Study On Activation Of Recycled Concrete Powder And Preparation Of Foamed Concrete

With the rapid development of China’s social economy,the process of urbanization is accelerating,and a large amount of construction waste generated by reconstruction,expansion and demolition projects becomes a waste resource that is difficult to deal with.Recycled aggregate and recycled concrete powder can be obtained by means of sorting,crushing and grinding waste concrete.Recycled aggregate can be used to prepare recycled concrete,but the reuse of recycled concrete powder has not been solved.Therefore,the study on the preparation of foamed concrete from recycled concrete powder not only responds to the national policy call of energy conservation and waste of building materials in recent years,but also has outstanding economic and social benefits of products.In this paper,a lot of experiments are carried out to stimulate the potential activity of recycled concrete powder and optimize the mix ratio of foamed concrete.First by respectively mixed with sodium hydroxide,calcium hydroxide,sodium silicate solution to recycled concrete powder-regeneration of mortar cement composite gelled material preparation,then macro mechanical properties test,to regeneration of mortar specimen to flexural strength,compressive strength of mortar bars to judge effect of exciting agent,optimizing the best exciting agent and its dosage,micro test on regeneration of mortar specimens to the mechanical performance test result.Finally,the foam concrete is prepared by using the best activator and the recycled concrete powder-cement composite cementitious material,and the compressive strength test and microscopic detection are carried out to obtain the best activator and recycled concrete powder content,and determine the optimal mix ratio of the foam concrete.The main conclusions are as follows:（1）Among the three kinds of activators,sodium hydroxide,sodium silicate solution and calcium hydroxide,adding calcium hydroxide has the best excitation effect.When the activity index reaches 1.5,the content of calcium hydroxide is 6%,and the content of recycled concrete powder is 15%,the compressive strength of mortar specimen after standard curing for 28 days reaches 29.4MPa,which is 48%higher than the reference sample without the activator.（2）regeneration of mortar specimen microscopic test results and mechanical performance test results perfectly,6%calcium hydroxide group samples than other groups of samples in the XRD test its hydration products Ca（OH）₂ diffraction peak intensity is the highest,the hydration heat test the heat quantity within 72h of the highest in thermogravimetric test its three main thermal weightlessness TG1,TG2,TG3is highest,its corresponding endothermic peak in DSC curve is strongest.（3）The optimal mix ratio of foamed concrete is:1080g cement,120g recycled concrete powder,648g water,78g hydrogen peroxide,48g silica fume,72g calcium hydroxide,3.6g rubber powder,48g anhydrous sodium sulfate.Its compressive strength after 28 days of standard curing is 4.9MPa and reaches C5 grade of foam concrete standard（JG/T 266-2011）.