The main raw materials of foam concrete are cement, lime, admixtures with certain diving hardness, foaming agents and foam stabilizers that stabilize the foam. If necessary, they should also be Add early strengthening agent and other admixtures.
1. Foaming agent
Foaming agent, also called foaming agent, is the most critical raw material for preparing foam concrete. Foaming agent is related to the number, shape and structure of foaming in concrete, and will inevitably affect the foaming. Quality of concrete structural members.
(1) Types of foaming agents Commonly used foaming agents for foam concrete include rosin rubber foaming agent, waste animal hair foaming agent and other foaming agents.
① Rosin rubber foam agent. Rosin gum foam agent is made by using alkaline substances to quantitatively neutralize the rosin acid in rosin to generate rosin soap, adding an appropriate amount of stabilizer - gum solution, and then adding an appropriate amount of water. This is a liquid Foaming agent makes it very convenient to prepare foam concrete.
② Waste animal hair foaming agent. Waste animal hair foam agent is a powdery substance made by dissolving waste animal hair in boiling sodium hydroxide solution, neutralizing and acidifying it with sulfuric acid, filtering out a reddish-brown liquid, and then concentrating, drying and grinding it. This foaming agent is a mixture of intermediates produced during the hydrolysis of animal hair and is a surface-active substance.
Other foaming agents. Other foaming agents mainly refer to resin saponin foaming agents, petroleum aluminum sulfate foaming agents and hydrolyzed blood glue foaming agents. Resin saponin foaming agent is made from saponin plants; petroleum aluminum sulfate foaming agent is formulated from kerosene accelerator, aluminum sulfate and sodium sulfate; hydrolyzed blood glue foaming agent is made from fresh (uncoagulated) animal blood, It is formulated with charged sodium, ferrous sulfate and gasification hook.
(2) Preparation of foam agent
① Preparation of glue solution. Wipe the glue clean, smash it into 4~6cm pieces with a hammer, weigh it with a balance, put it into the inner pot, then add the calculated water consumption (while increasing the water consumption by 2.5%~4.0%) and soak it for 2000h. When the colloid is completely softened, put the inner pot into the outer pot and heat it over water. Stir and cook while heating until all the colloids are dissolved. The cooking time should not exceed 2 hours.
② Preparation of rosin lye. Press the rosin carbon into powder, sieve it through a No. 100 fine sieve, prepare the alkali into an alkali solution and put it into a glass container. Weigh a certain amount of alkali solution and put it into the inner pot. When the water temperature in the outer pot is heated to 90~100℃, put the inner pot containing the alkali solution into the outer pot and continue heating until the temperature of the alkali solution reaches 70~80°C. ℃, slowly add the weighed rosin powder and stir as you add it. After adding the rosin powder, cook for 2 to 4 hours to fully saponify the rosin and turn it into a viscous liquid. When cooking, full consideration should be given to the evaporated water.
③ Preparation of foam agent. When the boiled rosin lye and glue are cooled to about 50°C, slowly add the glue into the rosin lye and stir quickly until there are small bubbles floating on the surface, that is, a foam agent is prepared.
(3) Foam quality identification The quality of foam directly affects the quality of foam concrete. The quality of foam should be identified from indicators such as toughness, foaming multiple, and bleeding amount.
①The toughness of foam. The toughness of foam is the characteristic that the foam will not be destroyed in the air within a specified period of time. It is often determined by the subsidence distance of the foam column per unit time. The specification stipulates that foam concrete can be prepared only when the settlement distance of the foam is no more than 10mm after 1 hour.
②Foaming multiple. The foaming ratio is the multiple that the foam volume is greater than the volume of the foaming agent aqueous solution. The specification stipulates that the foam can be used to prepare foam concrete only when its expansion ratio is not less than 20.
③Amount of bleeding. Bleeding volume refers to the volume of foam agent aqueous solution produced after the foam is destroyed. The specification stipulates that foam can be used to prepare foam concrete only when its bleeding volume per hour is no more than 80 mL.
2. Cement
To prepare foam concrete, Portland series cement can generally be used, such as Portland cement, ordinary Portland cement, slag Portland cement, volcanic ash Portland cement, powder Coal ash Portland cement and composite Portland cement, etc.; sulphoaluminate cement and high alumina cement can also be used according to actual conditions.
ingating foam concrete, according to the different curing methods, the cement type and strength grade used should not be the same. When using natural curing, cement with high early strength and high strength grade should be used, such as early strength (R-type) Portland cement, R-type ordinary Portland cement, sulfoaluminate cement and high alumina cement; When steam curing is used, some Portland cement mixed with admixtures can be used, and there are no special requirements for the strength grade of the cement. However, special attention should be paid to the fact that high alumina cement must not be used when steam curing is used.
3. Lime
If the foam concrete uses steam curing, an appropriate amount of lime can be added instead of cement as the calcium raw material. The quality of the lime used should comply with the standards proposed in aerated concrete.
4. Admixtures
The admixtures used to prepare foam concrete mainly include fly ash and boiling water.Powder and slag powder. The quality of fly ash is the same as that in aerated concrete. The quality requirements for zeolite powder and slag powder mainly include the following two aspects: a. The chemical composition should meet the requirements of cement mixing materials for slag and zeolite; b. Preparation of foam The fineness of concrete slag and zeolite should have a specific surface area greater than or equal to 3500cm2/g.
In some cases, quartz powder can also be used as a siliceous mixing material, but the foam concrete when mixed with quartz powder must be cured by autoclaving, and its ingredients are basically similar to aerated concrete.
5. Foam stabilizer
In order to ensure the quantity and stability of foam in foam concrete, an appropriate amount of foam stabilizer can be added when preparing foam. The type of foam stabilizer used is the same as that of aerated concrete. </p
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