1Hazards caused by water being heated to steam and damage to buildings and countermeasures
1.1 Volume change after water is heated to steam
The density of the water changes when the water is heated. Between 0 and 4°C, the density of water increases with increasing temperature, and the density of water at 4°C is the largest; as the temperature continues to rise, the density of water becomes smaller. The density of pure water at 0°C is 999.87 kg/m3, density at 1°C is 1 000 kg/m3, and density at l00°C is 958.38 kg/m3. At 101 kPa (1 atm), the volume of 1 MOLH2O at 0°C is 18 mL. When water is heated to 100°C, liquid water vaporizes into water vapor. At 100°C, the volume of 1 mol H20 at 101 kPa is about 3.06×10 4 mL. From this we can conclude that at 101 kPa, the volume of MOLH2O at 100°C is approximately 1700 times greater than the volume of 1 mol H20 at 0°C.
1.2 Hazard of Steam to Buildings
The maximum temperature of the black roof in summer can reach 85°C. According to the ideal gas equation, I mol water is completely vaporized, with a volume of 26 010 mL at 101 kPa and 85°C, and a volume change of 1445 times. If the volume occupied by 1 mol of water does not change, it is still calculated as the volume of liquid water at 0°C (18 mL). At 85°C, the water will produce a pressure of 1.46 × 108 Pa (l 445 atmospheres) on the surrounding buildings. This means that each m2 is under pressure of 1.46 x 108N.
Because buildings are made of inorganic materials such as silicates, these materials are porous and breathable, which can greatly reduce the pressure exerted by water vapor on buildings. Therefore, the actual pressure on buildings is much less than 1.46×. 108N/m2, but the pressure generated by water vapor on buildings is still very serious, especially in the parts of buildings with poor ventilation, this hazard is very obvious.
The harm of water vapor to buildings often causes peeling between the waterproof layer and the base layer, cracking of the waterproof layer, cracking of the lap seam, and the result that the life of the waterproof layer is greatly reduced, and drowning occurs under the waterproof layer.
1.3 Measures to Avoid Water Vapor Damage to Waterproof Layers
In order to prevent water vaporization from causing damage to the waterproof layer, we can take the following measures:
1.3.1 Ensure that the grass-roots layer is fully dry
In order to avoid the destructive pressure on the waterproof layer caused by water becoming water vapor, we should allow the water in the base layer to fully evaporate and dry before the waterproof layer is applied. The degree of dryness of the grassroots layer can be tested by the following method: 1 m2 roll is laid flat on the ground layer, and after 3 to 4 hours, the base layer covered by the coil and the coil are checked for watermarks. No watermark is considered as dry. Vapor barrier or waterproof layer can be constructed.
1.3.2 Setting the exhaust pipe
When the roof insulation is dry or the construction period is not required to wait until the construction of the waterproof layer after drying, exhaust pipes shall be provided on the roof. The purpose of setting the exhaust pipe on the roof is to allow the water vapor in the entire insulation layer to communicate with the atmosphere, and the pressure caused by the discharge of the water into the steam layer.
The arrangement method of the exhaust steam pipe is as follows: a. The partitioning layer of the roofing screed shall be installed vertically and horizontally and shall be connected to each other with a spacing of not more than 6 m; the split seam shall also be used as the exhaust steam path, and the exhaust steam path shall communicate with the exhaust pipe connected to the atmosphere. . At least one exhaust pipe shall be installed every 36 m2: b. Exhaust steam pipes shall be installed under the eaves or in the vertical and horizontal intersections of the exhaust pipes; c. Exhaust steam pipes shall be installed on the structural layer, and exhaust steam pipes passing through the insulation layer shall be Punch exhaust; d, exhaust pipes should be treated with water. Specific reference can be made to the provisions of Article 9.4.2 of GB "Technical Specifications for Roof Engineering".
1.3.3 Requirements for Waterproof Layers
First, the use of empty shop, sticky, sticky construction, fully dispersed water vapor pressure on the waterproof layer. Secondly, waterproof materials with high tensile strength should be selected to effectively prevent water vapor from damaging the waterproof layer.
2 The damage caused by freezing of water on buildings and its countermeasures
2.1 Volume changes after water freezes and pressure on surrounding buildings
Under normal atmospheric pressure, water will freeze when the temperature drops to 0°C. The density of pure water at 0°C is 999,87 kg/m3, and the density of ice at 0°C is 916.71 kg/m3. When the water freezes, the volume suddenly increases by about 9%; when the ice melts, the volume suddenly increases. Decrease. A 2 m-thick raft base slab, with a total depth of 0.2 mm, a length of 0.5 m and a depth of 0.5 m, in the process of ice formation from water, when completely surrounded by the basement , The lateral pressure of 200 MPa can be applied to the surrounding concrete. This is enough to destroy any high-strength reinforced concrete structure, but also will break or break through all flexible or rigid waterproof material.
2.2 Damage to Buildings Caused by Cold Icing
Most of the building materials are porous inorganic materials, and holes, gaps, and capillary channels exist inside these materials, which are prone to water absorption. In the repeated freezing and thawing process of water and ice, it will have a great destruction effect on buildings, such as: the surface of many building cement mortar, paint, waterproof layer and building peeling, concrete is frozen powder, is this Freeze-thaw results.
2.3 Countermeasures to avoid freezing injury
In order to prevent damage caused by freezing to buildings, we can take the following measures:
2.3.1 Remove stagnant water
Exclude the accumulation of water around the building. Without water, there are no conditions for freezing damage.
2.3.2 Improve the waterproof performance of buildings
We can prevent water from entering the building by improving the waterproof performance of the building, so as to prevent freezing damage. In the field of building waterproofing, waterproofing can generally be divided into the following three forms according to the waterproof method of the waterproof material:
1) Compact waterproof. In the process of mixing concrete, waterproof concrete and waterproof mortar are made by adopting a reasonable grading and adding admixtures such as expansive agent, water reducing agent, water repellent agent and polymer emulsion. By increasing the compactness of concrete and mortar, reducing cracks in concrete and mortar and capillary channels, and improving the impermeability of concrete and mortar; reinforcing materials such as steel bars, glass fibers, and polymer fibers can also be used in concrete and mortar. Improve the tensile strength of concrete and mortar and prevent them from cracking. If the concrete and mortar are 100% dense and the porosity is zero, it is possible to avoid the occurrence of frost damage. However, this is only an ideal state and cannot be achieved in actual construction. These measures taken by us can only reduce the porosity, reduce the degree of damage caused by freezing, and cannot fundamentally eliminate the presence of pores and the occurrence of frost damage.
2) Use hydrophobic waterproof. Since concrete and mortar cannot achieve 100% density, there must be some pores and capillaries. When mixing concrete and mortar, we can incorporate hydrophobic waterproofing agents and liquids, such as silicones, to form a hydrophobic film on the inner pores of the concrete and mortar, and on the inner wall of the capillary to reduce the water absorption of the silicate material and eliminate the capillary phenomenon. The production of water prevents the penetration of water into the concrete and mortar, so as to reduce the occurrence of freezing damage.
3) Waterproof film. The organic waterproof layer has the functions of waterproof and vapor barrier. The construction of an organic waterproof layer on the surface of the building will form a closed waterproof barrier on the surface of the building, which can block the invasion of water and prevent the occurrence of frost damage. This type of organic waterproof material may be a polymer modified bitumen waterproof sheet, a polymer type waterproof sheet (sheet) material, a polymer modified pitch type, and a polymer type waterproof coating.
In order to ensure the waterproof effect, the above three types of waterproof methods are often combined in practical projects.
3 Conclusion
Through the analysis of the changes in the physical properties of water during the gasification and solidification process, we know that the gasification and solidification of water can cause serious damage to buildings. This kind of damage is sometimes catastrophic. We can avoid or reduce the occurrence of this hazard through reasonable design and construction.
1.1 Volume change after water is heated to steam
The density of the water changes when the water is heated. Between 0 and 4°C, the density of water increases with increasing temperature, and the density of water at 4°C is the largest; as the temperature continues to rise, the density of water becomes smaller. The density of pure water at 0°C is 999.87 kg/m3, density at 1°C is 1 000 kg/m3, and density at l00°C is 958.38 kg/m3. At 101 kPa (1 atm), the volume of 1 MOLH2O at 0°C is 18 mL. When water is heated to 100°C, liquid water vaporizes into water vapor. At 100°C, the volume of 1 mol H20 at 101 kPa is about 3.06×10 4 mL. From this we can conclude that at 101 kPa, the volume of MOLH2O at 100°C is approximately 1700 times greater than the volume of 1 mol H20 at 0°C.
1.2 Hazard of Steam to Buildings
The maximum temperature of the black roof in summer can reach 85°C. According to the ideal gas equation, I mol water is completely vaporized, with a volume of 26 010 mL at 101 kPa and 85°C, and a volume change of 1445 times. If the volume occupied by 1 mol of water does not change, it is still calculated as the volume of liquid water at 0°C (18 mL). At 85°C, the water will produce a pressure of 1.46 × 108 Pa (l 445 atmospheres) on the surrounding buildings. This means that each m2 is under pressure of 1.46 x 108N.
Because buildings are made of inorganic materials such as silicates, these materials are porous and breathable, which can greatly reduce the pressure exerted by water vapor on buildings. Therefore, the actual pressure on buildings is much less than 1.46×. 108N/m2, but the pressure generated by water vapor on buildings is still very serious, especially in the parts of buildings with poor ventilation, this hazard is very obvious.
The harm of water vapor to buildings often causes peeling between the waterproof layer and the base layer, cracking of the waterproof layer, cracking of the lap seam, and the result that the life of the waterproof layer is greatly reduced, and drowning occurs under the waterproof layer.
1.3 Measures to Avoid Water Vapor Damage to Waterproof Layers
In order to prevent water vaporization from causing damage to the waterproof layer, we can take the following measures:
1.3.1 Ensure that the grass-roots layer is fully dry
In order to avoid the destructive pressure on the waterproof layer caused by water becoming water vapor, we should allow the water in the base layer to fully evaporate and dry before the waterproof layer is applied. The degree of dryness of the grassroots layer can be tested by the following method: 1 m2 roll is laid flat on the ground layer, and after 3 to 4 hours, the base layer covered by the coil and the coil are checked for watermarks. No watermark is considered as dry. Vapor barrier or waterproof layer can be constructed.
1.3.2 Setting the exhaust pipe
When the roof insulation is dry or the construction period is not required to wait until the construction of the waterproof layer after drying, exhaust pipes shall be provided on the roof. The purpose of setting the exhaust pipe on the roof is to allow the water vapor in the entire insulation layer to communicate with the atmosphere, and the pressure caused by the discharge of the water into the steam layer.
The arrangement method of the exhaust steam pipe is as follows: a. The partitioning layer of the roofing screed shall be installed vertically and horizontally and shall be connected to each other with a spacing of not more than 6 m; the split seam shall also be used as the exhaust steam path, and the exhaust steam path shall communicate with the exhaust pipe connected to the atmosphere. . At least one exhaust pipe shall be installed every 36 m2: b. Exhaust steam pipes shall be installed under the eaves or in the vertical and horizontal intersections of the exhaust pipes; c. Exhaust steam pipes shall be installed on the structural layer, and exhaust steam pipes passing through the insulation layer shall be Punch exhaust; d, exhaust pipes should be treated with water. Specific reference can be made to the provisions of Article 9.4.2 of GB "Technical Specifications for Roof Engineering".
1.3.3 Requirements for Waterproof Layers
First, the use of empty shop, sticky, sticky construction, fully dispersed water vapor pressure on the waterproof layer. Secondly, waterproof materials with high tensile strength should be selected to effectively prevent water vapor from damaging the waterproof layer.
2 The damage caused by freezing of water on buildings and its countermeasures
2.1 Volume changes after water freezes and pressure on surrounding buildings
Under normal atmospheric pressure, water will freeze when the temperature drops to 0°C. The density of pure water at 0°C is 999,87 kg/m3, and the density of ice at 0°C is 916.71 kg/m3. When the water freezes, the volume suddenly increases by about 9%; when the ice melts, the volume suddenly increases. Decrease. A 2 m-thick raft base slab, with a total depth of 0.2 mm, a length of 0.5 m and a depth of 0.5 m, in the process of ice formation from water, when completely surrounded by the basement , The lateral pressure of 200 MPa can be applied to the surrounding concrete. This is enough to destroy any high-strength reinforced concrete structure, but also will break or break through all flexible or rigid waterproof material.
2.2 Damage to Buildings Caused by Cold Icing
Most of the building materials are porous inorganic materials, and holes, gaps, and capillary channels exist inside these materials, which are prone to water absorption. In the repeated freezing and thawing process of water and ice, it will have a great destruction effect on buildings, such as: the surface of many building cement mortar, paint, waterproof layer and building peeling, concrete is frozen powder, is this Freeze-thaw results.
2.3 Countermeasures to avoid freezing injury
In order to prevent damage caused by freezing to buildings, we can take the following measures:
2.3.1 Remove stagnant water
Exclude the accumulation of water around the building. Without water, there are no conditions for freezing damage.
2.3.2 Improve the waterproof performance of buildings
We can prevent water from entering the building by improving the waterproof performance of the building, so as to prevent freezing damage. In the field of building waterproofing, waterproofing can generally be divided into the following three forms according to the waterproof method of the waterproof material:
1) Compact waterproof. In the process of mixing concrete, waterproof concrete and waterproof mortar are made by adopting a reasonable grading and adding admixtures such as expansive agent, water reducing agent, water repellent agent and polymer emulsion. By increasing the compactness of concrete and mortar, reducing cracks in concrete and mortar and capillary channels, and improving the impermeability of concrete and mortar; reinforcing materials such as steel bars, glass fibers, and polymer fibers can also be used in concrete and mortar. Improve the tensile strength of concrete and mortar and prevent them from cracking. If the concrete and mortar are 100% dense and the porosity is zero, it is possible to avoid the occurrence of frost damage. However, this is only an ideal state and cannot be achieved in actual construction. These measures taken by us can only reduce the porosity, reduce the degree of damage caused by freezing, and cannot fundamentally eliminate the presence of pores and the occurrence of frost damage.
2) Use hydrophobic waterproof. Since concrete and mortar cannot achieve 100% density, there must be some pores and capillaries. When mixing concrete and mortar, we can incorporate hydrophobic waterproofing agents and liquids, such as silicones, to form a hydrophobic film on the inner pores of the concrete and mortar, and on the inner wall of the capillary to reduce the water absorption of the silicate material and eliminate the capillary phenomenon. The production of water prevents the penetration of water into the concrete and mortar, so as to reduce the occurrence of freezing damage.
3) Waterproof film. The organic waterproof layer has the functions of waterproof and vapor barrier. The construction of an organic waterproof layer on the surface of the building will form a closed waterproof barrier on the surface of the building, which can block the invasion of water and prevent the occurrence of frost damage. This type of organic waterproof material may be a polymer modified bitumen waterproof sheet, a polymer type waterproof sheet (sheet) material, a polymer modified pitch type, and a polymer type waterproof coating.
In order to ensure the waterproof effect, the above three types of waterproof methods are often combined in practical projects.
3 Conclusion
Through the analysis of the changes in the physical properties of water during the gasification and solidification process, we know that the gasification and solidification of water can cause serious damage to buildings. This kind of damage is sometimes catastrophic. We can avoid or reduce the occurrence of this hazard through reasonable design and construction.