Research And Application Of Cement Foaming Agent Prepared By Using Chrome Shaving

About 1 million tons of solid waste from the tanning industry is produced in China every year.Chromium-containing leather scraps are the main solid waste,the main component of which is collagen,Therefore,it is of great environmental and economic value to recycle them.Protein foaming agent is one of the larger amounts of concrete foaming agent.If leather waste is used as raw material of concrete foaming agent,the purpose of recycling waste can be achieved.Organic thermal insulation materials because of its light weight,low thermal conductivity and other special properties,to occupy a dominant position in the building materials market,however,due to their flammability,there are huge hidden dangers during use,while foam concrete has attracted much attention as an inorganic insulation material due to its non-combustibility and low thermal conductivity.In this subject,sodium hydroxide was used to hydrolyze the collagen in the waste shavings,and a protein suitable as a primer for the foaming agent was obtained.The number average molecular weight was 13,992 Da and the weight average molecular weight was 28,556 Da.At the same time,benzene is used as solvent,natural rosin is used as raw material,phosphorus trichloride is used as chlorinating agent and natural rosin to obtain rosin acid chloride,and rosinyl chloride is grafted with collagen to prepare protein-based anionic surfactant.The conversion rate of rosin acid chloride is above 70 %,and the performance of the obtained surfactant is tested.The experimental surfactant has an HLB value of 16 and a critical micelle concentration of 1.05 g/L to 1.43g/L.The surface tension reaches between 33-41 mN/m,which is suitable as a foaming agent,and the emulsion stability is strong.The initial compounding was carried out using sodium dodecyl sulfate(SDS)with foaming performance as an index.As a result,it was found that the foaming performance was highest at the SDS doping amount of 0.3 %,continue to use sodium dodecyl benzene sulfonate(SDBS)and dodecanol to continue the comprehensive performance compounding,the results show that the addition amount of SDBS and dodecanol is 0.25 % and 0.6 %,respectively,reaching the building materials industry standard,the foaming height is 147 mm,and the half-life is 580 s.The settlement distance is 37 mm,the bleeding rate is 33%,and the expansion ratio is 23.The concrete modelwas poured using the prepared foaming agent.After 28 d of standard curing(20 °C,humidity 95 %),the compressive strength of foam concrete reached 1.1 MPa or more,and the thermal conductivity reached 0.084 W/(m·K).The dry density can reach 450 kg/m3 or less,and the performance is excellent,it is compared with the commercially available foaming agent.The experiment shows that this product has similarity with the commercially available foaming agent at a lower cost.The performance fully meets the standards of use in the building materials industry.Finally,the hydrolysis residue is used in the concrete to achieve full depletion of the waste.The result shows that the addition of the hydrolysis residue within 3 %has little effect on the strength of the concrete,and the chromium therein does not precipitate and has good stability.