Roof tile classification

Clay tiles
The main materials of the slope roof are various: wood, bark, bamboo strips, thatch, straw, and even stone chips. However, these materials have poor waterproofness and short lifespan. It was not until the appearance of artificially fired clay tiles that they were considered real roofing materials. The so-called "Qin bricks and Han tiles" refer to the appearance of clay tiles in my country more than 2,000 years ago. Clay tiles are made of clay with few impurities and good plasticity as the main raw material. They are made by adding water, stirring, embryo making, drying, and sintering. They can be divided into flat tiles and ridge tiles according to their uses, and into green tiles and red tiles according to their colors. According to the national standard "Clay Tiles" (GB1170-89), there are three types of flat tiles: I, II, and III, and the sizes of each type are 400mm×240mm, 380mm×225mm, and 360mm×220mm respectively. The minimum flexural load of a single tile shall not be less than 680N. The tiles covering a 1M2 roof shall not absorb more than 55kg of water. The frost resistance requirement is that there shall be no delamination, cracking or peeling after 15 freezing cycles. The impermeability requirement is that there shall be no dripping. Ridge tiles are divided into two grades: first-class and qualified. Their length and width dimensions are greater than or equal to 300 and 180 respectively. The bending and frost resistance of a single ridge tile are the same as those of flat tiles. Clay is mainly used for sloped roofs of civil and rural buildings.
1. Product classification, grade and specification
(1) Classification by production process
a. Flat tiles and ridge tiles made by pressing tiles after molding and baking are called pressed flat tiles and pressed ridge tiles;
b. Flat tiles and ridge tiles made by extruding tiles after baking are called extruded flat tiles and extruded ridge tiles;
c. Handmade ridge tiles are ridge tiles made by manual molding and baking.
(2) Classification by use
a. Clay flat tiles are used as waterproof covering materials for roofs, including pressed flat tiles and extruded flat tiles (referred to as flat tiles);
b. Clay ridge tiles are used as waterproof covering materials for the ridges of houses, including pressed ridge tiles, extruded ridge tiles and handmade ridge tiles (referred to as ridge tiles).
(3) Grades Products are divided into three grades: superior, first-class and qualified according to size deviation, appearance quality and physical and mechanical properties.
2. Size deviation measurement
(1) Pressed flat tiles measure effective length, extruded flat tiles measure actual length; flat tiles measure effective width. Accurate to 1mm, less than 1mm is rounded up to 1mm.
(2) The size of flat tiles should be checked at the middle of their actual length and width.
3. Appearance quality inspection
(1) Warp inspection
a. The warping of flat tiles should be checked with a warp inspection ruler.
b. The warping of flat tiles should mainly be checked on the tile surface and tile side. Insert the warp inspection ruler into the gap between the ruler and the flat tile, and measure the warping value at the maximum warping point.
c. Check the warping of ridge tiles with specially made samples. When checking, place the ridge tile head on sample A and place it naturally, and measure the maximum gap between its two bottom edges and the bottom surface of the sample. At the same time, place sample B on the end of the tile and measure the gap between the two feet of B and the bottom surface of A. The above maximum gap value δ is the warping value of the ridge tile.
(2) Crack inspection: measure the maximum straight-line distance between the two end points of the crack on the tile. A through crack refers to a crack that penetrates from the front of the tile to the back; for curved line and plum blossom cracks, calculate the maximum straight-line distance; when there are more than two cracks, the largest one is selected.
(3) Inspection of missing edges and corners: measure the maximum damage length of the defect on the tile surface. If the maximum depth of the missing edges and corners in the thickness direction of the tile is less than 4 mm, it will not be treated as missing edges and corners.
(4) Inspection of underfire tiles, mute tiles and lime burst tiles: Underfire and mute tiles are identified based on the color and knocking sound of the tiles. If it is really impossible to determine, the antifreeze test is used to determine. Measure the maximum diameter of the lime burst point on the tile. If it is not larger than 10mm, it will not be counted as lime burst tile.
4. Take 5 samples for the flexural load test. Place the naturally dried tiles with the front side facing up on two brackets of the testing machine with a span of L0. For the flat tile test, one bracket must be close to the tile hanging strip of the rear claw, and then a concentrated load is applied in the center. The bracket and the loading rod are both circular shafts with a diameter of 20￣30mm. The three shafts must be parallel to each other, and the load must be perpendicular to the tile surface. The load is applied uniformly at a speed of about 100N/s until the sample breaks. The load value at the time of fracture is the flexural load of the tile. Among them, the average value of the flexural load of 5 tiles is called the average flexural load value, and the minimum flexural load value of a single tile among the 5 tiles is called the minimum flexural load value.
5. Frost resistance test Take 5 samples, soak them in clean water for 24 hours, put them in a freezer that has been cooled to below -15℃ in advance, keep them frozen at -15～-20℃ for 3 hours, take them out and put them in water at 15~20℃ to thaw for 2 hours, which is called a freeze-thaw cycle. Repeat 15 freeze-thaw cycles, observe and record whether the tiles have delamination, cracking, peeling and other damage.
6. Saturated water absorption mass test Take 5 samples, soak them in clean water for 24 hours, wipe off the surface water droplets with a wet towel, weigh them to 1g, take the average value, multiply it by the number of tiles required to cover 1m of roof, which is called the saturated water absorption mass value of the tile.
7. Impermeability test Take 3 samples, clean the naturally dried flat tiles, and set a circle of sealing blocks with a height of 25mm around the outer edge of the front of the flat tiles as a water enclosure frame. The water enclosure area formed in this way should be close to the practical area of ​​the flat tiles. Place the prepared test piece on a bracket that is convenient for observation and keep it horizontal. The bracket should not be placed within the observation area. After it is stable, slowly inject clean water into the water frame. The water level must be greater than 15mm from the shallowest part of the tile surface. Keep this state for 3 hours and observe whether there are water drops on the back of the flat tile.