Research On Preparation Process For Alkali Activated Fly Ash Concrete Foam

This paper first introduces the currently research status of activated fly ash and foamconcrete, and then focus on the craft of how to prepare the foam concrete. With hydrogenperoxide as a foaming agent, the activity of fly ash is increased by alkali-activated way underthe premise of no cement mixing. Finally, the influence of ratio of water and foaming agentcontent for the basic performance and thermal insulation properties of alkali activated flyash concrete foam is studied in this paper. Besides, the pore structure characteristics of alkaliactivated fly ash concrete foam is also studied in this paper.According to the trial, it is concluded that the decomposition characteristics of hydrogenperoxide is related to the temperature, pH, calcium and concentration itself. At25℃, thedecomposition rate is0within1h. At85℃, the decomposition rate is only2.62%within1h.All of this indicate that the temperature has little effect on the decomposition of hydrogenperoxide compared with pH. When the value of PH is less than5, decomposition rate ofhydrogen peroxide is low. When the value of PH is more than5, its decomposition rate risesharply. Note that the decomposition achieve maximum when the value of PH is around9.Besides, the calcium and concentration itself also has some effect on the decomposition ofhydrogen peroxide. As the PH of fly ash slurry is alkaline, the decomposition rate of hydrogenperoxide should be controlled by reducing its concentration, increasing binder and addingrelated foam stabilizer to avoid the collapse which is caused by the quickly formed bubble.The results indicate that the dry density of foam concrete is within the range of0.39g cm-3~0.57g cm-3by using2%~4%NaOH as activator, but its intensity is low. By using5%~15%NaOH as activator, the obtained foam concrete has high intensity but also high drydensity. Furthermore, the foam concrete has good performance by using2%~4%NaOH and5%to15%lime as activator. It has high intensity and its dry density is around0.6g cm-3. Inaddition, extending the pre-activation time is helpful for stimulate the activity of fly ash. The comprehensive results indicate that the craft to preparer fly ash concrete foamincluding foam and stability of blowing agent, stimulated activation of fly ash and curingprocess for preparing pulp stirring. Its specific process is as follows. Fist, mix activated lime(10%) with fly ash (90%) evenly and dissolve NaOH (4%) in warm water. Second, pour it intothe well stirred fly ash and stir until it is mixed evenly and then place it. Third, take out theactivated powder3days later and add the early strength agent triethanolamine (0.05%),sodium sulfate (1.5%), foam stabilizer sodium phosphate (1%) and calcium stearate stabilizer(1%) into it and then stir evenly. Fourth, add the water with naphthalene superplasticier (1%)in to powder and rapidly stir for3minutes until it is mixed evenly. Finally, add the dilutedhydrogen peroxide (5%) to the slurry and rapidly stir for10seconds. Pour it into the model toform and remove model24hours later. Furthermore, wrap it with plastic film for insulationuntil conserve age.