In order to improve the uniformity of fresh foamed concrete slurry and reduce the temperature difference stress, the following measures are put forward, which can effectively reduce the foam mixing.
Cracks in the slurry and embryo.
(1) Use wood to make the mold for pouring foamed concrete.
Use wood to make the mold for pouring foamed concrete, and evenly spread plastic film on the inner wall of the mold.The flat plastic film can reduce the resistance of the mould side to the expansion of the slurry, so that the slurry middle and the edge of the initiation height is close, the uniformity has been improved.
(2) Add wood mould upper pressing plate
Adding wood mould upper pressing plate can make the whole mould have better heat preservation effect, and thus reduce the temperature difference of slurry parts.Under normal circumstances, when the foam concrete slurry is inflated, the upper surface is exposed, and the surface temperature of the slurry is lower than the internal temperature, which is easy to produce temperature crack.The upper pressing plate is made of plywood with a thickness of 10~30 mm, and its thermal conductivity is similar to that of other parts of the mold, which has certain thermal insulation effect and can also make the slurry temperature more uniform, thus reducing the slurry temperature difference.After adding on the wooden board, on the other hand, when the foam concrete slurry pouring into the mould, size expansion over mould height within a few minutes, will be affected by the clamp block, produce certain pressure in the slurry surface, which make the foam concrete slurry foaming force is more uniform, in the process of condensation sclerosis eventually greatly reduce the chances of cracks appear after hardening.
(3) Balanced platen method
The balanced platen method is to apply the platen (plywood) with a thickness of more than 10 mm on the surface of the foamed concrete slurry and a side length no less than that of the casting mold.The dead weight of the sandbag or the block and the platen ACTS the pressure on the upper surface of the foamed concrete slurry by evenly distributing the sandbag or the block on the platen as the load.The pressure on the surface should be controlled at 0.2 ~ 0.8kn /m2.After 10 ~ 200 min slurry coagulation, the pressure plate and its load are removed. After curing, the mold is removed. After cutting and packaging, the finished foam concrete board is made.A certain pressure is given on the top surface of the unhardened foamed concrete embryo body to balance the stress in the foaming process of the slurry, which can reduce the horizontal crack located 100 ~ 150mm below the foamed concrete top surface, basically eliminate the phenomenon that the pouring surface presents high middle material and low edge material, and reduce the amount of waste after cutting.
In addition, in the production process of foamed concrete slab, the quality of raw materials, proportion, heat preservation, moisture, curing, mold removal and transportation time, cutting time process and so on will have an impact on the formation and expansion of cracks.Some manufacturers in order to increase production, the foam concrete board in the sun exposure, exacerbating the spread of cracks, this kind of error should be avoided.