Study On Preparation And Performance Of Humidity Controlling Board Based On Diatomite

Diatomite is a kind of amorphous non-metallic mineral,which come from the diatomeae wreckage depositing in water and being transformed by natural environment,the main chemical composition is amorphous SiO2,and the mineral composition contain the opal and its variants with volcanic ash activity.As a result of the biological origin,diatomite has the unique porous nature structure and greatly specific surface area,which result in the formidable adsorption performance.In this experiment,the diatomite was taken as siliceous materials and the quicklime was calcareous materials.The gypsum,cement,fiber materials and wollastonite powders were mixed to prepare silicate products with hydrothermal synthesis technology.By optimizing the optimum molding process,proper curing system,a reasonable combination and ratio of raw materials,the products were made to maximize the humidity control function of diatomite on the basic of the strength and density.The results of experiments showed that the density and bending strength showed a rising trend with the increase of dewatering pressure.The Moisture absorption/desorption rate get the maximum when dewatering pressure is 2.78MPa.The bending strength shows the same trend under two curing systems,but the bending strength of atmospheric heat curing can reach 6.63MPa,which less than high-pressure steam curing.The results of wet technology experiments showed that it has a certain influence of surface area and chemical composition of diatomite,in which the maximum bending strength was appeared in Dongao 1#,on the contrary,Dongao 4#was the minimum.The board had the maximum bending strength while calcium silicon ratio in 2:6.When calcium silicon ratio in 1:6,the board had maximum moisture absorption/desorption rate,and moisture absorption rate up to 5.89%,moisture desorption rate 1.9%.With the increase of calcium silicon ratio,moisture absorption/desorption rate decrease,and moisture absorption speed decline but desorption no significant changes trend.Diatomite hydration products in internal holes increased with calcium silicon ratio,which was related to the properties of moisture absorption and desorption.The bending strength of the board showed a rising trend with the increase of the content of cement,but moisture absorption/desorption rate and speed had no distinct changes.The effect of desulfurizationg gypsum content could be ignored,when the content is 5%,the board had maximum moisture absorption/desorption rate and speed.Raw material composition on the bending strength was CaO/SiO2>wollastonite powders>gypsum,and moisture absorption/desorption rate was CaO/SiO2>gypsum>wollastonite powders.Considering all,choose the gypsum content 5%,wollastonite powders 8%,CaO/SiO2 in 1:6.The results of semi-dry technology experiments showed that with the changes of calcium silicon ratio,the bending strength react the same trend with wet mixing technology,which can reach 6.72MPa.Moisture absorption/desorption rate decline with the increase of calcium silicon ratio.The board didn’t reach the saturation point after 24h,48h date showed that moisture absorption rate can reach 6.89%,desorption rate can reach 1.97%.When calcium silicon ratio in 1:6,it was clearly to see diatomite pore structure.The reaction product is mainly attached to the surface of diatomite when calcium silicon ratio rise,which preserved the original pore structure.The content of wollastonite powders was 10%,the board had maximum bending strength,but when the content was 12%,it had maximum moisture absorption/desorption rate and speed.After absorption and desorption cycle test,absorption and desorption properties of the board has not attenuated.The absorption and desorption performances of humidity controlling board was better than gypsun and calcium silicate board,which is higher than related standards.