We all know that foam concrete itself has low strength, bulk density is not easy to control, and porosity problems. These problems make foam concrete in the application process will have some limitations. Then the high performance foam concrete in the strength and density of the adaptation can be perfect solution.
High performance foamed concrete should adopt modern concrete technology to make concrete on the basis of greatly improving the performance of ordinary foamed concrete, which has high influence on durability, workability, practicability, strength, volume stability and economy. However, as a special kind of concrete, high-performance foam concrete not only conforms to the general rules of ordinary concrete, but also has some characteristics of its own, and its composition material should meet the following technical requirements
It is necessary to pay attention to these problems when selecting raw materials for the preparation of high performance foamed concrete
1 Cement selection
All sorts of cement can be used to the preparation of foamed concrete, because of the foam concrete mixed with a lot of bubbles, delayed the cement hydration process, it is recommended to use rapid setting time of sulphur aluminate cement, high alumina cement, the early strength of Portland cement, magnesite cement, gypsum, etc., but, considering the durability of the preparation of high performance foam cement should choose ordinary Portland cement concrete, especially when applied to the wall, and other important parts.
2 foaming agent
Foaming agent is an important component in the preparation of foamed concrete and a key component determining the performance of foamed concrete. It affects the pore size, uniformity, hole sealing and other indexes of foamed concrete, and ultimately affects the mechanical properties and durability of foamed concrete. Therefore, the selection of suitable foaming agent becomes the key step in the preparation of high performance foamed concrete. Through a large number of experiments, the high performance foam should meet the needed for the preparation of foam concrete after the requirements of the characteristics of stability, uniform, fine, its unit volume contains organic matter (surface active substance) as small as possible, foaming agent into foam, containing a large amount of surfactant changes affect cement after mixed with cement, will reduce the material mechanical properties, the greater the stability of the foam, in most cases, the surface active substance content per unit volume will be, the more the greater the influence of cement is, it is unfavorable for the strength of the foam concrete measures such as. High stability of the foam its stability is very good, the bubble exquisite and tiny, but support the air foam stability is unit volume contains a lot of surface active substances, when added to cement, excess surfactant inevitably negative effects on the cement hydration, but conversely, poor stability of bubble may just after mixed in cement (sand), is a large amount of damage, is not suitable for the preparation of high foam concrete.
After experimental research for a long time, we feel good foaming agent should have less dosage, high expansion ratio (i.e., good technical and economic effect), stability issues (at least can support to the slurry condensation), high obturator rate, low water imbibition, does not affect the strength, wait for a characteristic, the decisive factors in evaluation of foaming agent is good not foam stability, but the stability of the foam slurry and the performance of the hardening of the thick.
3 Concrete additives
The application of various foamed concrete admixtures represented by water reducer is one of the marks of modern high performance concrete, and also one of the characteristics of high performance foamed concrete should be low water-binder ratio. At present, the domestic production of foam concrete when a large number of admixtures such as
high-efficiency water-reducing agent
is not common, cement (sand) slurry mixing, the use of cement cement ratio is generally around 0.5, or even higher. Different from other concrete, foam concrete preparation when mixed with bubble type water film, its constituent besides surfactant, air, is a large number of moisture, therefore on bubble contains water (because bubble ultimately broken into water), foam concrete of water-binder ratio above 0.6, after a large number of air and water into the mechanical properties of the foam concrete is very low, so the preparation of high performance foam concrete need with the help of high efficiency water reducing agent, slash when mixing cement (sand) water/cement ratio, in the laboratory using a new type of poly carboxylic acid salt water reducing agent, water/cement ratio can be reduced to 0.2 or so, Can greatly improve the strength of the substrate. In addition to water reducer, other commonly used admixtures used in high-performance foamed concrete (such as hydrophobic agent, coagulant, early strength agent, foam stabilizer, etc.) are also necessary components for the production of high-performance foamed concrete.
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