What Is Rigid Roof Insulation?

A rigid waterproof roof is a roof waterproof layer made of concrete. Expansion agent, water reducing agent, waterproofing agent and other additives are mixed in the concrete to make the concrete fine and dense after pouring, and it is difficult for water molecules to pass through, thereby achieving the purpose of waterproofing. The advantages of rigid waterproof roof are cheap price, good durability and convenient maintenance, but the disadvantages are high density, low tensile strength and small tensile strain.

Compared with coiled materials and film waterproof roofing, rigid waterproof roofing materials are easy to obtain, cheap, durable, and easy to maintain. However, rigid waterproofing layer materials have high apparent density, low tensile strength, and low ultimate tensile strain. It is susceptible to cracks due to the effects of dry and wet deformation, temperature deformation and structural deformation of concrete or mortar.

Therefore, the rigid waterproof roof is mainly suitable for waterproofing of Grade II roofing, and it can also be used as a waterproof layer in the multiple waterproofing fortifications of Grade I and II roofing; The roof of a roof, and the roof of a building subject to vibration or shock. Moreover, the joints of the rigid waterproof layer should be used in combination with flexible materials to ensure the reliability of waterproofing.

1. cement

Should be used

1) Pay attention to the engineering quality of the roof base, and the structural layer should be the whole cast-in-situ reinforced concrete. The position of structural negative tendons should be correct, the number should meet the design requirements, the thickness of concrete should meet the requirements, the mix ratio should be correct, and vibration and maintenance should be strengthened.

2) Strictly leveling and isolation layer construction. Clean up the base layer, brush the cement slurry together, and then use 1: 2 cement mortar as the leveling layer, thickness 10 mm ~ 20 mm, the local thick part should be divided into two or more leveling, and the last layer should be smoothed It is required to be firmly bonded to the base layer and have good strength, and consider it as a waterproof measure to ensure smooth slope and flat surface. The construction quality of the isolation layer is a key measure to ensure the quality of waterproofing. Before construction, the surface must be free of debris, flat and dry, to ensure that the construction is dense and uniform, and truly play a role in detachment.

3) Construct according to operating procedures to control the quality of the waterproof layer. Reasonable reinforcement, the mesh position is in the upper part of the waterproof layer, the end is hooked with hooks, the overlap length is 250 mm, the wire is broken at the position of the sub-slot, and the upper protective layer is not less than 10 mm. When pouring fine stone concrete, the slump should be frequently checked, and the board surface treatment process during construction must be strict. Vibration must be smooth and compact. Use a high-frequency, low-amplitude, low-power (0.5 kW) flat vibrator to vibrate it sideways Then, use a moderate-weight roller to roll horizontally and vertically.After the concrete surface is slurry, it can be considered compact. Use a wooden trowel to smooth it out, and the platen will be polished. After receiving the water, it should be polished again to ensure that the concrete is wiped three times, vibrating. Wipe it flat after it is compacted and lightened before the initial setting. The thickness of the rigid waterproof layer should meet the design requirements, should not be less than 40 mm, and the thickness should be uniform. It is strictly forbidden to sprinkle water, add cement slurry or dry cement on the concrete surface when applying pressure to avoid shelling, sand and cracks. The concrete in the divisional joints must be vibrated at one time, and the construction joints must not be left.

4) Control the pouring quality of concrete. The layer structure is self-waterproof construction. When vibrating the concrete, first vibrate it with a vibrating rod, the vibrating point is uniform, fast insert and slow pull, and then vibrate by 1/3 from the bottom to the top. The vibrator vibrates continuously at each position for 20 s to 40 s until the surface does not sink significantly, air bubbles do not appear, and mortar appears.

5) The roof slope construction shall be carried out in strict accordance with the design requirements. Mark the slope, draw the watershed, control the thickness of the slope layer, and strengthen the slope inspection and quality assessment during construction.

6) Carefully handle the details of the roof.

7) Leave construction joints in strict accordance with the requirements of design and construction specifications, and handle construction joints well. When continuing to pour concrete at the construction joint, the compressive strength of the original concrete is required to be not less than 1.2 MPa. The surface of the concrete should be chiseled and washed with water. A cement mortar with a thickness of 10 mm to 20 mm that is the same as the original slurry should be laid, and then vibrated Compact and self-waterproof.

8) The pipeline is pre-buried. Do a good job in the buried work of water and electricity pipelines and lightning protection belts. It is strictly forbidden to chisel the concrete slabs after pouring.

9) Strengthen concrete maintenance control.

10) Grouting around individual rear-through pipe. The perimeter of individual rear through-pipes must be grouted twice, and the holes should be cut into large and small bell mouths. Smooth plastic pipes should be pulled first and then installed to ensure the adhesion and compactness with concrete. ^[1]

The cause of the material itself

Concrete is an artificial stone.Although its compressive strength is very high, its tensile strength is very low, which is about 1/10 of the compressive strength. Therefore, once the concrete is pulled, the tensile stress generated can easily exceed its resistance. Tensile strength causes cracks.

Design reasons

1) Waterproof standards and fortification requirements have not been determined in strict accordance with national standards based on the type of building and the reasonable service life of the waterproof layer.

2) It is not based on the waterproof design principle of "combination of drainage prevention, rigid and flexible, multiple lines of defense, and mutual action". It does not pay attention to drainage design, and cannot perform reasonable drainage partitioning. Partial stagnant water has laid the bane for roof leakage.

3) The structural design is unreasonable. In the structural design, only the stress requirements of the structure are considered, and the influence of the structural deformation on the roof leakage is ignored.

4) The structural structure is unreasonable, and sufficient structural steel bars are not set at the support of the roof slab.

5) The detailed node design is unreasonable or rough, and there are many atlases applied. There is no return visit to the designed house. The practical experience is summarized and necessary processing is performed.

6) The roof structure level design is unreasonable. In accordance with the climatic conditions in the area, heat insulation and heat insulation layers should be added to reduce the deformation caused by temperature changes.

Reasons for construction

1) The construction was not strictly carried out in accordance with the roof waterproof construction operation rules, the operation procedures were wrong, and the construction was not standardized.

2) The material of cement, coarse and fine aggregate is poor, and the mix ratio and water-cement ratio are improper.

3) The concrete is not uniformly mixed, and the mixing time is not enough.

4) Concrete placement cannot be carried out continuously, and the location of construction joints is not reasonable.

5) The concrete is not compacted due to vibration, leakage, under-vibration or over-vibration.

6) After the concrete is vibrated, it cannot be cured in time or the curing time is not enough.

7) The detailed waterproofing practice is unreasonable.

Management reasons

1) The construction operators and management personnel have not strengthened the training and education, or paid less attention to the training and education, so that the quality of employees is lower.

2) There is no comprehensive grasp of material supply information, only attention to the price of materials, not enough attention to the quality of materials.

3) The construction technology passed through the field, the team meeting was superficial, and the key parts, key procedures, and weak links did not attract enough attention.

4) The protection of finished products is not valued or measures are taken improperly.

5) No set of quality management system or quality management system has been established. ^[1]

1) The designer should master various waterproof technologies, material properties, determine the roof waterproof level according to the nature, importance, use function and durability of the project.At the same time, fortify and adopt the structure according to the requirements of the roof waterproof level according to the engineering characteristics and regional natural conditions Layer self-waterproof, waterproof layer and other fortifications.

2) Reasonably arrange the structure and sub-slots so that the direction of the structural layer's force is consistent.

3) Provide an isolation layer. Paper reinforcement ash, hemp ash, low-grade cement mortar, dry linoleum, asphalt brushing, waste engine oil, etc. are used to completely separate the waterproof layer from the structural layer, thereby reducing the impact of structural layer deformation on the waterproof layer.

4) In the design of the roof slab structure, a sufficient amount of structural negative reinforcement or steel fiber concrete or prestressed concrete should be arranged at the corresponding location to improve its tensile capacity and prevent cracks from appearing.

5) Drainage and downpipe installation. The roof should adopt organized drainage, and the dual-slope drainage is preferred. According to the roof area and climatic conditions, sufficient rainwater pipes are set up, drainage areas are reasonably divided, and rainwater pipes are evenly arranged.

6) Strengthen the detail node design and improve the node practices.

7) Add insulation and insulation layers on the level to reduce deformation caused by temperature changes. ^[1]