Roof in heavy rain - waterproof

 

Rigid waterproof roof refers to the use of fine stone concrete or steel fiber concrete as a waterproof layer, which mainly relies on the compactness of concrete itself and takes certain structural measures (such as increasing reinforcement, setting isolation layer, setting partition joints, caulking with grease, etc.) to achieve the purpose of waterproofing.

 

Since the elasticity of the rigid waterproof layer is small, it is extremely sensitive to uneven settlement of the foundation, slight deformation of components, vibration of the house, temperature changes, etc., and is directly in contact with the atmosphere, so it is easy to deform and crack, and carbonize and weather on the surface. If the design is unreasonable and the construction is poor, it is very easy to leak and seepage.

 

Construction requirements
When the roof structure layer adopts assembled reinforced concrete slabs, steel fiber fine stone concrete with a strength grade of not less than C20 should be used for grouting. The fine stone concrete for grouting should be mixed with expansion agent. When the width of the roof panel seam is greater than 40mm or narrow at the top and wide at the bottom, structural steel bars must be set in the seam, and the seam at the end of the plate should be sealed. The intersection of the rigid waterproof layer and the gable, parapet and protruding roof structure should be treated with flexible sealing. An isolation layer should be set between the concrete waterproof layer and the base layer. The rigid waterproof roof should adopt structural slope adjustment, and the slope should be 2%~3%. Cement mortar should be used for slope adjustment of gutters and eaves. When the slope thickness is greater than 20mm, steel fiber fine stone concrete should be used.

 

The thickness of the steel fiber fine stone concrete waterproof layer should not be less than 40mm, and a bidirectional steel mesh with a spacing of ф4~ф6 and a spacing of 100~200mm should be configured. The steel mesh is set at the upper part of the fine stone concrete and disconnected at the partition joint. The thickness of its protective layer should not be less than 10mm.

 

The partition joint of the waterproof layer should be set at the supporting end of the roof panel, the turning point of the roof, and the intersection of the waterproof layer and the protruding roof structure, and should be aligned with the board joint. The vertical and horizontal spacing of the partition joint should not be greater than 6m, and the width of the partition joint should be 5-30mm. The sealing material must be embedded in the partition joint, and a protective layer should be set on the upper part.

 

Construction of rigid waterproof layer
The cross section of the partition joint should be made wide at the top and narrow at the bottom; when the cutting method is used for construction, the cutting depth of the partition joint should be 3/4 of the thickness of the waterproof layer. Steel fiber fine stone concrete should be mechanically mixed, and the mixing time should not be less than 2 minutes. The concrete of each partition plate must be poured once, and the concrete should be pressed twice after water absorption. Concrete should be cured 12~24 hours after pouring, and the curing time should not be less than 14 days. No one is allowed to go on the roof during the initial curing period. The construction temperature should be 5~35℃, and construction should be avoided under negative temperature or scorching sun.

 

Construction of isolation layer
Low-strength grade mortar, paper reinforced ash, non-woven fabrics, dry-laid rolls, plastic films and other materials are set under the steel fiber waterproof concrete of the rigid waterproof roof to play an isolation role, so that the structural layer is separated from the base layer or insulation layer and waterproof layer, and the deformation is not restricted to each other, so as to reduce the tensile stress of the waterproof layer and cause cracking of the rigid waterproof layer.

 

When transporting concrete on the surface of the isolation layer, a pad should be set. When tying the steel bars, the surface of the isolation layer must not be pierced. When pouring concrete, the isolation layer must not be vibrated.

 

Process principle
The steel fiber milled from the steel ingot is distributed in a three-dimensional disorder in the concrete, and has good bonding performance with the concrete, and the composite matrix can bear the load together. The bonding force between the steel fiber and the concrete matrix has a significant inhibitory effect on the expansion of microcracks in the matrix, thereby significantly improving the crack resistance of the concrete.

 

In addition, after the steel fiber concrete is subjected to force, the steel fiber will consume a lot of energy when it is debonded and pulled out of the matrix or broken. That is to say, when new microcracks appear in the matrix, the steel fibers perpendicular to the microcracks can still transmit part of the tension, which makes the steel fiber concrete show good plastic characteristics, making the concrete change from a brittle material to a pseudo-plastic material. Compared with ordinary concrete of the same grade, the plasticity and toughness are significantly increased, and the tensile and flexural strengths are also significantly improved.

 

Therefore, under the premise of no cracking, the maximum shrinkage rate of concrete allowed is greatly increased compared with ordinary concrete.