology has shown some very significant inroads since the technology was introduced in the late 1980’s. However, over the years there has been a melding of new various application field, new polyurea system and new technologies coming up. According to the experience of being engaged in research and development on polyurea for more than 15 years, Research Institute of Functional Materials commit their effort to study this new type technology from chemical formulation design, material properties, aging behavior, engineering application and so on in a long period. Huang Weibo, LU Ping studied the effect of curing temperature on morphology and properties of polyurea based on polyaspartic esters by using FTIR, EIS and AFM [11] (shown in Fig.1). The results indicated that

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curing temperature had great influence on morphology and properties of the polyureas. LU Ping et al. investigated a novel polyaspartic ester based anticorrosion polyurea coatings for marine infrastructure protection, it showed that this work could significantly improve the durability of marine structure [12] (shown in Fig.2). Huang Weibo, Liu Xudong et al. studied the surface preparation systems for polyurea protective coating of Beijing-Shanghai High Speed Railway Bridge concrete beams; the purpose of this research was to provide an all day weather surface preparation (Polyurethane based) for solving the delamination problem confusing polyurea industry ranging from raw materials suppliers and distributors, formulator/system suppliers, contractors, applicators, end-users and consultants. It provided comprehensive solution for Beijing-Shanghai high speed railway waterproof membrane application in myriad climatic factors of changes (shown in Fig.3).

4000 3000

40

60

80

100

2000 1000

trans

mitt

ance

/%

wa

b

a

ve number/cm-1

Fig.1 Infrared spectra of PAE based polyureas cured at different temperatures

a-20 ℃;b-80 ℃

0

2

4

6

8

10

12

14

16

18 outdoor insolation Salt fog aging

F2B2T3

Ta

rnis

h pe

recn

tage

/%

a

3

0

2

4

6

8

10 outdoor insolation Salt fog aging

F2B2T3

St

reng

th c

hang

e pe

recn

tage

/%

0.0

1.5

3.0

4.5

6.0

7.5

9.0 outdoor insolation Salt fog aging

F2B2

8 10 12

T3

El

ongn

atio

n ch

ange

per

ecnt

age/

%

b c

Fig. 2 Performances change percentage of T3、T2 and F2 after outdoor insolation and salt fog

exposure for 350days a- Tarnish percentage; b-Tensile strength; c- Elongation at break

0 2 4 6

1

2

3

4

5

6

onths)

1

43

3

5

3

1

1

1

1

11

Test Time(M

A

dhes

ion(

MPa

)

4

4

1

1

33

5

4

4

4

31

11

2

1

E1 E2 PU 50℃ , ( 90± 5) % E1 E2 PU 0℃ , ( 30± 5) %

Fig.3.Epoxy-1, Epoxy-2 and Polyurethane based surface preparation system adhesion test

results

3 Profile of Beijing-Shanghai High-Speed Railway

The Beijing-Shanghai High-Speed Railway, also known as the Jinghu High-Speed Railway, is a 1,318 kilometers long high-speed railway that will connect two major economic zones in the People’s Republic of China: the Bohai Sea Rim and the Yangtze River Delta [13]. The continuous operating speed is expected to be 350km/h (220 mph), with maximum speed up to 380 km/h (240 mph). The average commercial speed from Beijing to Shanghai will be 330 km/h (210 mph). The train travel time will reduced from 10 hours to 4 hours. The rolling stock used on this line will be the CRH trains. An estimated 220,000 passengers are expected to use the trains each day, which is double the current capacity. During rush hours there should be a train every five minutes [14]. The 164-km long viaduct between Danyang and Kunshan will be the longest bridge in the world. The line also includes 22 tunnels, 16.1km in total. 1196 km in length will be ballastless. The designed service life of Beijing-Shanghai Speed Railway is 100 years.

All of concrete beams of high-speed railway are long term subjected to 4

train-induced dynamic load, environment-induced deterioration and the concrete degrading rapidly. As the success of polyurea technology applying to Beijing-Tianjin inter-city railway, the whole line of Beijing-Shanghai High-Speed Railway is selected aromatic polyurea coating as a special membrane with functions of abrasion resistance, impact resistance, seamless and anti corrosion for 100 years’ durability of concrete.

According to “Temporary Technological Guideline for Spraying Polyurea As the Waterproofing Layer on the Bridge Beams of Beijing-Shanghai High Speed Railway” (Temporary Technological Guideline, lunched by Qingdao Technological University, China Railway Engineering Consulting Group Co., Ltd. and China Academy of Railway Sciences) [15], the construction design of aromatic polyurea application for Beijing-Shanghai High Speed Railway was shown in Fig.4. the construction of the protective layer system is divided into two stages, below bed plate and above bed plate exposed to sunlight. Table 2 presents the main performance index of special polyurea.

Fig.4 Polyurea protection coating construction design

Table.2 The main performance index No. Items Specifications

1 Solid content/% ≥ 98

2 Gel time/s ≤ 45

3 Tack free time/s ≤ 120

4 Tensile strength/MPa ≥ 16.0

5 Elongation at Break/% ≥ 450

6 Tear strength/(N/mm) ≥ 50

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7 Hardness/Shore A ≥ 90

8 Heat dilatation- magnification ratio/% ≤ 1.0

9 Adhesion/MPa ≥ 2.5

10 Peeling Strength/MPa ≥ 6.0

11 Water absorption/% ≤ 5.0

12 Low temperature bend property/℃ ≤ -40

13 Abrasion Resistance/(cm3/1.61km) ≤ 0.5

14 Impermeability 0.4MPa,2h impervious 15 Impact, Height arm of fall,100cm No Cracks, No Spalling

4 Challenges

According to “Polyurea Great Wall”， the biggest problems that the polyurea

industry is facing include surface preparation after short blasted concrete beams, coating delamination and failure, especially in cold and dry season in the north and hot and moist season in the south

Bridge concrete systems often require vapor barriers or other means of water- proofing to prevent water and corrosion medium intrusion, which can ultimately lead to delamination and failure of the coating system [16]. All grease compounds and other foreign matters on the surface should be removed by sand blasting, shot blasting, mechanical scarification or suitable chemical means. The concrete surface should also be prepared with a grip enhancing profile to aid the proper adhesion of the substrate and polyurea system. The shot blasting technology was considered as the best method of the substrate surface preparation that presented the highest values of bond strength in shear and in tension of all other considerable techniques [17]. Different from grinding technology which generated a large number of dusts and could not form completely rough surface applied in Beijing-Tianjin inner-city rail , short blasting technology was applied in Beijing-Shanghai High Speed Railway. All defects in the concrete should be routed and filled with an appropriate compatible material and surface preparation system. Any bug holes should be filled the same and any sharp or rough surfaces should be ground to avoid protrusions [18~19]. The concrete surface defects after shot blasting was shown in Fig.5.

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Fig.5 Concrete surface defects after shot blasting

Adhesion is the most significant factor that affected the performance of polyurea coatings. Protective coatings must tightly bond to the concrete substrate for long-term protection against corrosive environments. However, the interface adhesion is highly affected by a myriad of complicated conditions including material properties, construction conditions, the application method, the quality of concrete substrate, and the way that the concrete substrate was prepared for the surface preparation system. The direct consequence of the adhesion failure was polyurea coating delamination especially in cold winter. This severe phenomenon widely existed in the polyurea application of Beijing-Shanghai high speed railway and confused the whole polyurea industry. Therefore, it is essential to study the influences of these critical factors, so as to design more reliable coating system and improve the protective performance. Polyurea delamination on jobsite in hot summer and cold winter was shown in Fig.6.

Fig.6 Polyurea delamination on jobsite in hot summer and cold winter

The tack-free time is a measure of cure process in surface preparation system and will be correlated to the upcoming polyurea application generally. It is also an important indicator of the surface preparation system. It could be influenced by a variety of influencing factors such as ambient temperature, humidity, in particular during autumn-winter and winter- spring season.

5 Solutions From October, 2009 to October 2010, this polyurea project met a lot of troubles,

such as: cold and dry season in the north, hot and moist season in the south, thousands of bug holes on the surface of shot blasted concrete beams, strong wind, extreme cold and hot in winter and summer, etc. The most difficult case is to fill and level the surface of shot blasted concrete beams by putty and primers. There is no experience to fill and level the shot blasted High Performance Concrete beams with thousands of bug holes and defects.

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Firstly, the concrete surface was scraped with epoxy putty and primers. Epoxy system was found not compatible to polyurea especially in cold winter because of its nature properties: 1) difficult to cure or can not cure in low temperature; 2) high viscosity in low temperature; 3) brittleness after curing, the three points listed above were the main factors leading to the failure of upcoming polyurea coating.

According to the patent methods [20], a new kind of all weather based surface preparation system (Polyurethane based) was launched in June, 2009. It provided comprehensive solution for Beijing-Shanghai high speed railway polyurea application in myriad climatic factors.

It is extremely cold in Dec. 2009 to Feb. 2010. Hebei and Shandong provinces were

-10～-20 ℃ with dry, Anhui and Jiangsu provinces were 0～-5 ℃ with wet.

Polyurea was easy to delaminate from epoxy primers. Polyurethane based All Weather Substrates Preparation System was accelerated to cure with catalyst in winter to change this serious situation.

It is extremely hot in Jun. to Aug. 2010. Hebei and Shandong provinces were 40 ℃

with dry, Anhui and Jiangsu provinces were 40 ℃ with humidity. Polyurea was easy

to delaminate from epoxy primers. Polyurethane based All Weather Substrates Preparation System was adjusted to slow the cure with special solvents in summer to change this serious situation. 5.1 Jobsite tests

Simultaneously, epoxy based and Polyurethane based surface preparation systems of polyurea protective coatings for concrete were selected to investigate their adhesion characteristics, tack-free time and coverage effect under different ambient temperatures and humidity.

The main composition of the studied coating systems codified by E1, E2 and PU based were presented in Table 3. PU based surface preparation system was prepared according to the patent methods [20].

Table 3 Main composition of paint systems

Code Primer Putty Intermediate Topcoat Total

thickness(μm)

E1 Epoxy Epoxy

based

Aromatic

polyurea

Aliphatic

Acrylic–polyurethane 2220

E2 Epoxy Epoxy

based

Aromatic

polyurea

Aliphatic

Acrylic–polyurethane 2210

Polyurethane

based PU PU based

Aromatic

polyurea

Aliphatic

Acrylic–polyurethane 2150

The pull-off tests [21] (according to ASTM D4541-02) were used to determine the bonding strength of coatings to concrete under different ambient temperatures (T) and

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humidity (H). Bonding strength was determined by pulling the metal fixture of the substrate. A schematic diagram of the test used for adhesion was shown in Fig. 7.

Fig. 7. Schematic diagram of the test

5.2 Adhesion results The test results of adhesion in situ under different ambient condition were

presented in Fig. 8. It showed that the bonding strength development law, failure models, the maximum value and environment adaptability were different with the test time. Fig. 8 showed the bonding strength development law of Polyurethane based surface preparation system increased at first and then tended to be stable during the test period. E1 and E2 performed lower bonding strength than Polyurethane based system under the same condition. It indicated that the Polyurethane based system showed a better performance than E1 and E2 system. This phenomenon can be explained as follows: the Polyurethane based system was a kind of polyurethane based system which was applied in wet ambient it acted as moisture cured polyurethane system and under cold dry condition it acted as plural-component polyurethane system. The epoxy based showed an unsatisfactory effect performance, as viscosity and liquidity of epoxy based system (E1, E2) were very sensitive to the application temperature and humidity in site especially in cold winter it led to high changes of internal properties in coating system, which induced to the first signs of delamination.

01

2

3

4

5

6

7

2 4 6 8 10 12

4

4

4

5

5 4

4

43

111

13

11

1

2

4

3

4

554

4

34

55

3

E1(cold dry) E1(hot wet) E2(cold dry) E2(hot wet) PU PU

Test Time(Months)

1

Adh

esio

n(M

Pa)

Fig.8. Adhesion test results from jobsite

*1. The blue straight dash line stands for 2.5MPa according to Temporary Technological Guideline) 5.3 Tack free time tests

Tack free time was an important indicator of surface preparation system; it played a

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significant role in upcoming polyurea application. The tack free time tests of three kinds of systems on jobsite were given in Fig.9.

PU E1

Hot wet condition

--Cold dry c

ondition 0

2

4

6

8

10

E2

Tack

Fre

e Ti

me,

Hou

rs

Fig.9. Tack free time tests on jobsite. Fig.9 showed that the tack free time of Polyurethane based surface preparation

system was lower than E1 and E2 surface preparation system. The best tack free time was less than 4 hour according “Temporary Technological Guideline”. It can be obviously obtained that the tack free time of E1 and E2 system was far beyond the limit (4 hour) especially in low temperature, the tack free time prolong to about 7.3 hour even to 24 hour, it mainly due to the low temperature react activity of epoxy based system. The upcoming polyurea application would be delayed for long tack free time of E1 and E2 system. 5.4 Coverage effect At Beijing-Shanghai high speed rail way construction jobsite Kunshan, Jiangsu Province, the coverage effect tests of three kinds of surface preparation system were

conducted under the same environmental condition (T:2℃,H: 85%). The results were

given in Fig.10. As evident from the Figs, the coverage effect of EP1 and EP2 surface preparation system were not satisfactory. There were still a lot of bugholes, pinholes and defects (Fig.10a, b) on concrete surface. While Polyurethane based surface preparation system showed a good coverage effect, the coverage ratio reached 100%, there were nearly no defects on the prepared concrete surface.

a b

Fig. 10. Coverage effect (a) EP base treatment system (b) Polyurethane based base treatment system

6 Technical supports

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According to the experience of being engaged in research and development for decades of years, Qingdao Technological University took parting in drifting the Temporary Technological Guideline for this project, the work team technical support of Qingdao Technological University spread from Beijing to Shanghai in this whole railway line, the technical support contained as follows:

1). Polyurea construction design 2). Polyurea raw material preparation 3). Polyurea chemical formulation 4). Polyurea testing both in lab and in jobsite 5). Training course in jobsite

a) “Temporary Technological Guideline for Spraying Polyurea As the Waterproofing Layer on the Bridge Beams of Beijing-Shanghai High Speed Railway”.

b) The core content of the monograph “Spray Polyurea Elastomer Technology”.

c) The systems of GRACO-HXP3/MP and 20/35Pro/DI. d) Shot blasting machine, automatic spray rig, adhesion tester, thickness

gauge, temperature measurement instrument. e) Polyurethane based all-weather substrate processing system,

automatic/manual spray skill and technology. f) Trouble shooting and quick solution, fast identification method of pure

polyurea vs hybrid. 6). Consulting and technical service 7). Supervision and Quality control 8). Originating and holding working conference to resolve application problems Technical support was given in Fig.11.

a b

c d Fig.11 Technical support

a-Jobsite training; b-Jobsite consulting; c-Research in lab; d-Jobsite adhesion testing

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7 Conclusions Polyurea technology may be somewhat of a newcomer to the industry, but it has

shown a good deal of versatility and application use. It provides for an extremely good cost and time effective solution to a variety of protective coating applications over conventional technologies. With the excellent mechanical properties and the advanced applying application characters, Polyurea is catching the eyes of engineers in many industrial fields and has been increasingly investigated and applied in recent years. The Beijing-Shanghai High Speed Railway polyurea project writes wonderfully new and successful chapters in the history of polyurea. However, its success is inseparable from the concerted efforts of Qingdao Technological University, especially for new kind of surface preparation system, Polyurethane based surface preparation plays a significant role in the polyurea application of Beijing-Shanghai high speed railway, and it has completely solved the polyurea application problem all the year round.

Acknowledgement This study was supported by the Polyurea Development Associate China, Research Institute of Functional Materials of Qingdao Technological University and various industries.

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