Preparation Of Gypsum Based Building Materials Based On The Concept Of Solid Waste Collaboration Recycling And Performance Characterization

With the rapid development of China’s industrialization,a large number of industrial solid wastes have been produced,such as blast furnace slag（BFS）produced in iron-making,gypsum and carbide slag produced in chemical industry.These industrial solid wastes have complex components and large emissions,resulting in no good method for large-scale disposal alone.Persulfate cement is a green hydraulic cementitious material obtained by grinding mixture of BFS,gypsum and alkaline activator.The sulfate and alkaline activator can jointly stimulate the potential pozzolanic reaction activity of BFS.If this reaction principle is used for the collaborative resourceization of industrial solid wastes containing the above composition,the utilization level of industrial solid waste can be greatly improved.In this paper:1)persulfate cement using titanium gypsum based on this principle was used as cementitious material,coal gangue was used as aggregate to prepare C20grade concrete;2)persulfate cement using phosphogypsum was used to solidify iron ore tailings（IOT）;3)clinker of phosphogypsum and calcium carbide slag was prepared and used to prepare a newly BFS based cementitious material,and its properties were systematically characterized.Using persulfate cement of titanium gypsum as cementitious material and coal guangue of different particle size as coarse and fine aggregates,the specimens of concrete of titanium gypsum and coal gangue were prepared,and the properties of resulting specimens of concrete were systematically characterized.It was found that the compressive strength of resulting specimens of concrete was decreased with the increase of water-cement ratio and with the decrease of binder-aggregate ratio.Adding typeⅡ(SO₄^2--Al₂O₄)admixture could effectively improve the strength of resulting specimens of concrete,and could effectively improve the water resistance of them.The factors affecting the mechanical properties of resulting specimens of concrete were as follows:binder aggregate>water-cement ratio>admixture.As the water-cement ratio being 0.5,the binder-aggregate ratio being 1:1,and 5%typeⅡ(SO₄^2--Al₂O₄)admixture being introduced,the resulting specimen of concrete could obtain the best mechanical properties and water resistance,and its compressive strength reached 23.5 MPa.Persulfate cement with phosphogypsum,fly ash,BFS and alkali activator as raw materials was used as tailings solidifying agent（TSA）.The specimens of iron ore tailiings（IOT）solidified were prepared by batching of TSA and IOT according their setting proportion,then mixing,and pressing step by step.It was found that the compressive strength and flexural strength of resulting specimens of IOT solidified were gradually increased with the increase of TSA-IOT mass ratio and molding pressure.As the TSA-IOT mass ratio being 1:4 and the molding pressure being 20MPa,the compressive strength and flexure strength of the resulting specimen of IOT solidified reached 14.9 MPa and 9 MPa,respectively.After adding 3%PP fiber,the compressive strength and flexural strength of resulting specimen of IOT solidified could be significantly improved.The softening coefficient of resulting specimens of IOT solidified were more than 0.8,which means them having good water resistance.Clinker for persulfate cement was prepare using phosphogypsum,calcium carbide slag and straw as raw materials after them been batched,mixed,granulated and calcined at high temperature.The newly persulfate cement（NPC）was prepared after the the batching of the major of clinker and the BFS,and the minor of ordinary portland cement.It was found that the compressive strength and flexural strength of resulting specimens of standard mortar of NPC were firstly increased and then decreased with the increase of clinker content.As the clinker content being 45%,the flexural strength and compressive strength of resulting specimens of standard mortar of NPC reached the maximum values,which were 4.8 MPa and 31.8 MPa,respectively.The p H value and setting time of resulting specimens of NPC paste were gradually increased with the increase of clinker content.As the clinker content being45%,the p H value for 28 days and initial setting time of resulting specimen of NPC paste were 12.61 and 180 min,respectively.