Preparation Of High-porosity Sintering-free Fly Ash Ceramsite And Its Thermal Insulation Properties

Rapid economic growth has led to the deterioration of the environment,and a large amount of energy consumption has caused human beings to suffer the consequences.Global warming and haze are the bitter pill of human beings'inordinate activities.In the"Twelfth Five-Year Plan",China clearly put forward the goal of energy saving and emission reduction,and the construction industry was the first to bear the brunt.The energy consumption of the construction industry accounts for about one fifth of the total energy consumption of the society,which reminds us that we need to strengthen the thermal insulation performance of houses in order to reduce the energy consumption caused by heating and cooling from the source.Porous ceramsite is an excellent thermal insulation material.It can be used to make wall materials with light weight and good thermal insulation performance.However,at present,the most widely used ceramsite is made from clay and shale by sintering method,which often needs to be heated to thousands of degrees Celsius.This will cause environmental damage and energy consumption,which is contrary contrary to the current economic concept of green energy-saving advocated by various countries.Therefore,the preparation process of ceramsite needs to be improved.In this paper,microwave irradiation was introduced into the preparation process of ceramsite as a new heating method,and its feasibility was determined by experiments.At the same time,in order to optimize the thermal insulation performance of ceramsite,two easily decomposed chemicals,hydrogen peroxide and ammonium carbonate,were added to the preparation of ceramsite as pore formers.It was found that hydrogen peroxide could indeed increase the porosity and reduce the thermal conductivity of ceramsite,which was an excellent foaming agent choice.However,the decomposition of ammonium carbonate is too fast and difficult to control.The parameters of microwave oven for preparing ammonium carbonate sintering-free ceramsite needed to be re-tested.The power and time of the microwave irradiation were successively determined to be480 W and 5 min,by testing the properties of the sintering-free ceramsite.The sintering-free ceramsite prepared without pore former under these conditions was 800grade ceramsite,with cylinder compressive strength of 4.47 MPa,water absorption rate of30.14%in one hour and thermal conductivity of 0.190 W*?m*K?^-1.After adding hydrogen peroxide,under the same microwave treatment conditions,the prepared ceramisite was still 800 grade,but its cylinder compressive strength was reduced to 2.92 MPa,its water absorption and thermal conductivity were reduced to 28.74%and 0.178 W*?m*K?^-1,respectively.It can be seen that the addition of hydrogen peroxide can indeed improve the thermal insulation properties of ceramsite.At present,the optimal dosage of hydrogen peroxide could be determined between 7.5%and 10.0%of the mixture quality,which needed further tests to confirm.The parameters of microwave oven for preparing hydrogen peroxide ceramsite can also be regulated more carefully in order to achieve the highest performance improvement.Ammonium carbonate did not perform well in this experiment.Higher microwave irradiation power or time,larger dosage of ammonium carbonate would result in the fragmentation of large grains of ceramsite.If the microwave power,time or the dosage of ammonium carbonate is respectively controlled at a small value,the thermal conductivity of the ammonium carbonate ceramsite can be significantly reduced.Subsequent further adjustment of the dosage of ammonium carbonate and the parameters of the microwave oven can be continued to make the ammonium carbonate play a real role in the preparation of the sintering-free ceramsite.