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Foaming agent for concrete is exceptionally critical to the quality of foam concrete. An excellent foaming agent can make high-quality foam concrete. A high-quality foaming agent for concrete should have the following characteristics:
1. The more even the foam, tym lepiej, the bubble diameter should be the same size
The narrower the ideal pore size distribution of the pores, tym lepiej. To jest, the pore diameters of the pores should be as consistent as possible, and the difference should not be too significant. This corresponding requirement requires that the foam should be uniform and not different in size. The bubble diameter of the foam cannot be the same, but it should be similar. The range of the bubble diameter is as small as possible, and the difference between the maximum bubble diameter and the minimum bubble diameter should not be too significant. Jak wspomniano wcześniej, the pores formed by the foam are required to be uniform to avoid the concentration of compressive stress at the giant cells and reduce the compressive strength. If the size of the foam is uneven, the weight is concentrated in the giant bubble, which is very easy to cause it to become a weak link, and it will crack first when it is under pressure.
2. The higher the foam stability, tym lepiej, and the longer the foam stability time, tym lepiej
The foam with right balance has a tough liquid film and excellent mechanical strength and is not easy to be broken or excessively deformed under the extrusion of the slurry. Oprócz, ma zdolność samozatrzymywania wody, the moisture on the liquid film is not easy to be lost under the action of gravity and surface tension, and can maintain the thickness and integrity of the foam liquid film for a long time so that the foam can remain for a long time without breaking.
(1) The stability of the foam has three effects on the pores: it can prevent most of the foam from disappearing and is fixed in the foam concrete after the initial setting of the slurry to form pores. If the stability of the foam is not excellent, most or a small part of the foam will burst after pouring, and the pores formed will be few, and the slurry will collapse even shortly after pouring, which is commonly known as the collapse mould, causing the pouring to fail completely.
(2) Foam with excellent stability, the slurry is not easy to deform too much under squeezing, and has a specific resistance to pressure to keep itself approximately spherical, which can eventually form spherical pores with good pore shape;
(3) Foam with excellent stability, the liquid film is not easy to rupture in the slurry body, and it is not easy to form the communication hole created by the gas communication after the rupture. Dlatego, it eventually creates an ideal closed hole. The worse the foam stability, the fewer closed cells, and the more connected cells. Thus, the balance of the foam cannot be based on the fact that it does not collapse only after casting but should be found on the three indicators of non-collapse after casting, the resulting pores being approximately spherical, and no interconnection. Most people regard foam collapse as the measure of foam stability. This is a misunderstanding and the lowest standard of foam stability.
Foam stability can be measured by foam stabilization time when there is no standard testing instrument to determine its sinking distance. The foam stabilization time should meet the initial setting needs of the used gelling material. Because the slurry can only be fixed after the initial setting of the mud, and the shape of the foam is retained to make it become a pore.
Any cementitious material has an initial setting time, especially for the most widely used ordinary Portland cement, the initial setting is mostly later than 45min. If the foam stability is reduced, the cement and other cementing materials have not yet set, and the foam has burst, then the foam cannot form pores in the concrete. Zazwyczaj, the minimum requirements for foam stability should also be such that the foam stabilization time is longer than the initial setting time of the cementitious material by 10 Do 20 protokół. Due to the inconsistent initial setting time of various gelling materials, wymagania dotyczące czasu stabilizacji piany są również inne. Zazwyczaj, the foam stabilization time for the fast gelling material foam can be shorter, and the foam stabilization time for the slow gelling material foam should be as long as possible. Even if the temperature of the same kind of gelling material is different, the initial setting time is different, a zmiana jest dość znacząca. Na przykład, ordinary portland cement may initially set in less than 40 minut latem, but will not set in 80 minut w mroźną zimę poniżej 5 ℃. Dlatego, there is no uniform specific standard for the foam stabilization time, which should be determined according to the situation. Dostosowanie pianki do potrzeb różnych warunków użytkowania, the longer the stabilization time, tym lepiej. Ogólnie mówiąc, the foam stabilization time should meet the following requirements;
(1) When used in Portland cement and without setting accelerator, the stabilization time should be higher than 60min; ideally, it should be higher than 3h;
(2) When used in fast-setting cement such as sulfoaluminate cement, cement wysokoglinowy, cement glinowo-żelazowy, quick setting Portland cement, the stabilizing time should be higher than 30min, preferably higher than 60min;
(3) When used in magnesite cement, the foam stabilization time should be higher than 40min and preferably higher than 80min;
(4) When used for cementing materials mixed with a large amount of filler or fly ash and other active waste residues, należy również wydłużyć czas stabilizacji piany. The higher the amount of padding or active waste residue, tym dłuższy jest czas stabilizacji piany.
The specific foam stabilization time should be determined by a small test, based on the principle that the mould does not collapse after pouring, the pores are not connected after the formation, and the deformation is not excessive. The general policy is that the longer the bubble stabilization time, tym lepiej.
3. Im większa średnica pęcherzyka, tym lepiej, it should be more than 1mm
The requirements of pore size for pore size are the same, as are the criteria for bubble diameter. Many producers and some experts misled the pursuit of a foam pore size as small as 0.1mm. If the physical foaming diameter is large, the stability of the foam will be reduced, failing to produce foamed concrete. The same raw material and formula, the same equipment and process, zmienić tylko średnicę pianki, the compressive strength of 1mm foam diameter foam concrete is at least 20% higher than that of 0.1mm foam diameter foam concrete. Dlatego, it is wrong to pursue a large bubble diameter of more than 0.1mm, which is a mistake in the production of foam concrete and should be corrected.
4. Im niższa szybkość krwawienia piany, tym lepiej, unikaj stosowania mlecznej pianki
It has been introduced that foams are divided into milky foams with less water and less foam and sponge foams with less water and water, according to the water content. Wśród nich, milky foams are unqualified inferior foams and cannot be used.
After the foam is made, it gradually oozes out. Jego krwawienie składa się z dwóch części:
(1) Bleeding of foam liquid film. This part of the water is secreted from the liquid membrane, which is the water emitted by the liquid layer under the combined action of gravity drainage, drenaż napięcia powierzchniowego, i drenaż niszczący błonę płynną. Im grubszy jest płynny film pianki, tym większe krwawienie; the faster the foam bursts, tym większe krwawienie.
(2) The water between the bubbles. This part is the water that has not formed a bubble liquid film. Im gorsza wydajność spieniania środka spieniającego i maszyny spieniającej, the more water between foams that cannot create a foam liquid film. They are water that does not become bubbles.
When the foam’s bleeding rate is very high, it will be as thin as the floating juice, and it will not pile up, and the amount of water in the foam is considerable. When this kind of foam is added to the cement slurry, zaczyn cementowy staje się bardzo rzadki, but the foam is very little, the volume of the sludge is small, and the foam concrete density produced is very high, which does not meet the technical requirements.
Dlatego, nie można stosować mlecznej pianki. The appearance of the foam that meets the technical specifications should be a sponge-like beautiful small bubble, piled up like white clouds, like bombed cotton, i nie będzie płynąć losowo. Zawartość wody w tej piance jest minimalna. This shows that the foam liquid membrane has slight bleeding, pianka nie jest łatwa do złamania, pomiędzy bąbelkami jest mało wody, a ilość bąbelków jest znacząca, a większość objętości to bąbelki. What needs to be emphasized here is that the sponge-like foam must be a small bubble with a bubble diameter of less than 1 mm, not a giant balloon of a few millimetres or even tens of millimetres. Big bubbles are easy to pile up, like Baiyun, ale dlatego, że średnica pęcherzyka jest zbyt duża, jest również bez kwalifikacji.
The low water permeability of the foam is mainly required to ensure the number of bubbles in the foam and the porosity of the foam concrete, to jest, to ensure the foam concrete density.
5. Foam has no side effects on the gelled material
The cementing material is the primary source of the strength of the foam concrete. The addition of foam can not affect its gelation; to jest, it does not produce a negative effect of gelation. This is not something that all kinds of bubbles can achieve.
In long-term tests, we have found that many foams hinder the cementation of cement, magnezyt, i gips, which can reduce the strength of foamed concrete, and sometimes even the hardened concrete loses its power, like a piece of loose sand. The stability of these foams is excellent, and it does not disappear for a few hours, the appearance is like a sponge; the bleeding is deficient, the density is uniform. All aspects meet the technical requirements, but it is not compatible with the gelling material, so it cannot be used for production. This shows that the foam that is qualified in other aspects, such as affecting the strength, is ultimately unsatisfactory.
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