Technical Note

A Comparison of Xile Deep Penetration Sealer (DPS) and Traditional Waterproof Materials on Highway Bridge Waterproofing

(Written by Xiamen Xile Technology Co. Ltd.)

【Abstract】The article overviews some traditional waterproof materials that are deficiency for high way and high rail way and introduce a kind of water-base, penetrating and crystallization waterproof material that are applied on bridges and overpasses of high way and high railway to enhance concrete impermeability and compression strength, improve heat resistance, cl_ resistance and sticking strength for concrete usage life span and durability.

【Key words】waterproof of bridge floor, impermeability, compression strength, heat resistance, cl_  resistance and sticking strength

1. Common Deficiency of Highway Bridge Projects

Nowadays as the construction of highways and high-speed railways is developing in full swing, proprietors have attached increasing importance to the waterproofing of highway bridge floor. Traditional waterproof materials which have been applied in many highway bridge projects result in high maintenance costs and structural damage because of their intrinsic deficiencies that cannot be neglected. Common deficiencies of reinforced concrete structure of highway bridge projects include cracks, peeling, spalling, honeycombs, water leakage, exposure of reinforcement bar, corrosion of steel bars, insufficient bearing capacity. The fundamental cause of these deficiencies is insufficient durability of material, namely degradation of material.

The reinforced concrete structure is a kind of composite material made of aggregate of certain graduation, inert material and reinforcing bar, with cement hydrates as the cementing material. In this composite structure, the reinforcing steel bars ensure its strength of extension while the concrete provides the compression strength and protects the reinforcing bars. Hence, the degradation of reinforced concrete includes two aspects: degradation of concrete and corrosion of reinforcing steel bars. Degradation of concrete is the decline of its performance resulting from physical, chemical and biological effects of the surroundings which cause the denaturing reaction, dissolution and precipitation, crystallization and expansion, matrix cracking of certain elements of concrete during use. Degradation of concrete mainly includes carbonization of concrete (neutralization), dissolutive corrosion, alkali aggregate reaction (AAR), corrosion by erosive agents, freeze thawing damage, concrete crack. Not only will concrete degradation reduce performance of concrete, but it will also accelerate the corrosion of reinforcing steel bars in the concrete.

2. Technological approaches for improving concrete durability

Through analysis of factors affecting the durability of concrete, we found that the occurrence of durability issues such as freeze thawing, carbonization, corrosion and alkali aggregate reaction and concrete cracks is inextricably linked to the following 3 factors: (1) porosity of concrete; (2) alkali content of concrete; (3) presence of aqueous medium.

Hence, how to reduce the porosity and alkali content of concrete, and to come off effective concrete waterproof protection, has become a key issue to ensure concrete durability. Common practice includes the following measures: (1) adding sub-nano materials; (2) adding water-soluble polymers; (3) adding organic fibers; (4) applying super plasticizer, lowering the water-cement ratio, and increasing the density of concrete; (5) using air entraining agent to improve frost-resistance; (6) using special cement and mixed materials; (7) focusing on prevention, using low-alkali cement and mixed cement to control concrete alkali content and reduce alkali aggregate reaction.

Although advanced construction technology and improvement of construction quality can enhance concrete durability in some degree, but they are confined to the planning stage of concrete proportioning, that is to say, these measures is applicable for specific stages before or during concreting while inapplicable for solidified concrete. The common practice is to reinforce and repair the concrete with organic polymer material when there are major damages. However, under these circumstances (concrete porosity, alkali content of concrete and presence of aqueous medium) hidden danger cannot be removed completely, because organic polymer material can only protect the surface of concrete without any changes to both of the key factors of porosity and alkali content. Another fatal flaw of organic polymer material is its aging which gives rise to problems such as embrittlement and drop of bond strength, and reduces the protection effect of concrete, which leads to constant repair and immense maintenance costs as well as huge consumption of manpower and material resources.

Therefore, how to address the durability issue of concrete (buildings, bridges and structures) has been widely studied and discussed by experts and scholars all over the world. Over the recent years, the capillary crystalline Deep Penetration Sealer (DPS), widely used in the USA, provides a fundamental solution to concrete durability and has been applied and popularized in a large number of projects.

3. Analysis of other waterproof materials

In China, waterproof material for highway bridge floor used to be mainly modified emulsion asphalt, followed by membrane material for special highway bridge, apart from which no traditional water proof materials such as JS, emulsion coated material and cementitious waterproof material were used, because these three representative construction materials are not fit for the waterproofing of bridge floor. The reasons are as follows: (1) emulsion coated material and cementitious waterproof material as well as JS are not thick enough and it will increase cost to thicken them. (2) The painting and paving of these materials will affect the progress of item projects. (3) Materials of this type will not integrate with the concrete casting area at all. Neither can it last as long as the concrete. (4) Painting and paving materials of this kind will inevitably give rise to delamination with the concrete in the future. (5) During the transmission process of dynamic loads, they can be easily stripped, crushed and detached; (6) Due to that they are unable to integrate with the bridge floor and concrete structure of the road surface, they can’t reach the goal of protecting concrete durability and improving compression strength of concrete surface, as well as preventing chloride ion acid rain in the long run. At present, many problems occurred in the domestic use of modified emulsion asphalt and coiled material, for example, modified water-base asphalt of different producers varies widely in quality, with insufficient tackiness and short life span. It can easily melt in high temperature and cause delamination with the concrete, which ultimately entails tremendous volume of maintenance work and huge cost in the future. The paved coiled material also inevitably causes delamination with the concrete structural surface. Moreover it increases the construction costs and time to do a troweling layer and protective layer during the paving process. Meanwhile, it increases static loads of the bridge floor, which isn’t cost-effective with the price remaining high.

In conclusion, the waterbased deep penetration sealer – Xile DPS can overcome the deficiencies of traditional waterproof materials to the most extent. Its advantage will be elaborated on in this article. What is worth notice is that, it brings about favorable economic benefits. By doing simple calculating, we know that the cost of waterproofing of some domestic bridges using Xile DPS is much lower. Generally speaking, the construction cost of those using Xile DPS is 1/3 or even 1/2 lower than that of those using other materials. Besides, due to its physicochemical property, it ensures the bridge floor’s durability, density, cohesiveness and resistance to pressure. Its advantage is also very prominent in actual operation. It can be operated wet and sprayed directly, not subject to environmental constraints. With Xile DPS, the construction is very simple without having to do the screed layer and protective layer before or after painting. What’s more, the construction cost is moderate and the quality is reliable.

4. Basic requirements of waterproof material for highway bridges

As an important link of highway bridge construction, although waterproof accounts a small proportion of investment and requires small volume of work, it plays an indispensable role in the overall bridge maintenance and maximum protection of the bridge structure. Hence, importance should be attached to the selection of material, construction technique and quality guarantee during the construction of waterproof and anticorrosion projects, so as to ensure the durability of bridge floor. It is of significance to choose an appropriate waterproof material. An appropriate waterproof material for highway bridges should withstand long-term exposure to an adverse natural environment of storms and high temperature and meet the special requirements of highway bridge construction.

4.1 Impermeability

It is determined by the concrete’s structure and harsh nature environment. The internal pore space of the concrete structure will allow water, acidic and alkaline pollutants to infiltrate into the concrete structure and cause corrosion of reinforcing steel bars and concrete cracks. In order to prevent erosion and destruction of pollutants, waterproof material should have good impermeability.

4.2 Resistance to chloride ions

The corrosion of chloride is one of the key factors that deteriorate concrete. Once free CL- in the environment (including seawater, sea wind, deicing salts and saltwater drops from refrigerator wagons) penetrates into the concrete, diffluent CaCl2 and large amount of crystal water as well as solid compound with a several-fold larger size will be generated, accelerating the corrosion of reinforcing steel bars and causing expansion and cracking of concrete basal body. Therefore, waterproof material for highway bridges should exhibit good resistance to chloride ions.

4.3 Compression strength

The road surface directly bears dynamic loads from paved asphalt and cars transmitting on it and endures the destruction from temperature difference and exterior stress, therefore the material to be applied should display capability to enhance the compression strength and to improve concrete stability and durability.

4.4 Heat resistance

The highest temperature during bridge construction and paving asphalt could reach 150℃, and the friction and scraping caused by running vehicles, high temperature and intense sun exposure in summer contributes to high surface temperature. To ensure lasting effect of waterproof material, it should have excellent heat resistance.

4.5 Adhesive property

The bridge floor is a multi-layer structure, among which the waterproof layer should function as a means of cohesion and its adhesiveness should fulfill the perfect combination of different layers so as to allow uniform transmission of upper loads and to ensure the overall anti-load capability of the bridge floor even in the presence of waterproof layer, as well as to ensure solid combination of the concrete structural layer and the asphalt layer.

5. Basic properties of water-base capillary crystalline waterproof material

Waterproof material featuring excellent impermeability, heat resistance, cohesiveness, resistance to chloride ions and capability to enhance surface compression strength of concrete remain rare in current traditional markets home and abroad. Common waterproof materials boast of good impermeability, but fall short on enhancing surface compression strength and cohesiveness. Because of their own molecular structure and due to that traditional waterproof materials are composed of organic material, they can’t penetrate into the interior interspace of concrete and integrate with the concrete, thus fail to enhance the concrete surface density, which entails an waterproof layer during construction. By doing this, the paving of asphalt and cohesiveness of concrete will be affected. Meanwhile delamination and distortion will occur and reduce the anti-load capability.

Water-base capillary crystalline waterproof material that applies to the Water-base Capillary  Organic Waterproof Agent JC/T1018-2006 industry standard exhibits excellent performance in waterproof and anticorrosion of highway bridges. The following analysis by relevant technical indicators will illustrate the advantages of water-base capillary crystalline waterproof material.

5.1 Reliable impermeability

Water-base capillary crystalline material features good hydrophilicity which allows it to penetrate 20mm deep into the concrete. The alkali content in the interior of conventional concrete is at least 361 times more than that in the surface area. The water-base capillary crystalline material can penetrate into the interior of concrete and chemically react with alkali with the presence of water and generate silicone gel, covering the capillary channels. The layer of silicone gel once hydrated will become a solid, ventilate and acicular-structured substance and fill all capillary channels beneath the concrete surface, with its resultants being a permanent part of the concrete. Its penetration will reduce the alkali content within the concrete and prevent intrusion of external harmful substances. On condition of water presence, this process will keep repeating until the concrete is completely sealed up. It can be permanently waterproof, moistureproof and impermeable while enabling the sealed concrete to “breathe”. Test data of this technical indicator by reference to JC/T1018-2006 Standard is shown in the following table:

Serial number

Item

Standard

Test Result

7

impermeability/ impermeability height,mm

≤35

31

5.2 Evident effect of resistance to chloride ions

Water-base capillary crystalline material with water as its carrier penetrates into the interior of the concrete and chemically reacts with free alkali and generates silicone gel which seals the capillary channels and micro cracks within the concrete, forming an effective screen. Silicon crystal owns good chemical stability and does not react with any other substances. As a result, even if the chloride ion, the most active ion of nature, infiltrates along with water, the silicon crystal will not react with it, which effectively prevents the erosion of chloride ions and destruction of acids and alkalis. Test data of this technical indicator by reference to the CNS1232 and ASTM C39 standard is shown in the following table:

Treatment of Specimens

Matching Number

Untreated group

kgf/cm2

Treated group

kgf/cm2

Reduction Rate

%

PP210

139.38

106.82

23.36

PF210

106.67

85.79

20.32

PP350

81.51

60.79

25.42

PF350

77.43

49.62

35.92

5.3 Enhancement of concrete surface strength

Water-base capillary crystalline material reacts with alkaline substance of the concrete and generates silicone gel which imbeds the capillary channels of concrete structure and forms an indivisible screening layer. As a result the concrete surface density is enhanced. Moreover the intrinsic rigidity of silicon crystal strengthens the concrete structure and contributes the concrete surface strength up to 20%~30%. Hence water-base capillary crystalline material well facilitates the enhancement of concrete surface strength. Test data of this technical indicator by reference to the ASTM standard is shown in the following table:

Treatment of Specimens

Sample Number

Untreated Group

Mpa

Treated Group

Mpa

Enhancement Rate

%

20

36.00

42.50

18.06

21

31.00

42.00

35.48

Average Value

33.50

42.25

26.12

5.4 Excellent heat resistance

Major components of water-base capillary crystalline material contain inorganic minerals which react with free alkali in the interior pores of the concrete and generate crystals as part of the concrete structure. Such kind of reaction is condensation reaction other than reversible reaction. Due to these natural mineral components, it will not change under high temperature of 800℃. Therefore it can stand the high temperature when paving bituminous concrete and the high temperature in summer. The waterproof layer will not be destroyed either. And because it is not with a membrane surface, the collision between the construction machine and the concrete surface during paving asphalt will not impact the waterproofing. Test data of this technical indicator by reference to the DBJ-01-54-2001standard is shown in the following table:

Serial Number

Item

Standard

Test Result

6

heat resistance

80℃,72h,no chalking or fissure

no chalking or fissure

5.5 Good cohesiveness

Major components of water-base capillary crystalline material contain inorganic minerals whose molecular structure is way smaller than the pores within the concrete. Its waterproof mechanism is to penetrate into the interior of the concrete and form silicone gel to seal off capillary channels and micro cracks within the concrete. It has excellent compatibility and can form an inseparable whole with the concrete. Meanwhile, it can reduce desertification and chalking of the concrete surface and keep the surface layer dry and clean, thereby elevates the cohesiveness of the concrete and asphalt, which allows the asphalt to joint with the concrete surface without possibility of stripping. Test data of this technical indicator by reference to the CNS1232 and ASTM C39 standard is shown in the following table:

Treatment of Specimens

Sample Number

Rough Surface Treated Group

kgf/cm2

Treated Group

kgf/cm2

Reduction Rate

%

1

439

544

23.92

2

442

562

27.15

3

407

503

23.59

Average Value

429

536

24.89

6. Construction features of water-base capillary crystalline waterproof material

6.1 Convenient construction

Using water-base capillary crystalline waterproof material does not demand too much on construction equipment. For small-sized and fine operation projects, use hand-hold compression sprayers are advised. For concrete surface with larger operation area, use knapsack sprayers. Other auxiliary tools include cutters, chisels, wire brushes, hammers, rags and brooms, etc.

Water-base capillary crystalline waterproof material is environmentally friendly and does no harm to the health of human body and environment. The construction site is not subject to any constraints, as long as the ambient temperature is between 5℃-32℃.The material has a wide range of application and can be applied in various parts and nodes of bridge. It has no special requirements for surface condition and is suitable for different geometries without problems of edging or sealing; No strict requirement for basement layer surface, simply remove the water, dust and oil stain. The material can be applied on wet basal plane, either upstream or downstream.

6.2 High Efficiency

Before using water-base capillary crystalline waterproof material, dilution or mixing is not needed, nor is any ingredient. There is no need to do a troweling layer. The stock solution can be brushed, painted or sprayed on new or old concrete surface in one step. Efficiency of construction per capita can reach over 1000㎡/day. And no protective layer is needed after construction is completed.

6.3 Simple maintenance

Normal penetration time for water-base capillary crystalline waterproof material is 1-2 hours, final setting time normally less than 400 minutes. Therefore, gentle touch is allowed 30 minutes after the material is sprayed. In 3hours when the surface is dry, the ground can be walked on. In 24 hours other operations can proceed. Even if heavy rain is encountered 2 hours after the material is sprayed, its waterproof effect will not be influenced.

7 Conclusions

In summary, it is not difficult to find that in addressing degradation of highway and high-speed railway bridge concrete structure, water-base capillary crystalline waterproof material boasts of advantages in both theoretical technologies and application functions. Meanwhile, it is more relevant, economical, applicable and convenient compared to traditional waterproof materials. It can not only significantly improve waterproof capability and impermeability of bridge floor, but also effectively prevent aging, chalking, weathering and neutralizing of concrete. Moreover, its advantage is also prominent in actual operation process. It can be operated wet and sprayed directly, not subject to environmental constraints; the operation is very simple without having to do the troweling layer and protective layer before or after painting. With moderate construction cost, this material is worthwhile to be widely applied in future highway bridge projects. It deserves attention from relevant proprietors and construction units.

8. References

[1] Wang, D. (2001, June). Analysis of Permeable Crystallization Type Waterproofing Agent. China Building Waterproofing.

[2] Sun, J. & Chen, S. (2006, April 3). Protection of EVERCRETE DPS on Concrete Durability. China Building Materials.

[3] Sun, J. (2007, February). Simple Discussions About The Protection Of American EVERCRETE DPS On The Concrete Durability. Fujian Building Materials.

[4] Chen, S. & Tang, X. (2008, May 19). A Concise Comparison of Cementitious and Water-base Capillary Crystalline Waterproof Material. China Building Materials.

August 13, 2009
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